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555 multi-function appliance protector circuit

2016-09-27 09:45  
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555 multi-function appliance protector circuit
As the figure 15-7 shows, the protector circuit is composed of the DC voltage-stabilizing circuit, the delay circuit, the over-voltage under-voltage protection circuit and the execution circuit.etc. The IC1(7812) outputs the +12V DC voltage. The over-voltage under-voltage protection circuit is composed of the R2, RP2, DW1, VT1 and R1, RP1, DW2, VT2 and the NAND gate circuit D5,D6, the relay control VT3.etc. When the AC voltage is lower than 180V, the DW1 and DW2, VT1, VT2 cut off, D5 conducts and the VT3 is saturated conduction, the realy J closes, the contact point of J1-1 closes, pin-6 triggers, 555 resets, pin-3 outputs the low electrical level, SCR cuts off, the socket has no power. When the city electricity voltage is higher than 240V, DW2, VT2, D6 conduct.