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The protector circuit of 555 full auto fridge

2016-09-12 16:42  
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The protector circuit of 555 full auto fridge
IC1(555),R1~R3,RP1,RP2 ,VT1 and so on consist a over/low voltage circuit. In the voltage range of 170V~240V, the 2-lead of IC1 is in a low voltage, which offsets 555, the output terminal of 3-lead is in a high LEV. Across D3 and R7, the LEV is imposed on VT2 base electrode, and it cooperates with the time delay circuit so that VT2 saturates and becomes conducting, J pulls in and Ja-d are getting through, then the outlet gets power. When the voltage is under 170V or over 240V, the 2-lead of 555 is in a high LEV, and the circuit is reset, the 3-lead is in a low LEV. The time delay circuit consist of VT3,VT4,R8,C4 and so on.