ECE 4760: Final Project

Polygraph Machine

Two Channel Old Fashioned Polygraph

Joyce Cao (

Daria Efimov (

"Two Channel Polygraph Machine"

Project Sound Bite

Ask a group of people what a polygraph is and the most common answer you will receive is that a polygraph is a lie detector. But is it really? Contrary to common opinion, a polygraph will not give you a yes or no answer if you are lying or telling the truth. The polygraph is a combination of sensors that measure your body's response to various questions. Often times, a subject's heart rate, galvanic skin response, blood pressure, and breathing rate will be measured. Depending on how advanced the machine is, there could be more or less data taken. This data is then analyzed by a trained polygraph examiner who determines whether a particular question is causing a certain body response because you are being deceptive or for other reasons. The process of determining whether or not someone is lying is a lot more involved and complex than just being hooked up to a machine and can take up to three hours per session. For our final project we decided to build an old fashioned polygraph machine. Our polygraph measured one's heart rate, and breathing rate. All of the data was fed into the PIC32, processed, and then drawn on a piece of paper by servo controlled “needles”. The waveforms were also displayed on a TFT display. Modern polygraphs connect to a computer and utilize programs similar to Matlab to plot and analyse the data in real time. Our polygraph is more of a relic as it is a replica of machines used before computer data analysis became the standard for polygraph examinations.


Polygraph Machine