Can I use the computer ATX PSU to power my electronics circuits ?

[vsmGuy]

Can I use the computer ATX PSU to power my electronics circuits ?

I see many using their ATX SMPS as PSUs, but I noticed that the output current is typically in range 1A to 20A. For expl,e +12v is supplied at 10A

Most of the ICs we use have Icc (supply current) in 50mA range, for example, the popular MAX232 has Icc specified at 50mA

So if I were to connect 5v, 1A supply from ATX SMPS to supply MAX232, will it go bad ?

So how can I use the ATX SMPS to power my circuits ? Use a current limiting resistor ??

 

[b0j3]

You can use computer PSU. The current stated on the unit is just a max. current you can get from it.
Think about ohms law (voltage is fixed and load changes -> current changes).

I would still suggest you to make power supply by yourself.

 

[justDIY]

also consult the manual for your power supply, many need a minimum load on the rails to insure good regulation ... usually having an old hard drive plugged in is enough.

 

[ZIGGY_DAN]

You should be careful using a computer PSU because they are not double insulated and a loose live wire within a metal case can quickly become a nasty situation, i think some computer PSU's are double insulated although i have not seen any.

otherwise the PSU is perfectly suitable, you could use a current limiting resistor if you wish to limit the current to a device, if you need a constant current drawn from the rails to ensure good regulation, why not use a fan, that way you draw the required current and cool the power supply down a bit more than normal.

hope this helps

 

[letherby]

i've had some circuits blow up on me when using computer power supplys.
what happen was i connected a video amp to a tv when it blew up on me, i found that there was voltage from the tv ground to the earth of the power supply had a reading of 100volts.. seem to find the same problem with non-earth switch mode units would love to know why,,?

 

[Nigel Goodwin]

i've had some circuits blow up on me when using computer power supplys.
what happen was i connected a video amp to a tv when it blew up on me, i found that there was voltage from the tv ground to the earth of the power supply had a reading of 100volts.. seem to find the same problem with non-earth switch mode units would love to know why,,?

Without knowing exactly what you did, and what TV it was, it's hard to be 100% - but TV's are hardly ever earthed, most modern ones have an isolated chassis, but because it's not earthed it floats at half mains potential (connected via a high value resistor and special capacitor, to conduct static buildup away). Older sets, without an isolated chassis, have the chassis at full live half mains.

If you don't know what you're doing, DON'T mess with TV's!.

 

[justDIY]

You should be careful using a computer PSU because they are not double insulated and a loose live wire within a metal case can quickly become a nasty situation, i think some computer PSU's are double insulated although i have not seen any.

I've never seen the term double insulated use with a atx power supply ... they are fully isolated switch-mode psus ... there is but a slim chance of the mains reaching the DC output side.

its been my experience double-insulated is a term used with devices powered directly off the mains, like a drill or hair-dryer.

if you need a constant current drawn from the rails to ensure good regulation, why not use a fan, that way you draw the required current and cool the power supply down a bit more than normal.

it would need to be a fairly powerful fan, you want at least an amp or two on the 5v rail, usually 500ma will do for the 12v rail.

if active components aren't desired, then a load could be made out of power resistors.

 

[Nigel Goodwin]

I've never seen the term double insulated use with a atx power supply ... they are fully isolated switch-mode psus ... there is but a slim chance of the mains reaching the DC output side.

its been my experience double-insulated is a term used with devices powered directly off the mains, like a drill or hair-dryer.

Quite right, 'double-insulated' is a common term for a class II electrical appliance, which means it has no earth connection, and any exposed metalwork (screwheads or anything at all metal) must have a very high resistance when subjected to a high voltage between itself and the incoming mains lead (usually 3000V for the test).

A class I appliance has an earth lead, and must have a very low resistance between the earth wire and all metalwork - 25A current is passed through for the test!. It also has to have a specific high resistance between the mains wires (live and neutral) and the metalwork, again tested with a high voltage (but lower than class II).

A PC PSU would be a class I appliance, and TV's are almost always class II.

As part of my job I do PAT testing (Portable Appliance Test), there are also reduced levels of testing - which often have to be used, even down as low as a purely visible test (some things you don't want to apply 3000V to!).

 

[BeeBop]

Hi,
This use of a computer power supply is quite a common thing. Google for it and you should get a ton of links.
The usual method of drawing current from the rails is to use a 10 ohm 10 watt resistor on the 5 volt rails.
Ah, well, here are some links, but there are many others:
http://www.pavouk.comp.cz/hw/en_atxps.html

http://www.epanorama.net/links/psu_computer.html

A good wiki how to:
http://www.epanorama.net/links/psu_computer.html

Computer power supplies tend to be noisy, and in my opinion, it is hard to beat a linear supply.
Regards,
Robert

 

[AllVol]

ATX PSU's are handy little units, especially if you need dual supply for Op Amps, etc. I use a 12 volt auto brake light bulb for load, serving as an on-off indicator, current stabilizer and quick-drain of caps when the unit is turned off. Go to www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply for a complete how-to. Be sure to check out the discussion for refinements to the text.

AllVol

 

[BeeBop]

Ah!
Yes, the link I meant to post, under good wiki, is the one AllVol posted. I must have not coppied it, and pasted the same link twice. It was early in my day!! Sometimes I do the most idiotic things.
Robert