Engineering World Health Power Line Tester
Benjamin P. Humphrey1, David W. Slifer1 , Charles C. Wu1
Advisors: Dr. Paul H. King1 and Dr. Robert Malken2
1 Vanderbilt University, Nashville, TN
2 Duke University, Durham, NC
PROBLEM STATEMENT
PROTOTYPE
CURRENT DEVICES
Design a power line tester for use in hospitals in the developing world
that can determine the voltage present and if the outlet is wired correctly
BACKGROUND
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 developingworld 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.
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
• 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
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.
• 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
SAFETY ISSUES
IDEATION
EHW COUNTRIES
EWH currently works in the following developing countries:
• Africa: Tanzania, Ghana, Sierra Leone, Ghana, Liberia
• Central America: El Salvador, Honduras, Nicaragua
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.
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
• 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.
ECONOMICS
• 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.
FINAL IDEA
CONCLUSIONS
Figure 1. (Left) Map of the African countries that
EWH works in. (Right) Map of the Central
American countries that EWH works in.
DESIGN CRITERIA
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
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
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
•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.
Table 1. Table of the costs of the
entire project including unit price
and price per device.
• 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.
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.