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Dotstar has developed erratic behavior
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Dotstar has developed erratic behavior

by mroland on Mon Apr 15, 2019 1:14 am

I bought and have been working with my Dotstar LED strip (https://www.adafruit.com/product/2239?length=1) for a few weeks with no problems.

I was re-arranging my project build today and the strip has now developed erratic behavior. Mostly the LEDs are not working at all. If I tap the input wires and/or the strip around the first couple of LEDs the strip will light, but it will not animate as scripted. Sometimes only the first few LEDs will light.

I've soldered on new wires to the strip, but the strip has the same behavior.

I've verified 5V on the strip so that leads me to believe there's a problem with the signal (clock or data) on the strip. Any suggestions on how to troubleshoot this?

mroland
 
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Re: Dotstar has developed erratic behavior

by adafruit_support_mike on Mon Apr 15, 2019 3:10 am

Post a photo showing your hardware and connections and we'll take a look. 800x600 images usually work best.

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Re: Dotstar has developed erratic behavior

by mroland on Tue Apr 16, 2019 2:42 pm

Thanks for the reply. I'm attaching 2 photos:

Before: This is a screen cap of a video of a spectrum animation. This actually rotates around the circle. I was very happy about it!
Screen Shot 2019-04-16 at 11.38.31 AM.png
Screen Shot 2019-04-16 at 11.38.31 AM.png (618.32 KiB) Viewed 100 times


After: I worked on moving some components and was generally very gentle (no hard bends), but afterward the strip has communication problems.
IMG_3946.JPG
IMG_3946.JPG (419.35 KiB) Viewed 100 times

mroland
 
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Re: Dotstar has developed erratic behavior

by adafruit_support_mike on Tue Apr 16, 2019 11:55 pm

Thank you. From your description, it does sound like a connection issue.

Try using a fine-point probe like a bamboo skewer to tap individual wires and joints. Do the problems (or correct behavior) tend to occur when you make contact with a specific location?

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Re: Dotstar has developed erratic behavior

by mroland on Mon Sep 09, 2019 1:34 am

My broken Dotstar strip has been bothering me for nearly 5 months now, but tonight I finally had the opportunity to debug it.

I did as suggested and probed the first LED with a wooden toothpick. Occasionally I could get that pixel to light up, but nothing else.

At that point I decided to go ahead and cut off the first LED of the strip, and based on information at viewtopic.php?f=47&t=145976 and viewtopic.php?f=47&t=109258&p=545930, I soldered a 470 ohm resistor on the clock and data pins.

IMG_4477.JPG
IMG_4477.JPG (978.11 KiB) Viewed 39 times


And... that did it! It is now working as before, only 1 LED shorter.

mroland
 
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Joined: Sun Feb 25, 2018 5:20 pm

Re: Dotstar has developed erratic behavior

by oesterle on Mon Sep 09, 2019 5:01 pm

Congrats, mroland!

LED strip contacts can be a little challenging to solder. Here are some tips based on my own experience:
  • I make sure the strip contacts are clean. I like to use a little isopropyl alcohol to clean them up.
  • I check and clean my soldering iron tip before every use, and always use good quality solder with no-wash flux.
    Collin's Lab: Soldering has a great video on soldering, and what good and bad soldering connections look like. I watch it every few months to keep my craft up, or when I just want to hear Collin's soothing mentorship.
  • For connections that may undergo stress or flex, like the soldered ends of LED strips, I'll apply a generous dollop of hot glue over the soldered connection (and about 1/2"/12mm of the wire ends) to reinforce the connection, and give some strain relief.
Bonus points

Cheers,

Eric

oesterle
 
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Re: Dotstar has developed erratic behavior

by mroland on Mon Sep 09, 2019 5:58 pm

Thanks Eric. Great advice!

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Please be positive and constructive with your questions and comments.