Fun with the Alarm IC

Project Number: 83

OBJECTIVE: To show some new ways of using the alarm IC.

Description: Build the circuit shown and place the fan on the motor (M1), but leave the jumpers off for the time being. Turn on the slide switch (S1) and tap the whistle chip (WC), it makes a machine gun sound (with music in the background). Thoroughly cover the photoresistor (RP) with your hand and the sound becomes a siren. With the photoresistor covered, press the press switch (S2) and the sound becomes that of an ambulance. Uncover the photoresistor and the sound remains that of a machine gun whether the press switch is pressed or not. After a while the sound will stop, tap the whistle chip and it resumes. Connect the two jumpers as shown and tap the whistle chip to resume the sound. The lamp (L1) and the LED (D1) light and the motor spins. The sound continues, but it may become distorted as the motor speeds up. The motor draws a lot of power from the batteries (B1), and this may reduce the voltage to the music (U1) and alarm (U2) ICs, distorting the sound. The sound may even stop if your batteries are weak.