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April 1, 2011

Bench PSU

This is a bench-top power supply built to power my various electronics projects.  It is built from a PC Power and Cooling Silencer 470 watt PSU.



Here is the stock PSU:



Power ratings:
28A at 3.3V
32A at 5V
26A at 12V
.8A at -12V

Here is the inside of the PSU.  It is pretty crowded in there as it is.



Next I installed a switch on the front to turn it on and off:



I then cut all the connectors off.


I installed 5 banana jacks on the front: Ground, 3.3V, 5V, 12V, and -12V.



I then connected the wires to crimp-on connectors, which can be screwed to the back of the banana jacks.  Blue is -12V, red is 5V, orange is 3.3V, and yellow is 12V.  I used up to 3 wires per connector, and up to four connectors per jack in order to get the maximum possible current flow.


Switch:


Power LED:


Leads connected to the power jacks:



Switch connected:




In order to start, modern ATX power supplies require a load on them, so I used these ohmite resistors to put load on the 5V and 3.3V rails.


The 5 Ohm resistor on the 5V rail got quite hot, so I built a heatsink for it out of some scraps:




Completely assembled:



Powered on:




 


2 comments:

  1. I've thought about doing something like this for awhile. Good execution and good motivation for me to make my own.

    Thanks!

    P.S. You are doubtless aware, but for the benefit of the casual hobbyist considering building something like this: any voltage combo not using ground will be current limited by the leg of lesser ampacity; e.g. the 23V setup is limited by the -12V rating of .8 amp

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  2. Nice build. I've been using old power supplies for a while for experimenting but never made one this professional looking. I am curious why you put a switch on it as it seems to already have a switch below where the power cable plugs in. It also might be advantageous to note for those planning on doing this that the purple wire is a constant 5 volts even when the power supply is turned off. I always keep this wire handy because if I accidentally short two wires and it switches off, taking the purple wire to ground through a resistor for a split second seems to reset it. Might not work on all power supplies though.

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