APPLIANCE POWER CONSUMPTION



HOUSEHOLD POWER MONITORING SYSTEM

DESIGN REPORT

May 02-04

December 17, 2001

Client: Herb Harmison

Advisors: John Lamont

Ralph Patterson

Team: Stephen Woerdehoff

Paul Jonak

Yohan Blount

Jason Muehlmeier

Table of Contents

1. Abstract……………………………………………………………... 1

2. Acknowledgement………………………………………………...… 1

3. Definition of Terms…………………………………………………. 1

4. Introduction…………………………………………………………. 1-3

1. General Background…………………….……………….………. 1

2. Technical Problem…………………………….…………………. 1

3. Operating Environment……………………….…………………. 2

4. Intended Users and Uses……………………….………………… 2

5. Assumptions…………………………………..…………………. 2

6. Limitations…………………………………….…………………. 3

5. Design Requirements……………………………………………….. 3-5

1. Design Objectives………………………………..………………. 3

2. Functional Requirements………………………..…………….…. 3

3. Design Constraints…………………………………..…………… 4

4. Measurable Milestones………………………………..…………. 4

6. End-Product Description…………………………………………... 5

7. Approach and Design………………………………………………. 5-14

1. Approach and Design of Total Power Consumption Meter….…... 5

7.1.1 Technical Approach…………………………………………5

7.1.2 Technical Design……………………………………………6

7.1.3 Testing Description.………………………………………... 7

2. Approach and Design of Roaming Meter……...……..……….…. 7

7.2.1 Technical Approach…………………………………………8

7.2.2 Technical Design……………………………………………8

7.2.3 Testing Description.………………………………………... 9

3. Approach and Design of A/D………………………….………… 10

7.3.1 Technical Approach…………………………………………10

7.3.2 Technical Design……………………………………………10

7.3.3 Testing Description.………………………………………... 11

4. Approach and Design of Computer Recording System.…………. 11

7.4.1 Technical Approach…………………………………………11

7.4.2 Technical Design……………………………………………12

7.4.3 Testing Description.………………………………………... 12

7.5 Overall System Testing…………………………………………... 13

7.6 Risk and Risk Management……………………………………… 13

7.7 Recommendation for Continued Work…………………………... 14

8. Financial Budget……………………………………………………. 14

9. Personal Effort Budget…………………………………………….. 15-16

10. Project Schedule……………………………………………………. 17

11. Project Team Information…………………………………………. 18

12. Summary……………………………………………………………. 18

13. References…………………………………………………………… 19

Appendices………………………………………………………….. 20-24

Appendix A………………………………………………………..20

Appendix B………………………………………………………..21

Appendix C………………………………………………………..22

Appendix D………………………………………………………..23

Appendix E………………………………………………………..24

List of Figures

Figure 7.1.1 D’Arsonval Movement…………………………………………. 6

Figure 7.1.2 Total Power Consumption Meter Connection………………….. 7

Figure 7.2.1 Roaming Power Meter Connection…………………………….. 9

Figure 7.2.2 Wattmeter Needle Deflection…………………………………... 9

Figure 7.3.1 Operational Amplifier………………………………………….. 11

Figure 10.1: Project Schedule for 1st Semester………………………………. 17

Figure 10.2: Project Schedule for 2nd Semester……………………………… 17

List of Tables

Table 8.1 Financial Budget………………………………………………….. 14

Table 9.1 Original Personal Effort Budget…………………………………... 15

Table 9.2 Revised Personal Effort Budget……………………………………15

Table 9.3 Personal Effort to Date……………………………………………. 16

1. Abstract

With increasing power consumption and costs in the home, many homeowners would like to monitor their energy usage. The Household Power Monitoring System will allow the homeowner to monitor the individual and total power used by household devices. With this information, the user can find ways to reduce their power costs. The system will also allow the user to identify devices that are becoming inefficient or those that are likely to malfunction in the near future.

2. Acknowledgement

We would like to thank Mr. Herb Harmison and Dr. Glenn Hillesland for their input and donations to the project.

3. Definition of Terms

A/D – Analog to digital converter.

RF – Radio frequency.

X-10 – A protocol for communication over household wiring.

RS-232 – Serial port

4. Introduction

4.1 General Background

The purpose of this project is to give the user information about their power usage so they can make educated decisions according to their goals. The system will record the total usage of the home as well as selected individual loads as a function of time. This data will then be available for easy analysis utilizing a PC.

4.2 Technical Problem

The system will consist of four subsystems that will be integrated to give the final product. They are: total consumption wattmeter, roaming wattmeter, A/D, and computer interface and recording system. The two wattmeters will have a small analog output that will be sent to the A/D before being recorded by the computer.

Total Consumption Meter: The purpose of this device is to measure the total watts consumed by the home over the single-phase 240-Volt wiring. This will be done using current transformers to step down and measure current before entering the wattmeters. The wattmeters will be older analog meters that can be obtained inexpensively. The small analog output they produce will be turned into a digital signal for the computer using the A/D.

Roaming Wattmeter: This device measures the total watts consumed by the single-phase 120-Volt appliance being monitored. This will be done using an older wattmeter directly. The small analog output it produces will be turned into a digital signal for the computer using the A/D.

A/D: Outputs from the analog wattmeters will be converted to digital values and interfaced with the computer. The voltage output from the analog wattmeter will be small in magnitude and must be amplified before it is converted to a digital signal. An A/D chip will be used for the digital conversion and will have a sufficient sampling rate to accommodate the desired data collection speed. The chip will have a built in serial communication interface to connect directly to the computer via a serial port.

Computer Interface and Recording System: The computer system will receive data from the A/D via the serial port. This will be done using a program created with Visual Basic. The data will then be recorded prior to analysis using Microsoft Excel.

4.3 Operating Environment

This system will be located in a residential household, this environment is not very demanding however the system should be able to function despite the following. Possibly a fairly dirty environment with dust and other contaminants such as pet hair may be present. The system should be resistant to any electrical interference caused by operating appliances and other devices. Some resistance to both high and low temperatures would be needed, with an operating range between 30 and 110 degrees Fahrenheit. The roaming wattmeter should be somewhat robust and able to survive a drop in shipping or around the house.

4.4 Intended Users and Uses

The system is intended to be used in a residential setting. Home residents conscientious about their utility costs can track power usage and learn what devices cost the most to operate and how to save money. The system could be used to monitor larger appliances to determine if they need servicing or replacement.

4.5 Assumptions

What follows is a list of assumptions that are being made under the current plan. These assumptions may change as the project develops.

( The user will be familiar with operating a computer.

( The user will know basic spreadsheet operations.

( The user will have a computer capable of analyzing the collected data.

( The user will have a basic knowledge of electricity and the concept of power.

( The house will comply with the operating environment described above.

( The user will have access to average power consumption rates of appliances.

( The user will know the current utility rate for their location.

( The user will be able to operate a simple GUI.

( The home has reasonably balanced load legs in the breaker box.

4.6 Limitations

What follows is a list of limitations that are evident under the current plan. These limitations may change as the project develops.

( Wattmeters will be compatible with a maximum of a 200A service.

( Due to complexity, only one roaming meter will be produced.

( The house will have a modern, grounded electrical wiring system.

5. Design Requirements

5.1 Design Objectives

The following are design objectives that should be reached to realize the intended system.

( Total consumption meter will consist of two current transformers and two analog wattmeters wired in a 1-phase 240V manner. They will measure the total power consumed in the home. Their output will be sent to the A/D over hard wiring. There will also be voltage, current, and VARS measurement capability.

( Roaming wattmeter will be a portable device consisting of an analog wattmeter wired in a 1-phase 120V manor. It will measure the power consumption of a single household device and the voltage, current, and VARS. Its output will be communicated to the A/D over hard wiring.

( The A/D will consist of an operational amplifier and an A/D chip. It will receive input from the wattmeters. It will output a serial communication signal to the serial port.

( The computer interface system will be a Windows 95 compatible computer running a Visual Basic program that will access the serial port, scale the data, and record the data to a file.

( These subsystems will be integrated into an accurate, user-friendly system.

5.2 Functional Requirements

These functional requirements should make the end product useful and reliable in the intended operating environment.

( The system will be easy to use.

( The total consumption meter’s measured results should be within 5% of the actual power consumed as measured by the power utility’s meter.

( The wattmeters must have outputs suitable for the A/D subsystem to convert to serial data.

( The wattmeters will utilize older inexpensive devices.

( The roaming wattmeter will be able to measure the real power consumed by any 120V appliance.

( The computer interface system must collect data into a file that can be placed on a disk and can be imported into Excel.

( The roaming meter will communicate to the A/D via a hardwire link of sufficient length to make it useful.

( The A/D will communicate in RS 232 format with the computer.

( The system will not lose data if supply power to it is interrupted.

5.3 Design Constraints

These design constraints are intended to minimize interference in normal household activities such as causing static in television reception.

( The overall system will be inexpensive to implement.

( The system should not gravely disturb the aesthetic qualities or normalcy of life in the household.

( The system’s installation and operation will not pose any unreasonable risk to the safety of the user.

( The roaming wattmeter will be small enough to be conveniently portable.

5.4 Measurable Milestones

These milestones are deadlines to ensure the project is completed on schedule, they will be used to gauge the ongoing progress, and completion status of the project. The first percentage denotes the progress of that particular task. The second percentage represents the progress of the overall project when that task is complete. These are also listed on the Gantt chart on page 17. Success will be gauged by how much of the project is completed. The project will be considered a success if a final product is implemented and functions properly.

• Project Plan- The project plan to outline the project’s functionality and implementation will be completed by September 25. (100% Complete) (5% Overall)

• Revised Project Plan- A revised version of the project plan will be completed by October 9. (100% Complete) (6% Overall)

• Poster- A poster outlining the project’s design and functions will be completed by October 30. (100% Complete) (10% Overall)

• Design Report- A report detailing the project’s proposed design will be completed by December 4. (100% Complete) (25% Overall)

• Design Finalized- After more research is done on the subject, a final design will be decided on in February 2002. (30% Complete) (35% Overall)

• First Implementation- The separate subsystems are constructed in early March 2002. (5% Complete) (40% Overall)

• Initial Testing Begins- Individual subsystems will begin testing in late March 2002. (0% Complete) (50% Overall)

• Revised Design- The initial design will be improved, based on the first implementation and testing. (0% Complete) (60% Overall)

• Revised Design Testing- A revised design will enter the final testing stage in early April 2002. (0% Complete) (80% Overall)

• Final Implementation- A finished product will be completed in mid April 2002.

(0% Complete) (90% Overall)

• Final Report- A final report that summarizes the project design and resulting end product will be completed in late April 2002. (0% Complete) (98% Overall)

• Presentation- A presentation reporting the project’s final product will be given in late April 2002. (0% Complete) (100% Overall)

6. End-Product Description

The end product will be a system that will record total power used in the home as a function of time. A roaming wattmeter will be capable of measuring the consumption of an individual device. The information will be recorded on an obsolete PC. The user will periodically take data from the recording PC to a modern machine for display and analysis possibly using software developed specifically for this system.

7. Approach and Design

This system has four major components and will thus be designed in four parts. The four main parts to be designed and implemented are; the total consumption wattmeter, the roaming consumption wattmeter, the analog to digital converter, and the recording system. What follows is the design approach that will be followed to implement each of these four main parts and how they will be integrated.

7.1 Approach and Design of Total Power Consumption Meter

7.1.1 Technical Approach

The total consumption meter could be designed in many different ways. The possible design ideas are listed and discussed below.

( A digital wattmeter could be used that would measure the watts and interface directly to a computer recorder, thus eliminating the need to design an A/D and increasing system accuracy and decreasing complexity.

( A data logging watt-hour meter with recording ability could also be used, this system would require the user to periodically download the information that had been recorded into a PC for analysis. This would increase accuracy and cost while decreasing complexity.

( A watt-hour meter could be used and the user could monitor it and hand record values. These values could be then entered in a computer for analysis. This is by far the simplest approach and would work, however, the system would not be automated and wouldn’t be as helpful as it should be.

( A computer could be used to read in the current and voltage information. The computer would then calculate the phase angle between E and I, and use this to calculate watts being used. This would also give the user recorded values for voltage, current, and VARS as well. This information could be useful to the user if they chose to monitor the health of their loads, or to satisfy some curiosity that they may have about their power usage. This would be accurate if accurate enough instrument current and voltage transformers were obtained.

( An analog wattmeter could be used to indirectly measure the power consumption by measuring the true voltage and using a current transformer to measure a scaled down version of the current entering the home. This measurement can then be converted to a digital signal and put into the recording device. This system could be implemented relatively cheaply by utilizing older analog meters that can be obtained cheaply and current transformers that are also relatively cheap and within our budget.

7.1.2 Technical Design

Using a digital wattmeter would be ideal and simplify the system however the cost of such a device is outside the project budget. A data logging watt-hour meter would greatly simplify the system but this device too is outside our budget. A standard watt-hour meter would work and is obtainable, but would not be automated enough to be practical given the project goals. Implementing a subsystem that fed the voltage and current information into a computer for calculation would work well. The largest drawback to this system could be cost of quality voltage and current transformers.

It has been decided to implement the total consumption meter using two older analog wattmeters that can be obtained cheaply. This approach will simplify the design by allowing the wattmeters to do the calculations with current, voltage, and phase angle accurately. The output will be the terminals of the d’Arsonval movement as can be seen in Figure 7.1.1.

Since a home has two 120V lines and a neutral entering the breaker box the total consumption meter will have to have two separate wattmeters and their outputs will be added to give the total power. The connections of these two wattmeters can be seen in the schematic below, Figure 7.1.2.

Figure 7.1.2: Schematic of the wattmeters breaker panel connections in the home.

A standard home has a 200A service this means each hot leg (A and B in Figure 7.1.2) has the possibility of carrying 100A, if the electrician balanced the load legs reasonably as was assumed. Each individual wattmeter needs to be able to cope with 100A. The wattmeters being used can only accept 7.5A maximum. This means a 100A to 5A or 20:1 current transformer should be used to measure the current in each leg going into the breaker box. The computer that records the data will make up for this change by scaling its input data back up using a transfer function for the total consumption meter. This transfer function is described in the testing description below.

7.1.3 Testing Description

The following tests will be ran specifically on the total consumption wattmeter subsystem. The form that these tests will be recorded on is in Appendix A.

A-1) Test each wattmeter individually to make sure they function properly.

Acceptance criteria: Wattmeter reads the correct value.

A-2) Test the current transformers over as much of their operating band as possible to generate a plot of actual current vs. current out which can be used later to make a scaling factor or function that the computer will use to determine what the true power reading is.

Acceptance criteria: Data points are found to generate a plot that will cover the probable operating area, which is defined as 100A.

A-3) Test the output voltage at the coils of the d’Arsonval movement in the wattmeter over the whole operating range to see what kind of inputs can be expected at the A/D.

Acceptance criteria: if the d’Arsonval movement is linearly dependent on the voltage in the coils at the base of the needle over its whole operating range.

A-4) Implement the entire subsystem and generate a transfer function between the known power consumption as measured by the utility company’s watt-hour meter and the subsystems output to the A/D. This information will be used to fine-tune the A/D, and the scaling function the computer uses to generate the final data.

Acceptance criteria: if enough data points are found to generate a plot that will cover the probable operating area, which is defined as 100A.

7.2 Approach and Design of Roaming Meter

7.2.1 Technical Approach

Two approaches are being considered for the design of the roaming power monitor. The more difficult, but less costly, approach is to implement current and voltage transformers to scale down measurements before being input into the wattmeter from the household appliance being monitored. The use of (step-down) transformers allows a smaller low-rated analog wattmeter to be used as the base measurement tool. It is then expected that an electrical signal can be extracted from the wattmeter’s needle deflections that is proportional to the measurement itself. An A/D would make this signal usable by the central computer.

The easier, but more expensive, approach to the roaming wattmeter design would eliminate the need to tap the minute voltages inducing needle deflections by using a digital wattmeter instead. This is assumed to be more reliable and would obviously eliminate the need for an A/D stage being that the inputs to outputs from the internal transducer could be tapped directly.

7.2.2 Technical Design

The analog approach to measuring the real power consumption of an appliance is graphically represented in Figure 7.2.1. It is the same approach to measuring power as the total power consumption meter. Except in the case of household appliances, one of the 120V legs doesn’t exist.

[pic] [pic]

Figure 7.2.1 Figure 7.2.2

Voltage transformers and current transformers are used to tap into the power drawn by the appliance without disturbing the flow. These offer a scaled-down input to the analog wattmeter. This scaling would be taken into account by scaling that will take place in the computer. For instance, the turns ratio of the current transformer may be ½ while the turns ratio for the voltage transformer is ¼. The final data would be scaled by a factor of 8 inside the computer. Another scaling factor arises from the fact that an analog wattmeter offers no readily available electrical signal that is intended to proportionally represent the power it measures. Assuming that the wattmeter’s reading is reflected in a potential drop across its needle, the data can be taken in its raw form from the potential across the lugs that hold it in place (Figure 7.2.2).

The deflection may not even be linearly proportional to this potential drop. Needle movements are actually the product of internal flux forces and a pressure coil. If proportional voltage cannot be obtained, an extra difficulty is presented. This analog approach will either be abandoned or an attempt will be made to account for this error by implementing an experimentally determined transfer function E=f(P) after the data is read into the computer.

The digital-wattmeter approach to designing the roaming power monitor works in much same way. Transformers can be used to scale down the input as before. Extracting an electrical signal that is proportional to the measurement is in this case much easier since a digital wattmeter has its own transducer and A/D. Depending on the design of the wattmeter, the outputs leading from the transducer to the LCD could be tapped to obtain a ready signal.

The next step in either approach would be to implement a buffer amplifier stage leading from the wattmeter to the A/D chip before it goes to the serial port. The high impedance of an op-amp will prevent disturbances to the natural function of either wattmeter while taking the data signal.

7.2.3 Testing Description

The following tests will be run solely on the roaming wattmeter subsystem. These tests are the same as those that will be performed on the total consumption meter, this is due to the similarity of these two subsystems. The form that these tests will be recorded on is in Appendix B.

B-1) Test each wattmeter individually to make sure they function properly.

Acceptance criteria: Wattmeter reads the correct value.

B-2) Test the current transformers over as much of their operating band as possible to generate a plot of actual current vs. current out which can be used later to make a scaling factor or function that the computer will use to determine what the true power reading is.

Acceptance criteria: Data points are found to generate a plot that will cover the probable operating area, which is defined as 100A.

B-3) Test the output voltage at the coils of the d’Arsonval movement in the wattmeter over the whole operating range to see what kind of inputs can be expected at the A/D.

Acceptance criteria: if the d’Arsonval movement is linearly dependent on the voltage in the coils at the base of the needle over its whole operating range.

B-4) Implement the entire subsystem and generate a transfer function between the known power consumption as measured by the utility company’s watt-hour meter and the subsystems output to the A/D. This information will be used to fine-tune the A/D, and the scaling function the computer uses to generate the final data.

Acceptance criteria: if enough data points are found to generate a plot that will cover the probable operating area, which is defined as 100A.

7.3 Approach and Design of A/D

1. Technical Approach

Two options were considered for the A/D: purchasing a component or building one using MOSFET chips. Because of availability of A/D chips as samples from manufacturers and to avoid potential problems that may arise with building one, A/D sample chips will be ordered from several manufacturers. An additional advantage to using a purchased A/D is that many are available with a built in serial communication capability eliminating the need to convert the digital output to a serial signal by another component.

2. Technical design

A 16-bit A/D will be used. This will allow 65,536 digital output values, which will provide adequate precision. Modern commercial A/D chips with built in SCI’s operate with clock frequencies much higher than that of our overall data collection rate. Signals from the wattmeters will be small in voltage and will need to be amplified before being sent to the A/D. The amplifier will consist of a 741 operational amplifier and configured in the non-inverting high input impedance setup shown in Figure 7.3.1. A second stage to the amplifier may be needed to tailor the signal to the necessary voltage requirements of the signal going to the A/D chip.

[pic]

Figure 7.3.1: Operational amplifier that will increase wattmeter output prior to A/D chip.

3. Testing description

The following tests will be run specifically on the A/D subsystem. The form that these tests will be recorded on is in Appendix C.

C-1) A constant voltage will be input to the chip representing an analog signal. The chip output will be connected directly to a serial port of a PC. A computer program that polls the serial port and can give a text output of the results will be used to analyze the chip output.

Acceptance criteria: The test is successful if the expected output is received from the chip when different input voltages are applied

C-2) Voltages will be applied to the chip like those that are expected from the wattmeters. This is to insure that the A/D will work with the input it will probably see in the final system.

Acceptance criteria: Successful if the output of the A/D as seen in the computer is expected.

7.4 Approach and Design of Computer Recording System

7.4.1 Technical Approach

Possible alternatives for the design of the computer recording and display system were considered during the initial phases of the project.

( One possible design considered using the homeowner’s computer to collect and display the data. However, this idea has flaws. First, not all homeowners have computers available in their homes. Second, some homeowners use Mac or Linux operating systems. Not all the computer would be compatible with a Windows based program.

( A second possibility for a computer to record and display data would be to use a separate older, obsolete computer to record and store the data. The computer would be capable of running Windows 95 and the data collection program would run on that. Then, the data could be loaded onto a disk and analyzed using a spreadsheet that the homeowner has available. This solution is the most practical. First, the old computer can be obtained relatively cheap and it will run Windows 95 so it will be compatible with a Visual Basic program that will be written to collect the data.

( Another consideration in the design stage was the method of importing the data from the devices into the computer. Several alternatives were considered. First would be more modern ports such as the USB ports or parallel ports. However, these alternatives were discarded because of the difficulty in programming them to work for the project. Also, a network card and home network could be used to import the data into the computer, but this alternative is also complicated and cost prohibitive. The best solution then to import the data is the serial port. The serial port is fast enough for this project and it is simple to program using Visual Basic to collect data via the port. Also, most older computers already have a serial port available so the cost is not an issue.

7.4.2 Technical Design

Communication: The main recording device that measure total power consumed just above the breaker panel will be connected to the A/D which is equipped with a serial port. The A/D will communicate with the computer via RS-232 protocol, also known as the serial port. The computer will be placed near the fuse panel because the serial port cable has a limit of 50-100’ cable length.

Computer: The computer used must have at least a 486 processor with at least 4 MB of memory and at least 50-55 MB of hard drive space. Also, the computer needs to have a 3.5-inch floppy drive, although a CD-ROM drive would be more desirable. The computer must also have a serial port to connect to the A/D device. The computer will run the Windows 95 operating system. This is important so that we can run Visual Basic scripts on the computer. Using Visual Basic, the serial port can be accessed and the data sent from the A/D can be read in, scaled, and recorded.

Data: Once the data is collected by the computer via the serial port, the data will be scaled accordingly and stored into a text file. The text file can be downloaded to a disk. The user can import the data into an excel file and display the data via charts and graphs as desired by the user. Also, the data could be analyzed by a Visual Basic program and displayed in a real time format for the user on the host computer.

7.4.3 Testing Description

The following tests will be run specifically on the computer recording subsystem. This subsystem will be tested after the total power consumption wattmeter is working and the A/D converts the signal so it can be fed into the computer. The form that these tests will be recorded on is in Appendix D.

D-1) The A/D will be fed with a constant voltage (analog signal), the chip output will be connected to the serial port of the PC. The computer program will then poll the serial port and record the data.

Acceptance criteria: The test is successful if the expected output is received and recorded in the data file. Since a constant voltage is being used the data file should have one numerical value repeated throughout the file.

D-2) Test D-1 will be repeated over the whole range of A/D input values.

Acceptance criteria: Successful if the output of the text file varies over the whole spectrum of input values.

7.5 Overall System Testing

After the testing of the subsystems has been completed, the separate subsystems will be integrated and tested as a whole. The form that these tests will be recorded on is in Appendix E.

E-1) Put a constant A/D input and sample, scale, and record the data the computer.

Acceptance criteria: The computer reads the expected value, the output is scaled accordingly, and the data is stored in the data file.

E-2) Test that the data file can be saved to a disk and imported into an Excel spreadsheet file.

Acceptance criteria: The test is successful if the data is saved correctly to disk and the data is displayed in Excel on a modern computer.

E-3) Test that the power readings that the computer records are correct.

Acceptance criteria: The test is successful if the value recorded is within 5% of the utilities watt-hour meter.

6. Risk and Risk Management

There is one team member responsible for each of the four subsystems and if they were lost it would be a large setback. The roaming and the total consumption wattmeter designs are very alike so if one of those team members is lost the other will know how to complete the design. Also, the A/D and computer recording subsystems utilize similar aspects so if a member is lost the other member could fill in and complete the subsystem. This way each part of the project has two team members with the capability of completing that section of the design.

For the total consumption meter and the roaming wattmeter the biggest risk is that the d’Arsonval movement is not linearly dependent on the voltage or current in the coil at the base of the needle. Several experts have stated that they think this scheme should work, so there should be no problem. If this scheme doesn’t work the computer based wattmeter system will be implemented. This approach should be within budget though accuracy may be lost if the cost of quality current and voltage transformers is too great.

For the recording subsystem, if a suitable computer cannot be found the software may have to be coded in a DOS environment or an Apple platform rather than in a Windows environment. Otherwise, money from the project budget may have to be used to buy a suitable computer.

There is a chance that the serial communications interface on the A/D chip will not function properly with the serial port. Testing the operation of the chip before the wattmeter subsystems are completed will detect problems early. Separate A/D and SCI chips may be required if the samples received do not operate as needed.

7.7 Recommendation for Continued Work

The next step will be to start validating the design of the four separate subsystems. When this is done, they can be designed and tested individually then combined into a single system. The next step in each of the four subsystems is as follows.

For the wattmeters, the first step is to make the voltage at the coils of the d’Arsonval movement is proportional to the watts being measured and will make suitable output for an A/D conversion. The next step would then be to make a prototype that would validate the design and could be tested for accuracy. This step would prove the validity of this subsystems design.

For the recording computer, the first step is to obtain a suitable computer. The next step would be to develop software to access the serial port and save the data into a file for the user.

For the A/D subsystem, the first step is to learn about A/D’s and to obtain an A/D that will work for the project. The next step is to test the functionality of the A/D and develop the serial port communication for the chip.

8. Financial Budget

The current design is comprised of four main devices. The total consumption meter is estimated to cost $50 for purchase of current transformers, because wattmeters will be donated. The roaming wattmeter will be free of cost because no additional parts will be required other than the donated wattmeter. The A/D should also be free of cost because of availability of samples from manufacturers. The computer interface will be free of cost because the PC and software will be obtained by donation. It is estimated that small components, such as connectors or packaging, will cost $20. It is estimated that an electrician will incur a $100 charge to install current transformers in a breaker box, but the user may provide for this cost.

Table 8.1: Estimated financial budget for the project

|Item |Original Estimated Cost |Revised Estimated Cost |Money Spent |

|Equipment and parts |$150.00 |$70 |$0 |

|Poster |$50.00 |$40 |$40 |

|Personal computer |$0.00 |$0 |$0 |

|Labor |$0.00 |$100 |$0 |

|Total |$200.00 |$210 |$40 |

9. Personal Effort Budget

Team members will distribute their effort to different tasks depending on their particular expertise. The following tables are of original estimated effort, current revised estimated effort, and effort to date.

Table 9.1: Original estimated personal effort budget by team member and by task.

|Team Members |Individual monitoring device functioning |

|211A Westgate Cook |4300 Westbrook Dr, #24 |

|Ames, IA 50012 |Ames, IA 50014 |

|(515) 572-6037 |(515) 268-9814 |

|yblount@iastate.edu |jmue@iastate.edu |

|EE |EE |

| | |

|Paul Jonak |Stephen Woerdehoff |

|4625 Steinbeck St, #2 |1320 Gateway Hills, #501 |

|Ames, IA 50014 |Ames, IA 50014 |

|(515) 292-4666 |(515) 292-6183 |

|pjonak@iastate.edu |swoerdeh@iastate.edu |

|EE |EE |

Advisors

|John Lamont |Ralph Patterson III |

|1005 Idaho Ave |1807 24th St |

|Ames, IA 50014-3018 |Ames, IA 50010-4403 |

|(515) 292-5541 |(515) 232-9933 |

|jwlamont@iastate.edu |repiii@iastate.edu |

Client

|Herbert Harmison |

|2692 Meadow Glen Rd |

|Ames, IA 50014 |

|(515) 292-7059 |

|herbh@iastate.edu |

12. Summary

With increasing power costs and consumption in the home, it would be beneficial for the homeowner to monitor where and how much power is being used. This system will allow the user to do this accurately at a relatively small cost. This will be accomplished by using both new and older devices that are easy to obtain and accurately measure total power and display the results to the user.

13. References

(No references at this time.)

Appendix A

Testing Form A

Total Consumption Wattmeter Subsystem

Name ______________________________

Date _____________

Time _____________

Test (Circle one) A-1 A-2 A-3 A-4

Is this an: Initial Test or a Retest

PASS FAIL

Describe previous failure:

What has been done to fix last failure:

Describe Test Conditions:

Conditions of Failure:

Nature of Failure:

Recommended Fix:

Appendix B

Testing Form B

Roaming Wattmeter Subsystem

Name ______________________________

Date _____________

Time _____________

Test (Circle one) B-1 B-2 B-3 B-4

Is this an: Initial Test or a Retest

PASS FAIL

Describe previous failure:

What has been done to fix last failure:

Describe Test Conditions:

Conditions of Failure:

Nature of Failure:

Recommended Fix:

Appendix C

Testing Form C

A/D Subsystem

Name ______________________________

Date _____________

Time _____________

Test (Circle one) C-1 C-2

Is this an: Initial Test or a Retest

PASS FAIL

Describe previous failure:

What has been done to fix last failure:

Describe Test Conditions:

Conditions of Failure:

Nature of Failure:

Recommended Fix:

Appendix D

Testing Form D

Computer Recording Subsystem

Name ______________________________

Date _____________

Time _____________

Test (Circle one) D-1 D-2

Is this an: Initial Test or a Retest

PASS FAIL

Describe previous failure:

What has been done to fix last failure:

Describe Test Conditions:

Conditions of Failure:

Nature of Failure:

Recommended Fix:

Appendix E

Testing Form E

Overall System Testing

Name ______________________________

Date _____________

Time _____________

Test (Circle one) E-1 E-2 E-3

Is this an: Initial Test or a Retest

PASS FAIL

Describe previous failure:

What has been done to fix last failure:

Describe Test Conditions:

Conditions of Failure:

Nature of Failure:

Recommended Fix:

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Figure 7.1.1: Schematic of d’Arsonval movement

Figure 10.1: Project Schedule for first semester

Figure 10.2: Project Schedule for first semester

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