best/ easy way to test current capability of ATX ps?

Thread Starter

BillRush5

Joined Jan 13, 2013
24
What's the best/ easiest/ cheapest way to test the maximum current capability of an ATX computer power supply? If I have one rated at 12V@14A and I want to test for 10 amps, what would I use? I want to avoid burning up the test subject if possible. Thanks.
 

GopherT

Joined Nov 23, 2012
8,012
Make it drive an old-school car headlight. Be safe and make sure you understand they are very bright and get hot. Set it on concrete or something else safe. Also make sure you use good electrical contacts. You will need to tie the high-beam with the low-beam (normally 55W + 65W). This gives total of 120 watts, 10 amps.

Also, make sure you know how the ATX power supplies work, there is an enable wire that must be grounded - soft on/off. Various websites describe how to make ATX power supplys into bench power supplies. We just reconfigured one for a RepRap 3D printer power supply that must heat the build surface (10 amps at 12 volts + 10 amps at 5 volts).
 

mcgyvr

Joined Oct 15, 2009
5,394
Whats the point? The device is rated 12V @14 Amp.. Why would 10A be a problem?

But you will need a fixed or variable load, multiple thermcouples (datalogger) and then need to ensure the ratings of all the components are not exceeded.. (UL RTI values,etc..). Its not something a laymen should even worry about or attempt.
 

Thread Starter

BillRush5

Joined Jan 13, 2013
24
Whats the point? The device is rated 12V @14 Amp.. Why would 10A be a problem?
The point is that this is a modified supply from the original and I wanted to test the current to the maximum I plan to use. If I had left it as original, I wouldn't have even bothered with a new thread. :confused:

But you will need a fixed or variable load, multiple thermcouples (datalogger) and then need to ensure the ratings of all the components are not exceeded.. (UL RTI values,etc..). Its not something a laymen should even worry about or attempt.
Unnecessary. The supply already has the built in safeguards and those safeguards are working when the ratings are exceeded.

GopherT, thank you for your response. That will offer a reasonable test and I will get on it right away today.
 

PackratKing

Joined Jul 13, 2008
847
I have a selection of new or used " Calrod " hot-water tank elements, and even a couple old electric range burners for just such testing. most anything with a couple specs printed on them for volts and watts will do.
 

Audioguru

Joined Dec 20, 2007
11,249
An incandescent light bulb draws 10 times or more current when it is cool. Then the power supply might go into shutdown before the light bulb gets hot.
Use a heater instead.
 

mcgyvr

Joined Oct 15, 2009
5,394
The point is that this is a modified supply from the original and I wanted to test the current to the maximum I plan to use. If I had left it as original, I wouldn't have even bothered with a new thread. :confused:



Unnecessary. The supply already has the built in safeguards and those safeguards are working when the ratings are exceeded.

GopherT, thank you for your response. That will offer a reasonable test and I will get on it right away today.
That information should have been provided in your original post. We don't read minds.. Not to mention you still haven't mentioned what was "modified" so there is no way to address/answer your question properly at this point.
 

Thread Starter

BillRush5

Joined Jan 13, 2013
24
The car light idea worked out fine and was a good test. I was worried also that it might not light or shut down the supply, but it didn't. As someone else said, when the voltage is close to the ideal range, whether it is 12V, 5V, etc, regulation is good. However, if the 12V is reduced to 7.5V, there is a 0.8V drop. The workaround is to use the 5V and increase up to 7.5V but carefully not exceeding 14-15V on the 12V.

So, looks like care will be needed using the supply. I may be able to reinstall one of the limiting resistors so the maximum is 14-15V. However, with care, it is providing the voltages and currents I need.

Thanks again for all the input. The toughest part was taking the jump and working on a supply blind as I never did find the schematic, but so far it has all worked out for the best.

Mcgyver, you were helpful of course and sorry if I responded in undo haste.
 
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