New cheap Psu Stress test

I’ve just got together the bits for my first setup… Pb3, 2x apa102 5m strings (60/m) and a cheap no-brand 5v 40amp psu (couldn’t find the meanwell one at a sensible price, or anywhere in the EU… . )

It was fanless so the first thing I did was Jerry rig a 120mm pc fan on top.

I’ve got a party to light in 1 month, hoping to get some nice effects going… However I have a vivid imagination and I forsee the psu catching fire in a small, crowded room.

I was planning to rig everything up at home , then hammer the psu for a good few hours with all the leds on max white. Just to see if its OK. In theory it should be running well under spec, but you never know.

Is this a bad idea? Do the strips handle running at max for extended periods?

Advice appreciated.

Hey there!

In my experience, strips do handle running their max-rated power, but few people I know do extended run times at full intensity white simply because it probably shortens the life of the strips from the excess heat. In addition, as mentioned in that other thread, you’ll see how 70% is actually really bright, so most people run them there just to have fewer issues later.

Your system seems well-sized. You probably want to do a burn-in for a few reasons:

  1. Be sure your strips were well manufactured. But if you do have a bad one and it blows now, make sure you have time to buy a spare.
  2. Check your own wiring for hotspots from undersized conductors or bad joints.
  3. Check for voltage drop at high consumption that could cause flicker or drop below the voltage Pixelblaze needs.

It’s a good practice to fuse your power runs just outside the PSU. Especially if you’re using an off-brand power supply or one without a built-in overcurrent/overtemperature shutoff.

My advice would be to run them at full consumption for 5 minutes and feel around for wires and junctions that feel unusually hot. Then run actual program content (not pure white) at 80% for the length of your event, say 5 hours. That should be a good stress test.

You’ll probably find you don’t need the fan with real content, but it doesn’t hurt if you don’t mind the noise.

1 Like

Thanks for the tips, I’ll follow your advice. Regarding the fan, I didnt like the idea of stuff overheating if the psu is badly designed.40 amps is a meaty current. . It does apparently have overheat/current protection however. Looks fairly well made, although I didn’t open it up to check the soldering as I was tempted to do… Voiding the warranty didn’t seem clever.

The fan itself is a quality 12v noctua jobby I had spare… Running on 5v it still shifts notable air but is basically inaudible in a quiet room, so I’m happy to have it there. Not going to cause any issues at a party, or a library, if necessary.

1 Like

On a related note, what fuses do you generally use? I was thinking automotive 12v fuses would probably be suitable and easily found for 5v at 40a?

Suggestions appreciated, I’ve never seen a specific 5v fuse!

And regarding rating… Would I go with say, a single 40 or 50a fuse on the output of the psu, or a 20/30 amp fuse for each led strip?

I like to use APM / ATM stype (mini automotive fuses) and lots of other LED power distribution hardware like the Electromage Pro Expander board does as well.

I’d fuse them separately simply because it’s smaller wire to solder and it allows for independence. I’m assuming your PSU has at least 2 screw terminal pairs.

You definitely want to use 2 if possible, and fuses rated for as close to your load as possible. The function of a fuse only works if the fuse is the weak/breakable link in the circuit. If you use a single large fuse, it could let all of that current down any path, feeding up to 40A to a short somewhere. Better to limit that to 20A for each and let the fuse blow!

Yes, automotive fuses work well, and are easy to find. Using fuses with higher voltage ratings is just fine - its the current that you have to be careful not to over-spec.

You should also match your power wire gauge based on the fuse amperage that is feeding it. For example, A 20 amp fuse may not keep a 22 ga wire from burning up and catching fire. Think about house wiring, and how the wire gauge must be sufficient for the circuit breaker amperage.

1 Like