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CPU Power Supply Mod
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CPU Power Supply Mod
Howdy!
This project came out of wanting to etch my first useful PCB (up to now all the PCBs I've made have been tests). I have a old CPU power supply that's been laying around for awhile, so I decided to convert it to a PSU I could use on my bench.
First I started googling around for info on it, and found that it uses a standard computer PSU pin-out called ATX 2.x. The wikipedia article on it is here: https://en.wikipedia.org/wiki/ATX#Power_supply.
The specifications for the power supply are as follows:
I'm planing to make all the circuitry handle about 3A maximum current draw on each voltage (I'm going to fuse it for 2.5A for now though). If I ever want to be able to draw more current then that (which is not likely), I guess will just have to modify it some more.
- +3.3VDC/17A
- +5VDC/22A
- +5VDC/2A (Standby)
- +12VDC/18A
- -12VDC/0.8A
- 300W Max power
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So the first order of business - draw a schematic. Here it is:
View attachment 22136
I decided to use a PIC18F1220 for this project because I have quite a few laying around. A 1602 LCD will be used for the user interface – I'll need some way of telling the user which voltages are switched on. Three switches will work for user control (Select/up/down – or something like that).
P4 is a jumper (it connects PGD to ON1 and PGC to ON2) and is there for when the PIC is programmed – Since I ran out of I/Os I had to use the two pins that are for programming the PIC. And when the PIC is programmed, I don't want anything screwing up the communication between the computer and the PIC, so P4 should be unjumped while programming (is that even a word? ).
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Here's the PCB layout:
View attachment 22137
Yes, I know that the fuses overlap other parts - The plan is to have the fuses mounted on the back side of the circuit board and the rest of the parts on top. The relays are just some high current ones that I salvaged from a used circuit board (I think they where out of a broken fryer to be exact).
Unfortunately, I will have to solder about eight jumpers on where I couldn't figure out how to run a trace (not shown here, but they can be seen in the KiCAD file as un-routed traces). I guess I should have tried to optimize it a little more, but space was kind of lacking...
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On to etching!
View attachment 22140View attachment 22139
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