194
Circuit 169:
Lie detector with moving-coil instrument
Setup information
Install the two transistors and the three resistors as shown in
Fig. 2.169
followed by the seven jumper
wires. Two bare wire ends serve as skin sensor. Check the placement on the board again and only then
connect the battery.
Components required:
2 x 2N3904 transistors,
1 x 1 k
Ω
resistor,
1 x 22 k
Ω
resistor,
1 x 1 M
Ω
resistor,
1 x moving-coil instru-
ment, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.169:
Lie detector with
moving-coil instrument
Experiment
Our circuit is a simple DC voltage detector. As long as the two sensors are isolated from each other, the
needle is not moving. If you touch the sensor with your wet (but grease-free) hands, the needle deflection
will be more or less strong. If the anxiety level rises when a person lies intentionally, the 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. 3.169.
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...