555 household automatic lighting switch

Published:2011/5/22 18:57:00 Author:TaoXi | Keyword: household, automatic, lighting switch | From:SeekIC

As the figure 17-24 shows, you can use the photosensitive sensor and the magnetic switch to control 555's trigger state and power supply, at night, this circuit can automatically open and auto-off delay. The city electricity is stepped down and rectified by the circuit, then it becomes the 12V voltage to supply the 555. The controllable trigger delay circuit is composed of the 555 and R1，C2，VT1, RP1. In the day time, the VT1(3DU5) is in the low resistance state because of the illumination, so the 555's pin-4 has the low electrical level (<0.7V), the 555 is forced to reset, pin-3 has the low electrical level, SCR cuts off.



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