PC PSU as LED power source - anyone doing this ?

[smallhagrid]

I have a couple of used ATX PC PSUs that are not reliable for PC
use anymore - but still have a good +5VDC output.

Is anyone using these as power sources for fixed LED lighting ?
Seems to me they'd do a great job and could even be silenced if
there was a low enough power draw to remove the cooling fans.

I've used these before for testing/powering components with the
trick shown here:
http://modtown.co.uk/mt/article2.php?id=psumod

It takes about 2 minutes to do and makes an ATX PSU operable
with it's own power switch instead of via mainboard controlled.

I would love to hear of anyone's experiences with these !

Best Wishes,

mark

 

[SafetyBob]

Considered doing in the early days and I believe a few others did too in the beginning of their led experiences.

Gave it up mainly for two reasons: The first efficiency. There is alot of electrical stuff going on in those power supplies that waste power. The difference between a good old Advance Xitanium led transformer besides the obvious size difference in my opinion is night and day.......they use just the right amount of electricity to do the job, nothing more, nothing less.

If you have a bunch and want to play, fine, but for a finished project around the house......wife (or anyone else) will not care for the "electronic/computer look" for projects.

And reason number two which I already kinda let on is size. The smaller the better. Just makes the project or modification simply look better and more professional......like it was purchased that way.

Using those PC power supplies seemed really great until I came to this sight and found out there were a heck of a lot more options than using a cheap computer power supply. Now using one to test ideas, ect......perfect. Just not a finished project.

Others will chime in here too...........

Bob E.

 

[smallhagrid]

Thanks again Bob.

I do have a bunch and want to play wif wat I got !

Ain't got a house...or a wife (or even a GF) I'm just a poor old country boy who lives alone in a teeny place made for 1.
Ain't even got a TV 'cuz I gave away both of 'em.
So I figger that I run an old PSU, probably bared down to nuthin and hide it someplace and that's work OK for me and still use less power than the CFLs I use now, right ?

Best Wishes,

mark

 

[blasterman]

I use Computer PSU's, but for a different advantage. If I have an installation of LEDs, and there's a computer nearby, I'll simply plug into the existing computer via a molex and string it through a PCI slot in the back of the machine. In one respect, this means I'm powering the LEDs for free rather than wasting money and electricity on an additional LED power supply. If the computer is already there, why not use all that available power?

The disadvantages are obvious, and the main one is current regulation. There's no multiple of power LEDs that is practical with 12-volt, so you need either dedicated regulators for each LED, or put about 5-ohms of resistors on the line.

I've otherwise found computer PSU's to be rock stable with LEDs and *more* reliable than dedicated 120volt LED PSUs.

 

[smallhagrid]

Thank You !
I am soooo into using what is at hand rather than buying excess or wasting...

mark

 

[Mr_Light]

If you can find some wall-wart transformers with a voltage that works efficiently with some combination of power LEDs, then that can be very efficient and inexpensive. I ran across 7 identical 10Volt 1.5A power adapters on there way to the dumpster at work and am now using them to drive either one or two strings of three CREEs with a 1 OHM resistor. Seems very efficient.

The following tool is very helpful in figuring out what you can drive with what voltage, and it's relative efficiency.

LED series/parallel array wizard
http://led.linear1.org/led.wiz

 

[blasterman]

The problem with Wall-Wart's is many of them aren't fully rectified resulting in an annoying, high speed flicker with LED's.

It's as bad as working on a CRT set at 60hz.

 

[Benson]

The problem with Wall-Wart's is many of them aren't fully rectified resulting in an annoying, high speed flicker with LED's.

It's as bad as working on a CRT set at 60hz.

Precisely, at which flicker is completely indistinguishable to something like a third of people.

So not everyone's going to be bothered by them. Of course, the full-wave rectified ones only flicker at 120Hz, which bothers almost nobody, so they're better, but if you're lucky, you may get by with the half-wave ones. Or you can always just add a big electrolytic cap...

 

[Mr_Light]

I don't notice any flicker, but I think I will try the old shine the light on the ceiling fan trick which is a pretty good test.

 

[blasterman]

but I think I will try the old shine the light on the ceiling fan trick which is a pretty good test.

Just wave your hand in front of it using the LED as the primary light source - that's all it takes. If you see strobe motion, it's a choppy 12-volts. The problem is typically obvious and not subtle, and not all wall-warts are bad.

I've tested a few showerhead type LED bulbs that were actually sold with non rectified built in power supplies, and 100% of the people who looked at them found them annoying. Another reason to avoid them

Computer PSU's are a pretty clean and stable source of 12volt power with somewhat unlimited current potential. That's the problem though....all that current and trying to get multiples of LED to match 12-volts. I suppose you could combine the -5 and +5 ATX wires and get 10volts.

 

[smallhagrid]

Thanks for that great link !

If you can find some wall-wart transformers with a voltage that works efficiently with some combination of power LEDs, then that can be very efficient and inexpensive. I ran across 7 identical 10Volt 1.5A power adapters on there way to the dumpster at work and am now using them to drive either one or two strings of three CREEs with a 1 OHM resistor. Seems very efficient.

The following tool is very helpful in figuring out what you can drive with what voltage, and it's relative efficiency.

LED series/parallel array wizard
http://led.linear1.org/led.wiz

I have quite a collection of wall-warts and I do use them in any way I
can - why buy a new one when I can look in my junk box ?!
Also, I have strung together LEDs with just a wallwart powering them
and it worked OK for me too.

Best Wishes,

mark