Unit 2: ANALOG ELECTRONICS
Unit 2: ANALOG ELECTRONICS
Time: 38 Hours
Description
In this unit students perform a series of circuit construction activities to develop an understanding of analog components and circuit design. Students develop practical skills in troubleshooting and continue to demonstrate safe work practices in an electronic shop environment. Students learn the basis for electronic signal production and manipulation, particularly in the area of sound amplification and reproduction. Subsequently, students examine the procedures in creating printed circuit boards and the manufacturing processes in communication electronics.
Expectations
The following expectations are covered in this unit’s activities :
|Strand |Overall |Specific |
|Theory and Foundation |TVF.02.1W TVF.03.1W |TF2.05.1W TF2.07.1W |TF2.13.1W TF2.14.1W |
| | |TF2.08.1W |TF3.01.1W TF3.02.1W |
| | |TF2.10.1W TF2.12.1W |TF3.01.1W |
| | | |TF3.02.1W |
|Skills and Processes |SPV.01.1W |SP1.01.1W SP1.02.1W |SP2.05.1W SP2.06.1W |
| |SPV.02.1W |SP1.03.1W SP2.01.1W |SP3.01.1W SP4.01.1W |
| |SPV.04.1W |SP2.02.1W SP2.04.1W |SP4.02.1W SP4.03.1W |
|Impact and Consequences | |IC2.01.1W |IC2.02.1W |
See Appendix E for full description of TGJ3E expectations
HRDC NOC Specialized Skills
The activities in this unit are designed for occupations that require troubleshooting electrical signals, designing and building analog circuits, writing test reports, reading schematics and using testing equipment. Though most careers identified by HRDC as related to electronics can benefit from the skills and knowledge addressed in this unit, the following career categories are directly related to the activities in this unit:
|2133 |Electrical and Electronics Engineers |
|2241 |Electrical and Electronics Engineering Technologists and Technicians |
|2242 |Electronic Service Technicians (Household and Business Equipment) |
|2243 |Industrial Instrument Technicians and Mechanics |
|2244 |Aircraft Instrument, Electrical and Avionics Mechanics, Technicians and Inspectors |
|7245 |Telecommunications Line and Cable Workers |
|7246 |Telecommunications Installation and Repair Workers |
|7247 |Cable Television Service and Maintenance Technicians |
|7332 |Electric Appliance Servicers and Repairers |
|9483 |Electronics Assemblers, Fabricators, Inspectors and Testers |
|9484 |Assemblers and Inspectors, Electrical Appliance, Apparatus and Equipment Manufacturing |
Activities
The activities in this unit are designed to be sequential to give the student progressive challenges in circuit design, build and testing. Students learn the theory of electronics and analog circuitry through hands-on projects that are based on signal processing, measuring and calculation electrical parameters, and use of test instrumentation. By concentrating on the audio and visual portion of the electromagnetic spectrum, these projects are related to media productions in communications technology, and will give students the basic principles of telecommunications and photonics in later projects.
|Activity |Activity Title |Time (minutes) |
|1 |The 555 Timer |480 |
|2 |Audio Electronics: Signal Processing |600 |
|3 |Project Loudspeaker |1200 |
Prior Knowledge
Students should have some knowledge of basic test equipment and electronic principles as outlined in Unit 1. Teachers should review acceptable Internet use policies as established by the school board.
Before working in a shop environment, students must be aware of general shop rules and requirements, as well as safety rules for specific tools and machines (e.g. safe operation, guard placement and the use of safety glasses). Teachers should review safety rules discussed in Unit 1, and initiate discussion of new tools and processes to be used in this unit. Teachers must verify student’s knowledge of any new safety issues through either a signed “safety passport’ (Appendix B), and/or a check on safety knowledge. Shops must be kept professionally clean at all times. It is to the student's benefit to spend time at the end of each class to prepare the lab for the next class.
Unit Planning Notes
The activities in this unit are designed to provide the opportunity for students to see how electronic circuits and components perform, (particularly analog circuits), how to solve problems with electronic circuits, how to problem solve with prototyping and design procedures, and how to manufacture circuits using industry procedures.
Students are expected to maintain the technician’s test bench developed in Unit 1. (Refer to Unit 1: Activity 2). Teachers must remind all students that they must not turn on any circuit until it is approved and signed off. This unit requires a hands-on approach to circuit design and building, and therefore requires the preparation of physical resources, test equipment and associated tools.
If not already completed, the following tools should be prepared before initiating the activities:
|Test bench equipment: |Shop Equipment |
|oscilloscope |(for speaker cabinets or project boxes) |
|multimeter |table saw (with dado blades for rabbit cuts (optional)) |
|signal generator (suggested) |jointer |
|DC power supplies |sander |
|batteries |jigsaw/scrollsaw |
|circuit simulation software |router |
|wire cutters |Dremel tool |
|wire strippers |nibbler (optional) |
|needle nose pliers |nail gun (optional) |
|safety eyewear |power screwdriver (optional) |
|Supplies: | |
|555 timer |bins (i.e. Tupperware-type) for parts of student projects |
|556, 558 timers, (optional) |solder equipment and associated supplies |
|magnet wire or choke coils |(tweeter/midrange/woofer/subwoofer) as required |
|variety of diodes, transistors |MDF sheets, stick lumber for loudspeaker cabinets |
|variety of inductors |variety of capacitors and/or variable capacitors |
|L-Pads |variety of resistors and/or variable resistors |
|speaker wire | |
|loudspeakers | |
|jumper wires, or multi-conductor wire | |
|breadboards | |
Aspects of these activities are integrated with curriculum from other courses. For example: English expectations of report writing, research and technical documentation skills, Physics and Mathematics expectations for understanding the theoretical aspects of electronics overlap with the material in this unit. Computer courses, in particular Computer Engineering, are useful in dealing with knowledge of computer-based electronic applications and control systems. Design Technology will enhance understanding of consumer electronic product design and the product development process.
It would be beneficial if representatives from local manufacturing industries present in class or conduct tours. Visiting local colleges, university or private electronics labs are recommended for students to develop an awareness of typical electronics facility operations.
Teaching / Learning Strategies
This unit continues the hands-on project orientation with a variety of teaching and learning strategies, as described in Unit 1. Students will use their test bench setups (from Unit 1) in activities that incorporate designing/ building/ troubleshooting of analog electronic circuits.
Teachers should present students with an itemized list of tasks that need to be accomplished, including timeframes. Students must keep a daily log of their activities. Teachers should arrange activities to keep students busy at all times, i.e. report writing or drawing/illustration while awaiting paint drying or computer resources. Teachers may elect to post the current status of project tasks in the room for planning purposes.
The activities in this unit are designed as "Just In Time" activities, in other words, the facts or skills that are required for a particular task are taught just before they are needed. For example, when students require a resistor for their first circuit (Activity 1), they are presented with the resistor colour code and the use of resistive elements to control voltage or current to use in the activity.
Activity 1 engages students in investigating the physical parameters and usage of typical electronic devices and components. The first activity, using a 555 timer, it takes the student through the entire process of component designing, breadboard prototyping, computer based circuit simulation, and mathematical calculations in circuit design. Activity 2 involves an investigation of electrical signals through the fabrication and testing of an audio amplifier and loudspeaker crossover filter network. Activity 3 involves fabrication of printed circuit boards (PCB). Through these activities, students should have a good grounding in electronic circuit design and components and the measurement and manipulation of electrical signals.
Teachers can accommodate the variable learning rates of students by allowing increased time for activities, enhancing or compacting course content, assisting during evaluation processes, and/or facilitating peer-tutor assistance where possible.
Note: A construction shop has a different set of safety issues than the electronics facility. Teachers must be qualified to operate in a construction shop facility. A team-teaching approach may be necessary to take advantage of teachers’ individual strengths.
Assessment / Evaluation
Teachers must ensure that all students have an opportunity to demonstrate their mastery of the course expectations individually, even when working in a group. This can be accomplished through one-on-one daily conferencing, daily journal log entries, individual deliverables such as reports or presentations, or individually signed elements of reports or forms.
Assessment is an on-going daily process that may include review of a daily/weekly log, (See Appendix D: Sample Daily Log), observations of efforts in problem solving and critical thinking, participation in discussions and self and/or peer critiques. Students are evaluated on project deliverables such as completed circuit designs, test or project synopsis reports, and presentations based on the assessment charts presented in each activity.
Resources
|Crocodile Clips Simulation Software |Electronic Workbench Simulation Software |
|Spectrum Educational Supplies |111 Peter Street, Suite 801 |
|125 Mary Street |Toronto, Ontario M5V 2H1 |
|Aurora, Ontario L4G 1G3 |Phone: 416-977-5550 ext. 255 |
|Phone: 905-727-6265 | |
|Reference Texts |Reference Materials |
|Electronic Dictionary |Telephone Directories |
|Art of Electronics |Industrial Directories |
|Radio Shack booklists | |
Internet Sites
How Things Work-
Nuts and Volts Magazine-
The 555 Timer
Unit 2 Activity 1
480 minutes
Description
Students construct an astable oscillating circuit using the 555 timer IC. Students compare the results of formula calculations, circuit simulation software and circuit measurement results to ensure accuracy of calculations and measurements. Students develop a series of circuits based on the 555 timer IC to develop skills in circuit design, fabrication, testing and troubleshooting.
Strands and Expectations
|Strand |Overall |Specific |
|Theory and Foundation |TVF.02.1W |TF2.07.1W |TF3.01.1W |
| | |TF2.08.1W |TF3.02.1W |
| | |TF2.10.1W | |
|Skills and Processes |SPV.01.1W |SP1.01.1W SP1.02.1W |SP2.05.1W SP2.06.1W |
| |SPV.02.1W |SP1.03.1W SP2.01.1W |SP3.01.1W SP4.01.1W |
| |SPV.04.1W |SP2.02.1W SP2.04.1W |SP4.02.1W SP4.03.1W |
|Impact and Consequences | |IC2.01.1W |IC2.02.1W |
See Appendix E for full description of TGJ3E expectations
HRDC NOC Specialized Skills
2133 Electrical and Electronics Engineer
2133.1.1 2133.1.2 2133.1.3 2133.1.4 2133.1.6
2241 Electrical and electronics engineering technologists and technicians
Technologists 2241.1.1 2241.1.2 2241.1.3 2241.1.5
Technicians: 2241.2.1 2241.2.2 2241.2.4 2241.2.5 2241.2.6
2241.2.7 2241.2.8
2242 Electronic service technicians (household & business equipment)
2242.1.3 2242.1.4
7332 Electric appliance servicers and repairers
Small Appliance Repairers 7332.1.4
7245 Telecommunications line and cable workers
7245.1.5
7246 Telecommunications installation and repair workers
Telecommunications Service Testers 7246.3.2
9483 Electronics assemblers, fabricators, inspectors and testers
Assemblers 9483.2.2 9483.3.5 9483.4.1 9483.1.1
See Appendix F for full description of NOC Specialized Skills
HRDC NOC Essential Skills
|numeracy |decision making |writing |
|problem solving |reading |using documents |
See Appendix A for Essential Skill rubrics
Prior Knowledge
As students will use the test bench established in Unit 1, prior knowledge includes:
1. basic test equipment identification and associated terminology;
2. basic safety procedures, (but should be reviewed in any case);
3. simple algebraic equation manipulation;
4. simple graphic and report production techniques.
Planning Notes
Teachers must arrange the following equipment and supplies. Safety glasses should be made available to participants of the equipment tear down, ideally all students should be issued safety eyewear.
|Test bench equipment: |Supplies: |
|Oscilloscope |555 timer |
|function generator (for demo) |556, 558 timers, (optional) |
|stop watch |variety of capacitors and/or variable capacitors |
|frequency counter |variety of resistors and/or variable resistors |
|multimeter |jumper wires, or multi-conductor wire |
|capacitance meter |breadboards |
|DC power supplies or batteries (9V) |bins (i.e. Tupperware-type) for parts of student projects |
|circuit simulation software |small speakers for sound generator experiments |
|wire cutters | |
|wire strippers | |
|needle nose pliers | |
|safety eyewear | |
|calculators | |
Other resources necessary for this activity include:
• teacher-developed handout detailing assignment requirements, (Appendix 2.1.1);
• handout detailing schematic circuit for a 555 oscillating multivibrator (Appendix 2.1.2)
• handout detailing test report format (Appendix 2.1.3)
• sample working prototype (optional)
By introducing electronic circuit components and circuit basics in the context of solving a specified problem, students can be taught the basics of analog electronics and electronics theory to be applied in any further circuit-design problem. This hands-on approach is meant to take the place of "theory lessons" conducted in isolation of the application. Teachers will demonstrate components and techniques and allow time for students to apply this knowledge to the task of circuit building
Teaching / Learning Strategies
In this activity students build a 555 timer-circuit (multi-vibrator) from a schematic diagram to a specified frequency. This activity aims to develop the skills of schematic reading, circuit prototyping and testing, troubleshooting and test report writing. Students build a variety of circuits based on the 555 timer.
Stage 1
The first stage of this activity is divided into three components:
1. Calculating frequency of a 555 timer circuit using the mathematical formula;
2. Calculating frequency of a 555 timer circuit using circuit simulation software;
3. Calculating frequency of a 555 timer circuit by constructing a physical circuit and measuring resulting frequency.
In using these 3 methods, students can observe the importance of verifying results through a variety of methods. Students will also review the methods used to verify and troubleshoot electronic circuits.
Students are arranged in pairs or teams as required by classroom resources. (Ideally students work individually).
Students are handed the Project Design Brief, outlining the schematic of the multi-vibrator, the deliverables and associated timelines (Appendix 2.1.1). Teachers describe the procedures of prototyping circuits using breadboards, and reinforce their knowledge of Ohm's Law and the physical relationship of voltage/current/resistance. Electron flow and the basic elements of circuits such as power source, conductive paths and load are discussed. Basic passive components are demonstrated: resistor, capacitor, LED, IC, power source and other load components such as bells, speakers, buzzers, motors, etc.
Teachers describe the concepts of frequency, amplitude and electromagnetic waves. Teachers demonstrate the types of waves (square, sine, sawtooth) and the meaning of frequency and amplitude through the use of a function generator and oscilloscope. Teachers then describe how the 555 timer can be used to generate a square wave signal of determined frequency dependent on the values of external resistors and capacitors.
Teachers illustrate the formula for calculating frequency of the multivibrator, and set the target frequency for the student's first circuit, (a visible frequency such as 1 or 2 Hz). Students then calculate the values for components for their circuit by manipulating the equation. Students record their calculations in their test report notes.
Teachers demonstrate the symbols of a schematic diagram and their physical counterparts. After a brief introduction to resistors and the resistor colour code, Students then locate the appropriate values for their circuits. This is repeated for capacitors and LEDs. Safe handling and operational parameters of the 555 are discussed and given to students. Students collect their components and assemble the circuit with assistance from the teacher.
When teachers give the OK, students power their circuit and time their resultant frequency (through stopwatch or frequency counter). Students use troubleshooting techniques to determine problems if required. When successful, students will record results in their test report notes.
If available, students use circuit simulation software (such as Electronic Workbench, Tina or Crocodile Clips) to build a virtual representation of their circuit. Students run the simulation and obtain the frequency using the measured values of the physical components.
Students compare notes of the three methods of determining frequency, and make observational comments as to the closeness of the values. If any result is significantly apart from the others, or all three are different, then the student must record these results and diagnose the reasons for the discrepancy.
Stage 2
Students are given circuit diagrams of other circuits based on the 555 timer. The students task is to complete each circuit and compose a test report. These circuits include: (see Resources for this activity for circuit ideas)
• astable multivibrator with speaker in place of LED
• pulse generator (given a frequency, determine component values)
• toy organ
• chirp generator
• sound effects generator
• tone burst generator
• stepped-tone generator
• monostable or one-shot trigger
• cascaded timer (using two 555s or a 556)
• intervalometer
• event-failure alarm
• frequency divider
Teachers may elect to test student's knowledge of vocabulary through oral presentations or written tests.
Vocabulary
Students should be able to define the following terms, components and/or processes:
|analog electronics |digital electronics |resistance |
|resistor |ohms |colour code |
|Voltage |EMF |DC |
|Current |ampere |load |
|IC |555 timer |diode |
|LED |capacitance |capacitor |
|Farads |frequency |amplitude |
|period |pulse width |duty cycle |
|monostable |astable multivibrators |switch debouncer |
|electromagnetic wave |sine wave |square wave |
|Hertz (Hz) |function generator |voltmeter |
|ohmmeter |capacitance meter |frequency counter |
|oscilloscope |time base |beadboard |
|SI measurements: pico, micro, milli, kilo, mega | |
Assessment / Evaluation
Students will be assessed and evaluated on several aspects of this project:
• demonstration of vocabulary knowledge (verbally, oral presentation, written test);
• test reports (initiative, depth of content, presentation, originality);
• verbal presentation (depth of understanding of subject, quality and effort of presentation).
555 Timer Assessment Rubric
|Criteria |Level 1 |Level 2 |Level 3 |Level 4 |
|Students will: | | | | |
|Knowledge |Student displays limited |Student demonstrates some |Student demonstrates |Student exhibits exceptional |
|TVF.02.1W |knowledge of identified |knowledge of identified |considerable knowledge of |knowledge of concepts, |
|TF2.07.1W |concepts and terminology |concepts and terminology |identified concepts and |terminology and/or |
|TF2.08.1W | | |terminology |relationships |
|TF2.10.1W | | | | |
|TF3.01.1W | | | | |
|TF3.02.1W | | | | |
| |Demonstrates little initiative|Demonstrates limited |Demonstrates considerable |Demonstrates exceptional |
| |in learning terminology and |initiative in learning |initiative in learning |initiative in learning |
| |relationships |terminology and relationships |terminology and relationships |terminology and relationships |
|Inquiry |Only with constant |With occasional supervision |Safely and methodically |Safely and methodically |
|SPV.02.1W SP2.04.1W |supervision, safely assembles|and reminders, safely |assembles circuits |assembles circuits |
|SP2.05.1W |circuits |assembles circuits | | |
|SP2.06.1W | | | | |
| | | | | |
| |Demonstrates limited |Demonstrates some initiative |Demonstrates considerable |Demonstrates considerable |
| |initiative in troubleshooting |in troubleshooting circuits |initiative in troubleshooting |initiative in troubleshooting |
| |circuits | |circuits |circuits |
| |Needs constant supervision to |Needs supervision to follow |Follows procedures |Works efficiently and |
| |follow procedures |procedures but improves |independently and accurately |independently, helps others to|
| | | | |work efficiently |
|Communication |Student's report demonstrates |Student reports demonstrates |Student reports clearly |Student communicates |
|SP1.03.1W |limited clarity, knowledge of |some accuracy and requires |communicates the ideas and |meaningful information with an|
|SP2.01.1W |facts or accurate conclusions |some further effort to |issues and demonstrates |exceptional degree of clarity |
|SP3.01.1W | |communicate more clearly |insightful conclusions |& with a strong sense of |
|SP4.02.1W | | | |audience and purpose |
| |Reports and diagrams contain |Reports and diagrams contain |Considerable care in producing|Exceptional care in producing |
| |major heading omissions, |minor omissions, requires some|reports and diagrams, all |reports and diagrams, contains|
| |requires rewrite |remedial work. |elements covered. |evidence of extra research |
|Application |Student works safely and |Student works safely & cleanly|Student works safely, |Student assists and supervises|
|SPV.01.1W |cleanly only with constant |with some required supervision|cooperatively & cleanly with |others to work safely & |
|SPV.04.1W |supervision & reminders | |minimal supervision and |cleanly, demonstrates |
|SP1.01.1W | | |demonstrates some leadership |leadership skills |
|SP1.02.1W | | |skills | |
|SP2.02.1W | | | | |
|SP4.01.1W | | | | |
|SP4.03.1W | | | | |
| |Requires further work in |Requires more effort in |Demonstrates clear and concise|Demonstrates initiative in |
| |mathematical and scientific |mathematical and scientific |mathematical and scientific |applying mathematical and |
| |reasoning |reasoning in reporting |reasoning in reporting |scientific reasoning |
| | | | |throughout work |
Accommodations
Strategies to accommodate the variety of learning styles in the classroom may include:
• additional handouts to illustrate discussion material;
• additional time allowance for completion of poster materials;
• flexibility in acceptable formats for presentations;
• additional research assignments;
• concentrated assistance with concept identification;
• additional one-on-one time by teacher or peer tutors;
• alternative activities to meet student needs;
• providing enrichment opportunities such as requirements for more in-depth research.
If required, consultations should be held with students, parents, resource, guidance and special education departments when required to assist in creating an educational plan (IEP) for individual students.
Resources
Simulation Software
|Crocodile Clips |Electronic Workbench |
|Spectrum Educational Supplies |111 Peter Street, Suite 801 |
|125 Mary Street |Toronto, Ontario M5V 2H1 |
|Aurora, Ontario L4G 1G3 |Phone: 416-977-5550 ext. 255 |
|Phone: 905-727-6265 | |
| | |
Books, Texts
– Mims, Forrest M. Engineer's Mini-Notebook, (series). Radio Shack/Archer, USA. 555 Timer IC Circuits, 1984. Cat. 276-5010
– Petruzella, Frank D. Introduction to Electricity and Electronics. McGraw-Hill Ryerson, Toronto, 1986. ISBN 0-07-548899-X (Book 1), ISBN 0-07-548900-7 (Book 2)
Websites
Electronics for Beginners- ourworld.homepages/g_knott/
Alex’s Electronic Test Bench (glossary and resource catalog)- ~alexx/index.htm
ePanorama, portal for everything electronics-
Williamson Labs information on electronics- home.htm
Appendix 2.1.1: 555 Timer Design Brief
| | |
|Title: |Project: The 555 Timer |
| |Design and build a timer circuit for a |Course: |Communications Technology |
|Activity: |variety of digital and analog circuits | |Grade 11 Workplace |
| |8 -10 hours |Date: | |
|Time: | | | |
|RATIONALE |
| |
|Many circuits including digital switches, timers, counters, light and sound effects generators require a timing mechanism to produce a steady |
|digital pulse. One of the time-honoured methods uses a 555 IC, a linear IC that can be wired to produce a variety of pulses. Wiring a timer |
|using the 555 is a great project to learn about basic digital circuits, RC (resistor-capacitor) circuits, using test instruments such as |
|multimeters, capacitance meters and oscilloscopes, breadboarding and troubleshooting, all skills that are required to develop more sophisticated |
|electronics. This project will lead to many devices used on future electronics projects. |
|THE ASSIGNMENT |
| |
|Develop a timing circuit using the 555 timer IC. Use timing formulas to determine the frequency of the circuit and test instrumentation to |
|verify a working circuit. |
|LEARNING EXPECTATIONS: You will: |
| |
|design and construct electronic circuits using discreet components |
|test and verify operations of electronic circuits |
|calculate periods and frequencies using mathematical formula |
|use computer simulations to calculate circuit performance |
|write technical test reports |
|TOOLS AND MATERIALS |
|555 Timer handout |calculator |multimeter |oscilloscope |
|frequency counter |capacitance meter |breadboard |alligator clips |
|555 timer IC |variety of capacitors |resistors |LEDs |
|mini-speakers |power supply (9V battery or bench |simulation software | |
| |supply) | | |
|EVALUATION |
|# |Deliverable |# periods |Mark weighting (%) |Notes |
|1 |Test report |2 |40 |Math calculations, diagrams, test results, |
| | | | |observations |
|2 |Completed circuits |5 |40 |Clean, precise work |
|3 |Vocabulary test/report |2 |20 | |
| |TOTALS |9 |100 | |
|NOTES |
| |
|ALL CIRCUITS MUST BE INSPECTED BY TEACHER BEFORE POWER IS APPLIED |
| |
|All reports must be word processed, diagrams or images to be created using illustration or CAD software. |
| |
|Each individual in a group or team must hand in their own reports. |
| |
|WHEN IN DOUBT, ASK! |
|VOCABULARY |
| | | |
|analog electronics |555 timer |square wave |
|digital electronics |breadboard |frequency/Hertz |
|resistance/ohms |voltmeter |period |
|capacitance/Farads |ohmmeter |pulse width |
|capacitor |capacitance meter |duty cycle |
|resistor |frequency counter |monostable and astable multivibrators |
|colour code (resistors) |oscilloscope |switch debouncer |
|voltage/volts |time base |SI measurements: pico, micro, milli, kilo, mega |
|IC |signal | |
|PROJECT |
|STEP |STUDENT ACTIVITIES |
|1 |Read the 555 Timer Project Handout and review circuit designs to become familiar with and note the terminology, calculations and |
| |circuit diagrams. Calculate the pulse width or frequency of the circuit you have been given. Retain all calculations and notes for |
| |the final report. |
|2 |Obtain components, breadboard, etc. and build the circuit required. Obtain permission from the instructor to apply power to circuit.|
| |Test and troubleshoot till you have a working circuit. SHOW COMPLETE CIRCUIT FOR MARKING |
|3 |Develop the test report and include circuit diagrams, calculations and results in an engineering test report fashion. Include log |
| |sheets. Include vocabulary if required. HAND IN REPORT FOR MARKING |
|4 |Construct and test circuits based on the 555 and 556 timer ICs as given by your instructor. |
Appendix 2.1.2: 555 Timer Handbook
THE 555 TIMER PROJECT
Many devices, including clocks, timers, counters and even special effects generators require a source of constant pulses to do their job. This can be accomplished with oscillators or timers...in which the 555 timer is a common example. The 555-timer chip can be used for a variety of projects which require steady square pulses such as digital electronic mechanisms, timers, counters, switches, flashers and sound effects generators.
The 555 Timer Project will introduce you to basic electronics: components such as resistors, capacitors, diodes, ICs; breadboarding and wiring and measurement tools such as the multimeter, the oscilloscope, the frequency counter and the capacitance meter. After completing this project you should be ready to tackle the most complex circuits... it’s all down hill from here!
THE 555 TIMER
The timer can perform a variety of functions based on the circuitry surrounding it. It has 3 modes:
1. Monostable: “one-shot”, “pulse stretcher”; takes an analog signal such as a switch and produces a clean square pulse. It is used in switch debouncing, required in digital electronics for example.
1. Bistable: can flip from one state (high/low, on/off,...etc.) to the other; not used in timing circuits or from timer ICs.
2. Astable: “multivibrator”, “clock”, “square wave generator”; from input signal such as switch, will constantly flip from one state to the other in sequence.
We will be building an astable circuit. 555s operate from +4.5 V to +18 V, with +9 V to +12 V the most stable, however it is also great for +5 V TTL operations in digital electronics. We will concentrate on +9 V, using a 9-V battery.
NOTES:
For critical timing, 1% tolerance resistors should be used. Use a variable resistor to tune resistances if real critical. Capacitors generally have wide tolerances and plastic film is better. For capacitance from 1uF to 10uF, use tantalums. Over 10uF may require electrolytic, which have wide tolerances. Also note that the capacitor to ground on pin 5 is not required, but desirable for stability. A 0.01uF capacitor is desirable.
THE 555 PINOUT (see diagram)
The 555 Timer IC is an 8 pin DIP. The pinouts are noted below:
|Pin 1: |GROUND |connected to ground (reference voltage) |
|Pin 2: |TRIGGER |input, initiates timing sequence |
|Pin 3: |OUTPUT |output of IC, connected to other devices |
|Pin 4: |RESET |cancels current timing sequence |
|Pin 5: |EXT. CONTROL |not generally used, can be used for external control voltages |
|Pin 6: |THRESHOLD |sets internal switching point |
|Pin 7: |DISCHARGE |discharges external capacitor, senses end of cycle |
|Pin 8: |Vcc |positive voltage supply (+4.5 V to +18 V) |
[pic]
Notes:
MONOSTABLE MODE (see diagram)
The monostable mode is useful for “cleaning up” a switch such as a push button or toggle. These analog devices produce spikes which can produce unwanted effects. The monostable timer takes the switch’s signal and produces a clean square output. The monostable 555 timer requires a capacitor and a resistor to set the pulse width. Note that the output is LOW until triggered by a negative input pulse, then it will go HIGH with a length of pulse specified by:
T=1.1(R1)(C1)
where R1 is in ohms and C1 is in Farads.
For example:
R1=22Kohms
C1=0.33µF
T=1.1(R1)(C1)
T=1.1 X 22000 Ω X 0.00000033 F
T=0.008s
T=8 ms
|MONOSTABLE EXAMPLES |R1 |C1 |Pulse |
|Circuit 2 |100 K |25µF |2.75 ms |
|Circuit 3 |470 K |50µF |25 s |
|Circuit 4 |1 M |100µF |110 s |
This circuit can produce from pulse widths from about 10ms to the limits of R1 and C1. Try ranges of R1 from 100 Ω to 13M Ω, 10K to 1M are the best for stability and reliability. C1 should be 100pF minimally to avoid stray capacitance, use capacitors in parallel to create greater capacitance.
[pic]
Notes:
ASTABLE MODE (see diagram)
The 555 can be used in an astable mode to create clock circuits, tone generators, frequency dividers, light triggered timers, event failure alarms, etc. As the input goes HIGH, the output flips from HIGH and LOW in a continuos cycle. Two time periods must be calculated: the HIGH time period and the LOW time period, (the length of time it stays HIGH and LOW respectively). A complete cycle from HIGH to LOW is known as the period (T).
|TH = 0.693(C1)(R1 + R2) |
|TL = 0.693(C1)(R2) |
|TOTAL Period (T) = TH + TL |
|Frequency = [pic] |
therefore:
|Frequency = [pic] |
|EXAMPLE ASTABLE |R1 |R2 |C1 |Freq. (Hz) |
|Circuit 1 |470 K |470 K |0.22 µF |4.65 Hz |
|Circuit 2 |470 K |470 K |50 µF |0.02 Hz |
|Circuit 3 |2.2 K |4.7 K |0.01 µF |12 453 Hz |
Note that increasing capacitance decreases frequency. Also note that if the LED stays “ON”, it may that the frequency is too high for you to see the blinking. Try experimenting with different combinations.
The DUTY CYCLE is the ratio of TH/T, and is an indication of the amount of time the cycle is HIGH compared to LOW. A square wave would have a 50% duty cycle. Making the value of R1 very small compared to R2 will produce a close square wave.
The upper limit of timing with a 555 timer is approximately 10-15 minutes. Cascading 555s or using the dual timer (556) or quad timer (558) can provide longer timing sequences. Combining timers and connecting speakers can produce a variety of sound effects generators. (Use a capacitor in series with the speaker to protect it from DC voltages).
OTHER NOTES
Resistors: devices that restrict electric flow and act as “taps”, controlling the amount of flow (current) in a circuit. Is used to protect devices from high currents, direct current to circuit pathways and divide voltage (electrical pressure) into different circuit pathways. Measured in Ohms.
Capacitors: devices that can store a charge, (negative and positive) and hence act as temporary batteries. Caps are used as power storage; in series with resistors to change timing, (by holding and then slowing the release of current); and are used as filters to absorb low frequencies and pass on high frequencies. Capacitance in measured in Farads, most commonly micro-Farads (uF) or pico-Farads (pF).
LED: light emitting diode, emits light when forward biased.
[pic]
Notes:
555 Timer Project: Some Notes Concerning Capacitors
Capacitors come in a wide variety of types, materials, sizes, shapes, labels, colour codes, etc. and may be confusing for the beginning electronics student. They also come in fairly wide tolerances, so the use of a capacitance meter is recommended. Capacitance is measured in Farads, usually in microfarads (µF) or picofarads (pF). Capacitors also have a voltage rating, which is how much voltage it can take, in practise half that number is used for the working voltage. Variable caps are called trimmers.
A capacitor is constructed of two metal plates separated by an insulator called a dielectric. It stores electrical energy by building up voltages on the metal plates (opposite charges). Dielectrics used are air, mica, plastic, ceramic and metal oxide, and in the old days by oiled or waxed paper. The size of the metal plates, the distance between them and the dielectric material determines how much charge it can hold, called the capacitance. For large plates, they are rolled in cylinders to save space.
MICA CAPACITORS
high working voltages…determined by size, sealed against moisture, capacitance and tolerance marked by colour dots
CERAMIC AND MYLAR
ceramic: disc or cylindrical shapes, mylar: “drop” shaped, colour code can be bands, or dots, otherwise marked numerically
if whole number: picofarads, if decimal number: microfarads, Colour code always in picofarads, tolerance may be marked by letter, not marked is +/- 20%
miniature capacitors may have picofarad value marked in three letter code; first two numbers are digits followed by multiplier (or number of zeroes), i.e. 104Z
| |Tolerance |
|Letter |10 pF or LESS |OVER 10 pF |
| |(in +/- pF) |(in +/- %) |
|C |0.2 | |
|D |0.5 | |
|F |1.0 |1 |
|G |2.0 |2 |
|J | |5 |
|K | |10 |
|M | |20 |
|COLOUR |DIGITS |MULTIPLIER |Tol. > 10pF, in % |Tol. < 10pF, in pF |
|black |0 |1 |20 |2.0 |
|brown |1 |10 |1 | |
|red |2 |100 |2 | |
|orange |3 |1000 | | |
|yellow |4 | | | |
|green |5 | | | |
|blue |6 | |5 |0.5 |
|violet |7 | | | |
|gray |8 |0.01 | |0.25 |
|white |9 |0.1 |10 |1.0 |
ELECTROLYTIC CAPACITORS
usually greater than 1.0 µF, mostly polarized, .i.e., one lead is marked either negative or positive. Must be connected with correct polarity. Values often marked, sometimes with MFD, meaning µF.
Appendix 2.1.3: Engineering Test Report Format
All engineering test reports must include:
Overall
COVER SHEET, with: company name and logo
project title
your name
team member names
class
date
EACH PAGE includes: company name
class
date
Contents
PURPOSE OF PROJECT
DESCRIPTION OF PROJECT
include graphics, sketches, drawings, charts,
all graphics labeled and/or titled
METHODS includes calculations
PROJECT RESULTS
PROJECT SYNOPSIS analysis of results
what could be done better
how to improve next project results
how you could improve as a scientist or engineer
DAILY LOG compiled from daily journal entries
hours worked on project
Appendix 2.1.4: ELECTRONIC INSTRUMENTATION PRIMER
Multimeter
Measures voltage (“electron pressure”) in Volts (V)
Measures resistance (the “flow control”) in Ohms
Measures current (“the flow”) in Amperes (A)
These three make up Ohm’s Law: V=IR (Voltage= current x resistance). NOTE: resistance must be measured without power to the circuit, and current must be measured as part of the circuit: i.e. electrons must flow the meter to be measured.
Capacitance Meter
Measures capacitance, the amount of static charge that can be stored in a capacitor. Capacitance is measured in Farads, typically micro- or pico-Farads. (µF or pF)
Inductance Meter
Measures the amount of inductance, or reverse voltage generated by a coil or choke. Inductance is a factor of electromagnetics and is measured in Henrys (H). Can be thought of resistance due to a changing current/voltage.
Oscilloscope
Measures time varying signal, shows voltage change over time. Usually has 2 or more channels to compare signals.
Frequency Counter
Counts pulses or signal peaks in a time varying signal
Function Generator
A function generator (or signal generator) supplies a test signal or waveform to test circuitry. It usually can supply a square wave, (to test digital circuits), a sawtooth wave and a sine wave.
DC Power Supplies
DC Power Supplies supply clean direct current or steady voltage to the circuit, like a battery though cleaner and more stable.
Electron Motion
Electronic devices operate by the movement of electrons through conductors, e.g. wires, and electronic components. Electron parameters are described by the following basic quantities:
Charge
Symbol: q, unit: coulomb (C)
Charge is an amount of electrons. One coulomb is the charge of 6x1018 electrons.
Current
Symbol: I, unit: ampere or amp (A)
Current is the rate of flow of charge, i.e., the number of coulombs flowing past a point per second. One amp is equal to one coulomb per second.
Voltage
Symbol: V or E, unit: volt (V)
Voltage (also called potential, potential difference, potential drop, or electromotive force - EMF) is the electronic potential energy between two points, and is the driving force that causes charge to flow. One volt is defined as the potential difference that requires one joule of energy to move one coulomb of charge. Voltage is always measured relative to some other point in a circuit, e.g., the potential across a resistor. Voltage measurements made at a single point in a circuit are made relative to the earth (ground), which is assigned an "absolute" voltage of zero.
Impedance
Symbol: Z, unit: ohm
Impedance is the degree to which an electronic component impedes the flow of current. In general it is a frequency-dependent quantity. The impedance of a resistor is also called its resistance. The impedance of capacitors and inductors is also called their reactance. Capacitors consist of a dielectric material separating two parallel plates. They are used to hold charge or to transmit an ac signal and block a dc signal.
Capacitance
Symbol: C, unit: farad (F)
Q = CV, I = C(dV/dt)
Capacitance is the amount of charge a capacitor can hold per volt.
The ability of a dielectric material between conductors to store electricity when a difference of potential exists between the conductors. The unit of measurement is the Farad “F”, which is the capacitance value that will store a charge of one Coulomb when a one volt potential difference exists between the conductors. In AC, one Farad is the capacitance value which will permit one Ampere of current when the voltage across the capacitor changes at a rate of one Volt per second.
Inductance
Symbol: L, unit: henry (H)
Inductance is ... V = L(dI/dt)
An inductor is a coil of wire that stores energy as a magnetic field. The coil is usually wrapped around an iron-containing core, which increases the amount of energy that can be stored by the inductor.
Audio Electronics: Signal Processing
Unit 2 Activity 2
800 minutes
Description
Students develop bridge rectifiers, filters, and transistor and/or operational amplifier (op-amp) amplifiers to condition and amplify audio level signals. Through this activity, students learn the basics of semiconductors and their applications, as well as processing electromagnetic signals. This activity leads into Activity 3: Project Loudspeaker, in which audio signals are filtered and used to power speaker systems.
Strands and Expectations:
|Strand |Overall |Specific |
|Theory and Foundation |TVF.02.1W |TF2.05.1W TF2.10.1W |TF2.14.1W TF3.01.1W |
| | |TF2.12.1W TF2.13.1W |TF3.02.1W |
|Skills and Processes |SPV.01.1W SPV.02.1W SPV.04.1W|SP1.01.1W SP1.02.1W |SP2.05.1W SP2.06.1W |
| | |SP1.03.1W SP2.01.1W |SP3.01.1W SP4.01.1W |
| | |SP2.02.1W SP2.04.1W |SP4.02.1W SP4.03.1W |
|Impact and Consequences | |IC2.01.1W | |
See Appendix E for full description of TGJ3E expectations
HRDC NOC Specialized Skills
2133 Electrical and electronics engineers
2133.1.1 2133.1.3 2133.1.4 2133.1.6
2241 Electrical and electronics engineering technologists and technicians
Technologists:2241.1.1 2241.1.2 2241.1.3 2 241.1.4
2241.1.5 2241.1.6
Technicians: 2241.2.1 2241.2.2 2241.2.4 2241.2.5 2241.2.6
2241.2.7 2241.2.8
2242 Electronic service technicians (household and business equipment)
2242.1.1 2242.1.2 2242.1.3 2242.1.4 2242.1.5
2243 Industrial instrument technicians and mechanics
2243.1.2 2243.1.3 2243.1.4
2244 Aircraft instrument, electrical and avionics mechanics, technicians and inspectors
Aircraft Instrument Mechanics and Technicians 2244.1.1 2244.1.2
Avionics Mechanics and Technicians 2244.2.1
7245 Telecommunications line and cable workers
7245.1.4 7245.1.5
7246 Telecommunications installation and repair workers
Telephone Installers and Repairers 7246.1.1
Switch Network Installers and Repairers 7246.2.1 7246.2.2 7246.2.3
Telecommunications Service Testers 7246.3.2 7246.3.4 7246.3.5
Telecommunications Equipment Technicians 7246.4.2 7246.4.3
7247 Cable television service and maintenance technicians
Cable Television Service Technicians 7247.1.3
Cable Television Maintenance Technicians 7247.2.3
7332 Electric appliance servicers and repairers
Small Appliance Repairers 7332.1.3 7332.1.4
Major Appliance Repairers/Technicians 7332.2.3 7332.2.4 7332.2.5
9483 Electronics assemblers, fabricators, inspectors and testers
Assemblers 9483.1.1 9483.1.3
Inspectors 9483.3.1 9483.3.4 9483.3.5
Testers 9483.4.1 9483.4.3 9483.4.5
9484 Assemblers and inspectors, electrical appliance, apparatus and equipment manufacturing
Assemblers 9484.1.6
Inspectors and Testers 9484.2.1 9484.2.1
See Appendix F for full description of NOC Specialized Skills
HRDC NOC Essential Skills
|reading |job-task planning |problem solving |
|decision making |numeracy |working withothers |
See Appendix A for Essential Skill rubrics
Prior Knowledge
The test bench established in Unit 1 and equipment setup as in Unit 2: Activity 1 will be used in this activity. Prior knowledge includes:
– basic test equipment identification and associated terminology;
– basic safety procedures, (but should be reviewed in any case);
– prototyping circuits from schematics;
– schematic symbols of basic components;
– simple algebraic equation manipulation;
– simple graphic and report production techniques.
Planning Notes
In addition to the equipment and supplies listed in Unit 2: Activity 1, the following items are required:
|assorted diodes, transistors, op-amps |capacitance meter |
|relays, SCR's etc. if required for specific projects |4 ohm/8 ohm speakers |
|microphones (for amplifier input, optional) |AC step down transformers, (optional) |
|sound level meter (optional) |silicone wafers (for demonstration) |
There is a wide variety of amplifier circuits available. Teachers may choose to purchase kits (such as a 1W audio amplifier) to allow students to quickly practise signal processing and measurement techniques. See the end of this activity for examples, and Resources for sources of kits and components.
Other resources necessary for this activity include:
• teacher-developed handout detailing assignment requirements, (Appendix 2.2.1);
• handout detailing schematic circuits for amplifiers, etc. (Appendix 2.2.2)
• handout detailing test report format (see Appendix 2.1.3 in previous activity)
• sample working prototype circuits (optional)
The P-N junction, diode and transistor theories are covered in this activity. While some theory should be discussed before initiating circuit breadboarding, most semiconductor component and circuit basics are discussed in the context of solving a specified problem. This hands-on approach is meant to take the place of "theory lessons" conducted in isolation of the application. Teachers will demonstrate components and techniques, then allow time for students to apply this knowledge to the task of circuit building.
Teaching / Learning Strategies
This activity connects from Unit 2: Activity 1- The 555 Timer. Teachers may elect to establish new groups or teams for this activity or retain groups from the previous activity.
Audio Electronic Communications
Teachers initiate discussions related to the audio frequency portion of the electromagnetic spectrum (20Hz to 20MHz), continuing from Unit 2: Activity 1. Teachers should set-up a frequency generator, oscilloscope and loudspeaker to illustrate the sound associated with frequency to give students a sense of the audio spectrum. During the demonstration, teachers should point out the controls of the oscilloscope and function generator.
Teachers discuss the propagation of sound from source to home or car receivers. Teachers can use illustrations, physical equipment or a combination to highlight key concepts. Teachers should discuss the following concepts:
• audio spectrum characteristics (decibel scale)
• signal filtering, (concepts of attenuation, low pass, band pass and high pass of signal strength)
• RF propagation through antennas, (how signals are broadcast through the air)
• electromagnetic signal receiving (how antennas pick up and receive energy, problems in reception)
• transformation of electrical energy to mechanical reproduction in loudspeakers (parts of the electromagnetic speaker, operation of an electromagnetic coil)
Students are then asked to develop one or more of the above concepts in a short research report, including sketches or illustrations.
Rectifiers and Diodes
Teachers demonstrate amplitude and frequency modulation of sine waves. Teachers then demonstrate a half-wave rectifier to initiate investigations into the diode and the PN junction. Teachers can use the example of the LED to illustrate diode action. If time permits, a simple demonstration of a seven-segment display may also be used.
Students then construct a full-wave rectifier using discrete diodes. Note: teachers may elect to rectify stepped-down AC power sine waves, and discuss transformers and their operation at this time.
Capacitors are re-introduced (from Unit 2: Activity 1) for their function of filtering ripples. Students complete circuits and develop graphs showing the following:
1. unprocessed sine wave;
2. sine wave through half rectifier;
3. sine wave through full rectifier;
4. sine wave through full rectifier and capacitor filter;
5. sine wave through full rectifier and capacitor-choke filter (optional).
At this point, teachers may decide to have students construct a 5V regulated power supply from 60Hz AC. (optional task)
Bipolar and FET Transistor Amplifiers
Teachers continue discussion of semiconductors by extending discussions on the PN junction to the PNP and NPN junction. The properties of a transistor to act as a solid state switch and an amplifier of small signals is illustrated by constructing simple circuits and demonstrating the signals on the oscilloscope.
Students are then given circuit diagrams of basic transistor amplifiers to construct and produce a final presentation of their circuit work. Students are asked to produce a final report on their completed circuits.
Op-Amp Amplifier
Linear IC op amps are useful to demonstrate sound amplification. Teachers discuss a circuit diagram of a typical 741 or 380 op amp (perhaps using microphone input), and ask students to construct an inverted amplifier or voltage comparator. Students demonstrate their circuits to the class and complete a simple report on the results of their circuit testing.
Students to hand in a vocabulary list or write a formal test:
Vocabulary
Students should be able to define the following terms, components and/or processes:
|audio frequency |semiconductor |PN Junction |
|diode |forward bias |reverse bias |
|LED |zener voltage |seven-segment display |
|transistor |emitter/collector/base |NPN/PNP |
|current gain |heat sink |RF |
|AM/FM |rectifier |transformer |
|half-wave rectifier |full-wave rectifier |inductance |
|filter |choke |waveform |
|cathode |anode |amplifier |
|integrated circuit |linear IC |Op amp |
|comparator | | |
Assessment / Evaluation
Students will be assessed and evaluated on several aspects of this project;
• functional quality of circuits (clean and detailed work, safe procedures)
• Test Report on circuits (initiative, depth of content, presentation, originality)
• presentation (demonstration of depth of knowledge and research)
Assessment Rubric for Circuit Report, Diagrams and Presentation
|Criteria |Level 1 |Level 2 |Level 3 |Level 4 |
|Students will: | | | | |
|Knowledge |Student displays limited |Student demonstrates some |Student demonstrates |Student exhibits exceptional |
|TVF.02.1W |initiative in demonstrating |adequate initiative in |considerable initiative in |initiative and depth in |
|TF2.05.1W |knowledge of identified |demonstrating knowledge of |demonstrating knowledge of |demonstrating knowledge of |
|TF2.10.1W |equipment concepts, |identified equipment concepts,|identified concepts, |identified concepts, |
|TF2.12.1W |terminology and symbols; may |terminology and symbols; may |terminology and symbols; no |terminology and symbols; shows|
|TF2.13.1W |be missing important elements |be missing minor elements |missing required elements |evidence of further research |
|TF2.14.1W | | | | |
| |Missing some important details|Missing minor details of |Demonstrates knowledge of |Demonstrates extensive |
| |on communication systems as |communications systems as |communications systems as |knowledge of communications |
| |prescribed |prescribed |prescribed |systems beyond those |
| | | | |prescribed |
|Inquiry |Demonstrates some knowledge of|Demonstrates safe handling of|Demonstrates thorough and safe|Demonstrates ability to assist|
|SPV.01.1W |safe handling of |troubleshooting procedures, |handling of troubleshooting |others in following safe and |
| |troubleshooting procedures but|but requires remedial help in |procedures |thorough testing and |
| |requires constant remedial |following instructions | |troubleshooting procedures |
| |help in following instructions| | | |
|Communication |Report and presentation |Report and presentation |Report and presentation |Report and presentation |
|SP1.03.1W |demonstrates limited clarity |demonstrates adequate clarity |clearly communicates all |creatively communicates |
|SP2.01.1W |of information, knowledge of |of information (may have some |required concepts and ideas, |meaningful information with an|
|SP4.01.1W |vocabulary basics |content and/or formatting |demonstrates knowledgeable |exceptional degree of clarity |
|SP4.02.1W | |errors requiring remediation);|vocabulary |beyond required elements |
| | |adequate or basic knowledge of| | |
| | |vocabulary demonstrated | | |
|Application |Demonstrates some knowledge |Demonstrates adequate |Demonstrates working knowledge|Demonstrates additional |
|SPV.04.1W |into scientific and |knowledge into scientific and |into scientific and |research into scientific and |
|SP1.01.1W |mathematical principles but |mathematical principles |mathematical principles |mathematical principles |
|SP1.02.1W |requires remediation in |but may require some | | |
|SP2.02.1W |important details |remediation in minor details | | |
|SP4.01.1W | | | | |
|SP4.03.1W | | | | |
Assessment Rubric for Circuit Building
|Criteria |Level 1 |Level 2 |Level 3 |Level 4 |
|Students will: | | | | |
|Knowledge |Demonstrates understanding of |Demonstrates understanding of |Demonstrates understanding of |Demonstrates thorough and |
|TVF.02.1W |only some key terms, component|most key terms, component |all key terms, component |comprehensive understanding of|
|TF2.10.1W |functions |functions |functions and unit values |all terminology; component |
|TF3.01.1W | | | |functions and unit values |
|TF3.02.1W | | | | |
| |Student displays limited |Student demonstrates some |Student demonstrates |Student exhibits exceptional |
| |initiative in proper use of |adequate initiative in proper |considerable initiative in |initiative in use of |
| |terminology and symbols, |use of terminology and |proper use of terminology and |terminology and symbols and |
| |demonstrating knowledge of |symbols, demonstrating |symbols, demonstrating |demonstrating knowledge of |
| |identified concepts and |knowledge of identified |knowledge of identified |identified concepts and |
| |techniques |concepts and techniques |concepts and techniques |techniques |
|Inquiry |Demonstrates proper and safe |Demonstrates proper and safe |Demonstrates proper and safe |Establishes exceptional clean |
|SPV.02.1W |use of testing equipment with |use of testing equipment with |use of testing equipment as |and safe use of testing |
|SP2.04.1W |some important exceptions |minor exceptions |required |equipment beyond normal |
|SP2.05.1W | | | |requirements |
|SP2.06.1W | | | | |
| |Demonstrates some knowledge of|Demonstrates safe handling of |Demonstrates thorough and safe|Demonstrates ability to assist|
| |safe handling of testing, |testing, troubleshooting and |handling of testing, |others in following safe and |
| |troubleshooting and recording |recording procedures, but |troubleshooting and recording |thorough testing, |
| |procedures but requires |requires remedial help in |procedures |troubleshooting and recording |
| |constant remedial help in |following instructions | |procedures |
| |following instructions | | | |
|Communication |Test report requires important|Test report requires minimal |Test report is clear and |Test report contains |
|SP1.03.1W |remedial work; contains |remedial work; contains some |contains all required elements|researched elements beyond |
|SP2.01.1W |missing elements or errors, |minor missing elements or |without error, accurate |requirements; demonstrates |
| |limited documentation of |errors, mostly accurate |documentation of process |professional level work & |
| |process |documentation of process | |effort, accurate documentation|
| | | | |of process |
|Application |Requires constant prodding to |Requires some minimal prodding|Works well with colleagues in |Goes out of way to assist |
|SPV.01.1W |work with colleagues in |to work with colleagues in |completing assignment |others in completing |
|SPV.04.1W |completing assignment |completing assignment | |assignments |
|SP1.01.1W | | | | |
|SP1.02.1W | | | | |
|SP2.02.1W | | | | |
|SP4.01.1W | | | | |
|SP4.03.1W | | | | |
|IC2.01.1W | | | | |
| | | | | |
| | | | | |
| |Displays some major errors in |Displays minimal errors in |Displays correct measurement|Advanced knowledge of |
| |measurement techniques or |measurement techniques and/or |techniques and calculations |measurement techniques and |
| |calculations |calculations | |precision calculations |
| |Demonstrates some trouble in |Can identify all important |Can identify all hazards and |Can identify all general and |
| |identifying important hazards|hazards and demonstrates |demonstrates proper safety |specific hazards and |
| |and demonstrates proper safety|proper safety procedures with |procedures at all times |demonstrates a thoroughness in|
| |procedures with a high level |a low level of supervision | |applying proper safety |
| |of supervision required |required | |procedures at all times, |
| | | | |including before and after |
| | | | |class |
Accommodations
Teachers must use discretion in the depth of project material covered in this activity. There are plenty of circuit designs that can be developed for more advanced students, or teachers may elect to limit the amount of circuits to be built. All students should be able to demonstrate knowledge and skills in audio physics and sound reproduction technology.
Strategies to accommodate the variety of learning styles in the classroom may include:
• additional handouts such as drawings, terminology sheets, circuit designs, pictorial drawings, use of simulation labs to facilitate input;
• additional time allowance for completion of reports;
• flexibility in acceptable formats for reports;
• additional one-on-one time by teacher or peer tutors;
• concentrated one-on-one assistance in hands-on activities;
• additional research assignments;
• alternative activities to meet student needs;
• providing enrichment opportunities such as requirements for more in-depth research;
• additional responsibilities such as project or facility managers.
Resources
Suppliers
|ABRA Electronics Corp. |Addison Electronics Ltd. |
|5787 Pare |8018, 20e Avenue |
|Montreal, Que. H4P 1S1 |Montreal, P.Q. H1Z 3S7 |
|1-800-361-5237 |Tel: 514-376-1740 |
|Fax 514-731-0154 | |
|sales@abra- |Radio Shack |
| |(see local phone book) |
|Active Surplus |Electrolab Training Systems |
|345 Queen Street W. |Belleville |
|Toronto, Ontario M5V 2A4 | |
|1-800-465-KITS | |
Books, Texts
Petruzella, Frank D. Introduction to Electricity and Electronics. McGraw-Hill Ryerson, Toronto, 1986. ISBN 0-07-548899-X (Book 1), ISBN 0-07-548900-7 (Book 2)
Websites
Alex’s Electronic Test Bench (glossary and resource catalog)- ~alexx/index.htm
Electronics for Beginners- ourworld.homepages/g_knott/
ePanorama, portal for everything electronics-
Williamson Labs information on electronics- home.htm
Appendix 2.2.1: Audio Amplifier Design Brief
| | |
|Title: |Project: The Audio Amplifier |
|Activity: |Design and build an audio amplifier to amplify small |Course: |Communications Technology |
| |signals | |Grade 11 Workplace |
| | | | |
|Time: |8 -10 hours |Date: | |
|RATIONALE |
| |
|In any electronic-based communications product, small signals delivered through cable or antennas need to be amplified in order to drive speakers. By|
|utilizing transistors and/or operational amplifier (op amp) devices, you will design and develop a circuit that will take a small signal and amplify |
|the signal to drive speakers. This project helps you understand the uses and function of semi-conductor devices. You will use this knowledge to |
|design and build sound systems for a variety of uses. |
|THE ASSIGNMENT |
| |
|Develop a diode rectifier, as well as a transistor and/or op amp signal amplifier. |
|LEARNING EXPECTATIONS: You will: |
| |
|design and construct electronic circuits using discreet components |
|test and verify operations of electronic circuits |
|calculate periods and frequencies using mathematical formula |
|write technical test reports |
|TOOLS AND MATERIALS |
|amplifier circuit diagrams |calculator |multimeter |oscilloscope |
|frequency counter |capacitance meter |breadboard |variety of capacitors |
|resistors |LEDs |diodes |transistors |
|op amps (741 or 380) |mini-speakers |power supply (9V battery or bench |simulation software |
| | |supply) | |
|EVALUATION |
|# |Deliverable |Time (periods) |Mark weighting (%) |Notes |
|1 |Test report |2 |20 |Math calculations, diagrams, test results, |
| | | | |observations |
|2 |Completed circuits |4 |30 |Clean, precise work |
|3 |presentation |2 |30 |Knowledge of facts |
|4 |Vocabulary test/report |2 |20 | |
| |TOTALS |10 |100 | |
|NOTES |
| |
|ALL CIRCUITS MUST BE INSPECTED BY TEACHER BEFORE POWER IS APPLIED |
| |
|All reports must be word processed, diagrams or images to be created using illustration or CAD software. |
|Each individual in a group or team must hand in their own reports. |
| |
|WHEN IN DOUBT, ASK! |
|VOCABULARY |
|audio frequency |emitter/collector/base |filter |
|semiconductor |NPN/PNP |choke |
|PN Junction |current gain |waveform |
|diode |heat sink |cathode |
|forward bias |RF |anode |
|reverse bias |AM/FM |amplifier |
|LED |rectifier |integrated circuit |
|Zener voltage |transformer |linear IC |
|seven-segment display |half-wave rectifier |Op amp |
|transistor |full-wave rectifier |comparator |
| |inductance | |
|PROJECT |
|STEP |STUDENT ACTIVITIES |
|1 |Review the circuit diagrams and collect the necessary parts. Retain all calculations and notes for the final report. |
|2 |Obtain components, breadboard, etc. and build the circuit required. Obtain permission from the instructor to apply power to circuit.|
| |Test and troubleshoot till you have a working circuit. SHOW COMPLETE CIRCUIT FOR EVALUATION. |
|3 |Present your circuit to the class. Develop the test report and include circuit diagrams, calculations and results in an engineering |
| |test report fashion. Include log sheets. Include vocabulary if required. HAND IN REPORT FOR EVALUATION. |
|4 |Construct and test circuits based on transistor and op amp as given by your instructor. |
Appendix 2.2.2: 1-WATT AMPLIFIER- example circuit
[pic]
PARTS LIST
|R/1 4.7 Meg ohm Resistor |C/3 33 uf Electrolytic Capacitor |
|R/2 2.7 Meg ohm Resistor |C/4 0.022 uf Capacitor |
|R/3 33 ohm Resistor |C/5 220 uf Electrolytic Capacitor |
|R/4 1 K ohm Resistor |C/6 0.068 uf Capacitor |
|R/5 4.7 meg ohm Resistor |D/1 1N 4148 Diode |
|R/6 1.8 K ohm Resistor |P/1 Trim Pot |
|R/7 3.9 ohm Resistor |Q/1 2N 4401 NPN Transistor |
|R/8 10 ohm Resistor |Q/2 2N 4401 NPN Transistor |
|R/9 10 ohm Resistor |Q/3 2N 4403 PNP Transistor |
|R/10 10 ohm Resistor |Q/4 2N 4401 NPN Transistor |
|R/11 560 ohm Resistor |Q/5 2N 4403 PNP Transistor |
|R/12 22 ohm Resistor |W/1 Speaker Wire |
|C/1 0.22 uf Capacitor |SP/1 Speaker |
|C/2 0.22 uf Capacitor | |
Appendix 2.2.2: OP AMP AMPLIFIER- example circuit
[pic]
CIRCUIT NOTES
• R2 controls 741 preamplifier
• R3 controls speaker volume
• Use a fixed 100k resistor for R2 if circuit oscillates or gives distorted output
• Important: filter power supply connections with 0.1uf capacitors
Audio Electronics: Project Loudspeaker
Unit 2 Activity 3
1200 minutes
Description
Students design and construct a discreet component loudspeaker system with filter circuits, (crossover network). Through the design, construction and testing of filtered signal circuits, students gain an understanding of the principles of inductance, capacitance, electromagnetism, signal manipulation, sound frequency and sound reproduction in a communication system.
Strands and Expectations
|Strand |Overall |Specific |
|Theory and Foundation |TVF.02.1W TVF.03.1W |TF2.05.1W TF2.10.1W |TF3.01.1W TF3.02.1W |
| | |TF2.12.1W TF2.13.1W | |
|Skills and Processes |SPV.01.1W SPV.02.1W SPV.04.1W|SP1.01.1W |SP2.05.1W |
| | |SP1.02.1W |SP2.06.1W SP3.01.1W |
| | |SP1.03.1W |SP4.01.1W |
| | |SP2.01.1W |SP4.02.1W |
| | |SP2.02.1W |SP4.03.1W |
| | |SP2.04.1W | |
|Impact and Consequences | | | |
See Appendix E for full description of TGJ3E expectations
HRDC NOC Specialized Skills
2133 Electrical and electronics engineers
2133.1.2 2133.1.3 2133.1.6
2241 Electrical and electronics engineering technologists and technicians
Technologists: 2241.1.1 2241.1.3 2241.1.5 2241.1.6
Technicians: 2241.2.1 2241.2.2 2241.2.4 2241.2.5
2241.2.6 2241.2.8
9483 Electronics assemblers, fabricators, inspectors and testers
Testers 9483.4.1 9483.4.5
2242 Electronic service technicians (household and business equipment)
2242.1.1 2242.1.2 2242.1.3 2242.1.4 2242.1.5
2243 Industrial instrument technicians and mechanics
2243.1.2 2243.1.3 2243.1.4
9484 Assemblers and inspectors, electrical appliance, apparatus and equipment manufacturing
Inspectors and Testers 9484.2.1 9484.2.1
7332 Electric appliance servicers and repairers
Small Appliance Repairers 7332.1.3
Major Appliance Repairers/Technicians 7332.2.3 7332.2.5
7246 Telecommunications installation and repair workers
Telecommunications Service Testers 7246.3.4 7246.3.5
Telecommunications Equipment Technicians 7246.4.2
7245 Telecommunications line and cable workers
7245.1.4 7245.1.5
7247 Cable television service and maintenance technicians
Cable Television Service Technicians 7247.1.3
Cable Television Maintenance Technicians 7247.2.3
See Appendix F for full description of NOC Specialized Skills
HRDC NOC Essential Skills
|problem solving |computer use |decision making |
|job-task planning |finding information |numeracy |
See Appendix A for Essential Skill rubrics
Prior Knowledge
Students learn the basics of the electromagnetic spectrum in Activity 2. Prior knowledge therefore includes:
• Basic test equipment identification and associated terminology
• Basic safety procedures, (but should be reviewed in any case)
• Prototyping circuits from schematics
• Schematic symbols of basic components
• Simple algebraic equation manipulation
• Simple graphic and report production techniques
• Basic terminology of sound and electromagnetism
Planning Notes
This activity concentrates on the electronics behind the electromagnetic loudspeaker system. The project may lead into the actual construction of a loudspeaker enclosure, or may be restricted to using a prefabricated test box. Considerations before beginning this activity are:
• Constructing a loudspeaker enclosure entails a lengthy time allotment, (much more than allocated here), the use of a wood shop facility, a trained wood shop instructor, the materials and associated additional costs. Such an undertaking does take time and effort, and teachers may feel that it takes too much away from the rest of the course.
• Used commercial loudspeakers may be used, and therefore the activity would involve refurbishing the sound quality through the design and installation of a new crossover network. Optionally, kits may be purchased that would shorten the time and fund requirements.
• Students may be attracted to the program through this activity, and may want to have speaker systems built for their own use. Additionally, this activity could be used as a basis for a school or community project, or for a special event funding drive. You may decide to run this activity as a culminating performance task at the end of the semester.
• The expectations assessed and evaluated through this activity can be met through limiting the activity to the design and construction of the electronic circuits for pre-existing loudspeaker systems.
• A strategy to accomplish this project might be to develop a loudspeaker enclosure in an initial semester, then use that enclosure as a test system for following semesters.
• Alternatively, the design and construction of the enclosure or a set of test boxes may be accomplished in another course, such as Technological Design, Construction or Manufacturing in concert with the Communications Team.
The specific equipment and supplies required are:
• Component speakers such as tweeters, midranges, woofers, subwoofers
• Assorted chokes, capacitors, diodes, L-pads, fuses, speaker wire
• Breadboards, jumpers, perf boards, soldering stations
• Test bench instrumentation for audio spectrum signals
• sound level meter (optional)
• sound spectrum analyzer (optional)
• audio test CD or cassette (optional)
• enclosure or enclosure material if constructing speaker systems
Other resources necessary for this activity include:
• teacher-developed handout detailing assignment requirements, (Appendix 2.3.1);
• handouts/overheads detailing electromagnetic speaker parts and schematic circuits for crossover circuits, etc. (Appendix 2.3.2)
• handout detailing test report format (see Appendix 2.1.3 from previous activity)
• sample crossover networks (optional, from Addisons, Radio Shack, etc….see Resources)
Teaching / Learning Strategies
Loudspeaker Design
Teachers assemble a range of components including:
• Tweeter
• Midrange
• Woofer
• Subwoofer (optional)
• Dual cone car speaker (optional)
• Crossover network (best: multi-tap)
Referring to Appendix 2.3.1, teachers initiate discussion about the types of electrodynamic speakers. Teachers ask students to identify the obvious physical characteristics of the tweeter, midrange and woofer. Teachers discuss the physics behind sound reproduction, including electrodynamics, power vs. frequency, measuring sound with decibel scale, etc. Discussions are also initiated about frequency response, damping, distortion, power rating, impedance and dispersion.
Students are asked to take notes during discussions; teacher may provide forms with spaces to fill information to direct note taking. It is important to show students the physical speakers, in order for them to appreciate the concepts. If possible, the teacher may want to drive an old speaker through the audio spectrum to distortion to illustrate cone travel, clipping, power requirements to push air, etc.
Sound Physics
Teachers should reinforce earlier discussions on the audio spectrum. It would be instructive to use an audio test CD or frequency generator capable of 20Hz to 20MHz to drive types of speakers to illustrate frequency and amplitude concepts. The decibel scale is discussed. A sound-level meter would be useful here to demonstrate sound levels. An oscilloscope should be used to visually demonstrate changes in frequency. This topic leads into a demonstration of filter circuits.
Filter circuits
The concepts of crossover networks are addressed through a discussion and demonstration of the effects of passing a range of frequencies through a choke and a capacitor. Teachers describe the physics of what these components do to attenuate signals. Teachers demonstrate how to calculate component values to determine frequency cut-off values. (See Appendix 2.3.2) Students demonstrate signal attenuation with components, oscilloscope and function generators. Teachers give students various components and ask them to calculate cutoff frequencies, and demonstrate them on the test bench.
The orders of filter circuits are discussed and illustrated. Students are given a Design Brief to develop various filter circuits, (see Appendix 2.3.1). Students are then asked to develop a test report, evaluating what they have learned, and illustrating circuit diagrams.
Enclosures
Teachers discuss the terminology of speaker enclosure types, demonstrating enclosure types.
At this point, teachers either work to build a set of speaker enclosures, or else continue with constructing crossovers for existing speakers
Constructing Crossovers
Students are given specific frequency cutoff points and are asked to develop and test their circuit. Teachers evaluate student knowledge and skills in their circuit design. Once appraised, students build their circuit on perf board or equivalent. Students assemble and test the speaker system.
Assessment/Evaluation
Students will be assessed and evaluated on several aspects of this project;
• functional quality of circuits (clean and detailed work, safe procedures)
• Test Report on circuits (initiative, depth of content, presentation, originality)
• Presentation (demonstration of depth of knowledge and research)
Assessment Rubric for Project Loudspeaker
|Expectations |Level 1 |Level 2 |Level 3 |Level 4 |
|Students will: | | | | |
|Knowledge |Student displays limited |Student demonstrates some |Student demonstrates |Student exhibits exceptional |
|TVF.02.1W |initiative in demonstrating |adequate initiative in |considerable initiative in |initiative and depth in |
|TVF.03.1W |knowledge of identified |demonstrating knowledge of |demonstrating knowledge of |demonstrating knowledge of |
|TF2.05.1W |equipment concepts, |identified equipment concepts,|identified concepts, |identified concepts, |
|TF2.10.1W |terminology and symbols; may |terminology and symbols; may |terminology and symbols; no |terminology and symbols; shows|
|TF2.12.1W |be missing important elements |be missing minor elements |missing required elements |evidence of further research |
|TF2.13.1W | | | | |
|TF3.01.1W | | | | |
|TF3.02.1W | | | | |
| |Student displays limited |Student demonstrates some |Student demonstrates |Student exhibits exceptional |
| |initiative in proper use of |adequate initiative in proper |considerable initiative in |initiative in use of |
| |terminology and symbols, |use of terminology and |proper use of terminology and |terminology and symbols and |
| |demonstrating knowledge of |symbols, demonstrating |symbols, demonstrating |demonstrating knowledge of |
| |identified concepts and |knowledge of identified |knowledge of identified |identified concepts and |
| |techniques |concepts and techniques |concepts and techniques |techniques |
|Inquiry |Demonstrates proper and safe |Demonstrates proper and safe |Demonstrates proper and safe |Establishes exceptional clean |
|SPV.01.1W |use of testing equipment with |use of testing equipment with |use of testing equipment as |and safe use of testing |
|SPV.02.1W |some important exceptions |minor exceptions |required |equipment beyond normal |
|SP2.04.1W | | | |requirements |
|SP2.05.1W | | | | |
| | | | | |
| |Demonstrates some knowledge of|Demonstrates safe handling of |Demonstrates thorough and safe|Demonstrates ability to assist|
| |safe handling of testing, |testing, troubleshooting and |handling of testing, |others in following safe and |
| |troubleshooting and recording |recording procedures, but |troubleshooting and recording |thorough testing, |
| |procedures but requires |requires remedial help in |procedures |troubleshooting and recording |
| |constant remedial help in |following instructions | |procedures |
| |following instructions | | | |
|Communication |Report demonstrates limited |Report demonstrates adequate |Report clearly communicates |Report creatively communicates|
|SP1.03.1W |clarity of information, |clarity of information |all required concepts and |meaningful information with an|
|SP2.01.1W |knowledge of vocabulary basics|(content and/or formatting |ideas, demonstrates |exceptional degree of clarity |
|SP3.01.1W | |errors requiring remediation);|knowledgeable vocabulary |beyond required elements |
|SP4.01.1W | |adequate or basic knowledge of| | |
|SP4.02.1W | |vocabulary shown | | |
Project Loudspeaker rubric cont’d
|Application |Demonstrates some knowledge |Demonstrates adequate |Demonstrates working knowledge|Demonstrates additional |
|SPV.04.1W |into scientific and |knowledge into scientific and |into scientific and |research into scientific and |
|SP1.01.1W |mathematical principles but |mathematical principles but |mathematical principles |mathematical principles |
|SP1.02.1W |requires remediation in |may require some remediation | | |
|SP2.02.1W |important details |in minor details | | |
|SP2.06.1W | | | | |
|SP4.01.1W | | | | |
|SP4.03.1W | | | | |
| |Requires constant supervision,|Requires some supervision in |Keeps on task until |Demonstrates efficient use of |
| |but does accomplish task in |order to stay on task but does|completion, assists others on |time, organizes work team to |
| |time allotted |accomplish goals in time frame|team to accomplish goals |accomplish goals |
| | |allotment | | |
Accommodations
Teachers must determine the capabilities of their classrooms and use discretion in the depth of project material covered in this activity. Teachers may elect to limit the task to crossover network design and development, or extend the activity to design and build the entire system. All students should be able to demonstrate the knowledge and skills in audio physics and sound reproduction technology.
Strategies to accommodate the variety of learning styles in the classroom may include:
• additional handouts such as drawings, terminology sheets, circuit designs, pictorial drawings, use of simulation labs to facilitate input;
• additional time allowance for completion of reports;
• flexibility in acceptable formats for reports;
• additional one-on-one time by teacher or peer tutors;
• concentrated one-on-one assistance in hands-on activities;
• additional research assignments;
• alternative activities to meet student needs;
• providing enrichment opportunities such as requirements for more in-depth research;
• additional responsibilities such as project or facility managers.
Resources
Kits, Magazines, etc.
|Old Colony Sound Labs |Speaker Builder Magazine |
|PO Box 243 |PO Box 494, Dept LDC5 |
|Peterborough, NH 03458-0243 |Peterborough, NH 03458-0494 |
| | |
Suppliers
|Shopkit Industries (speaker kits) P.O Box 1573 |ABRA Electronics Corp. |
|Superior, Wisconsin USA 54880 |5787 Pare |
|Al Olson |Montreal, Que H4P 1S1 |
|ph. 1-800-236-4429 |1-800-361-5237 |
|ph. 1-715-392-5522 |Fax 514-731-0154 |
| |sales@abra- |
|Addison Electronics Ltd. (excellent source for speakers, etc.) |Active Surplus |
|8018, 20e Avenue |345 Queen Street W. |
|Montreal, P.Q. H1Z 3S7 |Toronto, Ontario |
|Tel: 514-376-1740 |M5V 2A4 |
| |1-800-465-KITS |
|Electrolab Training Systems |Radio Shack (crossovers) |
|Belleville |(see local phone book) |
| | |
Books, Texts
• Dickason, Vance. The Loudspeaker Design Cookbook. Audio Amateur Press, New Hampshire, 1995. ISBN 1-882580-100-9
• Petruzella, Frank D. Introduction to Electricity and Electronics. McGraw-Hill Ryerson, Toronto, 1986. ISBN 0-07-548899-X (Book 1), ISBN 0-07-548900-7 (Book 2)
Websites
The Speaker Building Page -
Audiomatica SA (manufacturer's of CLIO sound spectrum analyzer) –
-
Appendix 2.3.1: Project Loudspeaker Design Brief
| | |
|Title: |Project Loudspeaker |
| |Students design a crossover network for a three or two |Course: |Communications Technology |
|Activity: |way loudspeaker system | |Grade 11 Workplace |
|Time: |8 -10 hours |Date: | |
|RATIONALE |
| |
|Loudspeaker systems are ideal for demonstrating the physics and the concepts of electromagnetism, signal manipulation, test measurement systems and |
|signal reproduction. Through the design of a crossover network (a filter circuit), you will have the basic procedures to design and build any |
|electronic device that requires the transmission and receiving of electronic signals. |
|THE ASSIGNMENT |
| |
|You will design and build a crossover network for a two-way or three-way loudspeaker system. |
|LEARNING EXPECTATIONS: You will: |
| |
|manipulate electronic signals |
|calculate inductance and capacitance in order to direct signals to output devices |
|define and describe the types of audio speakers, enclosure types and physical parameters of speaker systems |
|test and analyze communication signals |
|describe the process of filtering electronic signals |
|illustrate circuit diagrams and write test reports |
|TOOLS AND MATERIALS |
|Crossover circuit diagrams |calculator |multimeter |oscilloscope |
|capacitance meter |inductance meter |breadboard |variety of capacitors |
|coils or chokes |resistors |fuses |L-Pads |
|audio amplifier |speakers (tweeter, midrange, |either test speaker enclosures or materials for fabricating speaker |
| |and/or woofer subwoofer) |enclosures |
|EVALUATION |
| |Deliverable |Time (periods) |Mark weighting (%) |Notes |
|# | | | | |
|1 |Test report |2 |20 |Math calculations, diagrams, test results, |
| | | | |observations |
|2 |Completed circuits |4 |30 |Clean, precise work |
|3 |Presentation |2 |30 |Knowledge of facts |
|4 |Vocabulary test/report |2 |20 | |
| |TOTALS |10 |100 | |
|NOTES |
| |
|ALL CIRCUITS MUST BE INSPECTED BY TEACHER BEFORE POWER IS APPLIED |
| |
|All reports must be word processed, diagrams or images to be created using illustration or CAD software. |
|Each individual in a group or team must hand in their own reports. |
| |
|WHEN IN DOUBT, ASK! |
|VOCABULARY |
|Audio frequency Inductance Midrange |
|Frequency response Tweeter Woofer |
|Amplitude Distortion Subwoofer |
|Power Clipping Enclosure |
|Decibels Hertz (Hz) Crossover network |
|Electromagnet Low pass filter L-pad |
|Coil Band pass filter Fuse |
|Choke Notch filter |
|Impedance High pass filter |
|capacitor Cutoff frequency |
|Capacitance Octave |
|PROJECT |
|STEP |STUDENT ACTIVITIES |
|1 |Review the circuit diagrams and collect the necessary parts. Retain all calculations and notes for the final report. |
|2 |Obtain components, breadboard, etc. and build the circuit required. Obtain permission from the instructor to apply power to circuit.|
| |Test and troubleshoot till you have a working circuit. SHOW COMPLETE CIRCUIT FOR MARKING |
|3 |Test circuits using speakers to listen for sound quality, and using meters to measure signal strength Develop the test report and |
| |include circuit diagrams, calculations and results in an engineering test report fashion. Include log sheets. Include vocabulary if|
| |required. HAND IN REPORT FOR MARKING |
|4 |Present your findings to class and instructor. |
Appendix 2.3.2: Support Materials for Project Speaker
PROJECT SPEAKER TERMINOLOGY
Sound pressure waves in fluids, gases or solids
Frequency number of peaks per given time period
Hertz unit of frequency, cycles per second (Hz)
Amplitude loudness or intensity of vibrations
Decibels -ratio of 2 sound amplitudes, (dB), logarithmic scale
-0dB: barely heard 1000Hz signal by human ear in quiet
environment
-change in 10dB: twice as loud
- 90dB: 109 or billion times louder
Sound
Pressure Level (SPL) amplitude of sound in decibels
Amplification increasing electrical signal amplitude
Echo (Reverberation) reflection of direct sound waves off of surfaces
PARTS OF ELECTRODYNAMIC SPEAKERS
(see diagram)
driver (coil and magnet)
frame or basket
bobbin
spider
suspension or surround
cone
dust cap
Piezoelectric speakers
Electrostatic speakers
TYPES OF SPEAKERS
Project Speaker
Woofers
low range, bass, 20 to 1000Hz
range from 4" to 16", usually 10" to 12"
made of felted paper, polypropylene
Midrange
broad spectrum, 1000Hz to 10kHz, most efficient 1kHz to 4kHz
best for voices, most instruments
range from 3" to 8"
paper, cloth, poly
some domed for wide dispersion
Tweeter
high or treble range, 4kHz to 20kHz
usually under 2"
paper, plastic, metals
suffer from narrow dispersion, horns, baffles, domes
used to disperse sound
Full Range
adequate for covering full spectrum
typically used in car systems
usually inexpensive
Coaxial/Triaxial
woofers and midranges or midranges and tweeters with
individual coils in common magnets
Whizzer Cones
woofers and midranges with separate cone attached to coil
improves frequency response
SPEAKER DESIGN FACTORS
Project Speaker
Power Rating
amount of power speakers can handle
rating in watts RMS
two ratings:
1) peak (short duration)
2) average (continuos)
if exceeded can overheat coil and cause permanent damage
improve by cooling systems, such as ferrofluid
most power absorbed by woofer (half of power between 75Hz and 500Hz)
typical woofer is 50W to 60W
Magnet Size
lager the magnet, the greater force to react to coil
usually 15 to 20 oz., some to 50 oz.
rare earth magnets best
Cone Material
cloth or paper distorts with age
poly lasts longer, takes more stress
Suspension
folded paper best for ported reflex
rolled polyfoam or butyl rubber more compliant for acoustical suspension
Impedance
resistance to AC signals, in ohms
most systems 8 ohms, some 4 ohms
depends on multiple speaker configuration
SPEAKER DESIGN PARAMETERS
Project Speaker
Frequency Response
range of frequencies an audio system can reproduce accurately
usually a variation of speaker output over the range of frequencies
flat means perfect response across spectrum
if dips in response- sound "colored"
measured in decibels (ratio of output power to input power)
the higher the dB, the greater the output power for any given input power
Sound Dispersion
spreading of sound leaving speaker
the wider the dispersion the better
speakers omnidirectional up to certain frequencies
tweeters worst
Dispersion limit frequencies:
15" 880Hz 4" 3.3kHz
12" 1.1kHz 2: 8kHz
8" 1.65kHz
Damping
cone should follow applied signal
unwanted motion due to unwanted signals should be damped out
speaker components that apply damping:
cone material (stiffness)
suspension (compliance to movement)
spider (made to restrict motion)
magnet (heavier = more shock absorbing)
enclosure (air pressure)
Sound Distortion
unwanted applied electrical and mechanical noise
changes or colours sound by altering or adding frequencies or amplitudes
Types:
Harmonic distortion:
– added frequencies in signal, or imperfect driver behavior at high volumes
Noise:
– damaged components, raspy sound, i.e., torn cone
Transient response:
– time delay in responding to rapid signal changes
Clipping:
– bottoming out of speaker, running out of travel, esp. woofers
CROSSOVER ELECTRONICS
Project Speaker
Wiring the Speaker
The louder it is, the more power, hence the larger (diameter) the wire required to prevent heat and reduce the voltage drop. Also the longer the distance, the larger the wire required (voltage drop).
|Wire Gauge |Capacity |
|AWG 14 |15A |
|AWG 16 |6A |
|AWG 18 |3A |
Speaker Polarity
General Rule: red = positive, black = negative or ground, (RCA plugs…note centre post polarity)
Impedance
Input and output impedance (frequency dependant resistance) must match, i.e. 8(, 4(
In series circuits, impedance doubles, in parallel circuits it halves.
L-Pads
better than fixed resistors to control volume of independent speakers in enclosures.
L-Pad: variable resistance, constant impedance
Fuses
used inline on the positive terminal to protect speaker from over-current load
A = [pic]
where A = fuse amperage, P = power of speaker in Watts, Z = impedance in ohms
Speaker Enclosures
too big: boomy sound
too small: flat bass sound
CROSSOVER NETWORKS
COMPONENTS
role of crossover is to protect tweeter or midrange from low freq. overload
crossover freq.: that freq. where you cut off response down to 3dB
Capacitors:
used to cutoff lows: (high pass filter), uses principle of RC lag
Coils:
cuts off highs, (low pass filter), uses principles of back EMF due to
magnetic field
TYPES OF CROSSOVERS
Note: common midrange crossover: 1500Hz-6000Hz
common tweeter crossover: 6000Hz-20kHz
2 kinds of crossover circuits: series and parallel circuits
crossovers named by number of drivers: 2 way or 3 way, etc.
3 kinds of crossover filters:
low pass
high pass
band pass
simplest: 1st order (cutoff slope 6dB/octave)
16. high pass capacitor in series with resistor
17. 3dB is where impedance of cap = impedance of tweeter
18. to move crossover point higher: use smaller capacitor
|Common 2 way |
|Woofer dia. |Freq. (Hz) |
|8” |2500 |
|10”-12” |1600 |
|Common 3 way |
|8” |1000/5000 |
|10”-12” |700/4500 |
|15” |600/4500 |
CALCULATING CAPACITOR (HIGH PASS) VALUE
C = 1/(2( f Xc)
or
C = 15900/(f Rt)
where Xc = capacitance reactance (reactance = “react against”)
Rt = impedance of tweeter
C = µF
f = frequency i.e. 4000Hz
CALCULATING CHOKE (LOW PASS) VALUE
Coils (also called chokes, inductors)
used in series with woofer, Inductance (L) measured in Henries or mH
L = 159 Rw/f
where Rw = impedance of woofer
f = crossover freq.
SPEAKER ENCLOSURE DESIGN
Project Speaker
Enclosures
"bare" speakers do not perform well because back sound waves can cancel some waves from the front, causing distortion
speakers are placed in "enclosures" to contain back waves, damp out unwanted frequencies, improve performance and efficiency, and enhance low frequencies
ENCLOSURE TYPES
Acoustic Suspension
air tight enclosure
speaker is cushioned or suspended by air inside enclosure (damping)
Infinite Baffle
very large sealed enclosure, low suspension or damping
Ported Reflex
also called ducted port, bass reflex, Helmholtz resonator)
tubed port in enclosure, open to front
size and length of port is critical for tuning
deeper bass response and higher efficiency
OTHERS
Double Woofer
Double Chamber Reflex
Tapered Pipe
Labyrinth or Transmission Line
DECIBEL SCALE
Project Speaker
|Sound Production |Decibel Scale (dB) |Notes |
|Explosion |130 | |
|Threshold of Pain |120 |Night Club |
|Auto Horn at 20 ft. |110 |Loud Music 30 W |
|Heavy Trucks at 20 ft. |100 | |
|Train Whistle at 500 ft. | 90 | |
|Vacuum Cleaner at 10 ft. | 80 | |
|Average Traffic at 100 ft. | 70 | |
|Normal Speech at 3 ft. | 60 |Soft Music 0.01 W |
|Light Traffic at 100 ft. | 50 | |
| | 40 | |
|Soft Whisper at 5 ft. | 30 | |
|Very Soft Whisper at 1 ft. | 20 | |
| | 10 | |
|Threshold of hearing | 0 | |
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