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power supply software switch hack

Posted on 2003-02-23
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Last Modified: 2010-04-26
Anyone know the proper way to hack a software power supply switch for use as a hard switch?  I am using the supply for electronic uses outside of a computer.  

Taking what seems to be the software switch - only connection with constant +5V - and grounding the white wire thorugh a 300ohm resistor (logic low) seems to turn the supply on.  Should I use a bigger or smaller resistor?  Is this the proper way to do this?  Any suggestions or improvements?
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Question by:dhammy69
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jhance earned 150 total points
ID: 8004715
The use of a 300 Ohm resistor seems reasonable.  You could, of course, use a smaller value since a "real" pushbutton switch on the PC front-panel shorts the "PO" signal to "GROUND" to signal a POWERON.

If you need to control this from a different piece of equipment, however, I'd recommend ISOLATION to prevent and ground differential or noise problems between the two units.  The best way to to this is via a RELAY or an OPTO-ISOLATOR device.  If you need more details about either of these, please let me know and I can draw some schematics for you.
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by:public
ID: 8005091
The supply is intended to be switched with a logic gate. No resistor is needed.. You can also use a transistor, optocoupler, mechanical relay, or any other similar device.
You can also permanently groung the pin, and only use the main ac switch in the back.
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by:dhammy69
ID: 8005468
I guess I was worried about pulling too much current by switching the white 'signal' straight to ground.  But I guess that is how it is designed to be used.  I will add a straight toggle switch (no resistor) and I'll be done - no need for isolating in this case.  Thanks!
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