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Modern electronic equipment
incorporate "push-to-on-push-to-off" switches that do not make the
clicking noise as with old equipment. An example of this is the
power button on a ATX computer cabinet. Here is a circuit that
does the same. It can be used to turn on/off any
electronic/electrical equipment that operates on any range of
voltages.
When the "ON/OFF" button is pressed once, the equipment goes on
and stays on. It goes off when the button is pressed again. The
circuit is straight forward. It uses a JK CMOS FlipFlop to with
its JK terminals tied high to achieve the toggling action. The
clock is provided by the push button used for on/off action. The
resistor and the capacitor near the on/off switch debounces the
contacts.
Note that when the circuit is switched on, the relay may land in a
on or off state. It can be brought to the off state by pressing
the RESET button.
Care should be taken that the relay's current does not exceed
100mA.
Since the IC is CMOS, it can be operated from 3V to 15V, but in
this circuit it is operated at 9V for a 9V relay. The relay
circuit needs to be modified for other operating voltages.
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