Engineering World Health Power Line TesterBenjamin P. Humphrey1, David W. Slifer1 , Charles C. Wu1

Advisors: Dr. Paul H. King1 and Dr. Robert Malken2

1 Vanderbilt University, Nashville, TN2 Duke University, Durham, NC

The power line tester needs to perform the following functions• Determine the amount of voltage present in the outlet• Determine if the outlet is wired correctly

The power line tester needs to meet these criterias:• Cost less than $5 per unit• The dimensions has to be no greater than a 3 x 3 x 3” box• The device needs to be maintenance free• The device has to withstand temperatures of 20 oC to 40 oC and the high

humidity of some of the developing countries

Engineering World Health (EWH) is a non-profit organization that works in many countries helping better the quality of life by improving medical care. Many of their technicians assist in the repair of medical devices. They also train the local physicians in the usage of the medical devices. Most of the goals of EWH are accomplished through a summer program for undergraduates. The students found that modern equipment that is often taken for granted in U.S. hospitals is in short supply in developing-world hospitals, which struggle simply to operate with uninterrupted electricity and are plagued. The power line tester will identify the faulty outlets for technicians to repair. Hence, expensive medical equipment will only be used in working outlets, saving the equipment and possibly people’s lives.

PROBLEM STATEMENT

BACKGROUND

EHW COUNTRIES

FUTURE DIRECTION/RECOMMEDATION

• Future work can be done to modify the power line tester to also incorporate Tanzania, Ghana, and Sierra Leone which works at 230V and 50 Hz.

• Investigation as to the effect of the frequency on the current device.• Validation tests for open ground, open neutral, and open hot.

IDEATIONSAFETY ISSUES

CONCLUSIONS

DESIGN CRITERIA

Design a power line tester for use in hospitals in the developing worldthat can determine the voltage present and if the outlet is wired correctly

CURRENT DEVICES

• Current commercial power line tester range anywhere from $1.99 to well over $100

• The various power line testers contain a digital display, light diodes, or light sensitive diodes.

• The cheaper power line testers use a pattern of light diodes to determine the voltage present and the type of outlet wiring

• The type of outlet wiring are open ground, reversed polarity, open hot, open neutral, hot ground wiring reversed, and hot on neutral with hot open

EWH currently works in the following developing countries:

• Africa: Tanzania, Ghana, Sierra Leone, Ghana, Liberia• Central America: El Salvador, Honduras, Nicaragua

• One of the major safety concerns was what would happen if the loose leads came in contact with another causing a short circuit

• A short circuit can damage the circuit or cause a surge to occur• A surge is an increase in voltage and current flow that can cause a wire

or circuit element to burn out or be weakened.• The increase in current flow can be harmful to the users’ health if they

come in contact with the exposed leads.

• The design met the criterias in place by the EWH

• Pricing validation shown in Table 1• Device was able to work at temperatures of 40

oC and 20 oC at various trials• The device was tested to be waterproof.

PROTOTYPE

• The first phase began by building the device on a breadboard as shown in the figure on the left

• Phase two of the prototyping consisted of building the circuit on a perforated breadboard using wire wrapping

• Phase three included designing the casing to protect the device and the use of Bakelite to provide extra protection to the circuit

•The left part of the circuit determines the voltage present. When there is less than 120V, the resistor in the lamps drops the voltage level lower than needed to light the lamp. When the voltage as at 120V there is enough voltage left over in the lamp after its resistor to light lamp. The second lamps are used to determine if there is 220V present in the circuit.•On the right side of the voltage source is the part of the circuit that determines if the outlet is wired correctly. The three lamps are set up so that certain light combinations indicate the wiring status. The wiring states that can be diagnosed are shown in the figure on the right.•The last part of this circuit is the LED, which is used to determine the ground fault circuit. It works in parallel with the diode to test for this.

The goal was to take the currently available products, find the cheapest solution and then see if it could be modified to meet the requirements set forth by EWH. Throughout the project, cost was the design focus. The first decision made was that cost could be reduced if both functions, voltage present and wiring correctness, along with the electrical standards were incorporated into one device because it would use less materials. To determine the voltage present, the cheapest solution involved the use of indicator lamps that would light if the outlet is outputting 120V. To determine if the outlet was wired correctly, the cheapest solution uses a pattern of indicator lamps similar to the current devices. The figure to the left shows the QFD diagram for this project. We gave cost and maintenance the highest weight because we felt that it was the most important aspect of this project

ECONOMICS

Figure 1. (Left) Map of the African countries that EWH works in. (Right) Map of the Central American countries that EWH works in.

Figure 2. (Top) Figure of a power line tester that can be purchased for $4.99. (Bottom) Another cheap power line tester that uses a pattern of light diodes

Figure 3. Figure of the Quality Function Diagram Function for this project that links the functions of the power line tester to the desired qualities.

Figure 4. (Left) Figure of the circuit of the device. (Middle) 3D image of the circuit on a breadboard. (Right) Pattern of lights to determine wiring status of outlet

Figure 5. (Left) Figure of the first phase of the project. (Right) Figure of the prototype in its final version including the casing and light diodes.

Table 1. Table of the costs of the entire project including unit price and price per device.

Acknowledgements: We would like to thank Angelia Slifer with editing and writing of the paper and Dr. A. B. Bonds for helping in the circuit design and providing suggestion of creating separate devices for the different electrical standards

FINAL IDEA

• This project is being done for a nonprofit organization.• The power line tester will be produced at extremely low costs making

free distribution to developing worlds a reality.

• Our power line tester will be freely distributed to developing countries that have limited resources and currently cannot supply their hospitals with power line testers.

• This device has little to no competition.