Pixie 3W Led Flicker

EL Wire/Tape/Panels, LEDs, pixels and strips, LCDs and TFTs, etc products from Adafruit

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ytai
 
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Joined: Sun Nov 20, 2011 12:15 pm

Re: Pixie 3W Led Flicker

Post by ytai »

When were those purchased? Can you please replace them with Adafruit and ask them to have them sent to me for analysis?
Sorry for the inconvenience, enjoy your Pixies!

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Systembolaget
 
Posts: 334
Joined: Wed Mar 08, 2017 1:01 pm

Re: Pixie 3W Led Flicker

Post by Systembolaget »

A suggestion for a future revision.

Maybe it is possible to use an MCPCB as is common for high-performance flashlight LEDs or at least make it possible to directly stick a heat-sink to the back of the LED by putting a hole into the PCB underneath the LED, and re-arranging the ICs around it, if they really have to be on the back of the PCB. The classic fischer elektronik fcool ICK LED R 28 x 15 G would work wonders for a 3W LED.

It would be great to have a high-brightness RGB LED like the Pixie on the market that, once properly heat-sink-able, also no longer requires thermal protection circuitry.

Thanks!

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LeviK
 
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Joined: Thu Jun 27, 2019 11:26 am

Re: Pixie 3W Led Flicker

Post by LeviK »

ytai wrote:First of all, big thanks to Adafruit for offering those replacements!!!

I'd like to elaborate a little about the status:

I've done extensive testing, was able to reproduce the flickering issue on a significant fraction of the units (severity varies). I've done dug up for the cause and have found a definite problem which is a very likely the root cause. It causes temperature readings during runtime to be very imprecise, so occasionally exceed the temperature limit even if the actual temperature is well below the limit. Of course, raising the limit will reduce the likelihood of that happening, but I strongly disrecommend it, since the unit *will* be able to overheat if you do that, possibly damaging itself or creating a hazard.

The fix for the problem it is a minor software tweak (those who are curious can check out the two recent commits on the public firmware repository). After having applied that fix I haven't seen that issue anymore and Adafruit have independently confirmed this observation. I do, however, want to do so more extensive testing before declaring victory, to avoid any further issues. This will take place over the next few days.

For those who are interested in trying to fix units themselves by reflashing the firmware, you're more than invited to try, but be advised that I won't be able to provide detailed guidance on things that are not specific to this product (such as, how to program a PIC MCU). Also be advised that once you put the firmware on the Pixie, there's still a temperature calibration process that needs to take place, which would require you to have some good basic skills in embedded work as well as tools. If anyone is still super-curious about that given Adafruit's offer to replace the defective units, I can provide some very high-level guidance (but no step-by-step tutorials, since this would be very time-consuming).

My sincere apologies for not identifying this issue before shipping the product. I'm hoping that with fixing this issue you'll experience the Pixie as a reliable and useful product. Thanks for all of you who took the time and patience to surface the issue and press on having it fixed!
Dear Ytai,
Thank you so much for your development on the Pixie, it really is great!
However for my project, I need a bespoke PCB Layout which will also have apropriate heatsinks. I have designed my PCBs, had one made and uploaded the code you have posted on github with MPLAB and a pickit3, unfortunatelly the LED doesn't light up at all with the strandtest code for arduino.

I tested the LED separately and it did work, the arduino is sending the signal, I checked with the oscilloscope. The layout is correct and there are no shorts on the board. If I directly send 2V to 4.5V (as if the chip outputs HIGH) to PGD or PGC, the colours light up respectively, so the current drivers works.

I am thinking I am having this issue because you said there is another step in calibrating the PIC after the sw upload?
Giving the fact that the LEDS will have a large heatsink on them, can you please release a software version without the temp protection?
Or give me some guidance on how to make them work if that is not the issue?
Here is a photo of the first version of my PCBs (they will be slightly tweeked) Image

Once again, thank you for your support!

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