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CM-200_Manual_031914.qxp_CM-200_Manual_031914 4/2/14 12:04 PM Page 51
Project #108
The Lie Detector
Turn on the slide switch (S1) and place your finger across points A & B. The speaker (SP2)
will output a tone and the LED (D1) will flash at the same frequency. Your finger acts as a
conductor connecting points A & B. When a person is lying, one thing the body starts to do
is sweat. The sweat makes the finger a better conductor by reducing its resistance.
As the resistance drops, the frequency of the tone increases. Lightly wet your
finger and place it across the two points again. Both the output tone and LED
flashing frequency increase. If your finger is wet enough, then the lamp will be
bright and the sound stops - indicating you are a big liar! Now change the
wetness of your finger by drying it and see how it affects the circuit. This is the
same principle used in lie detectors that are sold commercially.
Project #109
Project #110
Clicking Liar Slow Clicking Liar
Change the circuit by removing the
LED and 4th level 1-snaps and placing
the 0.1mF capacitor (C2) on top of the
whistle chip (WC), on level 5.
Project #111 Photo-Powered Recording
Build the circuit shown and press the
press switch (S2). It plays a recording
followed by one of three songs. Adjust
the amount of light on the
photoresistor (RP) to change the
volume and alter the tone. Wave your
fingers over the photoresistor for
some cool sound effects.
You can change the recorded
message. Turn on the slide switch
(S1), you hear a beep signaling that
you may begin recording. Talk into the
microphone (X1) up to 5 seconds, and
then turn off the slide switch. Partly
covering the photoresistor will reduce
the recording quality.
Replace the 0.1mF capacitor (C2) with
the 10mF capacitor (C3, “+” side on
left).
Project #112
Photo Whistle
Music
Use the preceding circuit. Replace
the speaker (SP2) with the whistle
chip (WC) and then place the 100W
resistor (R1) over it using a 1-snap.
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