Looking for latch circuit advice

[Jon Yaeger]

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

 

[Tim Wescott]

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

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.

 

[CFoley1064]

Subject: Looking for latch circuit advice

From: Jon Yaeger [email protected]
Date: 12/31/2004 11:32 AM Central Standard Time
Message-id: <BDFAF771.13080%[email protected]>

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

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 www.tech-chat.de

This should do the job.

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

Good luck
Chris

 

[Jon Yaeger]

I appreciate your advice - thank you!

Jon