PC PSU into a Lab PSU

[LaZeRz]

Hey guys

Well, I would like a lab PSU to test LD's on, set driver currents with and other stuff like that so I'd like to turn my old PC's 400w PSU in to a lab PSU

I have a vague idea on how to do it but I need help, so, if someone can try and tell me which colour wires are which voltage it would be greatly appreciated

Il post some pics up in a while

I'l probably drill some holes in the side for each voltage and put a label ontop

Thanks!

 

[LaZeRz]

Pics:

 

[laserpyro]

No Service-able components inside.:crackup:
We'll see...

 

[LaZeRz]

:eg:

We shall see, I realize why that stickers there.... Those two HUGE 200v caps are scary

 

[Kevlar]

I have looked into doing this in the past. I recently got a great deal on a bench PSU on ebay so I won't be doing it anytime soon but I have done some research. Here are a few links which looked most helpful to me. I hope they are as helpful to you. :beer:

Converting a PC Power Supply
PC Power Supply
How to Convert a Computer ATX Power Supply to a Lab Power Supply - wikiHow

 

[Trevor]

Those caps aren't that big...

I think you need to short the green wire to ground and put a load on a 5V rail - I used a 10Ohm 10W resistor.

-Trevor

 

[LaZeRz]

How exactly can I short the wire to ground? Sorry, I am on my iPod Now and my rooms pretty far from the router so internees slow (no, I'm not too lazy to move, I'm "sleeping")

I shall look into those links tomorrow Kevlar, although I want something kinda simple and that wikihow one is pretty complicated

Will just grouping all the different voltage wires work or do I need to add caps etc.

Thanks

 

[Trevor]

If I remember right I:

1. Soldered the green wire to a black wire (ground).
2. Soldered a 10Ohm 10W resistor to a 5V rail (connected to ground of course). This gives the PSU a load and makes it light up.
3. Clipped unwanted leads.

Your PSU might have difference color coding though. But since you do have a green wire, yours is probably the same as mine.

-Trevor

 

[LaZeRz]

Tomorrow after my exams I will clip all the wires and head off to an electronics shop to buy a resistor

Any pics of your PSU Trevor?

 

[Trevor]

I can take photos if you want when I get home form work. That'll be like 10 hours from now.

Your PSU is definitely coded the same way mine is (following the ATX standard). I think I used this tutorial:

How to Convert a Computer ATX Power Supply to a Lab Power Supply - wikiHow

Make sure to read the tips section. I decided to solder the green wire to ground so I could use the rear switch, based on what I read in that section.

-Trevor

 

[LaZeRz]

So any black wire can be used for ground right? And then do I just connect 1 black wire to each of the different voltage outputs?

 

[Trevor]

Yep, black is ground. That's pretty standard. I only put the load on a 5V rail, and I think the tutorial also says that.

-Trevor

 

[Asherz]

I setup one of these recently, the first one I tried building into the actual PSU enclosure, unfortunately one of the circuits I built shorted with a heatsink inside the PSU (scared the crap outta me.)

So I decided to build it into a separate enclosure.

For mine I took a 24 pin cable extender, cut one end of and used the connector that would allow me to plug the 24 pin from the PSU into it, I then mounted this on the side of my new plastic enclosure so I could plug any PSU in and out.

inside the enclosure, I built a circuit that allows a variable voltage between 1.5V & 12V, it actually uses very similar components to the DDL circuits we use around here

YOU literally have no idea how long I spent trying to find this web page again lol, it helped me a lot putting together a variable circuit for the power supply, but I couldn't find the dam page again, after doing a non related search I luckily came across it again:

LM317 Voltage Regulator

You take the yellow 12V+ and black GND input to the circuit, NOT 12v+ and 12V-, whilst that will give you 24V, the -12V line can normally only take around 0.5A of current.

I also recommend using an LM350, instead of LM317. It's exactly the same except it can take 3A instead of a measly 1.5A You will need a pretty decent heatsink here as well, I took one of some component on an old motherboard.

I followed this tutorial for the wiring of the LED/switch and the load resistor:

How to Convert a Computer ATX Power Supply to a Lab Power Supply - wikiHow

Goodluck! Hope this helps The variable PSU works great, it's especially handy as I can emulate inputs from different sized batteries easily and the output never drops or sags like batteries do.

 

[Trevor]

I must do that. That's a very useful link.

+1

-Trevor

 

[Asherz]

I must do that. That's a very useful link.

+1

-Trevor

Cheers, glad it's helpful. I literally spent like the last hour and a half trying to back track my steps to find the page, found it in the end after googling something like 10k potentiometer after I gave up looking for it

 

[LaZeRz]

OK, so Im gonna pick up a little project box and all the parts that I need for a adjustable voltage PSU

Il post back when I finish the project

+1 to everyone that I can rep

sorry cant rep you yet Kevlar

Also, what DMM would you reccomend me pick up while im at the electronics shop?

this : http://www.jaycar.com.au/productView.asp?ID=QM1320&keywords=digital+multimeter&form=KEYWORD

or this: http://www.jaycar.com.au/productView.asp?ID=QM1535&keywords=digital+multimeter&form=KEYWORD

EDIT: On second thought, I think it would be much better for me to do what ashers did and use a lm350/317 to make a variable voltage PSU because 12volts will be too much to power drivers with and 5 volts will be too little for linear drivers running a 445

So my shopping list just got heaps longer