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Simple Timer Circuit
This timer circuit has main component an IC
MC14001 which is a CMOS IC that contains 4 pieces of logic NOR gates with 2
inputs and 1 output. To make this circuit needs only two gates only, whereas
the other 2 pieces of unused gates.
This circuit will begin work when the button is pressed, then fills up 10nF
capacitor voltage approaches 12 volts, while the low voltage polarity
give an input to the NOR gate (pin 5). So that the output (pin 4) will be
high, which make the 3300 UF capacitor voltage will be filled with the
polarity reversed, and the negative voltage fed into the other NOR gate (pin
no 2 and 1) which makes the output (pin3) becomes high and activate the
relay. The relay will last until 3300 uF capacitor polarity voltage is
changed, that which will turn off the relay. Timer will change the time by
replacing the 3300uF capacitor with different values (the smaller will be
getting smaller all the time)
Figure 1. Simple timer circuit.
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