MadSci Network: Engineering |
Hi Ryan! Simple "lie detectors" are electronic circuits which measure the electrical resistance of
your skin. In theory, you sweat more when you lie, and the circuit responds to this (usually by changing the pitch of a beep sound.)
In reality this type of circuit is not a reliable lie-detector.
Many people do not sweat when lying, while other people get sweaty for many reasons, even when telling the truth.
However, "lie detector" circuits are fun to play with. Just be sure that you don't ever take the results seriously!
Circuit Central Schematic Archive, see "Simple Lie Detector"
For more information, search for "GSR" and "Galvanic Skin Response". Also search for "voice stress analyzer", which is a device that's purported to detect tremors in your voice as you lie. "VSA" devices are said to be very unreliable. Also search for "Polygraph", the lie detector sometimes used by the police. Even the reliability of the polygraph is questionable. See this entry from Skepticism Dictionary, also a book about cheating during polygraph tests.
Try the links in the MadSci Library for more information on Engineering.