555 long delay timer circuit 1

Published:2011/6/20 8:02:00 Author:TaoXi | Keyword: 555, long delay, timer circuit | From:SeekIC

This circuit is composed of the multivibrator (which is composed of the 555) and the monostable circuit. The oscillation frequency of the multivibrator f=1.44/(R1+R2+Rw)C1. The oscillation frequency of the figure parameters is about 600Hz. When the power turns on, the voltage of C5 can not change, so the set port has the low electrical level, the output port pin-3 has the high electrical level, the relay closes, the J1 closes to maintain the power supply; the J2 closes, the load operates. At this time, the internal disrharge tube which is connected with the pin-7 of the IC2 cuts off, the C3 is charged by the output of IC1 with the square-wave step type. When the threshold level is 2UDD/3, pin-3 has the low level, the timing time is up, the relay releases, the J1 and J2 cuts off, the load stops working.



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