Elenco Circuit Maker Sound Plus 200 - Manual (Page 45)

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Project #90
Cover the photoresistor (RP) and turn on the slide switch (S1). The LED
(D1) is bright, but it will very slowly get dimmer and dimmer as the 100mF
capacitor (C4) charges up. If you turn the slide switch off and back on
after the light goes out, it will NOT come on again. Press the press switch
(S2) to discharge the capacitor and reset the circuit.
If you uncover the photoresistor and let light shine on it, then the LED
will get dark quickly. The photoresistor has much lower resistance with
light on it, and this lower resistance allows the capacitor to charge up
faster.
Photo-Off Night Light
Project #91 Sunrise Light
Cover the photoresistor (RP) and turn on the slide switch (S1). The LED
(D1) is off, but if you wait a long time then it will eventually light up.
Uncover the photoresistor and the LED will light up in just a few seconds.
Press the press switch (S2) and reset the circuit.
The resistance of the photoresistor controls
how long it takes to charge up the 100mF
capacitor (C4). Once the capacitor is charged,
current can flow into the NPN transistor (Q2)
and turn on the LED. Pressing the press
switch discharges the capacitor.
CM-200_Manual_031914.qxp_CM-200_Manual_031914 4/2/14 12:04 PM Page 45