191
2.78 Lie detector
Circuit 166:
FET lie detector with LED indicator
Setup information
Install the transistor, the LED diode and the three resistors as shown in
Fig. 2.166.
The six jumper wires
come next. Two bare wire ends serve as skin sensor. Check the placement on the board and only then con-
nect the battery.
Components required:
1 x J111 FET transistor,
1 x red LED, 1 x 10 k
Ω
resistor, 1 x 22 k
Ω
resis-
tor, 1 x 1 M
Ω
resistor,
1 x breadboard, 1 x 9V
battery with clip con-
nector
Fig. 2.166:
FET lie detector
with LED indicator
Experiment
Our circuit is a simple DC voltage detector. As long as the two sensors are isolated from each other, the LED
remains dark. If you touch the sensor with your wet (but grease-free) hands, the LED will shine brightly. If
the anxiety level rises when a person lies intentionally, sweaty palms of the hands could be taken as an
indication that the person is not telling the truth.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.166.
Summary of Contents for ELECTRONICS EXPERIMENTS BOX
Page 4: ......
Page 265: ...267 Fig 3 56 Cir cuit 56 Audio limiter Fig 3 57 Circuit 57 Amplifier for a storm detector...
Page 269: ...271 Fig 3 64 Circuit 64 Stabilizer for 1 9 V Fig 3 65 Circuit 65 Stabilizer for 2 5 V...
Page 275: ...277 Fig 3 80 Circuit 80 Quiztimer 30 seconds Fig 3 81 Circuit 81 Handy diode tester...
Page 315: ...317 Fig 3 179 Circuit 179 HF generator 150 kHz Fig 3 180 Circuit 180 HF generator 420 kHz...
