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Flickering Neopixel colors w/ Trinket
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Flickering Neopixel colors w/ Trinket

by GDSever on Thu Aug 20, 2020 5:53 pm

I am having significant color flickering issues with some Neopixel Mini PCBs and a 5V Trinket. I built this exact same project (a color-shifting table lamp) about a year or so ago using some Neopixels I purchased in 2016/2017 back and didnt have any issues.

The Arduino code is exactly the same, I'm using the same kind of Trinket, and the only difference is I'm using Neopixel Mini PCBs I purchased in March of last year (2019).

Did something change with their design or components? I noticed the printing on the the mini PCBs is different (I still have 4 of the "older" ones)...

It seems like it might be a communication timing issue, but i dont even know how to begin to resolve that. They are spaced about 2.25" apart and there are only 9 of them, so it shouldnt be a distance issue. The flickering seems to start with the second one and gets worse the further down the chain it is.

And suggestions or guidance is greatly appreciated! I ordered some other Neopixel products recently to see if the problem is the same with those.
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Re: Flickering Neopixel colors w/ Trinket

by adafruit_support_bill on Fri Aug 21, 2020 6:02 am

If you post your code and some photos of your build we'll take a look and see if we can spot any possible issues.

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Re: Flickering Neopixel colors w/ Trinket

by GDSever on Fri Aug 21, 2020 7:45 am

Picture of the build and code is attached. I've also uploaded a couple videos to YouTube to demonstrate the issue.

Flickering w/ newer neopixel string about 2 1/4 inches apart:
https://youtu.be/7FAK4lQ9ZrA

Working w/ old NeoPixel ring purchased in 2016/2017:
https://youtu.be/gXlO71Y7ZXg

Same project built last year with the older NeoPixels that didn't have an issue:
https://www.facebook.com/severglasswork ... 8515256148
https://www.facebook.com/severglasswork ... 4557426877

Pieces of the source code should look familiar. I am also running it on the standard Trinket 5V (the "bit bang" one), not the M0. I can't figure out how to get the M0 to work correctly yet (although it's probably the 3.3V vs 5V issue).

Thank you in advance for taking a look. I am flexible in how to resolve this so long as I can string the pixels 2-2.5" apart, and it doesn't involve me re-coding everything in Python. :-)
Attachments
lampbase.zip
Source code for the lamp base project.
(3.22 KiB) Downloaded 1 time
GDS pixels string.jpg
String of newer NeoPixel mini PCBs strung together about 2.25 " apart
GDS pixels string.jpg (356.35 KiB) Viewed 38 times
GDS Breadboard.jpg
breadboard layout for testing the neopixels string
GDS Breadboard.jpg (309.38 KiB) Viewed 38 times
GDSever
 
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Re: Flickering Neopixel colors w/ Trinket

by adafruit_support_bill on Fri Aug 21, 2020 10:14 am

I don't see any issues in the code.

For the circuit:
You can omit the resistor on the signal line. It is not needed for shorter runs and is not effective at all located at the processor end of the run.
Double check your solder-joints - in particular those on the first and second pixel. A cold-joint or similar marginal connection could be affecting the signal past that point.

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Re: Flickering Neopixel colors w/ Trinket

by GDSever on Fri Aug 21, 2020 11:17 am

OK. Will do. Soldering surface pads is not one of my strong suits, so it's possible there is a cold joint or two in there impacting things. I also ordered some "breadboard ready" neopixels to see if the thru-hole connections are easier for me. Thanks again for taking a look - I'll let you know how it works out.
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Re: Flickering Neopixel colors w/ Trinket

by GDSever on Fri Aug 21, 2020 12:49 pm

I reworked the solder joints and made sure I didn't have any cold joints. The flickering issue persists. I'll try with the breadboard-ready neopixels when they arrive.

I am a little disappointed - I have another 41 of these newer Mini PCB NeoPixels (all labeled 2017-08-25 - I bought 50 last year) and now I'm concerned I won't be able to use them for anything. I still have 4 of the older Neopixels, but that obviously won't help me since the project requires 9. I'm tempted to solder the older ones just to see if they flicker too. I'm including pictures of the two so you can see the differences.
Attachments
Old v New - Pads.jpg
New (Top) vs. Old (bottom) Mini PCB Neopixels - Pad side
Old v New - Pads.jpg (276.03 KiB) Viewed 33 times
Old batch.jpg
Bag with the last 4 "old" Mini PCB Nepixels purchased in 2016/2017 timeframe
Old batch.jpg (281.3 KiB) Viewed 33 times
New batch.jpg
Bags for the new batch of Mini PCB Neopixels purchased in 2019
New batch.jpg (346.12 KiB) Viewed 33 times
GDSever
 
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Re: Flickering Neopixel colors w/ Trinket

by GDSever on Fri Aug 21, 2020 12:51 pm

Sorry - couldn't attach the last picture in my previous post b/c of the attachment limit.
Attachments
Old v New - Components.jpg
New (top) vs. Old (bottom) Mini PCB Neopixels - Component Side
Old v New - Components.jpg (254.99 KiB) Viewed 33 times
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Re: Flickering Neopixel colors w/ Trinket

by adafruit_support_bill on Fri Aug 21, 2020 12:59 pm

Electrically, these are the same as the breadboard ready type. The only difference is in the PCB form factor.

To rule out a bad pixel, disconnect the signal wire from the breadboard and replace it with a jumper wire.
Then touch the other end of the jumper wire to the DIN pin of the 3rd or 4th pixel and see if the rest of the pixels behave as expected.

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Re: Flickering Neopixel colors w/ Trinket

by GDSever on Fri Aug 21, 2020 1:02 pm

I'll try that as well. Thanks for the suggestion.
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Re: Flickering Neopixel colors w/ Trinket

by GDSever on Fri Aug 21, 2020 1:27 pm

I tested with the jumper wire as you proposed and each individual pixel functions properly.

The issue seems to occur between the DIN pad and the DOUT pad. When I switched the jumper from the DIN to the DOUT the next pixel in the chain works fine... but the ones after that next one flicker. I don't know what could be happening between the DIN and DOUT pads that could potentially impact the signal.

Based on your comment about the Breadboard-ready vs. Mini PCB pixels, I'm not feeling very optimistic that my results will be different, but I suppose we shall see. Maybe I just got a bum batch, or this is the universe's way of telling me to give up tinkering. :-(
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Re: Flickering Neopixel colors w/ Trinket

by adafruit_support_bill on Fri Aug 21, 2020 2:13 pm

Can you post some photos of the back of the pixels showing your soldering?

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Re: Flickering Neopixel colors w/ Trinket

by GDSever on Fri Aug 21, 2020 2:45 pm

Sure. I felt like I was going crazy so I started over with new pixels, different wire, and was as careful / clean as I could be during soldering. Here are those pixtures. I did a strand of 3, and as you can see from the video starting around 10 seconds, the flickering is there.

https://youtu.be/fN-V0BHlR7s
Attachments
A2 Pixel 1.jpg
A2 Pixel 1.jpg (222.31 KiB) Viewed 26 times
A2 Pixel 2.jpg
A2 Pixel 2.jpg (285.68 KiB) Viewed 26 times
A2 Pixel 3.jpg
A2 Pixel 3.jpg (287.71 KiB) Viewed 26 times
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Re: Flickering Neopixel colors w/ Trinket

by GDSever on Fri Aug 21, 2020 2:50 pm

The whole string all together - pad side
Attachments
Attempt 2 Solder.jpg
Attempt 2 Solder.jpg (297.33 KiB) Viewed 26 times
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Re: Flickering Neopixel colors w/ Trinket

by adafruit_support_bill on Fri Aug 21, 2020 3:27 pm

Those look OK. Strictly speaking, a little more solder than necessary: https://learn.adafruit.com/adafruit-gui ... tep-418541
But they do look like solid connections.

The distance between pixels should not be an issue. Unless there is some nearby electrical interference, we usually don't see problems until the distance gets to be a couple of feet or more.

What are you using to power this? Power supply noise is sometimes a problem. The electrolytic capacitor helps to smooth that out, but electrolytics are not so good with the higher frequencies. If you have a ceramic capacitor (the value is not critical) you could try wiring it in parallel with the electrolytic.

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Re: Flickering Neopixel colors w/ Trinket

by GDSever on Fri Aug 21, 2020 4:05 pm

My breadboard power supply is the 5V/3.3V one from our friends at SparkFun (PRT-00114). I have tried powering it with a 5V 2A supply (https://www.amazon.com/gp/product/B01G6 ... UTF8&psc=1) and have the same issue, so I don't think that's the problem.

Yeah, the solder was more than usual but I have a hard time gauging the not enough / too much / just right with surface pads. I'm a champ with thru-hole connections ;-)

I'll try the ceramic capacitor in parallel with the electrolytic. If that doesn't help, then I'll wait for the new order to come in and try those. If they work ok without flickering, I guess this batch from 2017-08-25 are just going in the garbage.
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Please be positive and constructive with your questions and comments.