WS2812B LEDs - reliability? - Page 1
Forum section: electronics / projects

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 13, 2014, 03:52:44 pm
content: Just assembled boards with a total of about 1500 WS2812B LEDs, and seeing about 2% failure rate.Some parts on reels (prior to assembly) have crazed/diffuse-looking windows, but this doesn't correlate with failures.Anyone else using lot of these & seeing this, or have I got a dodgy batch - can anyone recommend a reliable source ?

author: alimirjamali
author_rank: Regular Contributor
timestamp: August 13, 2014, 04:55:41 pm
content: Hi.Could you please share with us if the Integrated Driver Chips (control circuit) fail or the RGB LEDs?In the former case, the following units in the cascade would fail which would be a real bummer.That is a serious concern with these Neopixels.Thanks

author: Wilksey
author_rank: Super Contributor
timestamp: August 13, 2014, 08:47:25 pm
content: We build a ton of board with LEDs (we build the motorway message signs everyone loves, among other stuff), and we replace at least 20 LED's on different boards every week, which might not sound a lot so some, but we have had every manufacturer (or a representative of) that makes LED's in over the last 5 years or so and nobody's are perfect, we see a initial failure rate of 3-4% to 40% sometimes!Your 2% seems quite a good deal, each one of those signs has about 2000-2500 LED's minimum (depending on the sign).

author: David_AVD
author_rank: Super Contributor
timestamp: August 13, 2014, 09:15:55 pm
content: Mike, are the bad LEDs dead upon first power-up or do they fail after some time?

author: jancumps
author_rank: Unknown
timestamp: August 13, 2014, 09:21:02 pm
content: HamsterNZ, one of our forum members here, had a similar experience with these leds, explainedon the GadgetFactory forum.They found the following info onhttp://www.pololu.com/product/2548Quote

author: kingofkya
author_rank: Regular Contributor
timestamp: August 13, 2014, 09:26:27 pm
content: Some of the crazy people over here:http://doityourselfchristmas.com/andhttp://diychristmas.org/use many of the variation and for most people with say 150led string expect to replace one or 2 the first year, normal the issue data not being sent to the next chip ( Christmas light guys call them "pixels"). so %2 sound correct to me.A few of the people who buy in bulk and resell now have the mfg run a burn in test on the assembled light strings for a few days to a week to catch most of the failures. I am mostly talking about the older ws2811 and 2801 chips from what i have read its basically the same thing with the new integrated ones WS2812B that have the added fun of a different spec for some parts of the protocol(end of data bit if i remember right).Also most of the resellers use this guy Ray Wu (always ask for a quote his prices on site are always high)http://www.aliexpress.com/store/701799http://www.aliexpress.com/store/group/WS2812B-pixels-DMX-pixel-IC-and-controllers/701799_251310291.html

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 13, 2014, 10:12:10 pm
content: These came from Ray Wu.Only just built so looking at DOA failures - about half flickering & not forwarding, the others one colour out.This needs to last about 3 months - better suggest they get some spare boards...They are so cheap it's hard to believe they've been tested....

author: hamster_nz
author_rank: Super Contributor
timestamp: August 13, 2014, 11:43:12 pm
content: I have found that they can be killed just by glancing at them sideways - I was playing with a few sticks on a (non-ESD protected) bench, and nuked two in a night.I"ve seen some recommendations about caps on the power rails, and adding a 230 ohm resistor on the data-in for the first LED. The later one has strong data behind it - seehttp://www.eetimes.com/author.asp?doc_id=1320518&page_number=2for scope traces.

author: jeremy
author_rank: Super Contributor
timestamp: August 13, 2014, 11:49:01 pm
content: I bought a stack of these LEDs in that led tape stuff. They are the ones without a shift register in them. There are far more than 2% LEDs with unbalanced colour.But I did pay something silly like $1/meter

author: sleemanj
author_rank: Super Contributor
timestamp: August 14, 2014, 01:58:15 am
content: Quote from: mikeselectricstuff on August 13, 2014, 03:52:44 pmAdafruit uses lots of them, maybe get hold of Limor and see what her experience is with failure rates.

author: hamster_nz
author_rank: Super Contributor
timestamp: August 14, 2014, 03:03:03 am
content: Quote from: sleemanj on August 14, 2014, 01:58:15 amAdafruit's best practices are onhttps://learn.adafruit.com/adafruit-neopixel-uberguide/best-practices* Before connecting NeoPixels to any power source, add a large capacitor (1000 µF, 6.3V or higher) across the + and – terminals as shown above.* Place a 300 to 500 Ohm resistor between the Arduino data output pin and the input to the first NeoPixel. This resistor must be at the NeoPixel end of the wire to be effective! Some products already incorporate this resistor…if you’re not sure, add one…there’s no harm in doubling up!* Try to minimize the distance between the Arduino and first pixel.* Avoid connecting NeoPixels to a live circuit. If you simply must, always connect ground first, then +5V, then data. Disconnect in the reverse order.* If powering the pixels with a separate supply, apply power to the pixels before applying power to the microcontroller.* Observe the same precautions as you would for any static-sensitive part; ground yourself before handling, etc.* NeoPixels powered by 5v require a 5V data signal. If using a 3.3V microcontroller you must use a logic level shifter such as a 74HCT245. (If you are powering your NeoPixels with 3.7v, a 3.3v data signal is OK)* Make sure that your connections are secure. Alligator clips do not make reliable connections to the tiny solder pads on NeoPixel rings. Better to solder a small pigtail wire to the ring and attach the alligator clips to that.Some of our NeoPixel project guides fail to mention the above precautions…they were written before these lessons were learned, and will be updated as required. The design changes are usually minimal (e.g. add inline resistor on data pin in circuit diagrams).

author: amyk
author_rank: Super Contributor
timestamp: August 14, 2014, 04:55:14 am
content: Have you tried taking a look at the die to see if there's any visible catastrophic damage? The suggestions about ESD and EOS make sense - long strips of these that lack (or have insufficient) decoupling caps and the traces are long, which is conductive to ground bounce and inductive spikes (and these are PWM'd, making it probable that large current pulses will happen when their oscillators happen to sync up or beat together.)Here's what the die on one looks like:http://bunniestudios.com/blog/images/ntw_feb_2013_ic.jpg

author: artag
author_rank: Super Contributor
timestamp: June 15, 2017, 02:07:39 pm
content: Dragging up this old thread to keep stuff togetherI've been using a fair number of WS2812B pixels and have generally followed the advice here along with general good practice - avoiding ground shifts, terminating lines etc. and have had good results.However, I'm re-using a bunch of strips from an event last year, and am seeing a very high failure rate. Typically I'm having to repair (by cutting out a section of tape) about 1 per meter (average).This tape has been heavily abused by bending so I'm not all that surprised, but I am surprised that I can't see any damage. The problems appear as much in undamaged sections as badly mauled sections.In nearly every case, I get a led that shows up the wrong colour, or flickering, in tests. Those after it are corrupted. The odd thing is that pressure on the misbehaving led usually fixes it, either briefly or for some time. I'd suspect a solder joint breaking but can see no evidence of this. In fact, resoldering usually kills it completely.I'm wondering if the plastic package is cracking and breaking the bondwires.Has anyone else seen this ?

author: madworm
author_rank: Frequent Contributor
timestamp: June 15, 2017, 06:58:30 pm
content: Yes.I can't remember if it was with ws2812b or normal leds in plcc5050 package. I took photos, but can't find them.The plastic around the metal contacts is easily weakened by Heat, moves a little & the bond wire rips off.I was mostly affected as I did hand assembly. You can easily test with an iron. The pad with the smallest amount of metal usually breaks first. Solder quickly, lowest possible temperature & only once. Rework kills it often. I guess the plastic isn't the best.

author: klr5205
author_rank: Regular Contributor
timestamp: June 15, 2017, 08:20:41 pm
content: I have a project that utilizes a strip of approximately 250 WS2812b leds that also came from Ray Wu. So far I've had to cut out 2 bad leds that failed months apart from each other.Mine is a relatively punishing outdoor application at the moment though; apart from being outside, the strip gets rolled back onto its reel a half dozen times per year, so its not really the environment you'd hope for these.

author: Fungus
author_rank: Super Contributor
timestamp: June 18, 2017, 09:46:50 am
content: Every time you have something rigid (LED) attached to something flexible (strip) there's going to be stress when you handle it.If I'm going to be handling a strip a lot I but the 'outdoor' ones that come in the rubber tube. That really helps to distribute the stress along the PCB and avoid sharp bends.