Field Generation Subsystem - UCF Department of EECS



Coil Gun with Targeting SystemGroup 8Brian HoehnKwok NgRicardo ReidJosef Von NiederhausernEEL 4915Fall 2010Table of Contents TOC \o "1-3" \h \z \u Coil Gun Executive Summary Overview PAGEREF _Toc279856455 \h 1Similar Projects PAGEREF _Toc279856456 \h 2Field Generation Subsystem PAGEREF _Toc279856457 \h 3Projectile PAGEREF _Toc279856458 \h 4Barrel PAGEREF _Toc279856459 \h 6Rifling PAGEREF _Toc279856460 \h 7Force PAGEREF _Toc279856461 \h 8Wire size selection PAGEREF _Toc279856462 \h 19Magnetic Wire PAGEREF _Toc279856463 \h 20Heat Study PAGEREF _Toc279856464 \h 21Current Pulse Generation PAGEREF _Toc279856465 \h 23External Iron PAGEREF _Toc279856466 \h 25Velocity Detection PAGEREF _Toc279856467 \h 26Testing PAGEREF _Toc279856468 \h 30Heat Dissipation PAGEREF _Toc279856469 \h 33Magnetic Circuit PAGEREF _Toc279856470 \h 35Switching System PAGEREF _Toc279856471 \h 36Design PAGEREF _Toc279856472 \h 40Bleed Resistor PAGEREF _Toc279856473 \h 41Damping Resistor PAGEREF _Toc279856474 \h 43Digital Voltmeter PAGEREF _Toc279856475 \h 44Triggering System PAGEREF _Toc279856476 \h 44Motion Control and SensorSubsystem PAGEREF _Toc279856477 \h 47Motion Control PAGEREF _Toc279856478 \h 48DC Motor Vs AC Motor PAGEREF _Toc279856479 \h 49Stepper Parameters PAGEREF _Toc279856482 \h 54DC step motor controller PAGEREF _Toc279856483 \h 57Real Time Control PAGEREF _Toc279856484 \h 64DC Motor Controllers PAGEREF _Toc279856485 \h 64Sensor PAGEREF _Toc279856486 \h 68FOV request for this camera PAGEREF _Toc279856487 \h 68Power supply for camera and motors PAGEREF _Toc279856488 \h 69Camera Position Configuration PAGEREF _Toc279856489 \h 70Image collection and store PAGEREF _Toc279856490 \h 71Movement Algorithm PAGEREF _Toc279856491 \h 72Motion Vector Determination PAGEREF _Toc279856492 \h 73VIDEO DECODER PAGEREF _Toc279856493 \h 75Power system PAGEREF _Toc279856494 \h 77Power System Overview PAGEREF _Toc279856495 \h 77Power Supply PAGEREF _Toc279856496 \h 78Energy Sources PAGEREF _Toc279856497 \h 79Solar Cells and Panels PAGEREF _Toc279856498 \h 81AC to DC Power PAGEREF _Toc279856499 \h 82Stepping up AC vs. DC Power PAGEREF _Toc279856500 \h 84Regulators Comparison PAGEREF _Toc279856501 \h 85Linear Regulator PAGEREF _Toc279856502 \h 85Boost Regulators PAGEREF _Toc279856503 \h 86Buck Regulators PAGEREF _Toc279856504 \h 87Capacitor Charging Source PAGEREF _Toc279856505 \h 88Digital Voltmeter PAGEREF _Toc279856506 \h 90Digital Thermometer PAGEREF _Toc279856507 \h 91Testing Current PAGEREF _Toc279856508 \h 92Testing Voltage PAGEREF _Toc279856509 \h 93Circuitry Protection PAGEREF _Toc279856510 \h 95Controls and SoftwareSubsystem PAGEREF _Toc279856511 \h 96Position Determination PAGEREF _Toc279856512 \h 97Software Architecture PAGEREF _Toc279856513 \h 99Microcontroller PAGEREF _Toc279856514 \h 103Programming the Microcontroller PAGEREF _Toc279856515 \h 106Choosing a Microcontroller PAGEREF _Toc279856516 \h 106PIC Microcontrollers PAGEREF _Toc279856517 \h 109TI MSP430 PAGEREF _Toc279856518 \h 111FPGA PAGEREF _Toc279856519 \h 113FPGA Design Process PAGEREF _Toc279856520 \h 114Editing, Compiling, and Synthesizing: PAGEREF _Toc279856521 \h 114Choosing an FPGA PAGEREF _Toc279856522 \h 115User Interface PAGEREF _Toc279856523 \h 116Controls and Software Budget PAGEREF _Toc279856524 \h 119Executive Summery PAGEREF _Toc279856525 \h 123Partial Circuit Schematic Overview PAGEREF _Toc279856526 \h 125Circuit Schematics PAGEREF _Toc279856527 \h 126Milestones PAGEREF _Toc279856528 \h 127Coil Gun Executive Summary OverviewA pulsed linear induction motor commonly known as a coil gun is not considered an efficient system. Some enthusiast has achieved efficiencies of 10% but most range from one to two percent energy transfer. This project was initially motivated by a similar project found on YouTube. This was a high voltage self targeting coil gun designed by students at a University in California. Their project was able to track a laser pointer deliver a projectile using 400 volts. Additionally, their project was able to take inputs for the color designation of a target and automatically move to and fire. Additional motivation for building a coil gun was based on power systems. One of this group members is fascinated by power systems and felt this would be a challenging project. Another motivating factor was a fascination of group members with electromagnetic field. Additionally, several members of the group are fascinated with projectile weapons and the development and research of such. Group members who were not as motivated in the electromagnetic or power system aspect of this project were able to find subsystems which allowed them to research and design aspects which were similar to other projects considered by this group.From a firearm standpoint current technology does not allow for a military use of coil guns. One of the immediate benefits is the ability of a coil gun to fire a projectile relatively silent compared to conventional firearm. One of the major negative aspects of a coil guns when used military or law enforcement is the heavy cumbersome load needed to generate the current source. The weight necessary to accommodate the current source, a capacitor bank or battery, reduces mobility driving a mounted implementation. Even if the current source could be mitigated the strength of a coil is proportional to the number of turns which tends to create a heavier unbalanced barrel assembly. This project will use a mounted coil gun to achieve the maxim velocity possible. At the time of this paper the goal was to achieve 100 feet per seconds or approximately 31 meters per second. The design will allow for either manual or automatic firing modes. In the automatic firing mode, the coil gun will be able to optically track a target and fire.For design purposes the coil gun system was broken down into four functional subsystems; Field Generation Subsystem, Power Subsystems, Sensors and Motion Subsystem, and Controls and Software Subsystem. Each subsystem was managed by one of the group members as shown in the block diagram Figure 1. In this paper the subsystem will contain the research, design, and test specific to that subsystem. At the end of the paper a total system test will be given. This approach allowed each member to work on their respective subsystem and to compile the paper in a modular manner. An administrator does not mean that one person researched and designed the complete subsystem.Figure SEQ Figure \* ARABIC 1 Automated Coil Gun subsystemsSimilar ProjectsThe a search of the University of Central Florida School of Electrical Engineering and Computer Science web site revealed two previous coil gun projects. The first group was Group 8 during the Summer/Fall semesters of 2007. Group 8’s project was focused on a high arcing projectile, a mortar application of a coil gun, to achieve a given accuracy. Duringthe Fall2008/Spring2009 semesters Group 13 tackled the coil gun project. The primary propose of this groups project was to create a “high powered mass accelerator” which would accept user inputs. Group 13’s project is similar to this in that both projects are attempting to deliver a high power punch with theprojectile.A major difference between this project and Group 13’s is an automated optical targeting system.Field Generation SubsystemThe Field Generation subsystem primary purpose is to take a large current pulse of short duration and convert it to an electromagnetic field. The primary principle behind the field generation subsystem is to transfer as much energy from the energy storage, capacitor bank or battery, to the projectile. Unfortunately coil guns are inherently inefficient which complicates this task. The field generation subsystem was looked at from an analytical view. Matlab Mfiles were generated to calculate the field strength and can be found in Appendix C.Early on in the project decision-making process, consideration was given to the number of solenoids used. Multiple solenoids trigged at precision timing has advantages when trying to achieve high velocities. The timing of each solenoid could be triggered by an optical sensor place inside the barrel with a variable coefficient which could be manipulated for optimal acceleration. However, it was determined shortly after the project choice than one solenoid should be used to reduce the efforts of timing a series of solenoids. Since only one solenoid will be used higher efficiency is a priority in this project. This may prove to be an added difficulty in the project as coil guns are not known for their efficiency. A two percent energy transfer is considered a good efficiency for coil guns by the hobbyist community.In order to maximize force applied in the forward direction, the current pulse needs to be finished when the projectile has traversed one half of the coil. If the projectile passes the half way point and the current is still flowing the field exerts a force in the opposite direction resulting in a reduce muzzle velocity known as ‘Suck Back.’ The field generation subsystem internal and inter subsystem interface is show in block diagram Figure 2.Figure SEQ Figure \* ARABIC 2 Field generation Block DiagramProjectileThe first step in building a coil gun is to select a projectile. Several shapes and packages were considered for the projectile. Since velocity is a primary design choice in this project, with the benefits of low friction and light mass a spherical or BB shape would have been the intuitive choice for a projectile. The lighter mass would be impacted much greater by the same force on a heavier mass. Low friction would reduce the amount of energy wasted to heat and noise.However, further inspection of the magnetic system used to propel the projectile the force applied to the projectile is directly proportional to the amount of ferrous material. In selecting a projectile it was examined how the projectile affects the magnetic field. Several coil gun enthusiasts have done this before.Saturation is the point where all magnetic regions are aligned and a further increase in the strength of the magnetic field will not be beneficial to the system. The information for the saturation table 1 was taken from .com. Supermalloy would be an optimal projectile material but the price and availability is beyond the scope of this project. MaterialPermeabilityAt B = 20 GaussMaximumPermeability Saturation Flux densityB gaussCold rolled Steel180200021000Iron200500021500Purified iron500018000021500Supermalloy1000008000008000Table SEQ Table \* ARABIC 1 Saturation DensityIron or steel rods are also available which will fit better in the barrel with much less air gaps. These rods would provide the opportunity to vary the length of the projectile for optimization. However, currently a quarter inch number 2 Philips head bit one inch long is selected as the projectile. This projectile fits within the barrel but leaves some air gaps which translate into efficiency loss. Currently, the projectile is made from cold rolled steel due to the availability, consistent mass, length, and diameter. The Phillips head bits are readily available at any local hardware store. Further research of the projectile found that Barry Hansen had simulated the variation of the projectile to coil ratio shown as figure 3. It was found that the maximum work done was when the length of the projectile was 75% of the coil length. During the fabrication of this project the iron dowels from Lowes will be tested from lengths of 20mm to 5 mm to pick an optimum projectile. However, it is readily apparent that a spherical projectile would not be an efficient vehicle for energy transfer. In addition to the Phillips head bits a length of 16 gauge cold rolled steel was purchased. This will allow the variance of projectile length during the prototype phase.Figure SEQ Figure \* ARABIC 3 Variation of Projectile（Reprinted with Permission of Barry Hansen)It was considered to build a Mfile which would simulate the variance of the projectile while holding other things constant. However, this turned out to be a more difficult analysis than expected and seems to be beyond the scope of this project. As a result, it was determined this would be better done during the prototype phase. BarrelThe barrel choices were limited to what is available at local home improvements stores. When selecting a barrel several considerations should be taken into account. Permeability (μr) will allow the field to penetrate the barrel and engage the projectile. For non ferrous materials μr is approximately equal to free space (μ0). Low coefficient of friction (COF) will allow the projectile to be guided by the barrel with minimal energy loss. A brass barrel would have a low COF and since brass is not ferrous its permeability is not an issue.A barrel made of brass would provide a durable material which would increase total shots possible per barrel. The projectile path will be much more controlled in a rugged metallic barrel. However, the metallic conduction properties would increase a risk factor for safety issues. This could be mitigated with an insulator between the solenoid and the barrel. An insulator would increase the inner diameter of the solenoid and decrease the force exerted on the projectile.Another aspect of the barrel is eddy currents. Eddy currents are circulating currents in a conductor which will induce a magnetic field opposite to the original field. Obviously, eddy currents will reduce the velocity of the projectile, which is a major design point of this project. Slotting, or notching, the barrel will reduce the amount of eddy currents.Since this project is uninsured, maximum safety is a major design parameter. Safety and accessibility has driven the selection of a non-conducting barrel. Currently a quarter inch, or 8 mm, inner diameter polyvinyl chloride (pvc) commonly known as PVC pipe which is commonly used for refrigerator water lines, for ice makers and cold water, has been selected available at Home Depot or Lowes. The outer diameter of this barrel is 13 mm and will be the inner diameter of the driving solenoid. In an effort to increase consistency a rigged support structure could be implemented to reduce barrel vibrations induced by the projectile. This can be a dowel or forward support structure.RiflingTo give the coil gun the most accuracy as possible we have decided to look in to the possibility of rifling the barrel for which the projectile will travel through. Rifling is the idea creating grooves throughout the inside of the barrel. The grooves in the barrel force the projectile to spin. This spin stabilizes the projectile improving its aerodynamics and accuracy. Rifling is measured by the twists per inch, i.e. one turn in ten inches (1:10). To increase the speed of the rifling you would shorten the distance per twist, while increasing the distance per twist slow the speed of the rifling. The ‘speed’ of the rifling refers to the rotation of the projectile through the rifling not the actual velocity of the projectile. To determine the speed of the rifling, or twist rate, need for a specific projectile the shape, length and weight will all be taken into account. In most cases slower twist rates are used for projectiles that are short and have a larger diameter, and faster twist rates are used for projectiles that are long and have a small diameter. Since the projectile we will most likely being using is a drill bit, which is long and has a small diameter, we will use a twist rate of 1:10 or faster. To calculate a more precise twist rate we can use the Greenhill Formula that was developed by George Greenhill, in 1879, to do just that. The formula follows:Where:= 150 (use 180 for muzzle velocities higher than 2,800 f/s) = bullet's diameter in inches = bullet's length in inches= bullet's specific gravity (10.9 for lead-core bullets, which cancels out the second half of the equation)There is also a formula to calculate the projectile’s revolutions per minute due to the rifling. The formula to calculate the rotational speed of the projectile is MV(in fps) x (12/Twist rate in inches) x 60.Other than creating the rotation of the projectile, the rifling has other needs that need to be addressed. We want the rifling to be the correct size so that projectile will ‘swage’ when fired. We don’t want the diameter of the rifling to flux, consistency is a must. The spacing of the twist and groove width should also be uniform throughout the barrel. There any many methods to manufacture rifling in a barrel. The two techniques we will most likely use either the cut rifling method or the broached rifling method. The cut rifling, also known as single point cut rifling, is done by using a machine tool to cut one groove at a time. Instead of cutting on groove at time, all of the grooves can be cut in one motion using a progressive broach bit; this would be known as the broached rifling method. Due to the cost and unavailability of rifling a barrel or purchasing a pre-rifled barrel the idea of choosing to rifle the barrel of the coil gun seems to be a little unrealistic, and we will only be done if circumstances allow for it.ForceThe first step is to calculate the amount of force needed to move the 5 grams 31 m/s. Using an acceleration distance of 2 inches or 0.0508 meters and the end velocity of 31 meters per second, the acceleration period is calculated by:The acceleration is calculated by:Using Newton’s Second Law:Converting to Joules:Evaluation of the above process using the kinetic energy equation yields:The coefficient for Polyvinyl chloride (PVC) was not readily available so the force calculated above will be overestimated by 20% which gives 94.5 Newton’s of force. This may seem like a small amount but considering the poor efficiency of coil guns this will not be a menial task. The period of acceleration will also be the current pulse period. Using an average two percent energy transfer about 250 joules will be needed.Consideration was given on how to create a suitable current pulse. Since the force exerted in a magnetic field inside a hollow solenoid is directly proportional to the current. A large pulse, 1000 amperes, is desired for one to three milliseconds. This can be accomplished several ways. The most common is to use a bank of capacitors. One of the major benefits of using a capacitor bank is relatively short charge times. Additionally the capacitors will deplete quickly which broadens the triggering switch selection.= is the magnetic field in Teslas= permeability of free space= the number of turns per meter* = is the current in amperesWith the minimum design found above, an analytical optimization was performed. Analysis of a finite solenoid can be done by using equations found on . A diagram showing the dimensional analysis is shown in figure 4.Figure SEQ Figure \* ARABIC 4 Dimensional Coil AnalysesThe general equation for magnetic field strength of a finite air filled solenoid is given by:This equation was used to show the field as a function of power:Where is the unit less geometry factor:However, while attempting to simulate the above equation in it in Matlab erroneous inductances were exhibited resulting in the results being discarded. This was a major setback in for optimization of the coil gun. Being able to plot the field strength with respect to starting position would have been a beneficial design asset. However the ratio of Alpha and Beta were said to be optimized at 3 and 2 respectively. The alpha ratio was chose first and resulted in the outer diameter of 39 mm being selected. Early attempts at setting the Beta ratio to 2 severely reduced the amount of current running through the coil, 300 amperes. Therefore, this design was not able to optimize the Beta ratio as will be shown later on, and it was later calculated at 1.Continuing with the Matlab simulation, the magnetic field found at the midpoint of a coil is given by:Or:Where = the current density.All the above equations were simulated in Matlab and the following plots were generated. The equations were written to M files and all variables were held constant except one. This process was performed several times. When the final coil dimensional values were selected the final iteration was captured for this initial project documentation. Firs the length of the coil was varied as shown in Figure 5 this was done by holding all the values constant and setting up a loop which iteratively added one millimeter increments up to one meter. Figure 6 shows the magnetic field strength as calculated from the on axis mid point. The unbroken line is showing the partial wire input into the field strength. This is not particle. The program was corrected to take into account the wire gauge. A second iteration of the M file accounted for the wire diameter and would not allow for partial wires. This resulted in the jagged line shown below. Figure 7 shows a complete view of the coil length variations. Even if the calculated numerical values are incorrect the graph has merit in showing the diminishing return on field strength. This plot was used in conjunction with Barry Hansen’s inductor simulator and resistor, inductor, capacitor simulator to pick the nominal length of 26 millimeters.Figure SEQ Figure \* ARABIC 5 Varying Coil LengthFigure SEQ Figure \* ARABIC 6 Varying Coil LengthFigure SEQ Figure \* ARABIC 7 Varying Coil LengthAs the length of the coil increases the midpoint magnetic field increased. This variable was used to optimize current given an optimal inner and outer diameter. Holding the length constant the diameter of the coil was varied as shown in figure 8and produced the plot shown in figure 9. This was done using an iterative loop which varied the outer diameter of the coil from the inner diameter to one meter in 1 millimeter steps. Again the line is jagged to show the partial wire gauge steps did not increase the number of turns. The field strength shown on the left is measured at the center point on axis of the coil. Even if the calculated numerical values are incorrect the graph has merit in showing the diminishing return on field strength. Using this graph and the recommendation to set alpha to 3 the outer diameter was selected at 39 mm.Figure SEQ Figure \* ARABIC 8 Varying Coils Outer DiameterFigure SEQ Figure \* ARABIC 9 Varying Coil Outer DiameterThen the inner diameter of the coil was varied as shown in figure 10 to produce the plots shown in figure 11.Figure SEQ Figure \* ARABIC 10 Varying Coil Inner DiameterFigure SEQ Figure \* ARABIC 11 Varying Coil Inner DiameterThe final dimensional analysis was to vary the American Wire Gauge while holding all other things constant as shown in figure 12. As can been seen there is a significant gain as the American Wire Gauges increases, which is an actual decrease in the diameter and an increase in the turn density. Unfortunately, the current used in generating this plot, 848 amperes, would exceed the coils capacity to be able to dissipate heat for anything larger than 20 AWG.Figure SEQ Figure \* ARABIC 12 Varying American Wire Gauge (AWG)The first equation given in this section was used to vary the starting position shown as figure 13 of the projectile to produce the plots shown in figure 14.Figure SEQ Figure \* ARABIC 13 Varying Projectile Starting PositionFigure SEQ Figure \* ARABIC 14 Varying the Projectile Start PointAfter all the physical dimensions of the coil were varied, the current was varied to produce figure 15. This plot show the calculated strength of the on axis midpoint located within the coil. As anticipated the coil has function which is shown to be:Figure SEQ Figure \* ARABIC 15 Varying the CurrentBarry Hansen’s simulators located at were used to optimize the length of the coil. Holding the inner and outer diameters fixed and systematically adjusting the length produced Figure 16. It was noted that the length calculator in this simulator differed significantly from the unsuccessful Matlab simulation. A comparison of the two showed that it appears the Inductor simulator is not using Pi x 2r to calculate the circumference of the coil and hence the length of wire per turn. The values calculated using the simulator may be shorter than actual wire length. The code written for Matlab can be found in Appendix C.Figure SEQ Figure \* ARABIC 16 Inductor Simulator(Reprinted with permission of Barry Hansen)Using the inductances shown above the RLC simulator on the same website was used to show currents. The length of 26 mm was selected to give the most current by reducing the resistance and inductance. The RLC response is shown with the coil dimensional parameters as figure 17.Figure SEQ Figure \* ARABIC 17 RLC simulator(Reprinted with permission of Barry Hansen)Wire size selectionCurrent Density is defined as the amount of current flowing through a wire. As the current flowing through a wire increases some of the energy is dissipated as heat. If the wire in not able to dissipate fast enough the wire will melt. So consideration was given to the size of the wire used in the driving solenoid, since there will be a large pulse traversing it. Since the current used to produce the field will be of short duration the following equation given by the Handbook for Electrical Engineers for wire size used in fuses was used to select a nominal wire size.Where:= the current in Amperes= the area of wire in circular mils= the time current flows in second= is the melting point of conductor (for copper this is 1084.62° C)= is the ambient temperature (in Celsius)Using the average indoor temperature of 27° C the above equation was used to find the Current Time product. With the estimated 1000 amperes desired for the field generation this yielded three nominal choices 18, 16, and 14 American Wire Gauge (AWG) shown in table 2. These theoretical values were de-rated a further 20% to allow for a more realistic view. The smaller gauge wire will allow for more turns per meter and yield a stronger field. A larger gauge will allow for more current to flow with less wire resistivity. Additionally, the larger gauge will be able to dissipate heat faster than a thin wire and allow for a shorter firing interval. A MatLab Mfile was created and an iteratively ran though the following American Wire Gauges to show the time to melt at 1000 amperes. The turns per meter are useful to show the gain in field strength since field strength is proportional to the number of turns as shown below.AWGCurrent (amperes)Duration to melt (ms)De-rated20 %Turns/Meter(bare)14100019.015.2614.415100015.012.0689.816100011.99.5774.61710009.57.6869.91810007.56.0976.9Table SEQ Table \* ARABIC 2 Time to meltCurrently 16 AWG is selected for building the driving solenoid. Further investigation is needed to evaluate the thermal resistance of the insulator of the wire; this is to be done in the Magnetic Wire section. = Magnetic Field (tends to magnetize space)= Magnetic Flux Density (total magnetic effective results)Magnetic WireSince the magnetic field strength is proportional to the number of turns per unit of linear measurement, magnetic wire should be used. Magnetic wire is classified as an inner conductor, usually copper or aluminum, thinly coated with a thin polymer for insulation to maximize turns per inch. It is available in circular, square, rectangular, rounded square, or flat shapes. It should be noted that even though it’s called magnetic wire, the wire itself is not magnetic. Magnetic Wire is rated by the thermal capacity of the polymer. The National Electrical Manufacturers Association (NEMA) has set forth standards for categorizing Magnetic Wire (MW) with the nomenclature MW-NA where NA are alphanumeric values. Some common types of magnetic wire insulators are polyurethane, polyamide, polyester, polyester-polyimide, polyamide-polyimide (or amide-imide), and polyimide. Table 3 shows the Thermal Classes of insulators.Thermal ClassInsulation Type105° CPolyamide, Polyvinyl Acetal, Polyurethane, 130° CPolyurethane155° CPolyester, Polyester (amide), Polyester (amide) (imide), Polyurethane180° CPolyurethane 180, Polyurethane Nylon 180, Polyester Nylon, Polyester-imide, Polyester-amide-imide200° CGlass Fibers, Dacron Glass, Poylester 200,Polytetra fluoloethylene (Teflon)240° CPolyimide, Table 3 Thermal Classes of insulatorsHeat StudyThe power consumed by the coil was calculated as:This power delivered in this calculation is much higher than would be expected. The total energy converted to heat was then calculated by assuming a sin function for the current pulse:Since the firing period is very short, one to two milliseconds, no cooling will be considered to take place from the environment. Or in other words, all heat will be considered to dissipate in the wire and insulator per shot. This is important when considering the grade of Magnetic wire which will be used. Again the equation does not yield values which seem practical.Since the above calculations returned numbers which this group had very low confidence in an educated guess was made for the temperature rating of the coil. A spool of 64 feet of Magnetic Wire with an AWG of 16 was chosen for this project, BulkWire part number Wire-MW-16-1/2. The temperature rating is 200°C and is made from a modified polyester resin. There is an overcoat applied which is amidi imide resin which the website is calling a “High tech enameled insulation.” 64 feet or 19.5 meters of MW-16 is priced at $12.68.The coil will be wound with a coil guide made from a bolt the same diameter as the barrel. The ends the center part of the bolt from point A to point B is where the coil length will be controlled see figure 18. On opposing sides of the washers will be two nuts per side. Turning theses nuts in counter directions will make a solid point which can me manually adjusted as needed. When the first layer of coils is complete a thin drop of super glue will be applied to the top and bottom of the coil. This process will be performed for each new layer. When the adhesive has had sufficient time to dry it the coil can be safely removed and mounted on the barrel assembly.Figure SEQ Figure \* ARABIC 18 Hand Made Coil GuideMost of the fabrication for the field generation subsystem can be done in the garage. The winding of the coil can be done by hand. Using a bolt with the same diameter as the barrel a set of locking nuts can be used to create a coil guide used for winding the coil. Another method would be to attach the coil guide apparatus to drill and using a low setting have one person guide the coil while the other controls the drill. If done properly this would create a uniform and tight coil can be constructed. The preferred method is to use a lath. If a lath can be found which has a low enough rotational setting, one person could use the coil guide apparatus to wind the coil. Depending on the lath if it is a machine lath or a woodworking lath will determine the coil guide apparatus. A Machine lath will allow the use of the bolt coil guide apparatus. If a woodworking lath is to be used a wooden dowel the same diameter as the coil will be needed wooded washers would be made. The wooden washers would be made a larger dowel and drilled to the inner diameter of the barrel dowel. This would then be fastened to the wooden barrel dowel.Current Pulse GenerationAn industrial automotive battery was proposed and considered. The Duralast 12 volt 950 cold cranking amps (CCA) heavy industrial battery, Autozone part number (31-950), could provide a sufficient charge necessary for demonstration of the coil gun. However, concerns arose as to the practicality of using a battery. It was noted that the charge time for an industrial automotive battery is significantly longer than a capacitor bank. At approximately 60 pounds this would be a large and cumbersome current source. In addition to a battery and capacitor bank, it may be possible to use a transformer to provide a high current capacity on demand. This would be highly desirable option and allow for a rapid firing of the coil gun. One of the immediate problems with this is the need for a fast switch which could handle high currents. Finally, a capacitor bank could be used for the current source. According to wiki. capacitors used in coil guns should have a low equivalent series resistance. Intuitively this makes sense since the goal is to deliver maximum current to the coil. Readers were warned that super capacitors, appealing as they may be with high capacitance, were not to be used in coil gun applications. A pulse discharge will wreck the super capacitor. In addition to low equivalent series resistance a low equivalent series inductance is also good. However, if the inductance of the capacitor is much less than the inductor the equivalent series inductance can be ignored.For this project 5 millifarads are needed to generate the current pulse. Electrolytic capacitors were selected because they are inexpensive and have a high capacitance for their size. When designing the coil firing circuit it will be important to prevent any current from entering the electrolytic capacitors from the wrong polarity. This could cause a catastrophic failure of the capacitor. This will be done with diodes known as fly wheel diodes.The Type 450C 105°C Ultra-Ripple, Long-life, Inverter Grade, Radial Leaded capacitor was the capacitor of choice for the capacitor bank due to the low equivalent series resistance. The equivalent series resistance is 6.9 milli ohms and Five 1000 μ Farad capacitors in parallel would provide the desired 5000 μ Farads. However, due to unavailability of the part, Mouser part number 598-450C102M350AJ8, and manufacturer part number 450C102M350AJ8 this part was not selected. Secondary and design choice is the Type CGS High-Cap Screw Terminal Aluminum Electrolytic Capacitor. Manufacturer part number CGS102T350V4C, and Mouser part number 539-CGS350V102V4C. This is a 350 Volt 1000 μ Farad capacitor with an equivalent series resistance of 140 milli ohms. The price is $28.80 each. Five of these capacitors will make the capacitor bank which will provide access to 225 joules.The five capacitors will be connected in parallel using a copper bus. The screw termination of the capacitors will allow for holes to be drilled in a copper bar and fastened with screws.The calculated kinetic energy needed in the Force section was 4.8 joules. If a 2% energy transfer is assumed this would be barley enough to accelerate the projectile to 31 meters per second.External IronExternal iron can be used to reduce the reluctance of the coil. The external iron will guide the flux lines to the central axis of the solenoid. This should improve the energy transferred to the projectile. In order for the external iron to be effective, it should be used on all sides to include the ends, allowing just enough room for the barrel and projectile to pass through. Iron pipes used for plumbing, a common item found at the local hardware store, can be used for the external iron. Caps can be used for the ends of the barrel assembly. One of the major tradeoffs for this project is the additional weight that will be added. Since the barrel will be moved by servos a heavy firing tube is undesirable. Additionally, the coil will have a longer cool down time due to the enclosed system. Finally, it is possible that eddy currents in the external iron could be counter productive to the firing process. This could be reduced by notching the external iron. Figure 19 shows the external iron concentrating flux lines.Figure SEQ Figure \* ARABIC 19 External Iron Guiding Flux Lines(Reprinted with permission of Barry Hansen)Velocity DetectionSince the major design requirement is to achieve a velocity of 31 meters per second. A built in velocity sensor will be used to improve performance in the prototyping phase of this project. There are several methods to determine the velocity of a projectile. The methods covered in this project are electrical contact, mechanical contact, field sensing, and optical sensing.The electrical contact method would use the projectile to complete a circuit as it passes through a point in the barrel. This could start a counter which would be stopped as the projectile continues down the barrel. One of the major design issues with this system is that the projectile needs to make good contact to complete the circuit. This means that it must either fill the entirety of the barrel or have the electrical leads protruding into the barrel. This would be a poor design approach. Since maximum velocity is a primary design goal protrusions into the barrel would be counter productive. Additionally, since the design of the coil will need to be optimized in the prototype phase the projectile may be altered from its original design which could severely cripple the electrical contact velocity detection method. Even if the above concerns were mitigated, there is additional potential for the electrical contacts to reduce velocity.The second method, mechanical contact, is similar to the electrical contact method. This would use thin springs protruding into the barrel that would depress an electromechanical switch. Again two sensors would be need. The first would trigger a counter and the second would stop the counter. As discussed in the electrical contact sensor the mechanical contact would also inhibit the velocity of the projectile.The third method would be to use sensing coils at the end of the barrel. As the projectile passes through the sensing coil a current is induced which could be used to trigger a counter. When the projectile passes the final coil the counter would be stopped and the velocity could be determined by the distance between the two sensors and the time it took to traverse that distance. A major benefit to this type of velocity sensing is the noninterference into the barrel or with the projectile. It would also allow for the coils to be slide easily along the barrel for adjustment. Since the project is a coil gun the use of sensing coils is appealing. An article from Sensors Magazine was published about the United States Air Force used a coil sensing system at a laboratory on August 1, 1998. Kaman Instrumentation Corp. designed the Kamen KD-2300 Dual Sensor Velocity System. This system is used by the Impact Physics Lab 0.50 caliber light gas gun facility to measure and compare the projectile performances. This system uses a one megahertz carrier frequency to produce eddy currents in the projectile. The eddy currents allow the sensing coils to know exactly where the projectile is at. This system allows for the detection of high velocities up to 3000 feet per second and with an excellent precision. The coil sensing method would be an excellent project in itself. However, since this project is bound by the time and money the coil sensing method will not be used.The fourth method would be to use optical sensors to capture the velocity of the projectile. Similar to the inductive sensing coils, an optical sensing system would be unobtrusive. However, if the optical sensors are incorporated into the barrel they will not be adjustable like the coils. Holes will need to be drilled in the barrel and the sensors seated below the path of the projectile. The potential arises that the holes where the sensors were drilled will allow the projectile to catch and tumble or lose velocity. This is especially likely to happen when the projectile is not rounded or if the projectile does not fit the barrel. The theory for optical velocity sensing is simple. Using two sensors place in the barrel at known distances, the time it takes the projectile to get from the first sensor to the second the velocity can be calculated. The infrared light emitting diode will be constantly emitting. When the projectile passes through the between the light emitting diode and infrared sensor the sensor will trigger a counter. When the projectile passes through the second set of emitter sensors the counter will stop. For the optical sensing the infrared spectrum was chosen. Infrared signaling is commonly used in household applications with remote control devices being the most obvious. The benefits to using an infrared sensing system are that the visible lights will not trigger the sensor on accident. For the light emitting diode a SE3455-003, manufactured by Honeywell, was selected. This light emitting diode will output 935 nanometer wavelengths in a 90° beamwidth. For the optical sensor, a SD3410-002, also manufactured by Honey well, will be used. This sensor has a 90° or 12° nominal acceptance angel option and is mechanically and spectrally pared with the SE3455-003 light emitting diode. Both the sensor, Mouser part number 785-SD3410-002, and the light emitting diode, Mouser part number 785-SE3455-003, are currently available.When the sensor conducts the LM393 comparator, Mouser part number 863-LM393NG, will trigger a counter. The counter will be housed in a Programmable Integrated Circuit. PIC16 will be used as the counter. When the comparator initiates the PIC the program will start counting. The output of the PIC will be sent to an eight bit display as shown in figure 20.Figure SEQ Figure \* ARABIC 20 Speed trap Calculation(Reprinted with permission of Donnie James)The sensors will be positioned three inches apart with the last sensor a half an inch from the end of the barrel. Combined they create a speed trap. The speed trap is optical sensors are shown in figure 21.Figure SEQ Figure \* ARABIC 21 Optical SensorData collected from the optical speed trap will be compared to a look up table to arrive at the actual projectile velocity. Testing the optical speed trap can be done with a chronograph. Firing the projectile through a chronograph and comparing out puts will verify functionality of the optical speed trap. Thecomplete circuit is shown as figure 22.Figure SEQ Figure \* ARABIC 22 Total Speed trap(Reprinted with permission of Donnie James)TestingThe primary tests for the Field Generation Subsystem will be to show that the magnetic wire will be able to handle the current without damage to the wire or the insulator. After procuring the capacitor bank a length of wire will be tested against a large current source. This needs to be done early next semester so that if the enamel is insufficient a higher temperature magnetic wire can be procured. The final test will be to see if the field generated can achieve velocities of 31 meters per second or greater. This can be tested by several methods. The first method would be the linear drop test. This method uses the linear distance traveled from a given height to show the velocity. A simple equation, distance traveled = time * velocity. Setting the coil gun on a level surface 4.8 meters, the measuring the linear distance traveled by the projectile. Another method, if available will be to use a gun chronograph. The Chronographs use two optical sensors to determine the velocity. A built in Chronograph would be highly desirable for this project and would be much cheaper than purchasing new test equipment. Chronographs pricing starts at $50 dollars, if enough funds are left after purchasing components this test equipment will be procured. A paint ball chronograph will work just as well.Barry Hanson has devised a test to find the inductance and strength of the coil.Using a resistor decade box in series with the coil, adjust the decade box until the voltage is the same, across the decade box and the inductor. When the voltages are the same the resistor setting will be equal to the reactance of the coil. Where, n is the number of turns and f is the frequency.Measuring the coil strength can be done by setting the projectile on its back and placing the coil above it see figure 23. Connect the coil to a variable voltage source. Increasing the voltage until the projectile is barely touching the table. Once this is met record the voltage in a table comparing the height and voltage needed to lift the projectile. Mr. Hanson calls this voltage force a one G. This process will be contused for variation of elevation points. Figure SEQ Figure \* ARABIC 23 Coil Strength Test(Reprinted with permission of Barry Hansen)Use the following equations to complete the table.Since air filled coils have linear properties, up until saturation of course, the Force at maximum voltage can be calculated. Plotting the data collected in this table will produce a plot which will show the magnetic field strength in terms of G see figure 24. It should be noted that this is not a measure of actual Standard given by the International System of Units. It is however a method of measuring the field strength with respect to the projectile. Even though it is not an International System of Units standard the plot would be helpful in determining the nominal position for the starting projectile. Once this accurate and specific point has been found for the firing solenoid, a mechanical loading system will be built to deliver the projectile to the same nominal position consistently.Figure SEQ Figure \* ARABIC 24 Magnetic Field Strength Test(Reprinted with permission of Barry Hansen)Field Generation Design SummaryThe Field Generation subsystem was designed with the following parameters table 4 and cost estimate table 5. This subsystem will take one fourth of the estimated project cost.Parameters:Coil Length26 mmCoil Inductance0.352 m HCoil Resistance 0.184 ohmsInner Diameter13 mmOuter Diameter29 mmWire Gauge16 AWGWire InsulationHigh Tech EnamelProjectile Mass5 gramsProjectile Length25.4 mmProjectile Width6.35 mmTurns in coil171MW linear length13.97 m MW weight.16 kg Winding density7.5 turns/cmForce needed to accelerate 94.5 Acceleration Length0.0508 mWork needed4.805 joulesField strength at Coil Midpoint3.851 TeslaPower dissipated in coilCapacitors5 x 1000 μ FaradIR emitterSE3455-003IR SensorSD3410-002ComparatorLM393PICPIC16Current triggerSCRFire control trigger555 TimerTable SEQ Table \* ARABIC 4 Field Generation Design ParametersItemCost EaQtyTotalMagnetic Wire$12.681$12.68Capacitor$28.805$140.00PVC Barrel$21$2Projectile (bits)$81 Pkg$8External Iron$201$20IR LED$4.802$9.60IR Sensor$7.102$14.20LM393$0.501$0.50PIC16$2.001$2.008 bit display~$101$10SCR$1201$120555 timer$51$5Subsystem Total$343.98Table SEQ Table \* ARABIC 5 Field Generation Cost EstimateHeat DissipationThe coil gun is going to generate massive amounts of heat. There is a lot of heat coming from a lot of power dissipation among electrical devices. Magnetic fields generated by change in electrical fields create most of the heat. Keeping the heat to a minimum is going to be a huge obstacle. There are several manners of which the heat can be reduced. The key to keeping heat to a reasonable value is by making sure to account for the power generated by the device used to dissipate heat. Power generated by the heat dissipation devices should not interfere with the 300V being discharged of the gun. The usual choice for cooling an object is the use of fans. Fans are great coiling devices for the project because they can transfer the heat away from the gun. Heat is an adversary of every electrical component in the circuit. Taking care of the heat increases the efficiency of the gun. The use of natural air to cool the electrical component is not possible.Heat sinks can also be used as a cooling device. A heat sink transfers heat from one medium to another. In most cases the medium is air or liquid. Liquid cooling works a lot better but is very expensive. Liquid cooling involves liquids such as liquid nitrogen which is fairly expensive. Despite being expensive this is not the only drawback. It can be very dangerous due to its extremely low temperature. When this liquid comes in contact with human tissue it leads to frostbite. Another issue arises when it comes in contact with a hotter substance. It begins to boil immediately after contact and turns into a gas.Many circuit elements of the coil gun will be exposed to large amounts of heat. The charge resistor will experience a majority of the high amounts of heat, only second to the actual solenoid. Since the charge resistor for the gun is going to be light bulb power dissipation through heat is not an issue. The light bulb does a good job of dissipating the heat by emitting light. The diodes in the rectifier circuit are going to experience high switching current; therefore they are subject to high heat as well. To prohibit these from overheating a fan will likely be used to cool the devices. Capacitors might experience high heat because of the large amounts of energy being discharged. Keeping the capacitor bank cooled will reduce the risk of premature failure of an individual capacitor. This is a major concern because high voltage rated capacitors are puter fans are great choices for use in a coil gun. There are several different types of computer fans to choose from. There are fans designed for all purposes. Computer game enthusiasts use fans with high CFM. CFM stands for cubic feet per minute. A Cubic feet per minute refers to the measure of air flow that is generated by the fan. Fans also are described by their revolutions per minute or RPM. Fans with higher RPM have higher decibels. Some fans come with fans that can be adjusted electronically or manually. Fans that can be manually adjusted use a potentiometer to allow change of speed. Fans can be adjusted thermally or by computer hardware or software too. In the coil gun there isn’t a need to have an adjustable fan. Since computer fans are 12 V using a smaller voltage would cause the fan to run at a slower speed and is less noisy.For the coil gun multiple fans and heat sinks will be used to assist in dealing with heat dissipation. For the capacitor banks cap coolers will be used to deal with the heat that the AC to DC power convertor generates. The capacitor cap coolers are very effective for keeping the capacitors at a safe operating temperature. The weights of the capacitors coolers are fairly light. From first glance they appear to be a permanent attachment to the capacitor. The solenoid of the coil gun is going to need more than just a fan or heat sink to deal with heat dissipation. The heat dissipation in the solenoid is going to need some type of insulation to account for the high heat dissipation that is not just on the surface but internal as well. Surface heat is easy to cool because fans and heat sinks easily dissipate that heat, but internal heat dissipation can be troublesome. Internal heat usually depends on the type of conducting material and its resistance. The higher the resistance in the material usually means more power is being dissipated. To cool the internal heat it may be necessary to use different material, material size, or adding some type of thermal compound. Fans and heat sinks do not efficiently help with dealing with internal heat, they are more for the surface area of conducting material. Two small fans were chosen to cool electrical components of the coil gun. The two fans chosen to be used will be computer fans. The function of the fans will be to provide the gun with cool air while expelling the hot air as well. The size of each of the two fans is 80mm. This is the standard size that is currently used in desktop computers. Computer fans are excellent cooling devices. They have proven to be the essentials of desktop computers for years. The two fans may have built in potentiometers to increase fan speed if for some reason it is needed.Magnetic CircuitTo better understand the physics of a coil gun it is necessary to be knowledgeable of magnetic field generation. A magnetic circuit is closely related to that of a basic electrical circuit. In a magnetic circuit a magnetomotive force (mmf) denoted by the letter F provides a flux through a ferromagnetic core. The equation used to describe mmf is as follows:F=NiThe letter N is the number of turns in the coil and i is the current through the wire. The magnetomotive force should be looked at similar to the voltage source of an electrical circuit. The purpose of mmf is to create an electromagnetic field by passing current through a wire that contains multiple turns. The mmf has polarity as well. To determine the polarity of mmf we use the right hand rule. We take the fingers of the right hand and curl them the direction of the current through the wire, whichever way the thumb is pointing is the positive direction of the mmf. This concept is based on the basis of the Biot-Savart law. The Biot-Savart Law explains how a magnetic field denoted by the letter B is generated by an electric current. With Biot-Savart’s law we can calculate the magnetic field that is being generated by the current that we provide the gun with. B =?H. ? is simply the magnetic permeability of the material. H is the magnetic field intensity. The magnetic field intensity is the effort exerted by the current to create a magnetic field. This is explained through Ampere’s and Maxwell laws. To understand how we can increase the magnetic field we have to know the relation the magnetic field intensity has on the magnetic field. The magnetic field intensity, H is equal to mmf divided by length of the core. In a coil gun this is length the projectile travels before leaving the end of the solenoid. The main concept that should be evident between magnetic field and magnetic field is that they are proportionate to one another. In are design of the coil gun we will be looking to maximize the magnetic field and intensity.The magnetomotive force can be expressed in terms of flux and reluctance. The equation is as follows:F= ? RPhi in the equation is the flux. The flux can be thought of as the magnetic current that is produced by the magnetomotive force. The r is the reluctance, better known as the resistance of the magnetic circuit. The reluctance in the coil gun should be kept to a minimum so that flux will flow freely. The reluctance is dependent on two major factors the length and the cross sectional area of the solenoid. The reluctance is given by the equation:R = l?ATo obtain the least resistance in our circuit we must minimize the length of our solenoid as well as increase our cross-sectional area. We do have control of our length of solenoid but not over the cross-sectional area because of other factors pertaining to the projectile being used. It is important to visualize the conceptual idea of having minimal reluctance in the magnetic circuit and more flux. Permeability is going to play a vital role in the coil gun magnetic circuit. Air and the projectile are going to be the core of the magnetic circuit. The core is composed of ferromagnetic material. In the coil gun barrel assembly the iron bit is the ferromagnetic material which has a very high permeability. The high permeability means that the degree of magnetization is high. The projectile will be able to react to the magnetic field that is induced from the current traveling through the coil.Switching SystemIn order for the capacitor bank to release stored energy to the coil it must have a switching system. A switching system needs to be implemented in order to get current from the bank to the solenoid. Normally this can be done by any type of switch. With a high voltage, high current coil gun the use of a normal switch is not an option. A normal switch is not an option because they cannot handle high currents. The high currents will cause such devices to fail. The coil gun must use some type of switch which can handle a high current surge and block high voltages. There are multiple ways of which this can be done with a bipolar junction transistor, metal-oxide semiconductor, silicon-controlled rectifier, or an insulated gate bipolar transistor. All devices can control high current surges. For the coil gun it is ideal to want a device that will be able to switch on and off via current or voltage. The best device to implement switching is a transistor. This is not the only device that can be used for quickly switching the current from the capacitor bank to the solenoid. A SCR is a Silicon-controlled rectifier. Despite the name SCR it is nothing more than a thyristor. The name SCR represents a brand of thyristors but is commonly used to describe all types of them. It is composed of four layers including P and N type semiconductor materials. In the coil gun as soon as current travels through the silicon-controlled rectifier’s gate after exceeding its holding current, it will turn on. The holding current is dependent on the specifications of the silicon-controlled rectifier. When it is turned on it will then release the stored capacitor bank charges to the coil via current. The device will remain on as long as the current through the anode remains above the holding current. The silicon-controlled rectifier in the coil gun will stay on until after every shot. The problem with a silicon-controlled rectifier is its properties prohibit it from turning off. Once getting a current to flow through the gate the device is in active bias and conducting. At that point in time it cannot be turned off in the middle of the current pulse. Using a SCR in a coil gun might be necessary because of its low cost to voltage ratio. The figure 25 shows a silicon-controlled rectifier that is used in a high powered system. From the picture it does not look similar to a diode as seen in circuit schematics. It none the less functions very similar to a diode. The picture shows the little wire that represents the gate that the triggering system needs to be connected to.Figure SEQ Figure \* ARABIC 25 Silicon Controlled RectifierA bipolar junction transistor can be used for switching. For a coil gun it is beneficial to use an NPN type. A NPN transistor can be used as a switching device when the device is operated in saturation mode. For the bipolar transistor to operate in saturation mode there must be a large current supplied to the base. The current inputted in the base terminal allows the transistor to pass larger collector to emitter current. This transistor in a coil gun would not be ideal at all. The current supplied to the base current has to be as much as 10% of the collector to emitter current to have the device operate in saturation mode. Since the coil gun uses a high current surge from the collector to the emitter it would be inefficient to use this device.An IGBT is an Insulated Gate Bipolar Transistor is shown in figure 26. It is known for its fast switching while generating large pulses. An IGBT utilizes favorable characteristics from metal-oxide field effect transistors and bipolar junction transistors. The cross section of an IGBT shows its similarities to the two common transistors. It contains three terminals, one for the gate which comes from a MOSFET. This is helpful because it is easily gate driven as well. The other two terminals are similar to that of a BJT they are the emitter and collector terminals. IGBTs are commonly used in many appliances. In order to rapidly fire a coil gun it might be suitable to use one. There are drawbacks in using IGBTs shown in figure NN. They are a bit expensive at high current ratings. In order to activate an IGBT in a coil gun it is necessary to use a gate driver. Another issue that arises when using IGBTs is voltage spikes. If there is not an IGBT with a high enough voltage rating and a short distance in wire between the capacitor and IGBT voltage spikes become an issue when the IGBT is turned off.Figure SEQ Figure \* ARABIC 26 IGBTIt is possible to use an n-channel power MOSFET for the coil gun switching system. The problem with a power n-channel MOSFET with a coil or solenoid as a load is the back electromagnetic field. The back electromagnetic field would likely destroy the device over time. In a coil gun the back electromagnetic field would occur too frequently because a magnetic field is being generated each time the projectile is being shot. For a coil gun circuit there would need to be the addition of a flywheel diode in parallel with the solenoid to reduce the back electromagnetic field. The flywheel diode is used to suppress voltage spikes in switching circuits when the switching device is off. For our coil gun we will use a flywheel diode in our circuit as extra precaution against a back electromagnetic field. A flywheel diode is not a specific type of diode; it is simply a description of a diode in parallel with an inductive load of a switching circuit. A power MOSFET is shown in figure 27. The figure does not appear to be a standard MOSFET. That is because a power MOSFET has multiple MOSFETs combined. The additions of MOSFETs add strength to the power MOSFET so that it can handle more power. Figure SEQ Figure \* ARABIC 27 Power MOSFETTransistors are excellent switching devices in electronics. They are usually inexpensive in simple applications that do not require huge voltages or currents. It may be possible to use passive components to construct switching circuits but will require a lot of time and many passive component combinations. Transistors are active components that already come with beneficial characteristics to switching on and off a circuit. The ability to amplify makes it very useful even in a coil gun. Many of the transistors earlier mentioned allow large current and voltage to flow through the capacitor bank to the coil or solenoid. Despite their many advantages there were numerous drawbacks found from using the above devices for switching in a coil gun because of the high electromagnetic field that is produced. It is apparent that high electromagnetic fields in circuits are no good to electrical components, especially those made of silicon. Silicon products are great for high current and voltage circuits but inducing voltage to create current through magnetic fields cause complications. DesignIn the coil gun design a silicon-controlled rectifier was chosen. The rectifier will be able to switch on the large current needed to travel to the coil. The silicon-controlled rectifier chosen is 100 amps with a 1400 amp holding current. The duration rating needs to be short so a low current rating of below 6 milliseconds will be used. In choosing the rectifier current rating it was pertinent to know that a SCR can handle 10 times the current rating for brief periods of time. This exceeds the current done in simulation but is just a precaution if the group decides to increase voltage to obtain a higher velocity projectile with respect to the 400V capacitor power rating. Some difficulty was found while trying to choose the appropriate switching devices. Power n channel MOSFETs and NPN bipolar junction transistors were quickly eliminated from our choices. The problem with the power n-channel MOSFETs were the back electromagnetic field. The transistor would need a flywheel diode which isn’t a big issue since one is going to be used either way. The issue is there may still be enough back electromagnetic field to hinder the function of the MOSFET. The MOSFET transistor experiences voltage spikes when the device is off. The choice of using the NPN bipolar junction transistor as a switching device for a coil gun was far from consideration. This device presents too many problems in a coil gun circuit. It is highly inefficient when it comes to amplifying current. The base current would need to be almost 10 percent of the discharge current which is massive. An IGBT was the biggest competition for the silicon- controlled rectifier. It has many of the characteristics except for a major problem with voltage spikes. From the ones looked at for the design of the coil gun, most were very expensive. If price weren’t a concern this device would of likely been a good choice. The silicon-controlled rectifier will be connected between two parallel circuits. The anode terminal will be connected to the circuit with the flywheel diode and coil in parallel. The cathode terminal will be connected to the parallel capacitor bank. The gate current supplied to the device from a direct currentBleed ResistorWhen the coil gun is turned off there should be no type of activity going on. In an ideal coil gun system the stored energy would fully discharge once the gun has shot the projectile and is turned to the off position. This is not an Ideal coil gun, so issues in the circuitry will arise. The stored energy in the capacitor bank is going to need a way to filter out, when the gun is turned off. A bleed resistor will be used so rectify the situation; it ensures that capacitor bank is fully drained. The bleed resistor is a normal resistor that will be placed parallel to the high-power capacitor, which in this case is the capacitor bank. Choosing the value of the resistor can be found utilizing a few simple equations. It is important to choose the correct resistor because choosing a value too low can cause problems with heat due to power dissipation. The first thing done is find the charge time of the capacitor bank. The bleed time will be one hundred to a thousand times the value calculated for charge time. The equation to calculate the resistor value is give below:R=t/CThe letter t in the equation is the bleed time and C is the capacitance of the capacitor bank. The value for the coil gun of the capacitor will likely be over 100kΩ. Anything lower would overheat. To calculate the power used by the resistor take the voltage squared divided by the resistance that was calculated in the previous equation. This is the power rating that will be used when obtaining that resistor. The bleed resistor is an excellent safety addition. It ensures safety when storing the device for long periods of time that there is no storage of charge in the capacitor banks. This always prolongs the life of the capacitor bank too because no work is being done while the device is off. Every high-power device should have a bleed resistor. The bleed time is not too important for anything other than long term storage. It will not affect the charge time either, but it is a good thing to know because it illustrates how the capacitor bank is drained. If more capacitors are added to the capacitor bank of the coil gun, then a larger bleed resistor will be used. The above equation will help in calculating the actual resistance of the bleed resistor. Below are two tables with bleed resistances that will be used for the coil gun. The first table,shown as table 6, is for bleed resistances that are one hundred times the charge time. The second table,shown as table 7, is for bleed resistances that are a thousand times the charge time of the capacitor bank. The resistor values from the first table appear to be more reasonable values and easier to find. In the coil gun those will be used. From the values in the first table the average bleed resistance is 99.33 kΩ. As a precaution a 150 kΩ resistor will be used in the circuit.VoltageBleed TimeCapacitanceBleed ResistanceIn KΩ3002880.00472000723503920.00498000984005120.004128000128Table SEQ Table \* ARABIC 6 Bleed ResistanceVoltageBleed TimeCapacitanceBleed ResistanceIn KΩ30028800.00472000072035039200.00498000098040051200.00412800001280Table SEQ Table \* ARABIC 7 Bleed ResistanceDamping ResistorThe projectile should travel from the breech of the barrel forward. A possible problem that may occur is suck back. Suck back is when the projectile travels forward through the solenoid and then before completely leaving the solenoid is sucked back and shot out through the breech. It usually occurs when the timing of the current through the coil is incorrect. The current through the coil should not be on when the projectile has traveled half way through the coil. The addition of the flywheel diode or protection diode in the coil gun does prevent back electromagnetic field and protects the solenoid. It however does have a drawback that can cause suck back. Although the flywheel diode opposes back electromagnetic field, it may circulate current to the coil. If this occurs a damping resistor will need to be placed in the coil gun. The flywheel diode may possibly be removed from the circuit if the damping resistor is added. A damping resistor will make the RLC circuit critically damped. Since the circuit becomes critically damped there would be no need for a protection diode. The electrolytic capacitors only need protection when the RLC circuit is under damped. If the damping resistor is needed, it will be placed in series with the coil, capacitor bank, and silicon-controlled rectifier. The addition of the damping resistor will also reduce the potential of ringing than could occur after each discharge of the capacitor bank in the coil gun. The ringing in the capacitor bank after discharge can be somewhat annoying at times. Eliminating this constant ring would beneficial. Below is the equation used to calculate the value of the damping resistor that will be used in the circuit:R2C2-4LC=0R=4LCR= 4*352*10-64*10-3= .593 ΩThe equation above takes into account the capacitor banks equivalent series resistance, coil resistance, and the wire resistance. The R that is obtained above is the resistance to keep the series RLC circuit to be critically damped. It is evident that the resistance depends largely on the value of the capacitance. The inductance looks like it would be a factor since the equation has the inductance times a multiple of 4, but the value is extremely low. In the coil gun a resistance of .583 ohms will be used as the damping resistor.Digital VoltmeterIn most coil gun projects the designers choose to connect a voltmeter or multimeter to measure the voltage the gun is operating at. In this coil gun it was decided that it would be better to have a more permanent solution to measure voltage across the capacitor banks while they are being charged. A digital voltmeter will be included in the gun’s circuit to easily display voltage. An additional feature may be to have a current meter added as well. For the coil gun it is a necessity to monitor the voltage being used at all times to make sure the maximum voltage is not exceeded. The voltmeter ensures that the voltage across the capacitors does not exceed the maximum voltage rating of 400V. As a precaution the banks voltage will be well below the maximum voltage rating. Keeping a significantly lower voltage than the maximum voltage rating maximizes the life and quality of the capacitors. The digital voltmeter will be placed in parallel with the capacitor bank. The amp meter if added will be positioned in series with the parallel capacitor bank and the solenoid.Triggering SystemThere are few ways to design a triggering system for a coil gun. The three systems found that will be decided between are the open loop triggering system, the optical triggering system, and then finally the induced voltage sensing.The first method that will be discussed is the open loop triggering system shown in Figure 28. This method is executed by sending a pulse of current through the coil at an exact time period and then the current extinguishes itself. To best determine the time period to use a trial and error method is used. The design of the open loop triggering system will contain 555 timer circuits which are configure to output pulses. The figure below will be used to help describe the operation of the timer circuit. The output pin 3 and the discharge pin 7 are low in the non-triggered state. The capacitor C1 in the non-triggered state stays discharge. When a negative edge is sent through the node at the trigger pin 2 the discharge pin goes into a floating state and the output goes high. At that point C1 begins to charge, once the threshold pin 6 becomes two thirds Vcc the output then becomes low. Once this occurs pin 7 then becomes low and C1 discharges. Now the device is in a reset state. For this circuit, Pin 4 and 5 are not a part of the functionality. On this circuit Pin 4 acts as the active low and Pin 5 is coupled to the ground.Figure SEQ Figure \* ARABIC 28 Open Loop Triggering System(Reprinted with permission of Barry Hansen)The approximate output pulse is estimated using the following formula:tp=1.1*R1*C1This is achieved using the function of using two thirds of the voltage supply and solving for the time constant.Because of its pulse triggering signal is precision, despite the coil and power supply configuration, optical triggering is another system that is under consideration. Another plus to this system is the fact that this system is immune to electromagnetic interference for the most part. The figure below shows the configuration of the circuit discussed. The first circuit shown has two transistors, one being connected to the other through its emitter, a switch and the actual coil. The circuit below the first circuit is an improved version, and more likely choice for this project.For the first circuit, the phototransistor, or SFH309, conducts as the gate is not obstructed by the projectile. At this time the majority of the voltage drops through the resistor going into the collector, making the voltage low at the collector of the phototransistor. The voltage across the collector resistor controls the mosfet, or BUZ10, which in turn is the switching device. Once the projectile creates an obstruction to gate of the mosfet the current through the phototransistor becomes low and the voltage across the collector approaches the approximate value of the voltage supplied. At this point the mosfet is now on and the current is now flowing through the coil that drives the projectile. As the current starts flowing through the coil the projectile starts accelerating and leaves the gate clearing the obstruction of the gate. The collector voltage then lowers back down, the current starts flowing through the phototransistor, and the mosfet is turned back off. To help lower a voltage spike as the switch turns off a diode is placed across the coil driving the projectile. The diode across the coil is called the commutating diode.The next circuit, shown in Figure 29, is the improved version of the first circuit discussed. A comparator is created using an op-amp. The improved circuit can sink and source more current than the first circuit due to the op-amp. Since turning the mosfet on and off is controlled by applying a voltage to the gate and in turn removing the applied voltage to gate, the op-amp allows for a quicker on/off switch due to the lower resistance of the current source/sink than the phototransistor alone. Figure SEQ Figure \* ARABIC 29 Optical Triggering SystemsThe induced voltage triggering method is the final triggering method that will be discussed. The idea of this method is to use the magnetic flux from the coil and the projectile used. By investigating the induced voltage in the sensing coil, shown in the Figure 30 below, the idea of this triggering circuit starts to make sense. The waveform in the figure is created by the induced voltage in the coil. The biggest obstacle of this method is due to the fact that determining the relationship between the projectile and the induced voltage in coil requires a lot of trial and error to best achieve the most accurate timing that would we would like for the trigger.Figure SEQ Figure \* ARABIC 30 Voltages in the Sensing CoilOut of the three methods, the first two seem to be the better choices because of simplicity. Those two methods again are the open loop triggering system and the optical triggering system. To decide between these two methods we must delve deeper into more specifics of each system. Which system would be more reliable and which would be more inexpensive, is the main question that has to be asked. Because of simplicity the 555 timer seems to be the best choice for the triggering system.Motion Control and Sensor SubsystemMotion ControlThe motion control system of the coil gun is constructed by the FPGA, motor control connector, two servo motors and two motion planes. The FPGA provides the control PWM signal to the servo motors, and the servo motors make the two motion plane rotate right and left or up and down. Then, the barrel of the coil gun will move to same direction of the plane move. The most important part of the motion control which is the motor. In order to choose the proper motor for this project, the RPM and Motor Torque has been determined. For the RPM, if the motor move at the speed (v) of 3 m/s that mean the target can move 3 meters (dh) in 1 second in the horizontal direction. The distance (d) from the gun to the target is 2 meters. ∠A is the angel velocity of the require for the gun to follow the target, it can be calculate as ∠A= arctanc(dh/d)= 56.31o. And the RPM can convert by ∠A/360*60=9.385 R/M. The other Once the RPM has been determined, the next step is determine the torque require for move the gun. There two difference rotating plane in this project. One plane is directly attached to the gun and it makes the gun move up and down. Another plane is at the bottom, it make the gun move left and right. The weight of the barrel is 1 lb. However, it’s better to over estimating it, since it’s better to use the high power motor to list the light item than use the low power motor to list the heavy item. So total weight for the barrel is estimate to 1.5 lb. Tq = r*F which is 120 in-oz. For the bottom plane, even though, total weight is a little higher than the upper plane. However, the r is much small than the upper plane, so if use the same torque motor is powerful enough to move the plane move right or less. Figure 31 and Figure 32 show two different modes in the Fire control system. Either it cans manual control by the computer or it can track and shot the target by the corresponding color. In the manual mode, shown in figure 33, first the user control tracking system and told the motors to control gun point to the desired location then the user shoot the target by pushing the button on the fire control. Different from the Manual mode, the auto mode, Figure 34,user doesn’t’ need to tell the tracking system which target needs to point at. But user needs to tell the tracking system which color of target needs to track. Then the tracking system will tell the motors turn and make the gun follows the color target. Also at the same time, the sensor will tell detect the target is the right color target the user looking for. If the target color is wrong the sensor sent back the data to the tracking system and tell it stop tracking. Otherwise, the sensor will tell the fire control to shoot the target. Figure SEQ Figure \* ARABIC 31 Manual Mode ControlFigure SEQ Figure \* ARABIC 32 Auto Mode ControlDC Motor Vs AC MotorThere are many different types and sizes of electric motors. Electric motors can generally be divided into 3 types: alternating current (AC) motors, direct current (DC) motors and Universal motors. A DC motor will only run in the DC current source, on the other hand the AC motor only can run in the AC current source. The universal motors can use both AC current and DC current, however, it cost more money as well, so it has put aside from this project immediately. Compare both AC motor and DC motor. Usually the AC motor has larger size than the DC motor. As show on Figure 33 the AC motor is 4 times larger than then high torque DC step motor, for the small torque DC motor is only 1/20 of the size of AC motor. Also, AC motor and DC motor have different construction. Usually DC motors utilize permanent magnets so none of their energy needs to be used in the creation of an electromagnet as in AC motors, so the DC motor can obtain a relatively high amount of mechanical power than the AC motor. As mention above, this project require tow electronic motor in order to adjust the fire direction. The precision is very important for the gun fire system. Compare the precision of the DC motor and AC motor, the DC motor will be better than the AC motor. Of course it is possible to use an AC servo instead, but it requires using the encoder and decoder to send the message to the motor, that increase the difficulty of the design. As the all the consideration, the DC motor have been choice instead of the Ac motor. Figure SEQ Figure \* ARABIC 33 Size of DC motor and AC motorBrush Motor Vs Brushless MotorDC electric motor also can be divided in two types which include?brush?motors and brushless?motors. For all these types, brush electric motors are most common used. Since they are easy to build and very effective. However there is major drawback for this type of motor. They use?carbon?brushes to transfer electrical current to the rotating part, and these brushes wear over time and finally will result in the failure of the electric?motor for long run. For the DC brushless motor?eliminates the brushes, but it cost more money and requires much more complicated drive electronics to operate. So it is very hard to make a decision between chose between the DC brush and DC brushless in the very beginning. After doing further research, one found out that the DC step motor (one kind of the DC brushless motor). Since it is easier to control compare to the other type of motor. For example, if the voltage pulse sequences were applied to the DC motor, each of the plus will make the DC motor a given number of the degree, move no more or less. If the DC step motor have been chose, it much easier to prevent the overshoot than use the other motor. Another reason, DC motor movement is predictable. For, example, if the minimum angle per step is 1.8 degree. After it move 200 step or 200 pluses were applied, then the step motor will move 360 degree. If the brush motor was brush motor or the regular brush less motor were chose, if the same sequence of pluses were applied. They will never act the same, since they are very easy effect by the outside environment. (Temperature, battery power and smoothness of the operation surface) As a result, if two different brush motor were apply the same sequence of pluses, they will not have the same result. Of course this problem can be solve by adding an encoder and make the system become close loop system. Just like the DC servo motor, it has the internal encoder and the price is not too expensive for this project. So in the follow top will show what are the differences between them how to operate them. Different Internal Connection of DC MotorsThere are two different kinds of step motor which are permanent magnet and variable reluctance step motor. Both of them have different range of revolution, the coarsest one can turn 90 degree each step, while the higher resolution one can divide up to 1.8 even 0.72 degree each step. Do in the base research, 1.8 degree step motors cost around 10 dollars to 50 dollars, but the 0.72 degree step motor cost 30 dollars to 100 dollars. With the help of the appropriate step motor controller, the step motor can be run n half step, and some of the controllers can handle even smaller fractional steps or microsteps. The simple idea for the step motor run is the rotor all way trying to fixed angle and hold the angel until the torque exceeds the holding torque of the motor after the winding of the motor is energized, at the time the torque exceed the rotor will turn, try to keep it the equilibrium. Following is two example showing how different configuration works. The Figure 34 shows the typical schematic diagram for variable reluctance stepping which has three winding. As show on the figure the common wire connect to the positive side of the power supply and the winding are sequentially power up. As showing on this figure, the minimum step for this motor is 30 degree and there are 6 poles and 4 teeth for this motor, also each winding has been wrapped around tow opposition pole. At the time the winding number 1 is turn on, 2 and 3 is off. The rotor teeth in the vertical direction are attracted to the number 1 winding’s poles. If the winding number 2 is turn on and winding number 1 and winding number 3 turn off, then the rotor teeth in the horizontal teeth will be attracted by number 2 winding’s poles. If the power sequentially apply to the 3 windings then the power will motor can rotate continuously. Just like the figure showing the power sequence of the 3 windings can make the motor to rotate 2 revolutions. In here, 1 represents power on and 0 represent power off. Figure SEQ Figure \* ARABIC 34 Variable Reluctance Motors schematic diagramControl logic sequence of Variable reluctance Motors(Permitted was given by Professor Doug Jones)Two of wire will be connect to the center of the winds which call the center taps. Usually the center taps will connect to the positive direction of the power supply, and two ends of each winding are alternately grounded to the opposing direction of the power supply. As show on the Figure 35, if the current flowing from the center tap 1 to the winding end a, at this time, the top stator will attract by the North Pole, and the bottom stator will be attract by the South Pole. So the rotor will fix in to the corresponding position as well. If corresponding central tap and winding end turn on in the sequence of 1a, 2a, 1b and 2b. Then this rotor will continually rotate. The corresponding logic circuit will be as show below which can make the motor rotate 24 steps.Figure SEQ Figure \* ARABIC 35 unipolar stepping motors schematic diagramControl logic sequence of unipolar stepping motor(Permitted was given by Professor Doug Jones)The third type is the bipolar motor, as show on Figure 36 which has the identical mechanism as the unipolar motr, but it only have two windings without any center taps. The motor itself become simpler than the unipolar one but it request to reverse the polarity for each pair of the motor poles which make the drive circuitry more complex. For the bipolar motor is very command to use an H-bridge to for the control circuit of the windings. In order to make the controlled independently, H-bridge will allow the polarity of the power applied to the end of each winding. So it has different control circuit as show below in order to make the motor turn two revolutions, the plus and minus symbols for the different polarity of the power applied to each winding. Figure SEQ Figure \* ARABIC 36 Bipolar Moter stepping motors schematic diagramControl logic sequence of bipolar motor stepping motorsAll figures are showing the 30 degrees per step motor, for higher resolutions motor, the rotor will have more proportion and as well as the poles. Also different kind of the motor should apply different of the control sequence in order to make it work correct. For example, in this project, the 1.8 degree step motor will be use, the similar idea can apply to make it rotate, and the only different is the teeth number of the rotor or the wings. And the relationship between windings number w and teeth number will be invert. Also, some command configuration, such as biporlar, bifilar motor and multiphase motor, have not been discussed here, since they are not relate to this project. Stepper ParametersIn order to chose the motor to meet the specified performance requirements. Some motor parameters, such as dynamic torque, holding torque, phase inductance, torque stiffness and rotor inertia, have been known and understand first. Holding Torque Vs Dynamic TorqueHolding torque is the torque for the motor to prevent a static load from pulling the system out of step. Difference as holding torque, the dynamic torque is the torque when the motor in motion, it relate to the current in the stator electromagnet. Assume the full current is apply, the relationship between the dynamic torques and holding torques can be express the equation , where Td is the dynamic torques and the To is the holding torques. If the system has a perfect switching time relative to the rotor position (closed-loop control need to apply), then the system can reach the ideal level, at this time the Td will reach the maximum value as show on equation, which can get the Tmax=0.90To. If the motor was operate in the open loop control system, and then the minimum dynamic torque can be calculated by the equation , which can get the Tmin=0.63To. The typical dynamic torque is T=To(0.90+0.637)/2=0.768To. For the 2 phase bipolar motor, the dynamic torque only 76.8% as the holding torque. Step motor accuracy and holding TorqueThe step motor accuracy not only depends on the motor construction but also has the proportional relationship with the motor’s torque stiffness. On the other hand that mean the relationship between the torque and the angle displacement will be show as follow equation, which N is the number or the rotor teeth and To is the maximum holding torque. If calculate the derivate for both side, then we can get the equation where dT is change in the torque and the dq is the change in angle. dT/dq is represent the torque stiffness, which is depend on the value of the number of the rotor (N) and the maximum static holding torque(To). If the N and To is improve, then the torque stiffness will improve. Current Rise Time and TorqueThe majority loss in the torque is deal to when motor running in the high speed, the pulse switching times can become shorter than the motor phase current rising time. So the pulse will end before the phase current rise to certain level that can provide the request torque. In Figure 37 showing the simple example the how the motor phase inductance and the resistance R limit the phase current rise time, which also can express as the equation on the equation on the right side. In here, t is current rise time also can define as L/R, V is the power supply voltage, L is the motor phase inductance. In order to keep the rise time small, then V need to be as high as possible, but the L and R need to be as large as possible. As show on figure, if the voltage pulse switching time is t1, then at the end of the voltage pulse the current can rise to the 0.63 of the maximum value. When the voltage pulse switching time change to the t2 half of t1, at the end of the voltage pulse, the current can only can rise to 0.39 of the maximum current. If the one need to the optimized the performance of the system, the current has to reach 90% of the maximum current. That mean the 2.3 times of the t1 pulse switching time need to apply. Figure SEQ Figure \* ARABIC 37 Current Rise Time and TorqueDC motor SelectionConclude all the parameter and compare with the data sheet of DC motor usually, usually there is at least two parameters will list clearly. They are the RPM rotation per minute and Torque. And these tow parameters will be consider and cumulate when picking up the DC motor. The first factor is the RPM can make sure the motors to achieve the require velocity as desired for this project. The second factor is the minimum torque requires making the plane rotate in order to change the direction of the gun. It is different if this project is use the small rotating frame and large small rotating frame. If this project is used the small rotating frame it will require more RPM to achieve the desire velocity, but it will take less torque to move it. On the other hand, the large rotating frame, it doesn’t need higher RPM to achieve the desire velocity, but it will need more torque. In order to determine these two factors. Some of the requirements such as, the size of the rotating frame and the velocity of the target move, as list in the requirement, If those requirements were known then the minimum PRM can be determined. After the RPM is determined, the power that need to move the gun can be determined. Furthermore, the minimum torque needs to move the gun can be determined as well. As these two factors were determined, then one can design how powerful of the motor need to buy for this project. Of course, one can by a motor with very high speed and large torque, that is sure can move the gun but this will cost the unnecessary power consume as well as money. So the goal of this charter is determine the minimum power consume DC step motor for this project in order to save money. And the following will show how to choose the right size of the motor for this project. Determine the Motor RPMAs state in the request, the target will move at the speed at 3 m/s and gun is 2 meters from the target. As showing below the target will move 3 meter in 1 second from A to B. AC is the distant of from the gun to the target which is 2 meters. One need to calculate the angle of ∠ACB, and then one can get the angular velocity for the gun. ∠ABC=arctan(AB/AC)=56.31o. That means it needs to turn 56.31 degree in 1 second in order to follow the target. And the RPM can calculate by RPM=∠ABC/360*60=9.385 R/M. According to the research, most of the DC step motors is much higher than this RPM value, so for this project, this factor will be less consideration, but this factor can help to determine the stability for this project. Determining Motor TorqueOnce the RPM has been determined, the next step is determine the torque require for move the gun. There two difference rotating plane in this project. One plane is directly attached to the gun and it makes the gun move up and down. Another plane is at the bottom, it make the gun move left and right. The weights of the gun plus the two planes have been estimate to be 20 lb; of course the small weight will be easier to control. However, it’s better to over estimating it, since it’s better to use the high power motor to list the light item than use the low power motor to list the heavy item. In order to find out the force the follow equation need to use, F=W*Crr, W is the weight, and Crr is the rolling friction. And the power can be calculate by using equation P=F*v. Finally, the torque can be get by equation τ=P/w. If the gun’s weight is 25 lbs include the plane 1 lbs, the total weight is 26 lbs for the first motor need to move. According to the table 8below Crr for hard steel ball bearing on steel is 0.0002 to 0.0010. To be safe, the maximum rolling friction 0.001 will be use in the calculation. And final result of the torque is 8.185 ounce-force inch. This will be enough torque to move the upper plane up and down. The second plane will have different weight which is 25lbs and the rolling friction is higher than the first plane which is 0.5. Use the similar calculation and get the final result is 25.22 ouce-in.CrrbDescription0.0002 to 0.00100.5?mmRailroad steel wheel on steel rail0.0002 to 0.00100.1?mmHardened steel ball bearings on steel0.0022 to 0.005 0.1 mmproduction bicycle tires at 120?psi (8.3?bar) and 50?km/h, measured on rollersTable SEQ Table \* ARABIC 8 Rolling resistance coefficientDC step motor controllerBase Step Motor controller In this section, some elementary control circuit for difference kind of the motor will be discussed. In order have better explanation, all the circuits assume the motor’s rated voltage is small than the motor power supply voltage. Of course, this assumption will limit the motor performance. As show on the Figure 38, this is the typical controllers for a variable reluctance stepping motors. In this figure, boxes are used represent switches; a control unit, not shown, but is this project the control unite will be the FPGA board which can providing the control signal to turn on and turn off the switch at the appropriate time in order to spin the motor in certain way. The control unite will be control by the computer or interface controller (FPGA board in this project), with software or program language can directly generating the output signal (in this project a binary adder signal will use the control 4 lead of the DC step motor as show on Figure 39) to control the switches, However, since the current through the motor winding cannot be turned on the off instantaneously without involving infinite voltage, at this time the switch controlling a motor is opened, as the result, the voltage spike will damage the switch. So the kick back voltage needs to be take care off to prevent the damage of the system. There are tow ways to deal with this problem, one is bridge the motor winding with a diode, that can be able to conduct the full current through the motor winding, but it will only conduct briefly each time the switch is turned off, as the current through the winding decays. Another way is bridge the motor winding with a capacitor. At this time when the switch is closed, the capacitor will discharge through the switch to ground. When the switch is opened, the stored energy in the motor winding will charge the capacitor to a voltage significant above the supply voltage. Figure SEQ Figure \* ARABIC 38 Variable Reluctance Motors Controller(Permitted was given by Professor Doug Jones)Figure SEQ Figure \* ARABIC 39 Unipolar Motors Controller(Permitted was given by Professor Doug Jones)As mention before the full step the plot of torque versus angular position for the rotor relative to some initial equilibrium position will be approximate a sinusoid. So how would be a half step or micro stepping looks like. If two motor windings have been powered simultaneously that will produce a torque versus position curve that is the sum of the torque versus position curves for the two motor windings taken in isolation. For a two winding permanent magnet motor, the two curve will be S radians out of phase, and if the currents in the two winding are equal, the peak and the peaks and valleys of the sum will be displaces S/2 radian from the peaks of the original curve, as show in Figure 40 this is the basis of half stepping, the relation shipping between the single winding holding torque h1 and the two winding holding torque h2 will be express as follow h2 = 20.5h1. This assumes that no part of the magnetic circuit is saturated and that the torque versus position cures for each ideal sinusoid. The figure 41 is the torque versus angular position for microsteping control which allows even smaller steps by using different currents through the tow motor windings and the following formulas showing the key characteristics of the composite torque. h = ( a2 + b2 )0.5 and x = ( S / (/2) ) arctan( b / a ) where a is torque applied by winding with equilibrium at 0 radians; b is torque applied by winding with equilibrium at S radians; x is equilibrium position, in radians. Figure SEQ Figure \* ARABIC 40 Bipolar Motors Controller(Permitted was given by Professor Doug Jones)Figure SEQ Figure \* ARABIC 41 Half Stepping and Micro stepping(Permitted was given by Professor Doug Jones)Limiters of the Micro steppingThe micro stepping can reduce step angle to smaller. However, it also has its limited. The first limit is the dead zone limited. For example, Figure 42 presence of a dead zone has a significant impact on the utility of micro stepping! If the dead zone is x° wide, then micro stepping with a step size smaller than x° may not move the rotor at all. Thus, for systems intended to use high resolution micro stepping, it is very important to minimize static friction. The second problem involves the non-sinusoidal character of the torque versus shaft-angle curve on the real motor which is call the detent effects. The motor is at its expected position at every full step and at every half step, but there is a significant positioning error in the intermediate positions which is showing in figure The third problem arises because most applications of the micro stepping involve digital control. As the result, the current through each motor winding is quantized, controlled by a digital to analog converter. For instance, if PWM current limiting circuit is used, the current through each motr winding is not held perfectly constant, but rather, oscillate around the current control circuit’s set point. The effect of this quantization is easily seen if the available current through one motor winding is plotted on the X axis and available current through the other motor winding is plotted on the Y axis which is showing in the Figure 43Figure SEQ Figure \* ARABIC 42 Dead zone impactsFigure SEQ Figure \* ARABIC 43 Micro step AccuracyStep Motor Control Design and Difficulty: As show on the Figure 44 is the Unipolar step motor control sequence. If the circuit is turned on in the sequence of 1a , 2a, 1b, and 2b, that will make the motor turn clockwise. For reverse direction of the motor one just need to make the circuit turn on in the sequence of 2b, 1b, 2a, and 1a. In the step motor which plan to use can be divide to two group, white, orange , and blue is one group Black, yellow and red is another group. If connect the circuit from orange, red, blue and yellow then the motor will turn clockwise. In the reverse direction (yellow, blue, red and orange ), the motor turn will turn counter clockwise. Figure SEQ Figure \* ARABIC 44 Unipolar Step Motor Control Sequence(Permitted was given by Professor Doug Jones)So if one connect the circuit like Figure 45 below, the common wires connect to the power supply and winging wire connect to the one end of the switch. If one turn on the switch as shown on the sequence above. Then the step motor can turn the corresponding direction as state above. Digital switch is one of the options for this design, but the digital switch is expensive, For example, 2A LTC1477 is cost $6.95 for switch. So the total needs to cost $27.8 dollars to accomplish this design.Figure SEQ Figure \* ARABIC 45 Step Motor Controller wind Winging Location(Permitted was given by Professor Doug Jones)Another solution is use Power Mosfet to design the digital switch. The circuit will be as Figure 46 shown below. The IRF 1324 Power Mosfet has up to 24 minimum breakdown voltages. Also it has 195 A continuous Drain current. It can support enough voltage as well as the current for the motor use in the project. The drawback of this design, the FPGA output did not have enough output current to turn on the mosfet. To solve this problem, the comparator or Amplifier can be use to solve this drawback. LM339 comparator has been considering for this design. Since it can step up 4 inputs just use one IC, it has 1mA forward current and up to 20 mA reverse breakdown current. Most importance is the cost only 1 dollars for online price. Figure SEQ Figure \* ARABIC 46 Digital Switch CircuitReal Time ControlOpen loop Vs close loop motor control The real time control means the control system need to know when the next step should be taken and how should it operate. This question needs to depend on the application. The similarities between different applications are sufficient to justify the development of fairly complex general purpose stepping motor controllers. Most of the motor control may be based on open loop or closed loop control models. For example, figure is a control block diagram with shaft encoder to provide the feed back to the control system. If the shaft encoder is rotated into a position where the output of the shaft encoder translates to a control vector that holds the motor shaft in its initial position, the motor shaft will not rotate of itself, and if the motor shaft is rotated by force, it will stay wherever it is left. This position of the shaft encoder is relative to the motor as the neutral position. This insures this control system will always produce the maximum torque the motor is able to deliver at any speed with the limit. Open loop control is most often use in the step motor control system since the advantage of the step motor is can know the step what have done and predict the next step. As show on figure 47 , the basic principle is very similar to the close loop, but the different is the feedback loop is broken, instead use the simulation model of the response of the motor and load to the control vector. At any instant, the actual position of the rotor is unknown. However, the position can be predicting base on an assumed rotor position and velocity. So the simulation model has to been constructed in order to generate the simulated shaft encoder. As a result, the figure will have the same accurate as the motor control with a closed loop system. DC Motor ControllersThe first motor controller has been considered is Phidget Unipolar USB motor controller which as shown on the Figure 47. It has the usb port that makes it easier to be control by a computer. External power supply apply insure the power operate in its request power range. It has 2 motor connect in each side make it possible to control up to 4 unipolar step motors. Also, Phidgets also offer its own Application Programing Interface to be download that make it extremely easy to operate in by the Window, Linux and Mac OSX operate system. It also support VB6, ,C#.NET, C#, C++, LABVIEW, PYTHON, MAX/MSP and COCOA and so on different kind of popular computer program language. It offers the user the maximum amount of freedom to operate this board. It looks like it’s the perfect solution for this project to control a DC motor. However, the drawback for this controller is the price, it cost $73.05. It’s over the budget for this project. Figure SEQ Figure \* ARABIC 47 Phidgets Unipolar USB 4 Motor Stepper ControllerStep Motor Vs Servo Motor According to the research, step motor and the servo motor are very often use for position control. Compare for both step motor and servo motor. For the step motor, it is the open loop control, but the servo motor use the close loop control that can determines accuracy and resolution.; for the step motor, it can continue rotate but the servo motor usually has the rotation limit; step motor usual is a brushless motor it has long life than the servo motor; servo motor has higher output power relative compare to the step motor. So over all, the servo motor is better choice for this project. Nylon gear are very common in servos, they extremely smooth and is not easily to wear. Also, they are very light weight. But deal to lack in durability and strength. They haven’t been use for this project. Instead the nylon gear servo, metal gear servo was use, although the weight is heavier than the nylon gear, but the side load is much greater. Also, the drawback of this kind of gear is it will be slowly wear or lost. As show on the Figure 48 below, SAVOX SC-0252 is used in this project, this servo motor is only require 4.0 to 6.0V to operate and the weight of the servo motor is only 49g, but the torque of the motor is up to 10.5 kg-cm, and it can run at 0.19 s/60 degree. Compare to the step motor， sanyo Denki 85004， has been consider，which weight is 600 g, 10 time of the servo motor that has use now. and the this step motor only has 55.3 OZ-in of the torque. Figure SEQ Figure \* ARABIC 48 Savox Servo MotorMotor Control The real time control means the control system need to know when the next step should be taken and how should it operate. On the Figure 49 is a control block diagram with encoder to provide the feed back to the control system. When the encoder is rotated in a position where the output of the encoder translates to a control signal to hold the motor in the initial position, then the motor will not move by itself. If the motor is rotated by external force, it will stay wherever it is left before so that the system can provide the maximum torque to the motor. For open loop control is very often use in the step motor control system since the advantage of the step motor is it can predict what next step should be. As show on the Figure 50 , the feedback loop is broken. So the actual position of the rotor is unknown, however, one can construct the simulation mode to generate the encoder, so that it can predict the motor position as the close loop system did. Figure SEQ Figure \* ARABIC 49 Close Loop ControlFigure SEQ Figure \* ARABIC 50 Open Loop ContolDigilent PmodCON3 Servo Connector Module Board has been use for motor control. This board is not exactly a motor controller. It is only a connector board and makes the Digilent system board easily control the servo motors when the PWM signal generate by the system board. This connector board has 4 sets of the pins can connect up to 4 servo motors. Also, it has 1 terminal power supply block, which can power up 6V source which can insure sufficient power to run the servo motor at anywhere from 50 to 300 ounce/inch of the torque. There are 6 pins header for this connector board and it compatible for most of the Digilent system board as well as the BASYS FPGA Board which is use in this project. In this case, the BASYS FPGA Board will act as a motor controller to provide the control PWM signal to the motors. The PWM signal can be use to control the direction and degree of rotation. The range of the pulse signal is from 1ms to 2ms. 1ms plus signal will cause the motor to turn all the way in one direction. 2ms plus signal will cause the servo turn all the way in other direction. Figure SEQ Figure \* ARABIC 51 PmodCON3 Servo Connector Module BoardMotion Control ConcussionAs show on the Table 9 below, use the servo motor as who motion control has the advantage of low cost, ( save up to 50 dollars in the control circuit ). Servo motor also has higher torque but lower power consume advantage. The most importance, it is servo motor has much lower weight compare to the step motor. 　Step MotorServo MotorCost$19.99 $23.99 Torque120 oz-in146 oz-inWeight34.3 oz 1.8 ozPower 24V2V to 6VController Cost $70 $10 Table SEQ Table \* ARABIC 9 Step Motor Vs Servo MotorSensorFOV request for this cameraAfter decided what kind of the camera that can be used for this project, the next step is to determine what charities needs for the camera. For the charities one need to determine mainly 3 parts. The lens focal length and camera revolution. In order to determine these charities, some requirements need to be found out, such as FOV (field of view), Resolution and the Working distance.First one need to determine revolution, according the research in order to make the accurate measurement. This project needs to use of two pixels to represent the smallest feature we need to detect. The relationship between field of view, revolutions and smallest feature size as equation show below Sensor resolution (S) = (FOV / size of smallest feature) x 2Also the relationship between the Focal length, File of view sensor size and working distance has the following relationshipFocal length x FOV = sensor size x working distanceBy research we know that the lenses are manufactured with a limited number of standard focal lengths. Common lens focal lengths include 6 mm, 8 mm, 12.5 mm, 25 mm, and 50 mm. when the lenses with short focal lengths (less than 12 mm) produce image with a significant amount of distortion that will affect the sensor’s accuracy. As request in this project the working distance is 3 meters and the smallest feature size is 0.1 meter. The minimum FOV can be calculate as follow. Assume the camera plane in the center of the target screen. And this screen size is 2 meters by 3 meters. The minimum FOV for horizon is 2*tan-1((3/2)/10)=17.06 degrees. The same way to calculate the minimum FOV for horizontal is 2*tan-1((2/2)/10)=11.41 degrees.Knowing what kind of the camera and what minimum requiems for this project. Next goal is to choose the specific camera for this project. During the research each camera has a field of view, resolution and frame rate that has to be taken into account it did not restrict the choice because price and availability affected the decision. In most case field of vies is immediately available and therefore has not been the fact of affect the decision. A lot of the camera with this power and within the affable rang of this project. However, most of the retailer don’t offers enough technique information of the cameras but only with their detail project, there is not enough documentation that limits the choice of this project, which may have the risk for getting the information for this design. Due to the extensive searching, Table 10 shown below, the cheapest digital camera also it has the higher resolution. However, this camera does not have development style connectors so it has been eliminated from this project. Another cameraC3038 has exactly the data output as for the video decoder board; however, the design is complicated. So it also had been take out from this project. The last one is the Swna sw-p dscex, which has NTSC, it can directly plug in the video decoder board. Of course, the program needs to be designed in order to input the frame from the camera. 　IMC CH-8028C3038Swan sw-p dscexResolution800*600 Pixel356*292 Pixel380 TV lineFOV44.5 *57.434.4*20.745*100Lens Length 4.03.6mm6.0 mmFrame Rate30f/s15f/s30f/sData outYUV=4:2:2,RGB=5:6:5YCrCb 4:2:2, GRB 4:2:2, RGBYCrCb 4:2:2, GRB 4:2:2, RGBPower requirement3.3VDC3.3 VDC8-12VDCInterface USBIC2NTSCCost9.9931.9832.99Table SEQ Table \* ARABIC 10 Camera comparisonPower supply for camera and motorsWhen the power supply transform from the AC wall outlet, it out put the 120 V DC volts, but for the camera (9v) and DC step motors (24V) which is much smaller than the power supply than the camera and motors need. So the voltage dividers may be need to this project. In order to ensure that the camera and DC step motors have the require voltage and current need during operation one may use the DC regulator for this project. Also the other reason this project need to use the DC regulator because it can protect the power supply form damage if one component had an internal fault. For voltage one can simple use the similar circuit below to design the low voltage power supply. IC linear voltage regulators come in a variety of sizes, input and output ranges. One kind of regulator that fix this project is LM2937 3.3 voltage regulator made by National Semiconductor. This regulator is a small three-pin IC. It has a maximum range of 26V DC input. This project will use one for camera and two for motors. Linear regulator can easy build by Op-amps, building a linear regulator from a discrete components allows for more design freedom, if the time available Camera Position ConfigurationFigure SEQ Figure \* ARABIC 52 Camera Position ConfigurationsDifference camera position configuration has been developed and used, from the Figure 52 above, VM1 is monocular eye-in-hand mode, VM2 is monocular stand-alone mode, VM3 is binocular eye-in-hand mode and VM4 is binocular stand-alone. Different configurations have difference effect on the visual system. For example, the first one, VM1 is one of the most common use configurations. The camera is attached to the robot’s hand. The task of this configuration is to try to move the camera and get the image achieve the predefined image positions. The current and the desired position image will be save when the visual servoing starts. The second one is VM2 which also a one camera configuration, but the camera is set aside of the servo, so the camera in here use as a global sensor for the system. It usually required more accurate camera to perform the operation. Every time after it tasks the target it needs to retrieve to the initial position, so it can’t offer the smooth tracking procedure. But it can use for the suitable grasp operation. Different from one camera arrangement, VM3 and VM4 has two cameras in a stereo arrangement. This configuration cans simply estimation the depth without using the explicit models jus t like the one camera configuration. It can provide complete 3D information about the scene. But the trade off is it require twice or more computational time for each iteration. VM3, binocular eye-in-hand mode, is not very often use for servoing tasks since its limit base inaccuracy and the difficulty of reconstruction. The last configuration, VM4 binocular stand-alone is very often using in the servoing tasks. Since it’s not only can easily make the baseline long enough so that the depth estimates are become more accurate compare to the eye in hand stereo configuration. Also, this configuration increases the field of view which can make it easier to move robot and the target the object simultaneously. The proposal of this project is first detect the color object then calculate the position of the object, then control the motor to point the object. So that can haveenough time to process the calculation of the position use the monocular eye-in-hand mode can simplifythe design. Image collection and storeAs mention, the camera captures image and storing it in the computer as using for analyst. How do the pictures save in the computer? Every image that saves in the computer will represent as pixel in the computer which is a tiny dot of color in the computer screen and it containsthe color and locationinformation of the object. The image also have a set number of pixels per size of the image known as resolution, mean the number of pixel in square inch of the image. The same as camera, the higher resolution means there are more pixels in a set area, resulting in a higher quantity image, the bad thing about the higher quantity of image require higher performing of processor as well as higher. That is also limit of the project, so in this project the bad and white camera has been chose in order to reduce processor perform time.Image is stored in 2D matrices, which represent the location as well as the color of the pixel. All image have X and Y component. If the image is only black and white, then the data will store as 1 or 0 binary number. If the image is color image, it will store as a set of number. So, the less color involved the faster the image can be process. Below is showing the revolution of 5*6 black and white image data store in the computer. And it require 5*6*1=30 bits to store memory0 0 0 1 1 01 0 1 1 1 00 1 1 1 1 00 1 0 0 1 0The other example will show a grayscale (8bit) image, and it requires 5*7*8=280 bits memory. 0 0 55 255 0 055 0 252 255 255 0 00 255 255 55 255 0 00 255 0 0 255 0 0It is easy to see increase the revolution and information of the image it require addition memory to for the process. Otherwise, it will slow down the speed. Movement AlgorithmGeneral AnalystThere are five steps in the movement algorithm, they are the frame input, color detect, threshold, centroid and motion vector, as shown on Figure 53. The frames will detect by the camera in the sequence order and the first fame will be store in the memory as background fame. And the subsequent will compare to the background frame to determine the next operation. If the differences of the new frame with the background frame within the acceptable value, then the system will input another new frame. Otherwise the image will be past to next step to be threshold. After that, the centroid process will be operating to find the center mass of the object. Then the comparison will be process in order to find out the motion vectors between the center of the object and the center position of the whole image. Final, the pan and tile vector was finned to determine the motor movement. Figure SEQ Figure \* ARABIC 53 Schematic diagram of the real-timeClosed-loop tracking algorithmTreshold and Centroid After using the background subtraction to eliminating the background and the stationary object, the tresholded can be simplify by the binary image as show below equation. Where “a” is range of the treashold value and it also determine the accuracy of the tracking algorithm. The next step is to centroid of all the pixels about the threshold is calculated by the equation, where W and H is represented the width and the height of the frame. Then the central mass of the moving object is determined. Motion Vector DeterminationThe final step is to determine the motion vector. To achieve this, the perspective model for the camera will be constructing as below on figure. The original is the location of the camera or the initial location of the gun mouth. If the gun initial point is at the origin of the XYZ plane, so what angle it will change if the object moves to the point Q. As show on the Figure 54, X is the distance that the object moves in the horizontal direction. And Y is the distance the target move in the vertical direction. And assume Z is the distance from the camera lens to the target plane. Figure SEQ Figure \* ARABIC 54 Motion Vector DeterminationsGravity effect on the vertical direction The bullet more or less will affect by the gravity and this effect must be consideration on this project system. As show on the photo above the initial velocity is V, if we decompose it in to X direction Vx and Y direction Vy. t= X/Vx (Vx =Cos(a)*V and Y without the gravity the bullet should shoot at the value of Y=t*Vy (Vy=Sin(a). However, in the really situation the vertical distance the bullet travel will effect by the gravity. So the actuate distant the bullet in the Y direction will be Yac=Y-1/2*g*t^2. For this project, the distance the gun from the target is 3 meter and the initial velocity is 33 m/s. So the effect according to the angle change will be as show below on Figure 55.Figure SEQ Figure \* ARABIC 55 Gravity EffectVIDEO DECODERGeneral informationThe Video Decoder 1 Board (VDEC1), which shown on Figure 56, use the multi format video decoder chip, ADV7183B, can convert most of the analog video signal to the digital signal. This board offer the different video input format such as S-video inputs, component and composite, with the simple converter video socket use, then the camera can be attach to this board and operate. Also, the VDEC1 offer the offer the perfect solution for the Diligent board which Hirose FX2 connector, simple plug in, then can be operate properly. Figure SEQ Figure \* ARABIC 56 Video Decoder 1 Board Inputs and output connectorLimitation and AdvantageThe video input format can be specified by the I2C bus. In this project, the C3038 on board camera will be use. So the output format should use the YCrCb 4:2:2. The video capture design function should program on the FPGA board. Also, video stander information, such as color and brightness, will be detect by the camera, then transfer by the VDEC1 board, and finally analyze by the FPGA board. There is some limit of theVDC1 board, for example it limit in the input signal voltage is 3.3 V analog signal and it is not support the 5 V input signal, but this limitation can be solve by using the amplifier logic circuit to decrease the signal voltage. The advantage of using this board since it has ADV7183B chip which can oversamples the analog input by the factor f 4 also it has up to 54MHz sampling frequency that reduce the need of the requirement for an input filter. However, the antaliasing filter will be use in order to optimal the performance. The simple emitter follower circuit will be use to implementing the buffer for the antliasing filter, which reduce the cost for the filter and simplifier the design.Video SelectionThe VDEC1 is has 4 bits selector VID SEL[3:0] bits allows the user to chose the digital core into the requested video standard. In default, the VID SEL[3:0] will sent to 0000 which can auto detect the supporting format such as PAL, NTSC and SECAM. When the system set in the autodetection mode, it will picks the closest video standard and read back the through the status resister. The Table 11 shows the Global Status Registers information. And the following is show the example of using SECAM525. If the AD_SEC525_EN was set to 0 (default), the autodetection function will be enable. If the AD_SEC525_EN set to 1 the autodetection function will be unable. If the AD_N443_EN was set to 0, then the auto detection of NTSC will be disable, otherwise it will enable. If the AD_P60_EN was set to 0, the autodetection mode of PAL system with 60Hz field rate will disable. Otherwise, it will enable the detection. VID_SEL Description0000 (default) Autodetect (PAL BGHID) <–> NTSC J　(no pedestal), SECAM0001 Autodetect (PAL BGHID) <–> NTSC M　(pedestal), SECAM0010 Autodetect (PAL N) (pedestal) <–> NTSC J　(no pedestal), SECAM0011 Autodetect (PAL N) (pedestal) <–> NTSC M　(pedestal), SECAM0100 NTSC-J (1)0101 NTSC-M (1)0110 PAL600111 NTSC-.43 (1)1000 PAL-B/G/H/I/D1001 PAL-N (= PAL BGHID (with pedestal))1010PAL-M (without pedestal)1011 PAL-M1100 PAL-Combination N1101 PAL COMBINATION N (with pedestal)1110SECAM1111SECAM (with pedestal)Table SEQ Table \* ARABIC 11 Global Status Registers for VDEC1Power systemPower System OverviewThe power system is the main component in the coil gun. In the coil gun it will provide all electrical components with electricity throughout the whole circuit. It will provide currents to power switches, charge a capacitor bank, and power DC servomotors with controls used for automation and target acquisition. For the high voltage and high velocity gun the power system will likely be the most important part of the project. This subsystem will make sure that initial specifications for the project are met. With a careful design of this system the coil gun should be able to greatly exceed the current specified constraints. It will encompass all that has been learned in the years as engineering students at the University of Central Florida. The knowledge of electrical and magnetic fields will be refreshed and tested with this project, specifically this subsystem. The power system will have both types of sources AC and DC. It will be necessary to step up voltage through a transformer and convert AC to DC using circuit elements to create a power convertor. This DC power generates a direct current to then charge the capacitor bank. This of course is just the general concept. It should be kept in mind that the design of a strong triggering and switching system has to be established to account for the high currents and voltage. The energy in the coil gun is being stored in high voltage rated capacitors. Charge resistors will also be implemented in the circuit. The charge resistor together with the capacitor bank will establish the time needed to charge the coil gun before firing. An overview block diagram of the power subsystem is shown in Figure 57 below.Figure SEQ Figure \* ARABIC 57 Power Subsystem Block DiagramPower SupplyThe power supply for the gun can be any DC source. There are numerous options for DC sources. One option is to use a power supply from a computer. High power computer power supplies are now fairly cheap and easy to find. Computer supplies use an 115V or 230V AC input. A nice characteristic of a computer power supply unit is that it already converts AC to DC power. This characteristic eliminates the need to construct a full-wave rectifier in the coil gun circuit. In the coil gun the problem that one would run into using a computer power supply unit deals with the fail-safe of the unit. A capacitor bank cannot be hooked up to a computer PSU directly. The reason for this is that the voltage must be kept above a certain value to remain on. If it goes below that value it is designed to automatically shut off. In the coil gun, having the PSU and capacitor bank hooked directly together would be an issue because the voltage will vary with respect to time. The discharge of the gun or the PSU being turned on would cause the PSU to turn off due to the voltage being dragged too low. The only way to rectify the issue is to use a low resistance power resistor in series with the capacitor bank. The disadvantages of that are slower charging capacitors. This would add to the already slow charge time.A car battery charger is another method that can be used to charge capacitor banks. Most car batteries charge at slow rates because manufacturers are worried about the safety of persons using the product. It might be possible to manipulate the circuit into charging faster. They are cheaper than computer supply units. Battery chargers are the worst way to charge a capacitor when timing is a big concern. The time it takes to charge a capacitor is too long especially considering its capacitance. For the coil gun to be able to continuously be able to exert a projectile this could never be an option. It is too slow and very time consuming. The choice of repeated fire would likely not be an option.The best choice is likely AC power. It is inexpensive. With AC power the circuit can be manipulated a lot more. It will be easier to add rectifiers and boost converters if necessary. The time the capacitors banks take to charge will also be a lot quicker than using a normal car battery or standard power supply unit. The great thing about AC power is it is readily available. There is no need to worry about current running out like a battery. If the coil gun needed to power any additional controls or circuit devices it can easily be added with an AC source. If the additional devices needed direct current they could just be connected to another full wave bridge rectifier connected to the AC power source. The AC power from the standard outlet is 120V. The frequency for the analog signal is 60 Hz here in the United States. The frequency is not any concern for the coil gun. After the current goes through the convertor, only a small portion of the signal passes through. This small portion is not enough to make a big difference. Usually capacitors are put into circuits to eliminate the problem of a signal passing through. The capacitor bank has more than enough capacitance to eliminate the signal completely.Energy SourcesIt is possible to use an electrochemical cell battery for an energy source. The best choice of a battery would be one that has real low internal resistance. The lower the internal resistance the higher the power transfer from the battery. In a coil gun maximum power transfer is a desired characteristic. Lead-acid and nickel-cadmium batteries all have low internal resistance characteristics. The disadvantages for a coil gun include longer charge time and lower current. Battery voltages are DC power sources so varying voltages is not an option. This could hinder the goal of reaching at least 100 ft/s for projectile speed. The importance of being able to vary input voltages is the key to increase current through the solenoid. Capacitors are a favorable choice because they easily store large amounts of energy. In a coil gun all the energy it needs can come from a capacitor. To give the coil gun more energy and current more capacitors can be added to increase capacitance. The weight of a capacitor is dependent on its capacitance. Normally capacitors are not too heavy. For the capacitance in the coil gun capacitor bank weight should not be an issue. Capacitors for an energy source are great but expensive at high voltage ratings. Specification for the gun dictate 300V but capacitor rating will likely be 400V if chosen to account for variations in voltages from the power source. There are many types of capacitors to choose from that will be discussed later in the report.Using an inductor is also a possibility. Inductors possess the similar characteristic of a capacitor in that it can store energy. To use an inductor in a coil gun a number of factors need to be addressed. For the inductor to act as a storage system an additional inductor is needed. The inductors are set up like a transformer. The first inductor stores charges like a capacitor bank, and the second inductor is the output. It outputs the stored energy. The first inductor or primary windings induce a voltage on the secondary windings through a magnetic field creating an output current. There are disadvantages and reason it cannot be used in the coil gun that is being built. First off it is very bulky. The coil gun that is being designed is supposed to be lightweight. The addition of something of this magnitude added would add too much weight to the design. Another issue that arises is keeping the charge stored on the primary windings. Unlike a capacitor to store the energy in the primary windings a constant current needs to be present. Despite the disadvantages if weight was not an issue this would be perfect. The advantages of using this in a coil gun system are that the desired output current and voltage can easily be reached. In a transformer the desired voltage and current can be attained through adjusting the number of windings and input voltages.The best energy source to use in a coil gun is a capacitor. The capacitor was chosen because of it is versatility. Energy from the capacitor can be increased or decreased with the addition or subtraction of capacitors. There prices are expensive for high voltage rating but there are many types and sizes to choose from. A majority are also light weight, a benefit needed to keep the gun light. The transformer or inductors as an energy source was hard to consider because of its size. It had every advantage over the capacitors except for it being bulky. The one thing that stood out about the inductors was their ability to not only store energy like the capacitor but be able to step up or step down voltages. For a higher powered coil gun where extremely high voltages were a concern this would be a great energy source to use. The electrochemical battery as an energy source as energy was quickly shot down after thorough research. A main concern before the thought of even designing a coil gun was charge time. Charging a battery takes fairly long and would not reach the goals of the project. The chemical in the battery requires many safety precautions. Batteries can explode if they are charged after the point of energy capacitance. If for some reason the person charging the battery accidentally mismatched the positive and negative terminal the battery may explode. Batteries are good sources of direct current but not for long term use. Too many problems arise from repeated use of a battery. It was quickly scraped from the design process. Although batteries as energy source without capacitor banks was not feasible. It is possible to use a battery to charge a capacitor bank instead of using alternating current. Charging the capacitors through a battery does have some advantages. A circuit with a battery and a capacitor bank do not need a full-wave bridge rectifier to charge. This is because of the fact that batteries supply a direct current that does not need to be converted to another form of power. The only thing that would maybe be added to the circuit to deal with higher voltages is a boost regulator. This is of course if the battery being used had a small amount of voltage. Multiple batteries would have to be on standby incase the battery ran out. The coil gun would likely eat up a lot of energy from the battery. Using a battery to charge the coil gun might be good if the user wants the gun to be completely portable. Always having to change batteries would become a nuisance. Not to mention when the battery is running low it might be somewhat hard to calculate the charge time of the capacitor banks. The variable amount of charge in the battery might also affect the way the projectile is shot through the barrel. In the current coil gun specifications the projectile must be shot at a specific speed all the time. Anything deviated from that speed would present a problem in consistency This is the reason that an AC outlet has to be used. With an AC outlet there is no need to worry about deviations due to current. This is because the current coming from the outlet is always 120 volts at a frequency of 60 Hz. When the AC power is turned into DC power the current is still constant. The constant current is all that should be worried about when supplying current to charge the capacitors. From this constant current the charge time will always be the same.Solar Cells and PanelsThe current design of the coil gun prohibits it from being portable because of the dependency of an electrical outlet. Since the gun is being designed to be efficient and economically friendly the use of batteries will not be considered. If time permits the gun will be made so it can be portable as well. Solar cells and panels can slowly charge devices over a long period of time. They slowly charge devices because a single panel can only produce a small limited amount of power. In order to create a very large amount of power numerous panels will need to be used. The solar cells use energy that comes from the sun in the form of photons to produce electricity. Most solar cells are created using crystalline silicon wafers. These cells are very sensitive and brittle. They must be protected to ensure quality. Most solar panels are protected from the natural elements of rain, wind, and moisture by glass. The glass protects the superstrate and the substrate of the cells. Solar cells can be orientated in panels in a couple of ways. One way is positioning the cells in series. If solar cells are placed in series there is an additive voltage for each cell that is added. For more current transfer the cells can be orientated in parallel to achieve maximum current. Earlier in the report it was mentioned earlier about storing a coil gun with large amounts of energy can be dangerous. For this reason if the coil gun were to have solar cells to charge the gun when the gun is not in use there needs to be a switch to control this method of charge. The gun should be charged only when it is going to be fired sometime in the soon future. A switch would enable it to charge. When the gun is not going to be charged without an electrical outlet the switch should be turned to the off position. The gun will only be able to shoot one cycle because the charge time with solar panels is more than a thousand times the charge time of an electrical outlet. To charge the coil gun using solar cells requires it to be exposed to sunlight for many hours. Even with ten solar panels it would take a long time to charge the capacitor bank. This is okay because the solar cells are only a secondary source or it can even be considered to be a backup. Despite the drawbacks of solar cells there are many advantages. Solar cells use natural elements to produce energy. They do not use non-renewable resources therefore they are environmentally friendly. They also have long lifetimes as long as they are properly protected from moisture. Moisture corrodes metal contacts and interconnects. The cells can overheat but the solar panels usually consist of diodes that prevent overheating. Heat in the panels reduces operating efficiency as well. Since the energy source is sun light there is going to be heat either way.AC to DC PowerThe voltage in the coil gun will come from the standard 120V 60 Hz wall outlet. The 120V from the wall is an alternating current. This will be used to charge the capacitor bank. An alternating current is a bidirectional sinusoidal power source with voltage and current being out of phase. In order to effectively charge the capacitor bank the alternating current will be stepped up and need to be converted to a direct current. Alternating current cannot be used because a capacitor blocks directs currents but allows AC to pass through. The direct current is blocked and charges the capacitor bank because a direct current possesses infinite reactance. The conversion from an AC signal to a direct current will need some form of a converter. For conversion a simple circuit is needed. Almost all devices in a household use direct current to operate. The only real use for AC is to transfer power from one place to another. Using direct current for transferring power from long distances is very ineffective because the currents and voltage are always in phase.An easy way of converting AC to DC is to use a rectifier. The process by which the AC is being converted into DC is known as rectification. A rectifier consists of one or more diodes in a circuit connected in series with a resistor. Using only one diode in series with a resistor is better known as a half-wave rectifier. A half-wave rectifier filters either the top or bottom of the input and outputs either the upper or lower portion of the wave. It is very ineffective for power transfer in a coil gun. In a coil gun the power transfer should be maximized. It is of better advantage to use a full-wave rectifier. A full-wave rectifier is similar to a half-wave rectifier except it has more diodes in a different configuration. The configuration that the diodes are formed in is known as a bridge. The full-wave rectifier as you can see has four diodes connected to a resistor.A full-wave rectifier does not filter out an AC signal completely. It only filters out a majority of it. Rectification does not stop at a full or half-wave rectifier. A capacitor is usually introduced into the circuit in parallel to create a more true constant direct current. The larger the capacitor introduced the more constant direct current there will be. Since all of the current is going into a capacitor bank anyway, it may be possible to be able to get by with just a small value capacitor. This addition of the capacitor does not filter out the sinusoidal signal completely and may present a problem later with the triggering system. Hopefully the analog signal is real minor. In a coil gun the issue is not of any major concern. The problem can easily be addressed by additional circuit components if need be.For the AC to DC power conversion in the coil gun a device is needed. There was a choice of either buying an existing AC to DC converter or actually constructing one from scratch. Buying one from the store is no fun. Constructing one would be more of a challenge. Four diodes will be put in a bridge configuration. Each diode will have a current rating of twenty amperes. In the circuit all diodes will have the cathode on the right side of the diode facing towards the outputted direct current. The left side of the bridge is the alternating current and is connected directly to an outlet. The right side of the rectifier is outputting direct current and is connected between the triggering system and capacitor bank. No boost regulators of any type will be connected to the circuit. There should be enough direct current from the conversion to charge the capacitor banks in a reasonable amount of time. The current after the full-wave rectifier will be measured to make sure enough current exists after the power transfer. If the charge of the capacitors takes too long it may be necessary to step up the voltage because the current is too low or the charge resistor has too much resistance. Another way to get more current would be by possibly using diodes with higher current rating, which isn’t an issue because they are inexpensive. The temperature the diodes are operating could affect the power transfer as well. The heat dissipated across the diodes in the full-wave rectifier will also be monitored to make sure the current rated value of the diode chosen is the correct one. A half-wave rectifier was not an option because of its poor power transfer characteristics. It was very inefficient when compared to the full-wave bridge rectifier. To use a half-wave rectifier would have been too much of a hassle. The current and voltage would need to continually be stepped up from transformers. Stepping up AC vs. DC PowerStepping up AC or DC voltages may be required to achieve the goal of having high voltages throughout the coil gun circuit. This makes high voltage power transfer an important issue. For a coil gun there should be minimal power loss throughout the transferring of power. Most power loss can be controlled through added devices or simply by choosing the correct circuit elements to transfer power. The debate over whether stepping up AC or DC power has always been a debate. Years ago Thomas Edison and Nikola Tesla fought a war on which currents were better alternating current or direct current for electrical power. In the paragraphs below the difference between the two will be discussed to find out which is best for a coil gun system.The process for stepping AC power is a simple concept to grasp. AC power uses a transformer to either step up or step down the voltages or currents. In the coil gun minimal power loss is a positive. In the coil gun circuit the voltage coming from the outlet is low. The voltage from the outlet is only 120 V which is not very high. In the coil gun circuit a desired characteristic is to have low voltage and high current. A transformer usually has more power loss when there is low voltage and high current rather than high voltage and low current. Transferring high voltages for a coil gun is complicated. The safety would be an extra concern as well. It does not seem too complicated except for the added weight. Transformers are usually very heavy. One big thing that affects power loss in AC power is the skin effect. The skin effect describes how alternating current has higher resistances in the conductor or wire than direct current. Alternating currents have a greater advantage of transferring power long distances.st. This is perfect for In the coil a desired characteristic is to have low voltage and high current. If low. If the DC voltages can be stepped up and down using small circuits for smaller circuit configurations. Although they are not ideal for long distance power transfers they work fine for a small circuit like a coil gun. DC step up circuits use active and passive circuit elements to function. They are easy to use and very easy to design. The only concern is making sure the circuit elements can deal with the high flow of current. Power loss in the circuit can be an issue because of the way the voltage is being regulated. There can be multiple step ups or step downs to reach a specified voltage. The voltages in the coil gun will not be messed with too much. The desired current and voltage will for the most part remain constant before traveling into the capacitor banks. The addition of boost regulators for the DC voltage step ups might be put into consideration for current and voltage upgrades of the coil gun’s circuitry.The transformer that was chosen for the coil gun was the HT97817 step up transformer.? The transformer was purchased at an electronics surplus store for relatively cheap.? The price for the transformer at the surplus store was $8.00.? It is used but in good working condition.? This transformer steps up the 120V AC voltage to 480V AC voltage.? The primary of the transformer accepts 120 V AC.? The secondary of the transformer outputs 480V AC voltage.? The capacitor bank only needs 400V DC because of its voltage rating.? Charging the capacitor bank past the voltage rating can permanently damage the electrolytic capacitors.? As a precaution a voltage divider will be used to make sure the 400V DC is the maximum output. Despite the weight of the transformer it was the easiest solution for stepping up the AC voltage. It is a lot easier and cheaper to step up AC voltages than it is DC voltages.? The transformer weighs a little over 10 pounds. It is very heavy but will do the job.Regulators ComparisonLinear RegulatorIn designing the coil gun a linear regulator was taken into consideration. While designing the coil gun circuit there was a possibility that the circuit might need some type of voltage regulation. The voltage in the circuit and across electrical components needs to be below their threshold voltages or ratings. Different parts of the circuit are designed to withstand certain voltages. If at any time in the operation of the coil gun it exceeds those voltages problems arise. A linear voltage regulator can keep a constant voltage through the circuit. Linear voltage regulators are not efficient at all. They do the opposite of what switching regulators do. Linear regulators use either passive element in the breakdown region or active devices such as bipolar junction transistors and metal-oxide field effect transistors. These elements act as regulators. They act as regulators by functioning as a variable resistor would. For voltage regulation they are continually being adjusted to keep a constant specified voltage. The main problem with the linear regulator is the way it dissipates the extra voltage. The extra differential voltage is loss through an unconventional method. It loses it by dissipating heat. Dissipating heat wastes large amount of energy. The output voltage is the voltage that is used and controls the voltage throughout the circuit. The linear voltage regulator uses feedback controls to adjust the input voltage to keep the output voltage the same. The output is connected directly to the input voltage.The linear voltage regulator will not be used because it would hinder the ability of maximum power transfer in the coil gun circuit. The circuit is already designed to handle large amounts of currents. This implies that it can handle high voltage as well. There is no step up transformers or DC to DC step up convertor so the necessity of a voltage regulator is not an option. A linear voltage regulator might be useful if the specifications in the coil gun design were changed. If for some reason the speed of the coil gun shooting the projectile needed to be reduced there are two methods. One would be by only partially charging the capacitors. Another method would be by using a linear voltage regulator after the capacitor bank. This would cause there to be a lower voltage across the capacitor bank and their discharge would be significantly lower than normal. The significantly lower voltage than normal would release smaller amounts of current through the solenoid. The lower release of energy would cause the magnetic field of the coil to slow the projectile down. Slowing down the projectile is not recommended for the current design. If the current through the solenoid were reduced significantly the projectile may not fire through the barrel at all. The suck back of the projectile could occur. This would occur because the timing of the circuit would be off due to a variation in the current pulse through the coil. The timing of the circuit would need to be adjusted to properly shut the current off when the projectile travels half the distance of the coil. The linear voltage regulator cannot be used in the circuit. It presents too many problems and is not worth the trouble. The drastic change in current would likely present a problem with the holding current rating in the silicon-controlled rectifier as well. A switching regulator would be a more ideal regulator to use if voltage regulation was needed for the coil gun circuit. Boost RegulatorsBoost regulators were considered to help the coil gun deal with power transfer. A boost regulator is similar to a linear voltage regulator. Boost regulators have several advantages over the linear regulators. The switching efficiency of boost regulators is much higher. The major advantage of using one in a coil gun is that one can step up DC output voltages. It would be used directly after the AC to DC full wave bridge rectifier to step up the output voltages. This would decrease the charge time of the capacitor bank. The benefits of using boost regulators seem too good to be true. The reason the boost regulator will not be used in the gun comes from two factors. Boost regulators can be noisy and annoying just like the ringing of capacitor banks after being discharged. Another drawback to using a boost regulator is that it requires energy management to function properly. The energy management issue can be addressed just by adding a control loop. There is no real solution for the noise problem. The constant noise after trial and error of constantly testing the gun would be irritating. In the future if one were to be added it might be possible to sound proof the container containing the circuit. In a coil gun soundproofing the circuit box seems to be a little extreme. With a soundproof box the heat dissipation becomes a factor once again. The box would likely get too hot and hinder airflow throughout the box. The boost regulator is shown in Figure 57. The figure depicts the circuit elements that are need to construct the boost regulator for the coil gun circuit. It is just a basic concept and will need adjustments to possibly be used in the coil gun circuit.Figure SEQ Figure \* ARABIC 58 Boost RegulatorBuck RegulatorsA buck regulator is similar to a boost regulator. It contains all the components that a boost regulator has except for its configured in the different manner. A buck regulator consists of two switching devices; the switching devices are usually a diode and a transistor. These switching devices control the inductor that is connected to the load. When the switch in the circuit is on or connected the voltage from the source stores energy in the inductor. When the switch in the circuit is off the energy is discharged to the load. The function of the buck regulator is the complete opposite from that of a boost regulator. Instead of boosting DC voltage or stepping it up, it steps it down. A buck regulators main purpose is to step down direct current. In the coil gun if for some reason the input direct current were extremely high and the circuit could not handle it, it would be necessary to use a buck regulator. If the input direct current were too high it could damage certain components. Since every circuit component has a maximum current rating exceeding these currents can cause serious problems. The obvious problem is the overheating and malfunctioning of components. This could lead to components igniting on fire. A buck regulator will be used if the multimeter attached to the end of the full-wave bridge rectifier shows that the current going into the capacitor bank is too high for the capacitors or the wire chosen to handle. A high current does charge the capacitor bank faster which is usually a plus, but too much current can have just as many disadvantages as well. The buck regulator is shown in Figure 59. The figure depicts the circuit elements that are need to construct the buck regulator for the coil gun circuit. It is just a basic concept and will need adjustments to possibly be used in the coil gun circuit.Figure SEQ Figure \* ARABIC 59 Buck RegulatorCapacitor Charging SourceCapacitors store and release large amounts of energy. For a capacitor to become charged it must be able to create an electric field across the insulator. In order for an electric field to become present there has to be a potential difference between the two conductors that lie between the dielectric or insulator. The dielectric is non-conductive and does not permit charges to pass through but stores the energy produced by the electric field. Therefore there must be work done to move charges from one conductor to another. To charge a capacitor or capacitor bank it is necessary to use a direct current source. An alternating current source is not an option because at high frequencies current will flow directly through the capacitor without any type of lag. At high frequencies a capacitor has very little reactance. Since reactance is the opposition to alternating current, a small reactance would exhibit little opposition to current flow. AC circuits with capacitors are normally used for filters. A charging circuit must have three elements of which include: the power source, a resistor, and the capacitor. It is possible to connect multiple capacitors in parallel to increase the capacitance of the circuit. The capacitance of capacitors in parallel can be found by adding the capacitances up of all the capacitors connected in parallel. The voltage across a capacitor is initially zero. When a capacitor is connected in series with a power source and resistor current begins to flow gradually charging a capacitor. The longer current passes through the circuit the more charges are stored in the capacitor creating a higher voltage. The voltage across the resistor and the voltage across the capacitor are inversely proportional. It is for this reason, that there is less current going through the circuit as time progresses. This is pertinent because it helps us to understand why the rate of charging of a capacitor becomes slower with time. The time the capacitor in a charging circuit takes to charge is related to its time constant. The equation is below. In this equation R is the resistors resistance and C is the capacitance of the capacitor. T is indicative of the time it takes the charging current to fall 1/e of its initial current value. After 5RC the capacitor is nearly fully charged. In this equation R is the resistors resistance and C is the capacitance of the capacitor. T is indicative of the time it takes the charging current to fall 1/e of its initial current value. After 5RC the capacitor is nearly fully charged. T=RCA light bulb is an ideal charge resistor for a coil gun. Light bulbs have great characteristics for discharging capacitor banks, especially in our case where safety is a major concern. They have low resistances at low power and high resistances at high power, thus enabling a constant current sink. The problem with using a standard resistor is overheating. Since a coil gun uses large amounts of current and energy the resistor easily reaches its breakdown point. This point occurs when the average power dissipation can no longer be safely dissipated by the resistor. At this point the excessive power dissipation raises the temperature of the resistor at which it can no longer function causing it to burn out. When burn out occurs there is a possibility of a fire starting. Light bulbs are perfect for power dissipation, where high heat is a concern. The charge resistor for the coil gun is a light bulb. The type of light bulb chosen is a 125W flood light bulb. In Table 12 shown below is the charge time it takes to charge the capacitor bank at various voltages the coil gun will be operating at. As the operation voltage increases so does the charge time and resistance. VoltageCapacitance ResistanceCharge Time3000.0047202.883500.0049803.924000.00412805.12Table SEQ Table \* ARABIC 12 Capacitor Bank Charge TimeStandard 75 W Light Bulb vs. 125 W Flood Light BulbA light bulb was chosen to be used as a charge resistor. It was simple to choose one as the charge resistor because of its great characteristics. Another problem that arose was which bulb to choose. There are many different type of light bulbs with different power ratings. The choices were narrowed down to two bulbs shown in table 12 below. One bulb is a standard household bulb that is 75 W and found in almost every lamp in the house. The second was a 125W flood light bulb that is used primarily for flood lights. Below are the standard power equations that were used to choose the right bulb for the coil gun.P=V2RP=VIP=I2RVoltage:300.00VPowerCurrentResistance750.2512001250.42720???Voltage:350.00VPowerCurrentResistance750.211633.331250.36980???Voltage:400.00VPowerCurrentResistance750.192133.331250.311280Table SEQ Table \* ARABIC 13 Standard Bulb vs. Flood BulbThe table 13 above depicts each individual light bulb at the specified voltages. The table gives a better understanding of which light bulb is best for the charge resistor. The flood bulb allows more current to travel through the circuit and to the capacitors. An important concept to note is that as the voltage increases the current gradually decreases. The standard light bulb decreases at a slower rate when voltage is increased. In a coil gun with a significantly higher voltage then 400V the standard light bulb may have a better advantage. A major item in the table is the resistance. The standard bulb has an extremely high resistance than the flood bulb. This is pertinent because it means the bulb with the higher resistance takes longer to charge. The longer charging is relative to the equation for the RC time constant. It is clear which bulb will be used in the coil gun. The 125 Watt flood light bulb is perfect for this 400V coil gun.Digital VoltmeterIn most coil gun projects the designers choose to connect a voltmeter or multimeter to measure the voltage the gun is operating at. In this coil gun it was decided that it would be better to have a more permanent solution to measure voltage across the capacitor banks while they are being charged. A digital voltmeter will be included in the gun’s circuit to easily display voltage. An additional feature may be to have a current meter added as well. For the coil gun it is a necessity to monitor the voltage being used at all times to make sure the maximum voltage is not exceeded. The voltmeter ensures that the voltage across the capacitors does not exceed the maximum voltage rating of 400V. As a precaution the banks voltage will be well below the maximum voltage rating. Keeping a significantly lower voltage than the maximum voltage rating maximizes the life and quality of the capacitors. The digital voltmeter will be placed in parallel with the capacitor bank. The amp meter if added will be positioned in series with the parallel capacitor bank and the solenoid.Digital ThermometerIn the coil gun it is a good idea to keep track of the amount of heat being generated. Similar to other electronics, a certain temperature should not be exceeded or electrical failure will occur. Keeping track of the temperature of the coil gun is not a hard issue to address. A digital thermometer can be used to keep a record of how hot the gun is getting. In testing the coil gun the digital thermometer can be a quick reference in seeing if the gun is functioning correctly. If for some reason temperatures keep raising at fast rates it can be implied that there is a problem in the circuit. This means the circuit is on the verge of failing and the current through the gun should be immediately turned off.When the temperature that the coil gun cannot operate is reached it will be recorded. This temperature value will be important to know because then the coil gun can be tuned so it will never reach that temperature again. From that temperature value the circuit can be upgraded so that it will turn off before it reaches that temperature. This safety feature will save the coil guns components from ever being shorted or fried. The temperate value at which the projectile reaches its maximum speed will also be an important value to keep in mind. The circuit might be able to be tuned to only shoot at that temperature value as well. This is perfect and helps to identify any problems when the voltage being inputted into the circuit is being varied. The digital thermometer in conjunction with the fans and heat sink will be the key to dealing with power dissipation. The digital thermometer helps to pick the appropriate fan speeds. The fan speeds can be orientated on the output being displayed on the digital thermometer when the gun is in use. If the digital thermometer in the system is chosen to be used it will like come already preassembled. The circuit construction of one is fairly simple but making sure the value being displayed needs is the main priority. If for some reason the value being displayed was wrong because the digital thermometer circuit was not constructed properly it would be detrimental in the design of the heat dissipation process. The preassembled digital thermometer will be tested before it is actually used in the guns circuit. To make sure it is function properly it ambient temperatures will be taken from inside and outside. Once temperatures are verified only then will the digital thermometer be used. The display only uses small amounts of current to run. It will likely use the same power that is being used by the computer fans. The digital thermometer is a pertinent addition to the circuit. It may even be just as important as the voltmeter and current meter. It allows the user to easily analyze circuits and the problems that are arising. If the thermometer is added to the circuit it will provide valuable information to the user. It will also be able to be used for troubleshooting other circuit components.Testing CurrentThe current throughout the circuit should be tested. It is important to know the current through each electrical component to make sure that device can handle the current at that point. The peak current along with the time the peak stays constant should be identified too. Identifying this gives the designer the ability to modify the circuit to handle the peak currents. Knowing peak currents helps because then the proper electrical components can be switched out for higher or lower values depending on what the multimeter displays. Each component chosen was picked for either its current rating or voltage rating. The manufacturer spread sheet usually only designed for normal use. It doesn’t give specifications for high currents at short periods in time for such devices as a coil gun. Therefore a lot of the devices current and voltages rating at short durations were computed to choose the appropriate device. It is still possible that some of the devices may fail when in use. It is very difficult to estimate the peak currents and voltages with respect to time. To measure the current through the circuit a portable digital multimeter will be used. A multimeter will display the currents through that portion of the circuit if it is orientated in series with the device’s current it is trying to read. This will have to be done before the circuit is permanently connected. Once the circuit is permanent is will be difficult, if not impossible to measure the current at every single piece of the circuit. The testing of the circuit should be at the maximum voltage that the circuit is being designed to operate. That voltage is of course four hundred volts. This voltage is only after the capacitor bank is discharged. The portion of the circuit before the capacitor bank will stay the same even when the voltage is varied at the capacitor bank. The solenoid will have the highest peak current so that is the device that will get the most attention when the current is being measured.The current will first be measured from the beginning of the circuit which is the power source. Any outlet that the gun is to be used with will need to be tested. In order to test the outlet the two probes of the multimeter will be connected to each terminal of the outlet. This will measure the current that will be traveling from the outlet to the full-wave bridge rectifier that is converting alternating current into direct current. The current going into the bridge rectifier should not be more than 40 amps because the diodes can only handle a current of 20 amps each. Since the full-wave bridge rectifier has a split at the initial portion of the circuit it can handle twice its current rating, which is where the number 40 amps come from. The current should be measured from the top portion of the full-wave bridge rectifier and the lower portion as well. The wire resistance and the diode internal resistance should be extremely minor. The current through the charge resistor should be the same as the two values of the full-wave bridge rectifier combined. This is because the charge resistor is just before the full-wave bridge rectifier and is in series with the AC power source as well. When the capacitor bank switch is turned to the on position and the capacitor bank is charged to the max the current through the rest of the circuit should be zero. The current stays zero until the silicon-controlled rectifier receives a current through its gate to release the holding current. The current released from the capacitor can then be measured after its discharge. The current released from the capacitor bank is extremely large. This current travels to the solenoid. At this point it is important to measure the time at which the current stays at its peak value. The current for the whole discharged of the capacitors should be measure through the solenoid. From this a relationship of the current with respect to the time formulation can be derived. The current through the silicon-controlled rectifier should not be an issue. The device is designed to handle high currents. The only thing that should be looked at is the voltage across the electrical component. The current traveling through the gate may be measured to make sure enough current it being supplied to operate the device properly. There is a damping resistor connected to the cathode of the silicon-controlled rectifier. The current through the resistor should be the same as the current through the solenoid and silicon-controlled rectifier since all those components are in series.Testing VoltageIt is necessary to measure the voltage throughout the circuit. The voltage will be measured using either a voltmeter or multimeter. It is fairly easy to measure the voltage in any circuit. The voltage in the coil gun circuit can be measured by simply putting the voltmeter in parallel with any electrical component. This has a big advantage over measuring the current. The voltage can be tested even if the circuit is in its final design and permanent. The voltage of the electrical AC outlet will first be measured. The output voltage should range from 110V to 120V. From that point current flows through the charge resistor to the full-wave bridge rectifier. The voltage at the charge resistor should be measured. This is important because it can give the designer the ability to calculate the amount of heat that is being dissipated. Since the charge resistor is a light bulb there is not too much concern over the amount of heat being generated. Light bulbs are designed to deal with high power. If the charge resistor was a normal resistor there would likely be an issue with the high temperatures being generated. The voltages at the diodes of the full-wave bridge rectifier are measured as well. Diodes can handle high voltages because they have little internal resistance. The voltages at the capacitor bank are the most important voltages to measure. Even though there will be a digital voltmeter to measure the voltage that the capacitor banks are being charged to a voltmeter will be connecting there too. The capacitors are the most expensive part of the coil gun. If any one of those capacitors reaches above 400V or close it can permanently damage a capacitor. Replacing the capacitor would take some time. Having extra capacitors would be beneficial but the cost is too high. A lot of precaution will be taken to make sure the capacitors do not fail or malfunction. After measuring the voltage across the capacitor bank, the voltage of the solenoid will be measured. It should be 300 volts to 400 volts as well but it will still be measured to be sure. The current might have a large effect on the amount of voltage being produced. The voltage over the silicon-controlled rectifier will also be interesting to observe. There is no worry about the voltage because the one chose has a very high voltage rating. The voltage across the damping resistor should be real low. The value of the resistor is small so that is where that assumption comes from. Knowing the voltage may not be as important as knowing the current but none the less is pertinent. Voltage differences and changes in the circuit can also lead to better analysis of problems that may be present in the circuit. Every device needs a voltage present to operate. If no voltage is present in a device it can lead to the assumption that there is not enough power going through the circuit for it to properly operate. Too much voltage is the circuit can cause problems that deal with overload. There being excessive voltage can short electrical components and may even produce too much energy from power dissipation. Voltages can also affect the way the magnetic field is produced in the solenoid itself. The voltage when the coil gun is turned off should be measured as well. The peak voltages that might occur can damage the capacitor bank, silicon-controlled rectifier, or coil. The peak voltages can create an undesired back electromagnetic field.Circuitry ProtectionA high powered coil gun requires protection in the circuit. There needs to be a way the circuit deals with negative effects that will occur during operation. Some negative effects that can occur in a circuit are back electromagnetic fields, overheating, shorting, ringing, and power loss. Electrical components can also be negatively affected by these symptoms. Special precautions must be taken to rectify these symptoms or even keeping them from occurring all together. Keeping these negative effects from occurring can increase the safety of the coil gun and user operating it. Every circuit design needs some type of protection against things that could negatively occur.The capacitor bank has a number of different added electrical components. To keep the capacitors from warming up too much each will have cap coolers. The cap coolers will keep the capacitor bank at lower temperatures. The capacitor banks are the most costly part of the coil gun so every precaution will be taken to keep them from any type of damage. The temperatures of the capacitors are not expected to reach high temperatures even without the cap coolers. The cap coolers will simply add more protection and help the capacitor bank to operate normal through the entire discharge process. The negative effects of the magnetic fields can harm the capacitor bank when the device is off. After a discharge there can be back electromagnetic field that can damage the capacitor bank, silicon-controlled rectifier, and solenoid. The back electromagnetic field will be reducing, if not eliminated by adding a diode. The diode better known as a flywheel diode can help silicon and other electrical devices from being damaged by the field that is generated.The solenoid will undergo the most abuse in the circuit. The coil will experience large amounts of current through its wire. The wire must be able to handle extensive amounts of heat being generated from high currents for short duration times. The heat that is generated from the current through the coil will be minimized by using heat dissipating electronics. The heat dissipating components will be by coating the wire with insulation. The surface area of the wire is cooled by using fans and heat sinks. The solenoid experiences a majority of the electromagnetic field that is being generated to push through the projectile. The solenoid was also given a flywheel diode. This will protect it from the peak voltages that occur as a result of the back electromagnetic fields that are exerted on the wire. The wire will experience only small duration of current to protect it from overheating which it can easily do. The manufacturer specification sheets for the wire only give specifications for maximum current for normal use, not for short durations. The short pulses help to alleviate the amount of heat that can be generated if the coil were to have high current flow through for an extended amount of time.The silicon-controlled rectifier requires little protection from negative effects than can occur in the circuit. Most silicon-controlled rectifiers already come ready to function with circuits that have high currents and voltages. There is one thing that the silicon controlled-rectifier does react negatively with. That is the back electromagnetic field. A flywheel diode could be inserted in parallel with the silicon-controlled rectifier but that could cause another problem. To protect the silicon-controlled rectifier a resistor is connected to the cathode in series. The resistor in series makes the circuit critically damping. The estimated cost to build the Power Subsystem is $20 for various passive components.Controls and SoftwareSubsystemThe purpose of the Controls and Software Subsystem is to design the software to drive the coil gun, to determine how the coil gun is going to communicate with the software, and to choose devices that achieve these feats. Throughout this subsystem many ideas and options will be discussed on how to mesh these ideas to allow the coil gun to move and communicate with all the other subsystems correctly and efficiently. Some of the systems within the Controls and Software Subsystem that will be discussed are the position determination, which discuss different types of hardware and how it will communicate through other devices, the FPGA, the Microcontroller, the Software Architecture, and finally the User Interface, which will discuss how the user will interact with the coil gun’s software as a whole. The following diagram, Figure 60, is a function block diagram for the Controls and Software Subsystem and how it acts with the other subsystems in this coil gun project as a whole:Figure SEQ Figure \* ARABIC 60 Controls and Software subsystemPosition DeterminationThere are two viable options that will best serve the need to determine the position of the targeting of the coil gun. The first is an analog system called a resolver and the other is a digital component known as rotary encoder. Since the choice has been made to use an FPGA, the rotary encoder has been chosen over the resolver because it is digital versus analog and there would be no need to purchase an analog to digital converter.A rotary encoder is an electro-mechanical device which takes an angular position of a plane and converts it to digital code. Thus this would make a rotary encoder also an angle or position transducer. Rotary encoders are used frequently on servo motors of mechanical devices to track the position of the motor shaft. There are two types of rotary encoders. First there is an absolute rotary encoder and then there is the incremental rotary encoder. Determining the difference between these two types of rotary encoders is essential before we are able to make a decision on a model of any sorts.The absolute rotary encoder creates a digital code for each specific angle of the plane. Absolute rotary encoders also do not lose their position after the device is powered down, they can give absolute position once powered back up. There are four main types of absolute rotary encoders we have to choose from. The four different absolute rotary encoders are known as the mechanical absolute rotary encoder, the optical absolute rotary encoder, the fiber optic absolute rotary encoder, and finally the magnetic absolute rotary encoder. The fiber optic absolute rotary encoder is a non-metallic position sensor that works in extreme electromagnetic fields. Fiber optic absolute rotary encoders are ideal for mechanic and industrial inspection systems, such as an MRI due to the ability to operate in electromagnetic fields with ease. Though we are using an electromagnetic field to fire a projectile, it may not be extreme enough for us to be concerned about the effects on the rotary encoder. Fiber optic absolute rotary encoders also seem to be far out of our price range.The magnetic absolute rotary encoder is an accurate angular measurement device for over a full turn of 360 degrees. A two pole magnet rotates over the center of the chip to measure the angle. By this process the absolute angular position is given instantaneously. There is also no need for calibration in most cases for a magnetic rotary encoder. The magnetic absolute rotary encoder is highly reliable and ideal for applications in harsh environments. This would be considered closer to our price range for such an item, but I feel we could create problems since we will be creating an electromagnetic field with our coil which could affect the encoder.The mechanical absolute rotary encoder uses an insulated disk complete with concentric rings of opening, all being fixed to the plane. As the disc rotates, there are contacts, which are connected to separate electrical sensor. The metal of the disk is connected to a source of electrical current. A pattern is created, due the contacts coming in contact with the metal disk, in a binary sequence of every possible position. The mechanical absolute rotary encoder seems to be an efficient device and some model can be found that will meet our budget.Optical absolute rotary encoder has a disc like its mechanical counterpart, but instead of being made from metal it is made of either glass or plastic. To determine the disc’s position at any time, a light source and detector creates and reads an optical pattern. To read the code you will some sort of controlling device to determine the angle of the shaft; we will be using a microcontroller.Also known as a quadrature encoder, the incremental rotary encoder is another option we have to determine position of our plane. An incremental encoding will essentially generates pulses proportional to the position of the plane. The pulses are represented as a binary sequence, i.e. 5V would be a 1 and 0V would be a 0. The pulses are then counted, the counter will add or subtract the signal while turning. The incremental rotary encoder is most common rotary encoder due to low cost. For an incremental rotary encoder there are two outputs, known as quadrature outputs. The fact that they are only two outputs is reasoning for the incremental rotary encoder’s low cost. Though the incremental rotary encoders only use two sensors the accuracy the device is not compromised. Like the absolute rotary encoder, the incremental rotary encoder can be either mechanical or optical. Mechanical incremental rotary encoders do have problems that may affect our system. What has been found is that because mechanical incremental rotary encoders’ switches require debouncing they are limited to the rotational speeds they can handle.Optical Incremental rotary encoders are chosen over there counterpart, the mechanical incremental encoder, when there is a need for a high degree of precision or for a tolerance to higher revolutions per minute is a desired commodity. Choosing the ideal rotary encoder for this project is a difficult task because of the similarity is effectiveness and cost of some of the models. The team will most likely evaluate the choice of the specific rotary encoder later on into the project design.Software ArchitectureFor this coil gun project, the software architecture involves all of the functions and structures used to control the movement and targeting. The functions involved in the software architecture are the basic C functions and the other functions are function that will be created while designing the programs. Main():The first function that will be discussed is the ‘main’ function call. The ‘main’ function is one of the standard C programming functions. The execution of the program controlling all of the functions of the controlling of the coil gun will all go through the ‘main’ function. The program will stay within the ‘main’ function while being executed. At the end of the function instead of terminating it will return the beginning. To exit out of the ‘main’ the user will have to manually do so by using the proper protocol. While in the ‘main’ function the program will go through the other functions within the program. The program will also end after the program runs through the function which fires the coil gun. So either to ultimately end the program the user will either do so manually or the program will automatically do so after the program fully executes all its purposes. Inside the ‘main’ all of the local variables we need to be declared at the beginning of the function. Menu():The ‘menu’ function will be the first time the user interacts with the program using the ‘main’ function. The ‘menu’ function will prompt the user with a menu of choices. The choices that the ‘menu’ function will prompt the user with are first the manual targeting option or second the automatic targeting option. Looking at the software architecture block diagram shown below depending on the option selected the path through the ‘main’ function will be different. Once either option is chosen the program will then proceed to the ‘position’ function.Position():The ‘position’ function is the next step through the ‘main’ program. The ‘position’ function will be used to determine the position of which the barrel of the coil gun is directed at. To achieve this feat the function will communicate with the rotary encoders on the horizontal plane and the vertical plane. The encoders will tell the program at which angle each of the planes are at respectively with the horizontal axis and vertical axis. Once the position is determine through using the rotary encoders the function will save the information about the position into the functions variables. The ‘position’ function will be needed to be called later on in some of the other functions to access the information in the variables.Sensor():The next function to be discussed is the ‘sensor’ function. The ‘sensor’ function’s main purpose is to grab the data from the camera/sensor. The ‘sensor’ function will be accessed and used when the user has selected to use the automatic targeting choice at the ‘menu’ function earlier on in the program. The sensor/camera will located at the end of the barrel of the coil gun itself. To save power the camera/sensor will not be active at all times. Within the ‘sensor’ function the camera/sensor will be turned on and off when the data from the camera/sensor is needed or when the camera/sensor is no longer needed for the calculations. UserInput():The ‘user input’ function is a function is created to allow the user to decide where he/she would like to direct the coil gun’s barrel with respect to the location at which the coil gun’s barrel is currently at. The process for the ‘user input’ function will allow the user to input coordinates at which he would like for the coil gun to target or to use the directional keys to move the coil gun. PosDiffCalc():To determine how far to move the coil gun from left to right and up and down, the function ‘position difference calculator’ is called. The ‘position difference calculator’ will take the data from the ‘position’ function for the initial position and the then take the data from either ‘sensor’ function or the ‘user input’ function whether the user chose the manual targeting system or the automatic targeting system. After both of the variables are taken in from the other two functions the ‘position difference calculator’ function will be able to make its calculations. The ‘position difference calculator’ function will then take the absolute value of the subtraction of the variable from the ‘position’ function with either the variable of the ‘sensor’ function or the ‘user input’ function, as stated above to know whether or not the ‘sensor’ function variable or the ‘user input’ function variable is used is the choice the user made between the manual targeting system or the automatic targeting system.DCMotor():The ‘DC Motor’ function is the next function to be discussed. The ‘DC Motor’ function will be using the data from the variables in the ‘Position Difference Calculator’ function. The variables from the ‘Position Difference Calculation’ function will be used to determine the voltage that will be needed to be applied the DC servo motors and for how long that voltage will be needed to be applied for. Doing these calculation will allow for the DC servo motors to move the correction distance horizontally and vertically.Charge():The next function, the ‘Charge’ function, will begin the process of the actual firing of the coil gun. The ‘Charge’ function will turn the circuit on that will begin charging the capacitor banks. The ‘Charge’ will be called when the coil gun’s barrel directed at the specific target chosen by the user. Once the charging process has begun the ‘Charge’ function will begin receiving data from a measuring device telling the function what the value of each capacitor is.FireStandby():The ‘Fire Standby’ function will call the ‘Charge’ function. The ‘Fire Standby’ function will loop around taking in the capacitor values from the ‘Charge’ function. When the capacitor values are at the desired levels for firing the program will then proceed to the ‘Fire’ function. If the capacitor values are not at the desired levels then the ‘Fire Standby’ will loop back through acting as a standby. Fire():The final function that will be discussed is the ‘Fire’ function. The ‘Fire’ function will call to the ‘Fire Standby’ function. The ‘Fire’ does this call to make sure that the capacitor values are when we want them to be before unloading them. If the go ahead is given by the ‘Fire Standby’ function then the capacitor banks will be unloaded into the coil. Once the ‘Fire’ function unloads the capacitor bank into the coil the projectile will be fired. After the projectile is fired then the ‘Fire’ function sends the user back to the beginning of the ‘Main’ function and start over with the ‘menu’ function, allowing for the user to decided if he wants to continue to choose to the automatic targeting system or the manual targeting system or exit out of the program.A Block Diagram of the Software Architecture is shown in Figure 61 below:MenuSelect()autoSensor()Position()manualUserinput()Position()PosDiffCalc()PosDiffCalc()MAINDCMotor()FireStandby()Charge()Capacitors charged?Fire()Figure SEQ Figure \* ARABIC 61 Software Architecture Block DiagramMicrocontrollerA microcontroller is essentially a computer on an integrated circuit. Just like any other computer, a microcontroller has memory, a processor and is a programmable device. Microcontrollers are specially designed for embedded systems, rather than just general systems. Some systems, or products, that use microcontrollers are remote controls, power tools, home appliances, etc. Real time response is a necessity for an embedded and microcontrollers in turn provide real time response, which is why microcontrollers are a perfect fit of embedded systems. To allow for real time response, microcontrollers use interrupt routines. When an interrupt routine is processed the microcontroller completes that specific task before it continue can on with its next instructions. Since microcontrollers understand machine code, compilers and assemblers are used to turn high level programming languages, such as C and Java, into just that.Some other features of the microcontroller are the GPIO pins. Each microcontroller has several of these GPIO, and the purpose of these pins is to be programmed to be an input or an output state by the developer. Pins programmed to be an input pin purpose would be to read in outside signals and sensors. Pins programmed to be an output pin purpose would be to drive motors and other devices. Sometimes there is a need for a microcontroller to take in or output an analog signal, to do these processes an analog to digital converter or digital to analog converter would be needed. Timers are another tool that can be programmed into a microcontroller. One example is a PIT, programmable interval timer. A PIT has counter, once that counter reaches zero an interrupt is sent to the processor and indicating that the counter has finished. There are other timers such as a TPU, time processing unit, which would be used detect input events, generate output events, and so on. Another process that would be very beneficial to this project in general is the PWM, pulse width modulation. The PWM allows the CPU to control power converters, motors, etc. The last block researched would be used to transmit and receive data allowing communication with other devices in the system; this feature is known as the Universal Asynchronous Receiver/Transmitter, or the UART.As discussed above, shown below Figure 62 is a description of the pins of a microcontroller. This microcontroller is the PIC16F84A of the PIC microcontroller family.Figure SEQ Figure \* ARABIC 62 Courtesy of Microchip, permission givenThe next figure62 is the actual location of the pins on a microcontroller, or the pin diagram. Again this is the PIC16F84A 8 bit microcontroller of the PIC microcontroller family.Figure SEQ Figure \* ARABIC 63 Courtesy of Microchip, permission givenProgramming the MicrocontrollerTo program our chosen microcontroller C will be the chosen programming language. The program as a whole will consist of multiple classes for each of the microcontroller’s functions. The first class will be used to tell the microcontroller how to control each of the DC motors. This will control the voltage sent to each of the motors to controls the arms of the targeting system. The voltage applied lets the motors when and how far the move the arms. Another class will be used to tell the microcontroller to receive the information from each of the rotary encoders. The information from the vertical encoder will be used to determine the angle the coil gun’s barrel is pointing with respect to the horizontal plane. The information from the horizontal encoder will be used to determine the angle the coil gun’s barrel is pointing with respect to the vertical plane.Choosing a MicrocontrollerTo choose the right microcontroller research on many devices will need to be done. There are a few concerns as far as the hardware goes. For one, will the microcontroller chosen be able to handle the amount of devices going through it. Can the chosen microcontroller output instructions to the DC servo motors while possibly also receiving input from a video camera, which would be showing what the coil gun is targeting. There are multiple families of microcontrollers that will be decided between.Atmel AVRThe first family of microcontrollers that will be discussed is the Atmel AVR. The Atmel AVR was first developed in 1996. This microcontroller family is a modified Harvard architecture 8-bit single chip microcontroller. The Atmel AVR is also known for being one of the first microcontroller families to have a program storage system that used flash memory. To rid the need for external memory in most cases the Atmel AVR has flash, EEPROM and SRAM all integrated onto a single chip. The Atmel AVR’s program instructions are stored within the flash memory. Each of the program instructions usually take one or two 16 bit words. The size of the program memory for each of the models within the Atmel AVR family is described in its name. So if the model’s name contains 64 in it the model then has 64 kb of flash, and if the model’s name contains 32 in it the model then has 32 kb of flash. Within the internal data memory lies the register file, I/O registers and the SRAM. These can be found in the data address space. The Atmel AVR family of microcontrollers have 32 single-byte registers, and are within the 8-bit RISC (Reduced instruction set computing) devices classification. The working registers are the first 32 memory addresses and then are followed by the 64 I/O registers. In hex the first 32 would be 0000 to 001F and the next 64 would be 0020 to 005F. The SRAM would follow then follow he registers at 0060. The addressing and opcodes for the register file and I/O registers can be addressed as if they were in the SRAM. Internal EEPROM is common throughout all of the Atmel AVR family. EEPROM is usual because like flash memory when electrical power is lost the EEPROM can retain all its content. The EEPROM can only be accessed in the same process at which an external device would be accessed. This would be done by using point registers and read/write instructions. The reasoning for this is because the EEPROM memory is not mapped in to the addressable memory locations within the microcontroller. Having to use these methods to access the EEPROM, causes the access of the EEPROM to take more time than the other internal RAM devices. Writing to the EEPROM is a limited process. According to Atmel the EEPROM in this family of microcontrollers the number of writes an EEPROM can handle is one hundred thousand. The Atmel AVR family of microcontrollers uses a two stage, single level pipeline design. This design allows for the device to execute an instruction while also taking in the next instruction. The Atmel AVRs are fast when considering 8 bit microcontrollers. They are fast because for the most each instruction takes only one to two clock cycles. Rather than most 8 bit microcontrollers, the instruction set of the AVR family is more of an orthogonal style. Describing this orthogonal style can be done by going through a few examples. For instance the pointer registers X, Y, and Z all have different addressing capabilities from one another. Another example of this orthogonal style is that the register locations R0 – R15 addressing capabilities are different than the addressing capabilities of the registers at the locations R16 – R 31. Additionally the I/O ports 0 to 31 differ in addressing capabilities the I/O ports 32 to 63. Below is a block diagram, Figure 64, of one of the products in Atmel AVR family:Figure SEQ Figure \* ARABIC 64 Atmel AVR FamilyMost commonly the AVR family can handle clock speeds up to 20 MHz, while there are some models within the AVR that can handle upwards to 32 MHz from some devices. The more recent models of the AVR family no longer have the need for external clocks or resonator circuits, due to having an oscillator on the chip itself. A few of the AVR models contain a system clock prescaler, this prescaler can be configured during run time allowing optimization of the clock speed.The development tools for the AVR family can be inexpensive, in some cases even free. This could be a decided factor towards these models if the other families of microcontrollers have pricing development tools. The inexpensive development tools would include the development board, while the free development tools would be the development software. Some of these development tools and evaluation kits for the Atmel AVR consist of numerous starter kits. Some of these starter kits are the STK600, STK500, the AVR dragon, the AVR Butterfly, etc.On whole the Atmel AVR family of microcontrollers is a formable foe when deciding on the microcontroller of choice for this project. The Atmel AVR family of microcontrollers is efficient, fast, inexpensive, and can handle many processes that the project would need.PIC MicrocontrollersThe PIC family of microcontrollers is a family of Harvard architecture microcontrollers developed by the Microchip Technology company. This family of microcontrollers was derived from a microcontroller known as the PIC1640, which was developed by General Instruments. Initially the name PIC was meant to refer to the Programmable Interface Controller. The PIC family’s low cost, availability of the device and its development tools, and the ability to be re-programmed with flash memory makes the family intriguing to the industry while also being intriguing to the everyday hobbyist. The architecture of the PIC family of microcontrollers mainly consists of the following:The Harvard architecture that is commonly used with microcontrollers outside of the PIC family.Fixed length instructionsSingle cycle execution type of instructions, taking about 4 clock cycles.RAM locations functioning as registersHardware stack for return addressesData space mapped with CPU, port, peripheral registers, as well as the program counterThe RAM acts as the memory and registers, thus the memory space is not distinguished from the register space. Because the RAM acts like this it is commonly referred as just plainly the register file. All the microcontrollers in the PIC family use data and addressing in 8 bit lengths, in turn are called 8 bit microcontrollers. The PIC family of microcontrollers saves return addresses in a hardware call stack. The hardware stack is software accessible, unlike earlier microcontrollers. The PIC family can handle any from 30 instructions to 80 instructions depending on the model. The instruction set involves instructions to execute many operations on the registers directly. Below is a block diagram, Figure 65, of a microcontroller in the PIC family:Figure SEQ Figure \* ARABIC 65 Microcontroller in the PIC family Courtesy of Microchip (permission given)TI MSP430The final microcontroller family that will be discussed is Texas Instruments’ TI MSP430 family of microcontrollers. The MSP430 family is built around a 16 bit processing unit. Low power consuming embedded systems and low cost was the main focus when developing the MSP430 family of microcontrollers. Current drawn during the idle mode can be lower than 1 mA and 25 MHz is the top CPU speed, this allows for the low power consumption. There are six different Low-Power modes within the MSP430, as well. As seen below, the functional block diagram for the TI MSP430 is somewhat similar to other functional block diagrams of the other families of microcontrollers.A functional block diagram, Figure 66, of microcontroller from the TI MSP430 Figure SEQ Figure \* ARABIC 66 Microcontroller from the TI MSP430Courtesy of Texas InstrumentsDue to cost of using both a FPGA and a microcontroller, and we must use a FPGA to deal with video processing, the group has decided to do all processing on a FPGA.FPGAA FPGA, field programmable gate array, is an integrated circuit that is configured by the user using a HDL, or hardware description language. Using a FPGA allows for the user to design a system based on logic functions. Basic logic functions would be AND, OR, XOR, NOT, etc. These logic functions are created using gates of logic and bits of memory. The HDL language that is most common is known as Verilog VHDL. Verilog VHDL is a programming language similar to the C language, making the development and debug processes similar as well. Early single chip microprocessors had around ten thousand logic gates and ten thousand bits of memory, compared to present day FPGAs which could possible contain close to ten million logic gates and ten million bits of memory shown as Figure 67.Figure SEQ Figure \* ARABIC 67 FPGAAnother big difference in the FPGA versus its old counterpart, the microprocessor, is the logic gates are manipulated by the programmer. Even though this is the case, the development of the FPGA and a microprocessor are similar enough that if someone knew how to develop one or the other they could easily learn the other. A step by step comparison of the two design processes is shown in Table 14 below:MicroprocessorFPGAArchitectural designArchitectural designChoice of languageChoice of language???(Verilog, VHDL)???(C, JAVA)?Editing programsEditing programsCompiling programsCompiling programs???(.DLL, .OBJ)??Synthesizing programs??(.EDIF)Linking programsPlacing and routing programs???(.EXE)??(.VO, .SDF, .TTF)Loading programs to ROMLoading programs to FPGADebugging P programsDebugging FPGA programsDocumenting programsDocumenting programsDelivering programsDelivering programsTable SEQ Table \* ARABIC 14 Microprocessor FPGA ComparisonFPGA Design ProcessEditing, Compiling, and Synthesizing:Because Verilog is very similar to C type programming, any editor can be used. Though we can use any environment to code, I would prefer to use the environment suggested by the manufacture of the FPGA we choose.The compiling process for a FPGA is similar to any other compiling process. The process involves building the files created in the editing process to create the logic sequence desired. When the code is compiled the logic gate data are written to the registers, latches, out ports, buses, etc. of the FPGA.The synthesizing process, though seems similar at times, is different than the compiling process. Synthesizing takes your program logic and maps it into logic gates, rather than the processing instructions of the FPGA. The FPGA programs, once compiled, must eventually be embedded into the actual FPGA. This is done by using the IDE software to upload the program into the FPGA using an USB cable from the PC.Choosing an FPGAThere are a few manufactures of FPGAs and each of those manufactures have many models that can be used. Some of the manufactures that will be chosen from are Xilinx and AMTEL. The biggest concerns in choosing a FPGA to use for this project are cost and sophistication. When I say sophistication, I mean how many gates of logic and bits of memory are we going to need for the processes we will executing. One of the devices that will be looked at is the AMTEL FPSLIC. The device is a combination of both a FPGA and a microcontroller. Since the AMTEL FPSLIC is a FPGA and a microcontroller in one device, this allows for a hastier design and developing time versus having to integrate a microcontroller to an FPGA that are not molded together. The cost of the AMTEL FPSLIC is more than using a Xilinx FPGA and the Xilinx IDE, but I believe using the AMTEL FPSLIC for its advanced features could be the better choice. With the AMTEL FPSLIC we receive the development board and the IDE that is used to program the device. Having to learn the IDE that is used for the AMTEL FPSLIC could create a problem though not a major one. The biggest problem is the time constraint of trying to learn to use the development and debug process of a new environment, where as if the Xilinx FPGA was to be used it would be an IDE that the group already has experience with the software.Another device that will be considered is a FPGA of the Spartan series from Xilinx. One of the advantages of using a Xilinx FPGA is the fact that IDE is free to use, thus we would only need to purchase the development board instead of a starter kit. Since we would only need to buy the board from Xilinx we are probably looking at a cheaper solution than if we were to buy the starter kit.Within the Xilinx family the FPGA that would be chosen would be from the Spartan 3 family of FPGA. The eight family Spartan 3 can contain anywhere from 50,000 gates to five million gates, and is meant to meet cost sensitive projects.Below is a functional block diagram, figure 67, of a Spartan 3 FPGAFigure SEQ Figure \* ARABIC 68 Spartan 3 FPGA Courtesy of XilinxSo between the two FPGA systems discussed there advantages and disadvantages. With Xilinx we would be using a system that we are familiar with, though Xilinx system does not have a microcontroller embedded. With AMTEL FPSLIC it has an IDE that would need to be learned to use in a short period of time, but to its advantage it has a microcontroller embedded in its systems which in turn could end up being very useful. After further consideration due to the cost and familiarity of the device, a FPGA from the Xilinx Spartan 3 family of FPGAs will be chosen for this project. It has been found that a Spartan 3 FPGA and evaluation board can be found for the price of 129.00 on some sites, such as a store site on .User InterfaceFor the user interface there are multiple functions that we would like for it to cover. We would like for the user to have the choice of a manual and automatic setting. We would also like for the user interface to contain a password input. The motion control of the coil will be programmed into the microcontroller/fpga software and will be discussed in another section.For the manual setting, the idea would be to have two sub settings. The first setting would allow the user to input coordinates. When the coordinates have been input the coil gun’s targeting system will aim the coil gun directly towards the target. The way this would work is the vertical and horizontal coordinates would go into separate variables. For the vertical coordinate input we would take the difference of the input versus the current position. The code would be then executed differently depending on whether the new coordinate is less than the current or the new coordinate is greater than the current coordinate. The current position would then be increased or decreased by an index in a loop until the current position is equal to the inputted (new) coordinate.Pseudo code:Current position -> Xcurrent, YcurrentInputted position -> Xnew, YnewHorizontal difference = Xcurrent – XnewVertical difference = Ycurrent – YnewIf Horizontal difference < 0, Increase Xcurrent by indexIf Xcurrent not equal to Xnew stay in loop else continueIf Horizontal difference > 0, Decrease Xcurrent by indexIf Xcurrent not equal to Xnew stay in loop else continueIf Vertical difference < 0, Increase Ycurrent by indexIf Ycurrent not equal to Ynew stay in loop else continueIf Vertical difference > 0, Decrease Ycurrent by indexIf Ycurrent not equal to Ynew stay in loop else continueThe second setting would allow the user to use a controller to aim the coil gun. The likely outcome will be using the computer as the controller, thus using the arrow keys on the keyboard of the keyboard. The user would be given the option to input from the keyboard an 8(up), 2(down), 4(left), 6(right), 0(exit). Then depending on the input the current vertical and horizontal position will be increased or decreased by an index.Pseudo code:Current position -> Xcurrent, YcurrentAsk user for input 8,2,4,6, or 0If input is 8 increase Ycurrent by indexIf input is 2 decrease Ycurrent by indexIf input is 6 increase Xcurrent by indexIf input is 4 decrease Xcurrent by indexIf input is 0 return to main menuFor the automatic setting we will be using sensor to detect light/color. If the user selects to use the automatic setting the sensor will be turned on and begin saving data. When the sensor detects the light/color the program will compare the coordinates and compare with the current position of the coil gun. If the coordinates of the detection differ from the current position the coil gun will move to the coordinates of the object.Pseudo code:User chooses automatic settingTurn sensor onCurrent position -> Xcurrent, YcurrentRead Sensor If sensor detects color/light grab coordinatesHorizontal difference = Xcurrent – XnewVertical difference = Ycurrent – YnewIf Horizontal difference < 0, Increase Xcurrent by indexIf Xcurrent not equal to Xnew stay in loop else continueIf Horizontal difference > 0, Decrease Xcurrent by indexIf Xcurrent not equal to Xnew stay in loop else continueIf Vertical difference < 0, Increase Ycurrent by indexIf Ycurrent not equal to Ynew stay in loop else continueIf Vertical difference > 0, Decrease Ycurrent by indexIf Ycurrent not equal to Ynew stay in loop else continueFor access of the coil gun controller we would like for there to be a password that the user must enter. The password would consist of a number characters or digits. For simplicity the password chosen will most likely be hard coded into the program. To check for correctness of the password inputted a program will go through each character or digit one by one. Psuedo Code:Ask user for passwordCheck character 1If True continueElse prompt user for password againCheck character 2If True continueElse prompt user for password again…..continueCheck character 7If True, Prompt user with main menu (manual/auto)Else prompt user for password againAt this point and time the user will be granted access to the program allowing the user to decide between using an automatic or manual control system. To access the User Interface will be using a PC. The idea of using a separate LCD screen with buttons was discussed. It is felt that the idea of using a PC is viewed as the better option, for simplicity for the developer and the simplicity for the user.Controls and Software BudgetThe Controls and Software budget had to be thought out because it is a wide known fact that finding a FPGA for a low price is not going to be very easy. The microcontrollers and rotary encoders are going to be a little lower on the cost side. First for the FPGA the group was able to find a dealer online at that sells the Xilinx Spartan 3 FPGA from one hundred and twenty nine dollars. After shipping and handling from the dealer on the FPGA will approach approximately one hundred and fifty dollars. Though a specific rotary encoder has not been chosen by the group the group still has a pretty good idea about the price range. Most of the basic Rotary Encoders, excluding the fiber optic rotary encoders and the magnetic rotary encoders because they are quite pricy, seem to be in the range of around five dollars apiece. The group will be looking at purchasing two Rotary Encoders, thus the total price of two rotary encoders will be around ten dollars. Finally the last device that will need a pricing from the Controls and Software budget is the microcontroller. Since the group has decided to go with a microcontroller from the PIC family of microcontrollers, the price of the microcontroller will not be very expensive. The group is looking at a price of about five dollars for just about any of the models we choose from the PIC family of microcontrollers.Summary of Final Software DesignUser InterfaceIn the end the group ended using the onboard buttons, switches and seven- segment display as the User Interface, instead of integrating the coil gun through a laptop. The User in the end uses the switches to charge the coil gun’s capacitor bank and the fire the coil gun (discharge the capacitor bank). The mussel velocity is outputted to the User by way of the seven-segment display.FPGAThe FPGA that the group decided to use to embed the software this project is a FPGA of the Spartan series from Xilinx. One of the advantages of using a Xilinx FPGA is the fact that IDE is free to use, thus we would only need to purchase the development board.Within the Xilinx family the FPGA that would be chosen would be from the Spartan 3 family of FPGA. The eight family Spartan 3 can contain anywhere from 50,000 gates to five million gates, and is meant to meet cost sensitive projects.Below is a functional block diagram, FIGURE 8.1, of a Spartan 3 FPGA:Figure SEQ Figure \* ARABIC 69 Spartan 3 FPGA, Permission from Xilinx LLCSome of the features of the Spartan 3 board that project used directly is the seven segment display to display the mussel velocity and the I/O pin characteristics to input voltages and out voltages for different tasks. One of the tasks that will done by the FPGA using the input voltages and output voltages is the control of the servo motors this is done by sending out pulse width modulations through the output pins, which was discussed briefly in an earlier section. The second task that will be done using the FPGA is displaying the mussel velocity of the projectile using the provided seven segment display on the FPGA board. SOFTWAREFor this project all of the existing software is written in Verilog HDL. All of the Verilog code was written and implemented using the Xilinx 9.2 ISE Webpack. The main software tasks were to implement the speed trap to capture the mussel velocity and display that velocity on the seven segment display. The speed trap uses two optical sensors separated by 4 cm, that when on maintain a low voltage ~ 1.5V and as the projectile impedes the sensors view the voltage drops to zero. To calculate the velocity will count the number of clock cycles from when the first optical sensor drops to 0V up until the second optical sensor goes low. An example of the Verilog code is shown below in Figure 70:always@ (posedge clk ) if(!sensorIn)begin Startcount <= 1'b1; end else if(!sensorOut) begin Startcount <= 1'b0; endalways@ (posedge clk) if(Startcount == 1'b1) count = count + 1; else if(Startcount == 1'b0)begin velocity = (0.04/(count*0.00000002))*3.3; endFigure SEQ Figure \* ARABIC 70 Speed Trap CodeTo display the velocity using the built in seven segment display it took some manipulating of the fpga’s onboard 50 MHz clock. There are seven Pins for the seven segment display and four Pins to switch between each digit, therefore theoretically you can only display one digit at a time. Though we have the ability to display four digits, only three will be shown since the ideal mussel velocity will be around one hundred feet per second making the forth digit obsolete. To get around this a counter was created to allow the display to toggle between digits for a specified amount of clock cycles. Even still none of the digits are actually displayed at the same time, though to the human eye it appears to be. Another difficulty that was run into was the fact that we were trying to display a calculated integer. To extract each digit (hundred place, ten place, one place) the integer was first divided by one hundred and then mod by one hundred, then result from the mod function was used to calculate the next digit by dividing by ten and the one digit is then calculated by taking the mod of the ten digit. The code in Fdemonstrates how to extract each digit that is to be displayed from a calculated integer:always @(posedge clk) DIG2 = velocity/100; REM2 = velocity%100; DIG1 = REM2/10; REM1 = REM2%10; DIG0 = REM1/1; Figure SEQ Figure \* ARABIC 71 Digit ExtractionBelow is Figure 72 which includes example code of how to execute the toggle of the display:always @(posedge clk) if(count < 15020)begin count = count +1; if(count > 5000)begin toggle <= 4'b1101; DISPOUT <= DISP0; end if(count > 10000)begin toggle <= 4'b1011; DISPOUT <= DISP1; end if(count > 15000)begin toggle <= 4'b0111; DISPOUT <= DISP2; count = 0; end endFigure SEQ Figure \* ARABIC 72 Digit Output with ToggleExecutive SummeryThe overall design of a coil gun is complete. The coil gun proved to be harder to design than originally expected. It required very in depth research of magnetic fields. The concepts and theories of magnetic fields took the most time to comprehend. There were numerous equations and formulations derived to have the capability of even starting the research and design process. The magnetic fields were on a similar but different level of comprehension than normal electrical circuits. The comprehension required research in magneto-motive forces and fluxes. Theories from the Biot-Savat ‘s laws, Ampere’s laws, and Maxwell equations were the basis of the relevant research to magnetic fields. They were the theories and laws that were used to grasp the conceptual idea of getting the projectile to actually move. They were also the theories that put constraints and prohibited many different methods to be used by different electrical components. The main conceptual idea for the coil gun was to get a magnetic field to create via current through a coil to have a projectile shot from a barrel. That design of the magnetic proved difficult because it affected many devices that would help the configuration of the coil gun. The back electromagnetic fields became troublesome because they would negatively affect the operation of the coil guns circuit components. Choosing the capacitor bank was the most important part in the development of the coil gun. The development of currents, induction, and voltages were centered on the capacitor bank. They are the reason all of those values were chosen. Since the gun was built on certain goals and specifications the need for the capacitor bank to be the correct value was pertinent in the design process. The capacitors were the first and last electrical components chosen. They were continuously being adjusted to deal with the speed at which the projectile needed to be fired at. By using a RLC simulator the values of the capacitor bank were chosen on the bases of current pulses needed in order to achieve different projectile speeds. The capacitors took a lot of research to find its appropriate values. They were the most tedious to find because picking the wrong capacitors would be very expensive. After careful research the selected values were found. The capacitors like the magnetic fields presented many obstacles to overcome.Choosing the switching system to switch on the current from the capacitors was not too hard. The difficultly of the process was due to the numerous choices. There were many different transistor choices to be chosen for the design of the coil gun circuit. All of the choices presented valuable advantages to the circuit and were carefully considered. The disadvantages and advantages of the transistors were weighed to pick the most appropriate choice. The choice leaded to the selection of a silicon-controlled rectifier. The silicon-controlled rectifier met all of the circuit requirements and integrated into the circuit without having to compensate for any changes to circuit elements. This was very important because when the design is actually constructed currents and voltages may be varied.The type of wire was pertinent to the magnetic field generation. Without the proper selection of the wire the required magnetic field will not be able to be created. The wire selected was selected because it was capable of handling the transfer of large currents and voltages at short durations for peak current pulses. The selection of wire proved to be very tedious because of thermal sustainability. The coil needed to have wire that can support extremely high temperatures. The type of wire chosen is ready to withstand anything thrown at it. The wire being used will contribute to the coil gun operating successfully. The development of the magnetic field will be exerted through the wire winded around the barrel.The barrel was probably the easiest part of the design process. The barrel was designed on the basis that it would be able to allow a small projectile to be shot from. After the projectile was chosen it was easy to design the barrel for the coil gun. There was only one real requirement in picking the barrel and that was the material. For the magnetic field to be exerted properly on the projectile the barrel needed to be non-conductive. None the less the barrel was very important in the development of the coil gun design. Without the barrel the projectile would have no path to be shot. Without that extra non-conductive material between the coil and the projectile the gun would not be able to shoot.Partial Circuit Schematic OverviewThe main circuit shows how the coil gun circuit will be set up. The circuit begins with the power source. The power source being used is a standard United States 120V 60Hz alternating current power. The current from the power supply travels through a wire to the full- wave bridge rectifier. There are four diodes that are rated with 20 amps each. From this full-wave bridge rectifier the alternating current from the power source is converted to DC power. The current from the full-wave bridge rectifier is then sent through a 125 watt flood light bulb to the capacitor bank. The 125 watt bulb is used as the charge resistor for the capacitor bank. At the capacitor bank the current begins to charge until the maximum charge is reached. There is a switch connected to the capacitor bank to allow it to begin charging. The capacitor bank is connected in parallel with a diode, that diode is acting as the flywheel diode. The cathode end of the diode is facing upwards. When the capacitor bank is discharged the charges are released from the capacitor bank. Then there is a large current sent to the coil that is winded around the barrel. The capacitor bank has a capacitance of four millifarads. There is also a resistor connected in parallel to the capacitor bank. The resistor connected to the capacitor bank is the bleed resistor. The function of the bleed resistor is to drain the energy from the capacitors when it is stored or is not in use. The value of the bleed resistor that was chosen to be used is a hundred and fifty kiliohms. The solenoid is attached in parallel with a diode just like the capacitor bank is. This is the flywheel diode for the coil or inductor. In series with the end of the coil there is a silicon-controlled rectifier attached. This silicon-controlled rectifier is turned on only when a current is supplied to its gate. The gate of the silicon-controlled rectifier will be attached to a triggering system that is not shown in the figure. The cathode end of the silicon-controlled rectifier is attached to a resistor. This resistor is the damping resistor and keeps the circuit critically damped. The value of the damping resistor is .593 ohms. The circuit does not need to be grounded since it’s hooked up to an AC power outlet. It is automatically grounded through the outlet. Figure 68 below shows the main coil armature.Circuit Schematics and PCB boardFigure SEQ Figure \* ARABIC 73 Circuit SchematicsFigure 73 is the Schematic of the whole circuit of the coil gun. It constructs by four parts which are voltage transform, voltage rectifier, charge circuit and fire circuit. And the corresponding PCB design looks like as shown on Figure 74. Figure SEQ Figure \* ARABIC 74 PCB for Coil GunSubsystemCostField Generation$343.98Sensors and Motion Control$165Power$20Controls and Software$165Project Total$693.98Table 16 Coil Gun Total Budget BreakdownMilestonesThe following Gantt chart shows the schedule of the project. The Gantt chart displays the dates on the top of the chart. On the right side of the Gantt chart shows each of the milestones for the project in their own specific subsystem.Figure SEQ Figure \* ARABIC 75 MilestonesUser ManualMake sure all switches are in the OFF position, and load the projectile into the barrel of the Coil Gun.Connect the load the program into the FPGA, the Seven Segment Display should read 0000, and then connect the FPGA to the PCB.Plug in the AC power cable into the wall outlet. Locate the switch box on the back of the capacitor bank. Turn on both switches; one is for the AC Power and the other for the DC Power. You should hear a buzz from the transformer when the AC switch is in the ON position and a LED should light up when the DC switch is in the ON position.Now locate the two switches on the side of the capacitor bank box. The red switch is for the DC Voltage Meter; turn it to the ON position. The DC Voltage should then be reading about 0V. The white switch is to the Charging circuit; Turn it to the ON position. Now that the Charging switch is in the ON position we can Charge the capacitor bank by using switch 6 on the FPGA board. Once Switch 6 is in the logic 1 position, the DC Volt meter should display an increasing Voltage.When the DC Volt meter display 400V turn Switch 6 to the logic 0 position, the Voltage should then stop increasing and start to very slowly decrease.At this time the Coil Gun is ready to be fired. The Firing circuit is controlled by Switch 7. When you are ready to Fire turn Switch 7 to the logic 1 position. The Coil Gun will then Fire, at this time turn Switch 7 back to the logic 0 position. You will then see the mussel velocity of the projectile displayed on the Seven Segment Display. To Reset the Velocity press Button 0 on the FPGA.Turn all the switches to the OFF position. If the User would like to use the Coil Gun immediately reload the projectile into the barrel and continue at Step 4, else unplug the AC cable.Appendix ADate: Mon, Aug 2, 2010 at 11:57 AMSubject: Re: Permission to reference your web site.To: Josef Von Niederhausern <josef.von@>Hello Josef,?Yes you may use it.?Thanks,Donnie James----- Original Message ----- From:Josef Von NiederhausernTo:admin@Sent: Monday, August 02, 2010 7:47 AMSubject: Permission to reference your web site.Sir or Madam,For our senior design project we are building a coil gun.? Your website is very informative and helpful we are grateful to you for that. We would like your permission to use your images as figures in our write up. Of course we will credit your work and list your website, , as a reference.Thank You,Josef VonDirected to use: for permission from TIRE: Permission to use content?7/30/10 Ronald Wilsonron.wilson@To brian.hoehn@knights.ucf.eduFrom:Ronald Wilson (ron.wilson@)Sent:Fri 7/30/10 12:52 AMTo: brian.hoehn@knights.ucf.edu (brian.hoehn@knights.ucf.edu)Brian:Please do so.ron?From: brian.hoehn@knights.ucf.edu [mailto:brian.hoehn@knights.ucf.edu] Sent: Tuesday, July 27, 2010 4:28 PMTo: Ronald WilsonSubject: Permission to use content?Ron Wilson,My Electrical Engineering senior design group at the University of Central Florida is doing a project which includes a FPGA device. I would like to ask for your permission to use some figures and images from the following article. of the information used will be credited to your website. Thank you,BrianHoehnUniversity of Central FloridaRE: Permission requests?7/28/10 ?Marc.McCom?b@microchip?.comMarc.McComb@Add to contactsTo brian.hoehn@knights.ucf.eduFrom:Marc.McComb@Sent:Wed 7/28/10 7:58 PMTo: brian.hoehn@knights.ucf.eduAttachments, pictures and links in this message have been blocked for your safety. Show content | Always show content from this senderHi Brian:?Thanks for your email. Please visit this webpage that should answer your questions: you have any questions please let me know. ?Regards,?Marc McCombAcademic Program Sales Engineer?2355 West Chandler Blvd., Mailstop 9-BChandler, AZ85224-6199?office: 480-792-4391mobile: 480-478-5676?Need more information on Microchip's Academic Program or would like to become a Partner? Visit academic for more information.??From: brian.hoehn@knights.ucf.edu@MICROCHIP Sent: Tuesday, July 27, 2010 3:51 PMTo: University; Eric Lawson - C11906Subject: Permission requestsHello,My Electrical Engineering senior design group at the University of Central Florida is designing a coil gun for our project. We may be using one of your products and would like to ask for permission to include some of Microchip's data sheets, including figures and diagrams within the data sheets. All information used in the report from your website and data sheets with be credited to Microchip. Thank You,BrianHoehnUniversity of Central FloridaRE: Permission to reference your web site.?7/26/10 To 'Josef Von Niederhausern', chic0lindo@, brian.hoehn@knights.ucf.edu, gorvyng@From:Barry Hansen (barry@)Sent:Mon 7/26/10 4:07 PMTo: 'Josef Von Niederhausern' (josef.von@)Cc: chic0lindo@; brian.hoehn@knights.ucf.edu; gorvyng@Attachments, pictures and links in this message have been blocked for your safety. Show content | Always show content from this senderHi Josef (and everyone!),Thanks for checking, you are welcome of course to reference my coilgun website. Are you at the Univ of Central Florida? I’m not very familiar with it, but it must be a great school if they have anything to do with coilguns. ?Have a great day,Barry Hansen?From: Josef Von Niederhausern [mailto:josef.von@] Sent: Monday, July 26, 2010 8:03 AMTo: barry@Cc: chic0lindo@; brian.hoehn@knights.ucf.edu; gorvyng@Subject: Permission to reference your web site.?Mr. Hansen,For our senior design project we are building a coil gun.? Your website is very informative and helpful we are grateful to you for that. We would like your permission to use your images as figures in our write up. Of course we will credit your work and list your website, , as a reference.? The carbon copies listed are my co-designers.Thank You,Josef Von Niederhausern? HI Brian,You can accept this email as permission to use the datasheet in your project.Thank you,Cynthia Cynthia Zamorski?? Legal CounselXilinx, Inc.?? 2100 Logic Drive?? San Jose, California 95124(408) 879-4638?? Mobile (408) 892-189Quoting gorvy <gorvy@knights.ucf.edu>:> I am really interest in the content you mention in " Control of?> Stepping motors" and some of the graphs are very helpful for me to?> explain the how to control the stepping motor. so I want to ask you?> kindly if it's possible to use some of the graphs on my paper for my?> project. let me know. thank you.You are welcome to selectively quote and selevtively borrowillustrations from my material on the web, on the condition thatyou properly cite your sources and give appropriate credit inthe tradition of good scholarship. Thank you for asking.-- Doug Jones-- jones@cs.uiowa.eduAppendix B - References[1]Xilinx (2010) FPGA and CPLD Solutions, [2]MicroChip Technology Inc. (2010) PIC family of Microcontrollers Research , [3]Texas Instruments Inc. (1995-2010) TI MSP430, [4]Atmel Corporation (2010) Atmel AVR [5]Steve Trahey (2008) Choosing a code wheel: A detailed look at how encoders work[6] Douglas W. Jones “Micro stepping of Stepping Motors” [7] Jieun Kwon and Yuncheol Baek “Real-time Interactive Media Design with Camera Motion Tracking” [8] Ted T.Lin “Understand Stepper Parameters Before Making Measurements” [9] Orientalmotor “AC or DC? Brushed or Brushless?”[10] Andrew Caballero & Ian Stine “Auto-Targeting Sentry Gun with Friend/Foe Recognition”[11] Pridgets Products for USB Sensing and Control (2010), [12]Servo Motor Control (2009), [13] “Programming-Computer Vision Tutorial” C- M files or Codefunction [S] = fuse(AWG)% given A and S % Wire Sizes used in Fuses% % The Standard Handbook for Electrical Engineers lists the following formula:% % 33 * (I/A)^2 * S = log( (Tm - Ta) / (234 + Ta) + 1 )% * I = current in Amperes% * A = area of wire in circ. mils% * S = time the current flows in seconds% * Tm = melting point, C (copper's melting point is 1083 C)% * Ta = ambient temp, CA = (5*92^((36-AWG)/39))^2;Ta = 27;Tm = 1083;rs= log10((Tm - Ta)/(234 + Ta) + 1 );srs = rs*(A^2)/33;S = (srs/.001)^.5;function [ dn ] = AWG_dn( AWG )% finds the diameter of AWG in mmdn = .127*92^((36-AWG)/39);function [ area ] = AWG_An_Meter( AWG )area = (pi/4)*(.001*AWG_dn( AWG ))^2;function [ B ] = B_tesla_midcoil_j(l,r1,r2,i,AWG)% B_tesla_midcoil_j(l,r1,r2,i,AWG)u0 = 1.26*10^-6; % permability of free spacen1=sqrt(r2^2+(l/2)^2)+r2; % neumeratord1=sqrt(r1^2+(l/2)^2)+r1; % denominatordn= AWG_dn(AWG)*.001; % diameter of wire (meters)rn = dn/2; % radius of wire (meters)layers=floor((r2-r1)/2/dn); % number of layersturnlayer = floor((l)/dn); % number of turns (linear)n = layers*turnlayer; % total turns% disp('winding density')n_density = 1/l*n; % turn density per meter % disp('Feild')wire_cross_area = pi*(rn)^2; % in meters^2coil_cross_area = l*(r2-r1); %coil cross sectional areaj = i*n/coil_cross_area; %current density for coil cross sectional areaB = u0*j*l/2*log(n1/d1);function [ An ] = AWGturnmeter( AWG )% A is cross sectional area d is diameter in inches% d = .005*92^((36-AWG)/39);% A = pi/4*d^2;D = (0.000127*92^((36-AWG)/39));An=1/D;function [B] = B_tesla_midcoil(l,r1,r2,i,AWG)% B_tesla_midcoil(l,r1,r2,i,AWG)% Finds the on axis strength of magentic field in the midoimt of a coil% also finds: inducatnce, turn density, u0 = 1.26*10^-6; % permability of free spacen1=sqrt(r2^2+(l/2)^2)+r2; % neumeratord1=sqrt(r1^2+(l/2)^2)+r1; % denominatordn= AWG_dn(AWG)*.001; % diameter of wire (meters)rn = dn/2; % radius of wire (meters)layers=floor((r2-r1)/2/dn); % number of layersturnlayer = floor((l)/dn); % number of turns (linear)n = layers*turnlayer; % total turns% disp('winding density')n_density = 1/l*n; % turn density per meter % disp('Feild')B = u0*i*n/2/(r2-r1)*log(n1/d1); % streangth of field in tesla's% z = i*n/(r2-r1) %%%Checker% lh = u0/2*log(n1/d1)function [ B ] = B_tesla2(l,r1,r2,x,i,AWG)% B_tesla2(l,r1,r2,x,i,AWG)% l length of coil, r1 inner radius, r2 outter radius, x2 begining coil% to point B, x1 end of coil to point B, n number of turns, i current,% rho is conductor resisitivity in units of ohms-length must match that% of r1, lambda is cross sectional area of wire, P is Power% G is maximum when alpha = 3 and beta = 2% rho= 1.724*10^-8; % resistivity of copper per hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.htmlrho= 1.68*10^-8; % resistivity of copper per wikiu0 = 1.26*10^-6;x1 = x-l/2;x2 = x+l/2;B_alpha = r2/r1;B_beta = l/(2*r1);B_gamma = (x1+x2)/(2*r1);dn= AWG_dn(AWG)*.001; % diameter of wire (meters)rn = dn/2; % radius of wire (meters)layers=floor((r2-r1)/2/dn); % number of layersturnlayer = floor((l)/dn); % number of turns (linear)n = layers*turnlayer; % total turnsn_density = 1/l*n % turn density per meter%%%%%%%%%%%%%%%%%%% finds average radius of layerscount = 1;atotal = -rn+r1;while count ~= layers+1; atotal = atotal + dn; a_tot(1,count) = atotal; %finds the average radius of the layers from center axis count = count+1;end%finds the average radius of the layers from center axisaverage_radius_of_turn = sum(a_tot)/layers; %finds the average radius of the layers from center axisc= r2-r1; induct = .8*average_radius_of_turn^2*n^2/(6*average_radius_of_turn+9*l+10*c) % inductance of coil in Hlength_of_wire = sum(2*pi*turnlayer*a_tot(1,:));wire_cross_area = pi*(rn)^2 % in meters^2% resistance = rho*length_of_wire/wire_cross_area % linear resistanceP=i*i*resistance %power consumed by coillambda = (r2^2-r1^2)/r2^2; % end cross area% lambda = (r2-r1)*l; % length wise crossarean1= B_alpha + (B_alpha^2 + (B_gamma + B_beta)^2)^.5; %numerator 1d1 = 1 + (1 + (B_gamma + B_beta)^2)^.5; %denominator 1n2= B_alpha + (B_alpha^2 + (B_gamma - B_beta)^2)^.5; %numerator 2d2 = 1 + (1 + (B_gamma - B_beta)^2)^.5; %denominator 2C1 = (8*pi*B_beta*(B_alpha^2-1))^-.5; % factor 1G2 = (B_gamma + B_beta)*log1p(n1/d1); % factor 2G3 = -(B_gamma - B_beta)*log1p(n2/d2); % factor 3G = C1*(G2+G3); % unitless G factorB1=((P*lambda)/(r1*rho))^.5; % coefficient 2B = u0*B1*G; % feild strength in teslasfunction [ B ] = B_tesla(r1,r2,l,x,n,i)% B_tesla(r1,r2,l,x,n,i)u0 = 1.26*10^-6;x1 = x-l/2;x2 = x+l/2;n1=sqrt(r2^2+x2^2)+r2;d1=sqrt(r1^2+x2^2)+r1;n2=sqrt(r2^2+x1^2)+r2;d2=sqrt(r1^2+x1^2)+r1;n = 1/l*n;g = x2*log(n1/d1)-x1*log(n2/d2)B = u0*i*n/2/(r2-r1)*g; ................
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