Looking for latch circuit advice

Dec 31, 2004 3 Replies

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Jon Yaeger 21 years ago

I've got an ATX power supply that I'd like to turn on and off using a momentary contact switch. I won't be using it with a computer that has a flip-flop type latch circuit - I'll have to breadboard a simple circuit that will do the trick.

There is a 5V DC signal available as a trickle supply. The power supply also has a signal lead with 5V which turns on the unit when grounded. It doesn't latch on.

To summarize, I want a circuit to latch the power supply on (using its own

5V signal & circuit) when the momentary SPST switch is depressed; and off when it is pressed again.

Does anyone know of a suitable on-line circuit?

TIA,

Jon

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Tim Wescott 21 years ago

You should be able to do this with a toggle flip-flop and a debounce circuit. At most this would take a 555 timer and a 7476 -- or save space and do it with a PIC.

Tim Wescott Wescott Design Services http://www.wescottdesign.com

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CFoley1064 21 years ago

Hi, Jon. Make it easy on yourself, and use a small push-on/push-off switch, like Radio Shack p/n 275-617 for $2.29 USD. KISS principle (Keep It Safe & Simple).

However, if you insist, get yourself a CMOS inverter IC and do something like this (view in fixed font or M$ Notepad): ___ .------|___|------. | 10K | | | | | o--| >O--o---| >O-' | |/ | |/ | .-. | | |220K | | | | T '-' | --- | || '--o o---o-----||--. || | .1uF | === GND created by Andy´s ASCII-Circuit v1.24.140803 Beta

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This should do the job.

Questions of this type usually get a better reception on sci.electronics.basics.

Good luck Chris

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