Build a bentop power supply

[Macrosill]

http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply

[klanger]

Here's another
http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM

[tonyjmartin]

Forgive my ignorance on power supplies. I know just enough about computers to swap drives, etc., and leave the actual repairs to someone who spent their hard-earned dough to get the training.

For converting these power supplies to a bench top unit, or for powering LED stings, can someone explain the capacity I can expect when combining the +/- outputs? I notice that the minus capacities are usually rated very low, and these tutorials mention using the +/- outputs to achieve various voltages, but there is no mention of how to determine the resulting amp capacity when doing so.

For example, I'm looking at ATX power supplies in the 400-600 watt range, with +12vdc outputs rated 18-24A maximum. If I combine the +/-12vdc outputs, can I expect a +24vdc output with a "reasonable" current capacity? Or at the other possible voltage combinations?

Thanks in advance!

Tony

[teberle]

I just finished power supply conversion. I plan to use it to power my 12v halloween props. Thanks for the links.

Tony,
Take a look at the documentation on the 2 links above as they provide how to combine the voltages. I did check the +/-12vdc output combination and the volt meter showed +24vdc.

[tonyjmartin]

Tony,
Take a look at the documentation on the 2 links above as they provide how to combine the voltages. I did check the +/-12vdc output combination and the volt meter showed +24vdc.

As I would expect it to. I read both the links thoroughly before posting my inquiry, so combining the voltages to yield a sum voltage was not in question. My question was as to what amperage could be expected when combining the voltages, specifically the +/-12vdc outputs, since they are rated at different amperages.

[lytnin]

If you double the voltage, I would expect that the Amperage would be halved to maintain the power output.

Power (w) = (V)olts * (A)mps

Cheers

[teberle]

As I would expect it to. I read both the links thoroughly before posting my inquiry, so combining the voltages to yield a sum voltage was not in question. My question was as to what amperage could be expected when combining the voltages, specifically the +/-12vdc outputs, since they are rated at different amperages.

Sorry mis-read your post.

[P. Short]

I would expect that the combined current rating would be the lesser of the two...typically the -12V rating.

--

Phil

[tonyjmartin]

There appears to be a bit of confusion, so I'll try to clarify.

From the wikihow link on building a benchtop supply, the spec's are (see also picture below):

+5V, 30A
+12V, 12A
-5V, 0.5A
-12V, 0.8

So if I desire to generate +24vdc. can I use the +/-12vdc outputs from a standard ATX power supply, and if so, am I going to get a 24vdc output with a useful working amperage? Or would it be best to use a power supply that has a dedicated 24vdc output?

I suppose the same sort of question could be addressed to using the +/-5vdc outputs to generate a +10vdc output.

Hope this helps to understand what I'm getting at.

Thanks in advance!

Tony

[P. Short]

If you are using the +12V and -12V outputs to make a 24V supply, all that it would be good for is 0.8A (the lesser of the two current outputs). Same thing for using +5V and -5V to make a 10V supply, the current limit would be 0.5A in this case.

--

Phil

[wjohn]

So if I desire to generate +24vdc. can I use the +/-12vdc outputs from a standard ATX power supply, and if so, am I going to get a 24vdc output with a useful working amperage?
Tony

Tony,

best suggestion I could give you is to look for a dedicated Switch Mode Power supply at 24VDC for the task you have. ATX pwoer supplies, as note by Phil, are good at +5V and +12V, but not much else.

http://cgi.ebay.com/24VDC-14-6Amp-350W-Regulated-Switching-Power-Supply-NEW_W0QQitemZ230158661861QQihZ013QQcategoryZ48708Q QrdZ1QQssPageNameZWD2VQQcmdZViewItem

is an example.

John.

[AI]

The negitive 12 volts from these supplys is generly vary low. The max current you could get at 24 volts would depend on the lowest rating witch would be the -12 volts. Hope this helps. AI