Gemma and NeoPixel problems after short circuit
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Gemma and NeoPixel problems after short circuit

by doncoleman on Tue Oct 22, 2013 10:33 pm

I'm trying to get a Gemma and a NeoPixel ring working based on this tutorial http://learn.adafruit.com/superhero-pow ... t/build-it. I don't have the single neopixel so the code is adjusted to use 16 LED.

I think I short circuited a neopixel ring, since only the first 6 lights light up.

I'm wondering if I also damaged the Gemma.

I have a 2nd neopixel ring. Whenever the USB on my macbook is plugged in, all the lights are at 255,255,255. When the USB is disconnected, and it runs on battery, the lights go back to blue.

Is it possible that the Gemma is damaged and the USB is overpowering the neopixels?

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Re: Gemma and NeoPixel problems after short circuit

by 1chicagodave on Wed Oct 23, 2013 1:19 am

Can you post a photo or two of your project?

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Re: Gemma and NeoPixel problems after short circuit

by doncoleman on Wed Oct 23, 2013 9:32 pm

Here's the broken neopixel ring. The sketch lights all 16 lights, but it stops at the power wire.
broken_neopixel.jpg
broken_neopixel.jpg (77.52 KiB) Viewed 586 times


Here's a different neopixel ring running the same sketch.
good_neopixel.jpg
good_neopixel.jpg (76.03 KiB) Viewed 586 times


I don't have a good picture of the Gemma, but when the power input is USB or a new battery, the pixels go to 100% white, even if they are set to red. Is there something I can measure to see if I cooked Pin 1 or the whole Gemma?

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Re: Gemma and NeoPixel problems after short circuit

by adafruit_support_mike on Thu Oct 24, 2013 12:19 am

Just to check: the device in the picture is a Flora not a Gemma. You said you don't have a good photo of the Gemma, so am I right in thinking you connected the Flora to show how the NeoPixel ring looks?

If that's correct, you can test your Gemma by loading a simple "blink an LED at 1Hz" sketch into it for each pin. Two or three voltage dividers and `analogRead()` will tell you whether the ADC is working correctly, and a voltmeter will confirm the outputs from the Vout, 3.3v, and GND pins.

WRT the ring that only lights part-way, it looks like the first non-working NeoPixel is dead.

NeoPixels use a rather neat communication protocol: each chip consumes the first 32 bits of input it sees on the data line, then copies everything else to its next neighbor. That makes life easier for a logic device controlling a string of them, but if one chip dies, the rest of the string loses its data connection.

WRT the all-white output from a strong power supply, does that happen with both rings and when running from both the Flora and the Gemma?
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Re: Gemma and NeoPixel problems after short circuit

by doncoleman on Thu Oct 24, 2013 1:00 am

Yes I switched to the Flora to diagnose the NeoPixel rings.

Is there a way I can jumper around the dead NeoPixel to make the ring work again?

I'll test the Gemma like you suggest.

The all white lights when powered from USB or a fully charged https://adafru.it/1317 battery only happen on the Gemma. Everything works find on the Flora.

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Re: Gemma and NeoPixel problems after short circuit

by adafruit_support_mike on Thu Oct 24, 2013 3:31 pm

doncoleman wrote:Is there a way I can jumper around the dead NeoPixel to make the ring work again?

Sure. If you're comfortable soldering SMT components, you can remove the dead NeoPixel and replace it with one of these: http://www.adafruit.com/products/1379

A less-officially-correct solution would be to run a jumper from the data-IN pin of the dead NeoPixel to the data-IN pin of the next one.

doncoleman wrote:The all white lights when powered from USB or a fully charged https://adafru.it/1317 battery only happen on the Gemma. Everything works find on the Flora.

Hmm.. that does sound like something's wrong with the Gemma.
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Re: Gemma and NeoPixel problems after short circuit

by doncoleman on Thu Oct 24, 2013 6:14 pm

Thanks Mike.

I'll jumper around the bad pixel for now, and try replacing it later.

The Gemma is probably cooked. I have a few more on the way, so I'm not going to worry about it for now.

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Re: Gemma and NeoPixel problems after short circuit

by adafruit_support_mike on Fri Oct 25, 2013 12:41 am

Remember that the 'take a frame of data and pass the rest along' protocol will shift all your color values one step down the chain. If you want to keep two rings in sync with each other, you'll face a bookkeeping challenge in the code.
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Re: Gemma and NeoPixel problems after short circuit

by doncoleman on Tue Oct 29, 2013 10:24 pm

I think I tracked down the problem with the lights being very bright. It appears to be a problem with OS X 10.8 programming Gemma (and Trinket.) This page http://learn.adafruit.com/introducing-g ... rduino-ide says there's a problem with 10.9 and Adafruit Arduino IDE 1.0.5. I had the problem with 10.8. Maybe it was something with XCode 5?

The hardware works OK when I run Adafruit Arduino IDE 1.0.5 on OS X 10.7.

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Re: Gemma and NeoPixel problems after short circuit

by adafruit_support_mike on Wed Oct 30, 2013 2:45 am

I shouldn't think it was a problem with Xcode.. that's a completely different toolchain. The OS X version of the Arduino IDE has a built-in copy of gcc..

.. actually, I just checked, and it appears to have four distinct copies of gcc. Props for thoroughness I guess.

It's interesting that the problem seems to be associated with Mavericks though. We know there are other things that don't quite work, so we'll mark this down as one more data point.

In the meantime, yay for having a platform that works! ;-)
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Re: Gemma and NeoPixel problems after short circuit

by metcalfepete on Fri Jan 31, 2014 10:50 pm

I just recieved my Gemma and 16 LED Neo Pixel ring this morning.
I'm seeing a similar issue, only the first 5/16 LEDs is lighting up.

I'm assuming that its a short.
Can I mail the ring back, and get an exchange ?

Thanks
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Re: Gemma and NeoPixel problems after short circuit

by adafruit_support_mike on Sat Feb 01, 2014 1:09 am

We'll need to check a few things here in the forum to build the support casefile, but if we confirm a hardware failure we'll get you a replacement. We test all our NeoPixel rings before they're approved for sale, so we need to figure out what happened between then and now.

Post a photo of your ring as you have it hooked up now (800x600 is a good size for images) along with your code (in CODE tags please).
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Re: Gemma and NeoPixel problems after short circuit

by metcalfepete on Sat Feb 08, 2014 11:37 am

Problem solved, operator error.
My kids and I are loving the Gemma and neopixels.
Using alligators clips on the ring however proved to be tricky than we though.
The clips were shorting a pin and it looked like a failure.
Thanks for you quick response.
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Re: Gemma and NeoPixel problems after short circuit

by pburgess on Sat Feb 08, 2014 3:37 pm

Not the first time. I've added a note to the NeoPixel Überguide to warn of this. Thanks for the feedback!
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