Project #272 photoresistor control, Project #273 microphone control – Elenco Projects 102-305 User Manual
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Project #272
Photoresistor Control
OBJECTIVE: To use a photoresistor to control the brightness of
an LED.
In this circuit, the brightness of the LED (D1) depends on how much
light shines directly on the photoresistor (RP). If the photoresistor
were held next to a flashlight or other bright light, then the LED would
be very bright.
The resistance of the photoresistor decreases as more light shines on
it. Photoresistors are used in applications such as streetlamps, which
come on as it gets dark due to night or a severe storm.
Project #273
Microphone Control
OBJECTIVE: To use a microphone to control the brightness of an
LED.
In this circuit, blowing on the microphone (X1) changes the LED (D1)
brightness.
The resistance of the microphone changes when you blow on it. You
can replace the microphone with one of the resistors to see what
resistor value it is closest to.