Burkhard Kainka
About the article

Resounding Truth

An acoustic lie detector

Resounding Truth
There are those cool-headed types, who can lie through their teeth with a straight face. But in the end it is just a matter of asking the right questions. Sooner or later everyone will get sweaty palms.Lie detectors are always a great deal of fun at parties. Who is prepared to face up to the challenge from technology? And also: who is able to defeat the machine! The latter is also very dependent on the actual situation — the questioner must not make it too easy for the test subject! When the tension increases, even the best liar can’t avoid a subtle but inevitable physiological reaction: sweaty palms.
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Component list
R1,R2 = 27kOhm
C1 = 4n7
IC1 = NE555
BZ1 = buzzer
2 PCB solder pins
2 solder pin receptacles soldered to long wires (stripped ends)
6 pieces of (bare) wire
PCB, prototyping board, order code UPBS-1
9 V-battery with clip-on leads
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