LIGHT_SENSITIVE_OSCILLATOR

Published:2009/7/3 2:39:00 Author:May | From:SeekIC

Uses 555 timer connected so frequency increases directly with intensity of light. Free-running frequency and duty cycle of timer operating in astable mode are controlled by two resistors and one capacitor. R3 sets upper frequency limit at about 6.5 kHz, and dark resistance of photocell R2 sets lower limit at about 1 Hz. Loudspeaker provides audio output, while LED flashes for visual indication when frequency goes below about 12 Hz.Applications include detection of lightning flashes, use as optical radar for blind, and use as sunrise alarm.-C. R. Graf, Build a Light Sensitive Audio Oscillator, EDN Magazine, Aug. 5, 1976, p 83.



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