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Old 07-23-2008, 01:17 AM
BWHH BWHH is offline
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Default Constant to Momentary Relay PC Applications

Hi All,

I'm looking to build a simple circuit that would take a contstant 12v feed and momentarily trip a relay.

The plan is to use this:

To turn a PC on and off, but the trigger on the PC only needs the power switch to be closed momentarily.

Any ideas?

Thanks for the help!
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Old 07-23-2008, 02:25 AM
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SgtWookie SgtWookie is offline
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If a PC is plugged in, there is a 5V source that's always available.

Check out the specifications for the power supply in your PC by form factor.

There is really no need for an external supply.

But perhaps there is. You need to give more details.
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If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
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Old 07-23-2008, 04:10 PM
BWHH BWHH is offline
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What I want to do is power up a PC using the remote control. The problem is, a power switch on a PC is momentary.

This would be independent of the system's PSU. All I'm really trying to do is replace the simple momentary power switch on the PC with a remote control. With the remote I've linked, I would need a way to take its 12v output to trip a relay, but the relay would need to disengage in a second or two max.
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Old 01-23-2009, 04:47 AM
rezmax rezmax is offline
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Default Momentary switch

This will solve your problem.
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Old 08-04-2009, 11:30 PM
p_circuit p_circuit is offline
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Default Constant to memory_circuit diagram

The diagram shows that the capacitor is installed between the ignition switch a nd the ground> Is this correct?

Is that a standard automotive relay?> I though you need a 2 way coild relay for the momentary function to work.

Does the value of the resistor matter in relation to the cap?

Is the resistor installed on the ground end of the relay?

Does the resistor bring the capacitor back to 0v after the ignition source is switched off?
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