I have an installation of about 700 WS2812’s that has had a few LEDs go bad. The strange thing is that when I replace a bad pixel, then an upstream one starts acting up and needs to be replaced. It has happened 3 times now!
I’m running off a Particle Photon with a level shifter, and a 5V 12A power supply, injecting power at the beginning and about 2/3 down the strip, using capacitors. I DON’T have the data line resistor on this particular installation, so I’m wondering if that could somehow be related (though I’d expect that to cause problems with the first LED, not ones way down the strip).
Anyone seen this kind of behavior or have theories on what could be happening?
Are you replacing the faulty pixels with the exact same batch of pixels? As in you are using a spare batch left over from the production of the installation? or did you purchase new ones?
Great questions. I’m driving my LEDs at about 20% brightness. My PSU is probably about 5.2V (that’s what I’ve measured from others just like it. It’s a Meanwell, constant voltage. The upstream ones are not immediately before the failed one – they are further up the strip.
And actually today I had a different installation (using about 800 WS2813’s) where somewhere around 400 pixels in, it quit behaving correctly (e.g. an “every LED” pattern would start showing every other LED starting at that point) and the lights weren’t working entirely after about pixel ~600. When I replaced the pixel at ~400, the spot at ~600 started working again!
So there are some strange effects happening between pixels that are quite far away from each other.
@Ryan_Cush 5.2V should be fine, 20% brightness also, it is not even near the brightness that caused my problems. I have WS2812b setups that are have been running almost continuously for a few years at 50% or less brightness flawlessly.
Are you running the strips in a particularly hot environment ? Otherwise, I would guess you got a bad batch of devices.
I’m using a Particle Photon (with a level shifter). The behaviors I’ve seen are:
an led that won’t turn off — it will render any color correctly, but when turned to black, it stays blue or green.
an led that doesn’t correctly pass the pattern info downstream. It passes the color ok but “every led” becomes “every other led”
an led that just stops responding entirely. Every led after it could be lit or off, but they won’t update at all. Maybe this is a stronger case of #2.
I can understand an led going bad and exhibiting one of these behaviors. What concerns me is when I replace the problematic led and suddenly another one that’s 50 or 100 away starts going bad!
@Ryan_Cush I’ve had the same problem (#3). My only guess is that it’s a bad batch. I’ve had this happen on many different circuits with the same batch of leds. I’ve thrown them out.
I wonder if something about my PS is causing problems? To avoid the hassle of injecting power at every 5m, we run the lights at generally 10%-20% brightness, which lets us do ~25m with only 1 or 2 secondary power injections, and it looks great at night and pretty decent during the day. Could under-powering the LEDs cause these kinds of effects?
@Ryan_Cush I guess under-powering could cause some weird effects on your LEDs but it should not be permanent. Once nominal, clean power is applied, the LEDs should behave normally.
Have you tried powering them down for 10-20 seconds before re-applying power ? I found my flaky LEDs magically recovered after being driven full bright white too long and then allowed to cool down.
Ive seen the same thing as Franck. Ive had two entire reels do this and it took me forever to figure out since I had sliced it up into many smaller pieces. Once I replaced it with some new ones I bought a few months after it worked just fine.
I recently had this issue with a bunch of WS2812b rings. For me brightness resolved the issue. However, I would suggest that you drop your voltage down as much as the PSU will allow. That seemed to help as well. They really don’t need more than 3.3v at each LED to perform properly.