The flash signpost light circuit

Published:2011/6/17 8:05:00 Author:Borg | Keyword: flash signpost light | From:SeekIC

E.g 7 the flash signpost circuitSee as figure 20-7, the circuit consists of the transforming rectifier circuit, light control switch and non-steady multi-resonance oscillator, etc.The light dependent triode 3DU5 is in a low impedance due to the light in the daytime, which makes the power switch pipe TWH878 block due to the low control voltage of 5-pin, and IC(555) doesn't work without power, SCR is blocked, the light is OFF. The it's dark outside, 3DU5 is in a high impedance without light, which makes the voltage on 5-pin of TWH8778 higher than 1.6v, the switch pipe is conducting, IC is oscillating because of getting power. The oscillating frequency is f=1.44(R2+R3)C2.The frequency responding to the figured parameter is about 1Hz.



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