Using push button for On/Off

[Sid2286]

Hi,
I was wondering how to use a push button for On and Off Application. Just like how it is in laptops or computers.
i'm out of ideas...please help...I don't want to use a slide switch.

Regards,
Sid

[SherpaDoug]

Keep track of the current state, either On or Off. When the button is pressed, and the press is qualified by whatever switch debouncing* you choose to use, change the current state to the other state.

* Note that mechanical switches tend to bounce when pressed and give a quick series of switch closures. One simple debouncing method would be to sense the switch close, then wait 10ms and see if the switch is still closed before deciding this is a single valid switch closure.
_________________
The search for better is endless. Instead simply find very good and get the job done.

[John P]

I'm assuming that you're asking about a circuit where you could turn a system on with a pushbutton, then turn it off again with the same button. This doesn't do exactly that, but it does allow a processor to control its own power. You could easily add an "off" button to the processor, telling it to kill its own power, or you could add circuitry to monitor the "on" button so if it's held for 5 seconds, that would also tell the processor to kill power, once the button is released. The circuit is designed to be mounted in a hand-held box where conductivity through the user's skin would turn power on, so it's sensitive to low currents.