WS2812B and series resistor?

T Chap

Under "best practices" for the WS2812B, it says to put a 300-500 ohm resistor in series. If using the TC4427 with the schematic Jon aka Jonnymac posted, I though I have heard some of you say you are not using it. I used this schematic and did not use a resistor. I have 2 dead blue LED's out of 16 WS2812B's, and trying to look for how this happened. There is a good chance that my supply to the LED array was connected direct from the 5VDC wall mount supply (which outputs around 6VDC) accidentally for about a few seconds. Then I caught the mistake and rewired it to have the 5V regulator powering the WS2812B array. All was fine for about 2 weeks, then over a period of a few days, 2 blue LED's died. Seems really strange to have only blue die on 2 chips.

I don't see what the resistor would be affecting down stream, the dead LED's are #8, #10 (0..15). I am thinking the LED's were stressed under 6V for that brief few seconds, and took a while to fail.

JonnyMac

I must be the luckiest guy in the world with these devices, because I have never used an inline resistor and never had a problem -- and I do a lot of work with these LEDs. Still, there have been some very thoughtful posts that suggest putting a resistor in the data line between the output driver and the first WS2812b. I don't remember seeing that "best practices" note, but I am going to go looking for it.

Publison

May be related to ground issue.

http://forums.parallax.com/showthread.php/158429-WS2812B-Propeller-Issue?highlight=WS2812B

Also check similar threads under that thread..

T Chap

https://learn.adafruit.com/adafruit-neopixel-uberguide/best-practices

Here is the link that says to use a series resistor.

I am using Jon's exact TC4417 schematic, no resistor in series.

I replaced the blown WS2812B, turned on power and blue was dead again! Replaced it again and the blue is fine now. This is chip 9 in the series. All others are fine before and after. Maybe a heat issue? I used a hot air pencil and rarely take the time to attempt a true heat profile when using an air pencil(The first set of chips were using an oven with a profile I have used on thousands of boards, still blue died on 2 chips). But how is Red working even if it is a reflow issue? Maybe blue is more fragile.

Smaller, battery-operated projects (e.g. FLORA and sewables) are usually fine omitting the capacitor and/or the resistor, but more substantive projects incorporating NeoPixel rings, matrices or a meter or more of NeoPixel strip, or using a plug-in power supply should definitely include both!