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Modifying ATX Power Supply for 12v Power - Easiest Method?

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  • Power Supplies
  • Power
  • Components
Last response: in Components
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November 7, 2012 2:53:08 AM

I'm building a small box with toggle switches on it. I want each toggle switches to turn on something simple (mostly just LED lights). I was trying to think of how to power the box, and I thought about using an old atx case power supply since I've got an old computer I could pull it out of.

I'm seeking advice because I have no experience with wiring at all.. and I don't want to burn the house down. :) 

If I jump the green and black wires on the motherboard plug so that I can turn on the supply, couldn't I just buy a simple molex Y-splitter and plug it into an available molex plug, and then cut the yellow and black wires and use those for the power and ground?

Here are the Y-splitters I'm referring to:

http://www.amazon.com/Computer-Molex-Power-Supply-Split...

Cut off the plugs from the Y, and run the yellow and black wires to my switch and then run a power wire from the switch to the LED light or case fan or whatever I'm powering off of that switch.

The switches I'm using are 12v automotive toggle switches.

Would this provide the power I need? Would it be too much power? Should I put in an inline fuse or a ohm resistor or something to make it safer?

I appreciate any opinions.. I'm curious if anyone has ever used a molex plug in this kind of way and how it worked. :) 

More about : modifying atx power supply 12v power easiest method

a b ) Power supply
November 7, 2012 12:50:20 PM

Personally I would put a molex receptacle in your 'box' so that there's no need to cut wires and also make replacing the power supply super easy if you had to. I would also find a male 20/24 pin motherboard header for the same reasons.

Why not use the pc's power supply that this will be part of? LED's dont draw alot of power so you wont have to worry about overloading it and then you wont need a second power supply of the 20/24pin header just to wire the on/off switch. You could wire the on/off switch so that the 12v line passes thru it first thing thereby controlling all the led's.

As for adding in a fuse that would be a definite yes.

As for adding resistors I think you'll find that it will be required so that you limit the current thru the led's (unless you plan on using preassembled kits that already have that built in like some led strips used on cars)
a b ) Power supply
November 7, 2012 1:40:02 PM

I am not an electrical engineer, so take this with a grain of salt...

If you just cut both the green and black wires and twist them together, can't you turn on and off the PSU just by flipping the power switch in the back?

Sorry if that is what you meant already, but I wasn't entirely sure that is what you were thinking.
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