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ATX PSU to Work Bench PS - Adjustable Voltage and Current question Answered

I am working on converting an old 600W ATX PSU to a bench power supply for me to use for some lab work.  Not everything that I will be plugging into it will have built in current limiting capabilities.  The guide/setup i found on here that I will most likely be following are:  https://www.instructables.com/id/DIY-PSU-into-Bench-Power-supply/  &  http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply

The first link is how I would like mine to end up looking.

My PSU is rated as:
+3.3V @ 32A
+5v @ 50A
+12v @ 24A
-12v @ 1A
-5v @ .5A

My end goal is to be able to control the voltage and current output from each binding post.  I will be hooking up a multimeter to this as well and am thinking that i could control what it monitors by some dipswitch setup or switching setup(as far as to which binding posts it's monitoring).

I do understand that V = IR.  So keeping 5v but only wanting 3A, i would increase the resistance which is why at first i thought i could play a POT in the circuit.  However after seeing how the voltage regulation was hooked up, I am confused how to do so now since it was connected in the fashion i thought i would need to control the current.  (https://www.instructables.com/files/orig/F2D/LMFU/FYYNECNH/F2DLMFUFYYNECNH.jpg)

I would probably use a LM338 since it would allow for more current but again, i would love to be able to have the full 50A available all at one shot but i don't think those IC's allow for that.

I am extremely new to all of this and am still learning as well, so if i was able to communicate what i am looking to do correctly and you have a way of explaining it to me, a picture would be awesome if you have the time to create one. :D

TYIA for any suggestions.


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The Skinnerz
The Skinnerz

10 years ago

For the voltage regulation, commonly available regultors such as these can handle about 5A, enough for virtually all digital electronics. For higher currents, you may want to consider a PWM system with a decent sized smoothing cap, and a suitable processor to control the switching (could double up as a signal generator)

As for the current regulation, you are going to need a fast blowing fuse or trip switch to protect the PSU if you happen to short it, as they are easy to break, and very difficult to fix.

What are you planning to plug in that will draw 50A?

Another thing on the current regulation:
If the voltage supplied is fixed, the current draw by the load depends on the resistance of the load, so adding a pot will only increase total current draw. You can only measure and limit and measure the current, not control it. However, you can regulate the current by varying the voltage.