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ChrisOFNA
04-25-2006, 02:36 AM
My friend said I can take his post and post it elsewhere. This is how you can make an old computer power supply (400W preferred, I dont know if any lower watt would work) into a power supply you can use for chargers, motor break in, and lathes. Its a cheap CHEAP alternative than the 60-100 a made power supply works. Sticky this if possible.

You will need an ATX power supply and a 21W/5W or so car stop / tail light bulb (dual filament) and socket with ground tab/wire.

There are a number of multi-plugs on the power supply, we’ll do each one separately.

20 way long, thin one (10 on each side):

Pick out the green wire and one of the black wires, cut them off the plug, strip them and solder them together. Insulate the connection with heat shrink.

Pick another black wire, cut it and solder it to the ground wire on your stop/tail light socket. Insulate the connection with heat shrink.
Pick a red wire and solder it to the stop light (21W) wire of your stop/tail light socket. Insulate the connection with heat shrink.
Pick a yellow wire and solder it to the tail light (5W) wire of your stop/tail light socket. Insulate the connection with heat shrink.

Plug in the power supply and the fans should start. The light should come on too, the stop filament (the thicker one) should be relatively dim and the tail one should be bright. If it’s the opposite, reverse the connections for the red and yellow wires.

Unplug the power cord.

There are several cable harnesses with four way plugs on them. Cut all the yellow wires at the first plug they come to, strip them and join them all together. Cut the same number of black wires and strip and join them too. Some may only have one yellow wire, in which case you’ll only need one black wire. Solder the yellow wire(s) to a red alligator clip, and the black wire(s) to a black alligator clip. This pair, yellow (+) and black (-) are your 12 volt supply for charging, etc.

Off the same harness, pick a red and black wire. Solder the red wire to a red alligator clip, and the black wire to a black alligator clip. This is your 5 volt supply for running your motor lathe.

On the 20 way connector, pick an orange and a black wire. Solder the orange wire to a red alligator clip, and the black wire to a black alligator clip. This is your 3.3 volt supply for breaking in electric motors.

Bundle all of the other wires up and ziptie out of the way. I recommend that you use zipties to bundle each pair of wires for the 12V, 5V, and 3.3V supplies together, and then label each pair so you don’t forget which is which. Hitting your newly cut motor with 12V is going to do more then break it in.

You can use all of these outputs at once if you want.

FAQ’s:

Is there a way to wire an on/off switch rather than having to plug and unplug the power supply constantly?

Instead of joining the green wire to the black one permanently, you could put a switch there. Shorting green to black sends a power on command to the power supply, if the green wire is open, the power supply shuts down.

What is the purpose of the stop/tail light bulb and socket?

It acts as a minimum load to stabilize the power supply, they don’t like having no load at all. It also makes the output voltages more accurate as the internal regulator has got something to do. Some people use resistors (1 ohm/25 amp), but the lamp is easy to get and does the job well.

mOOsE
04-25-2006, 02:45 AM
and always test these on a built in breaker or a socket with a breaker......and outside if possible..IMO

ChrisOFNA
04-25-2006, 04:31 PM
My friend has built about 10 of these this way... Im pretty sure its well tested.

mOOsE
04-25-2006, 11:47 PM
you should always test it in a safe place, no matter what though ya know....
You should even test name power supplies in a safe place. Just my opinion though. I am also running a computer powersupply, very old computer power supply but very powerfull.

ChrisOFNA
04-25-2006, 11:51 PM
Ahh ok... I have to apologize, i thought you were saying it was gonna catch on fire when you plug it in...

bermbuster
04-26-2006, 12:21 AM
can you let the alligator clips touch each other???? :eek:
It is a good idea to use shielded clips and make sure they dont touch (dead short)

ChrisOFNA
04-26-2006, 12:34 AM
no, you cant... i use sheilded ones