Photosensitive oscillation circuit

Published:2011/4/29 23:16:00 Author:Nicole | Keyword: photosensitive oscillation | From:SeekIC

The pulse oscillator is composed of timer 555, the timing resistor consists of photosensitive tube internal resistance R2, resistance R3 and R1, the photosensitive tube internal resistance R2 changes in relation to light intensity. The oscillator frequency is decided by timing resistor and timing capacitor 0.01μF. So when the light intensity changes, the oscillator frequency changes too. After transformer drives loudspeaker, the pulse singal of 555 output terminal ③ sends out noise, it can identify the light intensity according to the pitch of monitor tone. If it is low in pitch, then the light is weak; if it is high in pitch, then the light is strong. LED is in series with transformer, when the frequency is lower than 12Hz, it will flash and provide a visible singal.



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