Automatic power switch for ATX power supplies

If you have a computer, for example, wants to operate for a long time like a server,  when using a standard ATX power supply the  problem exist  after a power failure that the computer is’nt automaticaly turn on. A few motherboards can do those  function, just to set using the BIOS Setup, and the other way is to make the automatic power switch.

An ATX power supply is normally controlled by the motherboard.  ATX power supply provides a  5 V standby voltage, when  power is used. This standby power  controls a small circuit on the mainboard,  also the power switch that connected to the housing. If you push this switch, it triggers the power-on management of the power supply to ground, which will turn the led and power supply  turn on . This will enable all system voltages. As long as the motherboard doesn’t put the power-on wire to ground, nothing will happens. As mentioned, there are motherboards that recognize the standby power switch after setting  the BIOS setup.  However there are no such  motherboard remains after switching on the mains voltage from the first.In order to solve this problem can be found at the various methods. The most frequently methods is to connect using  jumper on the power line cable connector (normally green) with a ground wire ( black ). This method works in principle, but has the disadvantage that its can  permanently destroying the output driver of the corresponding control logic, and so the motherboard. Thats why this circuit is build :


The design of the circuit is pretty simple. The quickest way to build the circuit is using a breadboard.  but if you need to etch a Pcb,  here is the pcb layout:

automatic power switch pcb layout

Bottom pcb layout

Top pcb layout

Top pcb layout

The installation in the computer is simple. There are few pictures from a thin-client computer made, where it’s possible to understand . First  you have to measure  at the power-on connector on the motherboard using a multimeter, which of the two pins to ground. Not like a real button you can find that the above circuit isn’t just about to plug to the motherboard. Then separated on the standby line and a ground wire on the power supply, requires a terminal block between and then closes the circuit to it

Important Note: The copy of this circuit at your own risk. The author of this site assumes no liability, in particular ensuring that the circuit works as described above. It is also can not take liability for any damage caused by this circuit.



Gallery of Automatic power switch for ATX power supplies

Tags: atx power supply automatic power switch

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