555 nighttime automatic bright showing light circuit

Published:2011/5/23 1:58:00 Author:TaoXi | Keyword: nighttime, automatic, bright showing, light circuit | From:SeekIC

As the figure 17-37 shows, this circuit is composed of a photoelectric switch and a oscillator, it can be used to automatically show the signs and barriers. The phototransistor VT1(3DU5) has the low resistance because of the illumination, VT2 cuts off, VT3 conducts, SCR cuts off because of the G port has the low electrical level, the indicating light turns off. At night, the c-e of the 3DU5 tube has the high resistance, VT2 conducts, VT3 cuts off, SCR conducts, and the IC starts working. The astable multivibrator is composed of the IC and RP1，R5，R6，C1, T=0.693(RP1+R5+R6)C1, the oscillation period is in the range of 2 to 10 seconds.



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