First LED frequently burning out on NeoPixels

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steinhausler
 
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First LED frequently burning out on NeoPixels

Post by steinhausler »

Hi Adafruit team!

Summary
I am working with a few Adafruit NeoPixel Rings (24) and NeoPixel Matrix (8x8) and I keep having the same problem - after a short time the 1st LED on the NeoPixels burn out. Both for the Ring and the Matrix (used consecutively, not together). The only way that I am able to get the remaining LEDs to light up (e.g. do the strand test) is by holding the DIN wire to the "foot" (soldering points?) of one of the second LED.

Setup
I've followed the best practices and have a 1000 micro Farad / 10V capacitor attached (see picture ADA1) to the power supply (5V/2A). I am also using a 560 Ohm between the Pin 6 and the DIN wire to the boards.
I use an Antistatic mat when handling the NeoPixels and unplug the power-supply before I remove any of the wires from my breadboard.
I upload the "StringTest" to the Arduino Uno board without problems. The LEDs on the Arduino flash (Pin 13) and the ON LED stays on.

My schematic is pretty simple (see picture ADA2):
5V/2A External power ---> Capacitor
Power ---> +5V Pin on NeoPixel
Power ---> Vin on Arduino Uno
Ground ---> GND on NeoPixel
Ground ---> GND on Arduino Uno

Pin 6 ---> 560 Ohm resistor ---> DIN on NeoPixel

Results
I successfully used one 8x8 Matrix for a day but then the following day (no change in setup) the first LED had burnt out.
When I connect all the wires as described above, the first LED will either glow Red or Magenta. For a short instance the other LEDs flash white but then turn off and stay off (see picture ADA3). As mentioned, the only way I can get the other LEDs to perform the strand test (ADA4) is by brushing the DIN cable against one of the other LED's soldering points.

I am measuring the following voltages:
@Powersupply = 5.1V to 5.5V
@after Capacitor = 5.1V to 5.4V
@+5V on NeoPixel = 5.15V
@DIN on NeoPixel = 140mV
@DOUT on NeoPixel = 0

I am seeing similar issues with Ring x24. Here however 3 LEDs are not lighting up. Each LED next to the two PWR pins and the one LED next to the IN pin seem to be dead (see picture ADA5) and again, I can only get the remaining LEDs to light up by brushing the DIN cable against any of the other LED soldering points.

For the short time I got the NeoPixels to work I loved what they were doing and the ease with which I could program them but before I buy a whole bunch more for my project (I estimate that I will need 35 Rings and 70 Matrix boards) I would like to work out what I am doing wrong here. I am definitely a newcomer to this whole world so it is quite likely that I am making some pretty obvious mistake. I've also attached pictures of my soldering points (ADA6,7,8) - perhaps those are the culprits.

As I live in Germany I had to purchase my NeoPixels through one of your distributors - I hope you are still able to help me though as I am starting to go a little nuts with my lack of progress.

Thank you very much in advance for your time and help! Please let me know if you need anything else.

Cheers,
Toby
P.S. Just realized I can only add 3 images so I picked the ones showing the LEDs that are / are not working. Let me know if I should send you the others.
Attachments
Matrix 8x8 - First LED on, others do not work unless DIN "brushed" against second LED
Matrix 8x8 - First LED on, others do not work unless DIN "brushed" against second LED
ADA3.JPG (214.66 KiB) Viewed 5059 times
Matrix 8x8 - First LED stays on, other LEDs perform strand test
Matrix 8x8 - First LED stays on, other LEDs perform strand test
ADA4.JPG (108.11 KiB) Viewed 5059 times
Ring 24 - 3 LEDs not working, each one next to solder pin
Ring 24 - 3 LEDs not working, each one next to solder pin
ADA5.jpg (263.94 KiB) Viewed 5063 times

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adafruit_support_mike
 
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Re: First LED frequently burning out on NeoPixels

Post by adafruit_support_mike »

You're not the first person to have this problem, but we haven't isolated the exact cause yet.

The Best Practices list contains almost everything we've thought of so far, but we have a new idea we're asking people to try: put a 100k resistor between the DI and GND connections at the point where those signals connect to the strip/ring/matrix.

It's possible that your wiring is picking up induced current from wall power, flourescent lights, or other nearby radio emitters. It won't be much current, but even a few hundred nanoamps could potentially cause trouble:
ws2812.jpg
ws2812.jpg (34.87 KiB) Viewed 5056 times
Since you're having these problems in spite of following our current best practices.. and especially since I'm asking you to test an idea for us.. let's get you a new matrix and ring.

Send a note to [email protected] with a link to this thread and the folks there will get you the new hardware.

steinhausler
 
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Re: First LED frequently burning out on NeoPixels

Post by steinhausler »

Hi there!
Thank you for your help and really quick reply.
Just to make sure - should I try this test on the already "wonky" NeoPixels (i.e. do you think that would fix it?) or only on all future/new NeoPixels that I connect?

Thanks again,
Toby

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adafruit_support_bill
 
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Re: First LED frequently burning out on NeoPixels

Post by adafruit_support_bill »

should I try this test on the already "wonky" NeoPixels (i.e. do you think that would fix it?)
It won't fix an already damaged pixel, but by all means, test it out with the next pixel in line.

steinhausler
 
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Re: First LED frequently burning out on NeoPixels

Post by steinhausler »

Did you mean like this? --> see pictures (1 & 2)

I tried this on one of the "wonky" NeoPixels just in case it was supposed to fix it...sadly it didn't.

FYI - the other LEDs still light up as before if I brush the DIN against the other LED solder points.

Thanks,
Toby
Attachments
100 Ohm resistor across GND and DIN on NeoPixel
100 Ohm resistor across GND and DIN on NeoPixel
2.jpg (317.75 KiB) Viewed 5028 times
1.jpg
1.jpg (355.47 KiB) Viewed 5028 times

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adafruit_support_bill
 
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Re: First LED frequently burning out on NeoPixels

Post by adafruit_support_bill »

I tried this on one of the "wonky" NeoPixels just in case it was supposed to fix it...sadly it didn't.
No. It won't fix a burnt out pixel.
the other LEDs still light up as before if I brush the DIN against the other LED solder points.
If you can 'tack-solder' the DIN wire to the next led and add in the 100K resistor to ground, we can see if that works reliably for you while waiting for your replacements.

alexhofsteede
 
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Re: First LED frequently burning out on NeoPixels

Post by alexhofsteede »

Is this 100k resistor thing confirmed as fixing this issue, and now the best practice for neopixel strips?

I am also having the first pixel on my neopixel strip burn out pretty frequently, and have to cut if off and re-solder my leads onto the next one in line. It would be nice to have a solution before my strip gets too short :)

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adafruit_support_bill
 
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Re: First LED frequently burning out on NeoPixels

Post by adafruit_support_bill »

The 100K to ground does seem to solve the problem in most cases. We are also testing some buffer-circuits and will be updating Best Practices as we go.

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chemdoc77
 
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Re: First LED frequently burning out on NeoPixels

Post by chemdoc77 »

Hi Everyone:

The two resistors fix works!

Last January, I obtained a 1 meter 30 NeoPixels/M strip and 2 meters of a 60NeoPixels/M strip. Unlike the breadboard NeoPixels, the NeoPixel Sticks and 8X8 NeoPixels panel which I have had a lot of fun with, the 1 meter strip kept burning out NeoPixels. I stopped using it when I had only 20 of the original 30 NeoPixels left and I did not even try using the 2 meter strip.

I saw this post a few weeks ago. I made a quick proto board with both resistors and it works.

I have connected, disconnected and powered up the 20 NeoPixels of the 30 NeoPixels/M strip, many times. I have not had any more problems with this strip, i.e. no burnt out NeoPixels.

I have connected, disconnected and powered up the 2 meter length of the 60 NeoPixels/M strip, many times. I have not had any problems with this strip, i.e. no burnt out NeoPixels.

I have learned to use a despiking capacitor with the power supply. I have learned to only connect NeoPixels to unpowered circuits. I have learned to only touch NeoPixels products and the wires going to those products with a properly grounded ground strap on. Finally, I have learned to make sure the two resistors fix is connected to the first NeoPixel of any NeoPixel product.

Many thanks to all at Adafruit for solving this problem.

Best Regards,
Ken
aka - Chemdoc77

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modernman
 
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Re: First LED frequently burning out on NeoPixels

Post by modernman »

Question: Is the 100K shunt resistor between Vcc and DIN recommended/ required/ or not necessary?

I am attempting to properly drive my neopixels.

I am reaching out for clarification on Neopixel best practices regardless if powering by a Trinket, Gemma, Uno or power supply.

I am unclear if best practices includes the 100K shunt between DIN and GND.

Please instruct.

How much of the following correct?:
1.) Always Include resistor (300-500 Ohm) on Data In (closest to DIN as possible.)
2.) Always Include capacitor across GND and Vcc.
(1000 µF preferred, smaller for Gemma ok --anything better than nothing e.g. 200µF 500µF )
3.) Include 100K shunt between DIN and GND

Thank you. Bryce

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emkay
 
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Re: First LED frequently burning out on NeoPixels

Post by emkay »

Just wondering if the data shunt is still recommended as well. Sorry for bringing up an older thread. Especially curious since it's not mentioned in the uberguide. Having some first LED's going dead as well. Trying to scope the various causes...doesn't seem to be inrush current since the power supply output appears to be adequately filter. So one of the suspicions left is some kind of spike on the data lines.

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adafruit_support_bill
 
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Re: First LED frequently burning out on NeoPixels

Post by adafruit_support_bill »

The frequency of first-pixel burnout has dropped dramatically since we started recommending the series resistor and power supply caps - and also building the series resistor into many of our neopixel products.
That said, there may be cases where a shunt resistor helps. And It is unlikely to hurt.

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