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555 adjustable timer circuit for hours

2015-02-04 17:40  
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555 adjustable timer circuit for hours
As shown in the figure 12-17, the circuit is composed of rectifier circuit, actable multivibrator IC1, count circuit IC2, unijunction oscillator and SCR AC switch. The rectifier circuit outputs 10V DC voltage, once the switch K is turned on, the CMOS type 555 starts to oscillate. The oscillation frequency can be changed by adjusting RP1, it is continuously tunable from 0.1~1Hz. IC2(CC4040) is a 12 bit binary serial counting/frequency divider. When the switch K is closed, due to the voltage of C9 can not suddenly changed, R terminal(11 foot) has a positive peak pulse voltage, it puts each trigger of CC4040 integrated block on 0 .