Electronics > Beginners
Addressable LED hell
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tszaboo:
I had a product with a WS2818 (or whatever) on it. It was designed by a junior engineer who then left the company before I took over the department. First thing that had to go. It was easily the most fragile component, causing errors in something like 5% of the time.
Board perfectly assembled, the BGA CPU runnign on it perfecly, dead 20 cent LED. I replaced it with a proper LED sold (probably not made) in the west, a TI I2C LED controller next to it. Sure it was more expensive, but the trade-off was 1% more expensive board for 5% of faulty boards. Ah yeah, and the LED had a tiny 8 bit microcontroller next to it, because the CPU running Linux couldn't handle the timing requirements. With it's own firmware and everything. Stupidest idea ever.

So dont place these POS LEDs on anything other than LED strips. It is just not worth it.
jeremy:
I’ve used a ton of these LEDs without issue, and I have even cooked them until they are yellow and they are still fine  :-//

They do however need quite good decoupling because they use pretty fast edge rates, and each LED has a re-driver for the serial data. Should have a 100n cap on *every* LED. It can also be pretty surprising how much power they use; I have tested some to be 60mA per LED when showing white, add a few together and you’ve got a good recipe for brownouts. So you should also have wide traces powering them, as much as you can cope with.

With that said, I much prefer the APA102C LEDs; they perform the same job, but are synchronous (ie use a clock as well as data) and are SPI compatible, so you can DMA data to them pretty easily.

Edit: also no, moisture doesn’t matter for your purposes
Mr. Scram:

--- Quote from: NANDBlog on May 20, 2019, 11:25:49 am ---I had a product with a WS2818 (or whatever) on it. It was designed by a junior engineer who then left the company before I took over the department. First thing that had to go. It was easily the most fragile component, causing errors in something like 5% of the time.
Board perfectly assembled, the BGA CPU runnign on it perfecly, dead 20 cent LED. I replaced it with a proper LED sold (probably not made) in the west, a TI I2C LED controller next to it. Sure it was more expensive, but the trade-off was 1% more expensive board for 5% of faulty boards. Ah yeah, and the LED had a tiny 8 bit microcontroller next to it, because the CPU running Linux couldn't handle the timing requirements. With it's own firmware and everything. Stupidest idea ever.

So dont place these POS LEDs on anything other than LED strips. It is just not worth it.

--- End quote ---
It surprises me none of the real players has released a version yet. It seems plenty of people would rather use a part with an appropriate pedigree.
janoc:
These parts are fairly fragile (ESD kills it, the driver seems latchup-prone, etc.) and some are outright dodgy, see e.g.:

https://www.eevblog.com/forum/projects/ws2812b-leds-reliability/

(some good tips there)

or:

https://wp.josh.com/2016/10/29/a-quick-test-for-crappy-ws2812b-neopixels/

Basically, if you want reliability, avoid these unless you have a 100% reliable supplier ...
cbowen:
Thanks everyone for their input. I really, really appreciate it. I'm going to stop wasting everyone's time at this point, and redo the boards with carrier board footprints, just for proof of concept. I'm thinking place the holes over the pads, fill the hole with paste, iron needle tip in, and go?

@Buriedcode, you recommended using a wire. I'm not sure how that would work with surface mount pads. I'm afraid if the wire would be filling the hole, it would prevent the solder from making it down to the pad and having a good connection.

@Artag, Yes, I was planning on using the through hole variety where the plans would normally call for side-mount LED's to try to make the POC easier. Unfortunately, in the above case, I can't use them in this spot because there's components on the other side.

@Blueskull, that is very kind of you to offer your soldering skills.

@Jeremy, I've seen the Dotstars. So more reliable on the data end and smoother animations?

@Mr. Scram, I would happily pay $1 a piece for something reliable. : )
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