Flashing Pixel on 8x8 NeoPixel Matrix
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Flashing Pixel on 8x8 NeoPixel Matrix

by jacoberrol on Sun Oct 06, 2013 4:53 pm

I'm new to Arduino and in my first project I am programming some animations on an 8x8 NeoPixel matrix with an Uno. I need it to be portable, so I'm using a 12V DC power supply (8 AA batteries) going through a Buck converter to supply 5V DC to the NeoPixel Matrix. Everything works great in this configuration.

I wanted to save on batteries while I work on the project, so I decided to use a 5V AC/DC power supply in place of the batteries+buck converter. When I connected that directly to the matrix, the pixels were REALLY bright and they started acting kinda random. I disconnected the AC/DC power supply and went back to my batteries.

Now, my matrix is working as it did before, except for one pixel that blinks green intermittently. All other pixels work fine except this one. If I run a simple program...

void loop() {
matrix.show();
delay(1000);
}

I will see green for 3 seconds and then off for 2 seconds.

My questions:
1. Is it possible that I damaged the matrix with AC/DC power supply? If so, is intermittently blinking color a typical failure mode?
2. I tested the output of the power supply before connecting and it measured 5V... Why would it have made the matrix so much brighter? And why would it have damaged the matrix?

Thanks!

Jake
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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by adafruit_support_rick on Sun Oct 06, 2013 5:27 pm

Are you sure you didn't connect 5V AC to the matrix? It certainly sounds like you burned out one pixel. Maybe it acted as a fuse and protected the rest of the pixels.

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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by jacoberrol on Sun Oct 06, 2013 5:52 pm

Attaching a pic of the AC/DC adapter. I've noticed some other pixels are intermittently blinking the wrong color as well, but with much less frequency. I also attached a picture of the matrix. It's working for the most part, just some of the pixels blinking randomly. Is that a symptom of a burned out pixel? It's weird because they still light up. I've burned out LED's before and they just don't light up after that.
Attachments
photo (1).JPG
This is the matrix working (except for one green pixel blinking)
photo (1).JPG (120.04 KiB) Viewed 1405 times
photo.JPG
This is the AC/DC Adapter I used
photo.JPG (111.21 KiB) Viewed 1405 times
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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by adafruit_support_rick on Sun Oct 06, 2013 5:59 pm

You really don't want to sit things on an anti-static bag, as they are conductive.

All I can think is that the wall-wart voltage spikes under load. The NeoPixels are sensitive to voltage, and won't take more than 6V.

Each NeoPixel has a driver chip embedded in it - that's probably what got damaged, and that's why the LED still sort of seems to work.

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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by adafruit on Mon Oct 07, 2013 12:12 pm

Hmm unfortuantely that isn't the 5V 2A supply we have in the shop, so we don't know whether it was well made or not.
It could be really noisy and have high voltage spikes & that could have damaged the pixels. Or perhaps it was connected backwards? that would also damage it
also - dont forget to have a common ground wire between your arduino and the power supply! that can cause odd behavior
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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by jacoberrol on Mon Oct 07, 2013 3:16 pm

Thanks for all of the advice. Sounds like I damaged my board. Either from placing it on the "conductive" static bag, or by plugging into the wall-wart AC/DC adapter. (My guess is the latter).

What is a good material for me to place my Arduino project on?

Jake
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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by adafruit_support_rick on Mon Oct 07, 2013 3:27 pm

wood, paper, rubber. We have rubber feet in the store:
http://www.adafruit.com/products/550

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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by jacoberrol on Sun Oct 20, 2013 5:21 pm

Hi, following up on this post. I purchased a new neopixel matrix and connected it to the battery supply. Everything is working fine except i'm getting the same blinking green led :(

It doesn't matter what program I run, I get the same behavior... even sample programs. It seems like a software issue to me. Is it possible to put a bug in the arduino bootloader? I am totally mystified right now.
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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by adafruit_support_rick on Sun Oct 20, 2013 5:32 pm

What happens if you run the strandtest sketch that comes with the neopixel library?

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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by jacoberrol on Mon Oct 21, 2013 7:15 pm

Ok, I tried your suggestion and the plot thickens... I modified strandtest to use 64 pixels since I have an 8x8 matrix. The initial run worked correctly; no blinking green light. However, if I use the setBrightness() function I'm able to recreate the issue predictably. For example, when I do setBrightness(10), the first pixel will blink green for the first three sequeneces of the test and then start working normally. The blinking behavior occurs again after the test returns to the beginning sequence... Again very predictable, which is why it seems like software to me.
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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by pburgess on Tue Oct 22, 2013 11:18 am

Can we get a clear photo of the complete wiring between Arduino and matrix?
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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by jacoberrol on Tue Oct 22, 2013 7:53 pm

Here is an example of the behavior.

In this video, I'm running strandtest and it works as expected (full brightness)
http://youtu.be/ZCEiPWxY4QA

In this video I have the brightness turned down and you can see the first pixel blinking green:
http://youtu.be/gX17cX-8IA0
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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by jacoberrol on Tue Oct 22, 2013 8:01 pm

Here is the wiring... pretty basic. Just have the #7 output going to Din.
Attachments
matrix_wiring.JPG
Matrix wiring
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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by adafruit_support_rick on Wed Oct 23, 2013 7:56 am

You need a common ground between the Arduino and the matrix.

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Re: Flashing Pixel on 8x8 NeoPixel Matrix

by xl97 on Wed Oct 23, 2013 12:29 pm

adafruit wrote:also - dont forget to have a common ground wire between your arduino and the power supply! that can cause odd behavior


adafruit_support_rick wrote:You need a common ground between the Arduino and the matrix.




I'm thinking you should try adding the common ground. :)
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