how to find what causes a LED strip ws2812 to work partially ?

HI All,

i having trouble with my ambient light project.
though it worked fine for a few weeks, all of a sudden less than half of the strip (the closer to PSU half) has been act strange and than stop to work. the rest of the strip work fine and still responsive.
how do i discover which led is the culprit?
is it possible that only part of the strip burnt or only one led?
any suggestions for a quick test without ruin the led configuration on TV assembly.

thanks in advance

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TalT410 months ago

why after several weeks with my LED strip some led tends to stuck or stutter and with it the rest of the strip (up the din stream)? This mostly happens under white light.

It seems like led slaving... You replace the cultprit enjoy some time and than the problems starts again.

whenever I open the strip I set ambibox on color dynamic until LEDs stop to stutter and warms up than I can change setting to capture, until I get to white light it begin to stutter again... Please help

Usually the first LED in the series is the culprit as the signal goes in the DIN and out the DOUT then on to the next LEDs DIN.

What makes me wonder is if you are wired into the LED strip in two locations or the right end.

TalT3 (author)  Josehf Murchison1 year ago

well the DIN and GND connected to an arduino on the start of the strip and the PSU's +5 and GND connected to the end of the strip (where actually the leds start to malfunction).

so if i understand correctly the culprit is the first burnt led in the middle of the strip? the rest found after it supposed to work?

would a wire bridge over the led's DINs would fix it?

thanks

It will be either the first burnt out one OR the one just before it Without a Doubt !

From time to time they will just randomly die, but it is usually caused by,

A:) Poor control of Voltage levels

B:) Sudden rush of current when they are first powered,

C:) a Data in (or) out pin has been damaged.

Just replace the led that isn't turning on and the working one right before it. Like Josehf said you can just bridge it if you like, Just cut the track with a small knife so it doesn't interact with the dead ones. **Still best to just cut out the two leds and replace them.

https://learn.adafruit.com/adafruit-neopixel-uberg...

^Good Guide for WS281(x)^

Just use a 300-500 Ohm resistor on the first Led ( This will help limit Signal current from damaging the Data pins. You only need it on the First one)

and use a 1500 µF (6V+) Capacitor across your power supply (This is used to reduce the Initial surge of current from Turing on the Power supply

Lastly what power supply are you using?

A wall wart of even a PC supply will have a momentary voltage burst when the first turn on (could be up to 18V+). I allways use a linear regulator or a DC/DC converter to make sure the output is Exactly 5V.

Either way, Read through that Link and have fun! :D

ok, cutting and replacing indeed do the job nicely.

Added a cap (1500uF 10V) before the PSU junction and the extension, seems to work fine and no more voltage drop.

Only one strange issue, the leds on half till most part of the strip become buggy and stutter from a certain high brightness threshold.... Any thought?

Thanks

Glad it helped !

Were does the difference in brightness srat? next to the damaged leds?

Did you replace both the dead one *And* the one just before it that still works, and did you use led's from the same roll ?

If neither work then I would start to look at the programming side of things.

Otherwise there is a chance that running them without the Cap may have damaged the whole chain.

TalT3 (author)  Wired_Mist1 year ago

i replaced 3 leds around the problematic one just in case.

it seem the first half connected directly to the PSU is more susceptible when i increase the leds brightness and even more where all leds are on white color, everyone gets to stuter and flick on and off and change colors.

is it related to the extension i made of the PSU till the middle of the strip? should i had to do anything else except of just extent and connect to the +/GND joints? maybe block/disconnect the PS coming from the first half?

also it seems after some working time, the leds become more robust to higher brightness...

thanks

Thats strange...

Sounds like the leds at the front may have been damaged :(

Wouldn't worry about the power connections. personally I would solder it onto each end of the strip, but it shouldn't make much difference.

You can verify the voltage level is 5V right across the strip but it sounds like you have done that already.

Maybe try reducing the brightness and see if that helps, otherwise you may need to replace the Strip >.<

Either way, you may want to look into how much a replacement strip will cost, May be worth the re-investment

TalT3 (author)  Wired_Mist1 year ago

thanks for your detailed reply, when you say first you mean in the data path?

i actually follow that link and have a 470ohm between the DIN and the arduino and a smaller Cap (will be change) on the PSU. which BTW is a 5V 10A regular PSU from eBay, on max brightness i can actually see yellowing of the leds.

as said below my plan to fix the V drop i have, is to extend another +5/GND wires to the middle of the strip with another 6.3V 1000uF Cap , any thought? do i actually need another cap on the bridge?

actually all this happened after power failure in my home, though i have wall protecting socket...

Yes, the first led is the series. Look for a pin labeled "DI" that is the one you solder the resistor before you solder it to your controller.

If you are using less then 50 leds you don't need to add the second power connection, but it won't hurt either. If you do you shouldn't need a second cap as long as you solder the cap to the power supply before you branch off into the two lines.

Jumping the LED might work as long as the DIN signal is not grounding in the LED.

Make sure it is not a bad connection to the +5 or ground. Sometimes in these strips if there is a bend in the strip it will work for a time and then just stop. so make sure you are getting power at all the joint tabs.

I forgot to ask do you have a meter for checking the connections?

TalT3 (author)  Josehf Murchison1 year ago

yes i have a multimeter except for voltage drop everything connected, though i cant check the DINs to see who is short circuit the rest.

for the V drop i plan to extend another +5/GND wires to the middle of the strip with another 6.3V 1000uF Cap , any thought?

OK that sounds good.

To check the DINs turn the light on and use a jumper wire and jump across the end LEDs of the section that is not working one at a time holding the jumper in place and see if the LEDs in the rest of the string comes on.

Its recommended to feed the Din and clock lines to the first LED with 470 Ohm resistors.

rickharris1 year ago

https://www.youtube.com/user/bigclivedotcom/videos

had much good advice on LED lamps and strips.

Usually the LED's are in segments of 3 or 4.
As you will need a SMD reflow or SMD solder station I guess it is much faster and easier to cut out the faulty part.
Simply replace it with a good section.