4 Interesting polygraph circuits (detects skin resistance changes)

Let's take a look at some interesting "lie detector" small circuits, which are the principle of detecting the skin resistance between fingers.

Lie detector circuit 1

The circuit detects the resistance between your fingers to produce oscillations. Dry fingers will detect a resistance of up to 100,000 ohms, which will make the circuit sound at low frequency oscillation. If the subject is nervous, he sweats, which lowers the skin's resistance and causes the circuit to oscillate at a higher frequency.

The photo shows the circuit built into the PC board with a separate touch pad.

Lie Detector circuit 2

The circuit detects the resistance between your fingers and if the skin resistance drops, the false led is lit. The 47K adjustable resistor adjusts the sensitivity of the probe when it touches the finger.

Lie Detector circuit 3

The circuit detects the resistance between your fingers and displays a change in the resistance size with 4 LEDs. When you press the detection electrode hard, more and more LED lights are lit.

Lie Detector circuit 4

The circuit detects the resistance between your fingers. As you press the detection electrodes hard, more and more LED lights are lit. This circuit is simpler than the 3 circuit of the polygraph circuit.

4 Interesting polygraph circuits (detects skin resistance changes)