Push button start-stop computer psu without motherboard

[Bobsone]

Hi
First I have posted a question about this in another forum, https://www.electronicspoint.com/th...stop-computer-psu-without-motherboard.276936/

Second, I am a novice, I have a little experience with building circuits so I can claim enough knowledge to get myself into trouble...

Following a response to my other thread I was looking for a solution where I could use a constant 5v supply to switch a second 5v to ground to start stop a computer psu with the cases push button when there is no motherboard.

My online searches brought me to your forum, specifically to a 2011 thread https://www.edaboard.com/threads/202518/, specifically, the following image from an answer posted by hotwaterwizard looked interesting;

**broken link removed**

As I understand things, this uses a 5v supply to NE555 and to the relay which with the activation of S1 should switch X2-2 between X1-1 and X1-3.

So, am I correct that this would solve my problem (perhaps with a different relay) I.e. use the constant 5v supply (purple wire) to switch the green 5v wire to ground to start-stop the psu with a push button. Also, what are X3-1 and X3-2 for and what is the purpose of the 5v to ground through X1-2 and X1-1 circuit?

Regards

 

[FvM]

The circuit can control a ATX power supply without a relays by simply connecting T1 collector to PS_ON# (green) and 5V to +5VSB (purple) and GND (black).

 

[Bobsone]

I have now picked up the case so I can confirm the PSU operation. Good news, it has a purple wire which functions as expected, but the front panel switch is a push button (non latching) unit.

With regard to the attached circuit, I haven’t seen a switch (S1) drawn that way before, can you tell me if am I correct in concluding that S1 is a push button latching switch?


Also, if S1 is a latching switch, does the circuit also have a latching process, or will I need a different design to maintain a green wire to ground-open when the front panel button is pressed and released?

Thanks

 

[FvM]

The latching circuit for PS_ON# is part of the motherboard, the linked circuit implements a similar function with a push-button. NE555 is used as latch.

If you have a latching switch, no additional electronics would be required.