BACK_UP_BEEPER

Published:2009/7/6 3:39:00 Author:May | From:SeekIC

Put the car in reverse and the circuit provides a loud, audible beep at the rate of about one per second (1 Hz). Half of U1, a 556 dual oscillator/timer, is used as a slow-pulse oscillator with a rate of about 1 Hz. Components R2, R1, and C1 form the long time constant. You can calculate on time by t=.7 (R1 + R2) C1 or 1.15 seconds. The off time is shorter than the on time, at.77 second. Enabling pin 4 (reset) is held high to keep the oscillator freerunning when voltage is applied to pin 14. The output at pin 5 is coupled to pin 10 of U1 enabling oscillator 2. Oscillator 2 of U1 produces an audio output of about 1 kHz, as determined by C2, R3, and R4. Pin 10 (reset) of oscillator 2 is connected to the pin 5 output of oscillator 1. So when pin 5 becomes positive, the oscillator beeps a short pulsed tone of 1 kHz.



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