An acoustic lie detector
Published in issue 332, May 2004
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.
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
Click below to download a PDF copy of this article from Elektor magazine.
Please note. In view of the complexity of international markets, Elektor cannot guarantee the availability of components for this project.