Disappointed with brightness

I’m not sure if I’ve got poor quality strips (apa102). But I’m sitting in a room with 10m of 60/m laid out on the floor pointing up… Connected to a 200w supply.

According to the seller its 18w/m

Thats 180w of led power in a single room… Given its usually nice and bright with a pair of 15w led lamps, it should be absolutely blinding in here when I crank the strips up near white (or even on a single pure colour, that’s still twice the normal wattage I have in here…)

However Its much, much dimmer in here that it would be usually… Is this normal? Are some apa102 's brighter than others? I need to get an ammeter in series with them to see what they are drawing… The psu and cables are ice cold…

This is interesting. Do you mind sharing where you bought them?

It’s in italian I’m afraid but you can probably get the idea:

APA102 - Striscia luminosa impermeabile IP65, 60 LED/m, 5 m, DC 5 V, Pixel RGB, colore nero, PCB https://amzn.eu/d/1qXAWEJ

If it is a power issue, often you will start losing blue/green first. If there’s a color shift towards red then I would suspect power.

The 18W / meter figure works out like this: 60 pixels at 0.02A per element, times 3 elements (R+G+B), times 5 volts. 60 * 0.02 * 3 * 5 = 18.

That is how much power they could draw, though that isn’t directly how much light will be output. You may end up with closer to 3/5th of that on the actual LED, the rest is converted to heat as part of the current regulation circuit inside the LEDs. So light output might be closer to 11W equivalent LED lighting per meter compared to an LED lamp which will typically use a more efficient power conversion circuit.

It’s worth checking settings to make sure you don’t have a lower max brightness setting, and the brightness slider is all the way up. Either of those can limit the total brightness/power used.

1 Like

Ok so I wired my multimeter up to measure the current, and downloaded the “white fade” pattern.

First thing I noticed was the far ends of the strips went yellow as max brightness was reached… This was resolved by connecting both ends of strips to psu…

The other thing I noticed, and rather more critical… Max current draw with both strips in parallel, was 6.2 amps.

Rather far off the theoretical 30 something. Web app was set to 100 percent brightness limit and everything else maxed out…

Any suggestions?

Ok so I noticed that the brightness increased noticeably and the yellow fade at ends dissappeared when I removed multimeter from the circuit. Obviously it has significant internal resistance, which is a bit useless for an ammeter.

So I’m back at square one, but still have a suspicion that they are not as bright as they should be…

Could you measure the voltage at the middle of the strip across the rails when both ends are connected to power? Please take a reading with the output brightness set to 0, and one with it set to full on an all-white pattern.

i could certainly do that, although that leads to another question which has been bugging me… these strips have a silicone coating on them… ip65. is there a recognised technique for exposing the solder pads and not poisoning myself with fumes when i solder to them?

If they are the kind with a tube (often listed as IP67), the tubes are easily cut and can be (slightly less easily) re-glued with RTV silicone to re-waterproof.

The kind where the silicone is stuck to the strip (IP65) are more of a pain. The material can be cut and scraped away, carefully, to expose copper pads. It takes some patience. Often these have sticky backing (as your’s appears to have), which can be carefully scored and removed, and usually the copper pads for power/data are also on the underside. Any residue from that gunk will seriously impede solderability.