Light-Controlled Flicker

Project Number: 45

OBJECTIVE: To make a circuit that uses light to control the blinking of another light.

Description: This circuit does not use the noisy speaker (SP); it uses a nice, quiet LED (D1). Turn on the slide switch (S1), the LED flickers. Wait a few seconds, then cover the photoresistor (RP) and the flicker stops. The flicker is controlled by the photoresistor, uncover it and the flicker resumes. People who are deaf need lights to tell them when a doorbell is ringing. They also use circuits like this to tell them if an alarm has been triggered or if an oven is ready. Can you think of other uses?