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555 home appliance finger touching protector circuit

2016-09-27 14:53  
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555 home appliance finger touching protector circuit
As the figure 15-10 shows, the protector is composed of the finger touching monostable circuit, the music circuit, the control circuit and the step-down rectifier power supply circuit. This device can be used in the applications of children' finger touching fan metal mesh and other electrical equipments' safety protection. The monostable delay circuit is composed of the 555 and the R2,C1, when the fingers touch with the metal mesh or the sequin TP which is connected with the protective cover, the human sensing signal gets into the 555's trigger port - pin-2, the 555 sets, pin-3 has the high electrical level, VT1 cuts off, the SCR cuts off because there is no trigger current, so the motor M stops. The stop time (the monostable temporary stability time) td=1.1R2C1, the parameter of the figure is about 6 seconds. If the person leaves, the motor will automatic recover operation after 6 seconds.