Fixing a broken Blinkytape
Hi,
I'm trying to fix a Blinkytape that is only working for the first 4 pixels (pixels 5 and beyond are not lighting up).
I have tried the button reset and reuploading firmware - that gets the first 4 pixels to show the rainbow pattern again, but the others still do nothing. I can also change (using the latest PatternPaint for Mac) the pattern of the first 4 pixels.
Oh, one other interesting thing, when plugging in the strip, most of the time, all the pixels blink on for a moment then go out (occasionally, only a few [plus the first 4] blink).
I'm guessing that there is a problem in the connection between the 4th and 5th pixel, but I'm not sure if there's a reasonable way to go in and fix it (or if it could also be a problem lower down in the chain).
Any suggestions? My first thought is to remove the end-caps, slide the plastic sheath down and try to see if adding some solder along the joint between the 4th and 5th pixels might do something. If that did work, then putting some sort of thin splint between those pixels and pulling the plastic sheath back over.
Thanks!
Stan
Comments
Your guess sounds correct. It's likely a crack in the copper trace on the board. Usually the easiest thing to do is to cut off the LED on either side of the problem (so LED 4 and 5 in your case), and then re-solder the strip together. If you cut directly down the center of space between the two LEDs, there should be enough exposed copper to make it possible to solder the strip back together. And yes, sliding the silicone tube down is probably the best way to get at it- it's how they're made. One tip is to attach a string to the end of the tape that you'll need to pull out later- that way you can pull the strip back through the tube layer.
If you have a multimeter, you can try measuring the connections between:
+5v on LED 4 and +5v on LED5
gnd on LED 4 and gnd on LED5
DOUT on LED 4 and DIN on LED5
The datasheet for the LEDs is here:
http://www.seeedstudio.com/document/pdf/WS2812B Datasheet.pdf
That would tell you if it's a broken connection; a more complicated procedure would then be to solder a tiny wire between the two LEDs to repair that specific connection. It's also possible that one of the LEDs has actually gone bad, in which case you need to remove it- but it's hard to tell which one is the culprit, since it could be the output circuit on LED4, or the input circuit on LED5. I still recommend just cutting them both off, since it's the strongest way to make the repair.