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Thread: t3.2 & Octows2811 over heating

  1. #1
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    t3.2 & Octows2811 over heating

    Hey all! I have a teensy 3.2 on top of the octows2811 adapter running 1288 neopixels. Both the chip on the teensy and the ethernet output ports on the Octo are getting supper hot. I've had it running for a couple weekends and it hasn't fried but it shouldn't be getting that hot right? I had it wired with 18ga from the 5v psu but the ground wire was getting super hot as well. So I re-wired everything with two +5v and two grounds both at 14ga now. All the wires are now cooler. Should be more than enough to power the leds and the teensy. I have the grounds screwed into the grounding pads on the Octo. The two 5v lines I have running into a cap bank, 4000uF per 5v line, 8000UF total. All grounds of caps connected to single ground, connected to psu ground and Octo ground. From one of the 5v lines I have a usb cable that powers the teensy, since the voltage regulator steps down the power from the usb input. The neopixels are powered from the cap bank and the data and ground are from the Cat6 cables. I can upload photos if unclear.

    PSU I'm using: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    Should I run a parallel ground wire from the leds to the psu so all the current isn't going straight into the Octo? I also read that I may need to cut the trace from the Vin & VUSB?

    I have the usb wired to an external port so I can program without going into the enclosure and unplugging the usb on the teensy every time. Wired up a switch to cut power from the psu so it doesn't feed into the computers usb cable while I'm programming.

    Would it be better to wire the 5v straight to the Vin and cut the Vin/VUSB trace and add a diode so I can plug in and program without back feeding the psu power to my computer?

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    Quote Originally Posted by Zeropoint42 View Post
    I also read that I may need to cut the trace from the Vin & VUSB?
    No. Not "may". If I understand your circuit correctly, you MUST cut that trace. You are feeding 5v in from USB and 5v from your Power Supply. That's very bad and you might damage a number of things. Cutting the trace is required to break the connection to 5v USB power. Your Power Supply will then power both the LEDs and the Teensy.

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    Quote Originally Posted by Zeropoint42 View Post
    Would it be better to wire the 5v straight to the Vin and cut the Vin/VUSB trace and add a diode so I can plug in and program without back feeding the psu power to my computer?
    My first reply was made as quick as I could once I understood that the PS and USB power were being shorted together. I've now read farther and want to respond to that...

    Yes, cut the trace. You're split both 5v and GND, one leg for LEDs, the other for Teensy, is very good. Keep in mind, your LEDs will take (10's of ?) Amps while the Teensy will take milliamps.

    Quote Originally Posted by Zeropoint42 View Post
    Wired up a switch to cut power from the psu so it doesn't feed into the computers usb cable while I'm programming.
    I'm not clear on the switch and the exact circuit details. You'll get the best help here if you include a circuit diagram and a picture of your wiring.

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    The switch does the same thing as cutting the trace. When I want to program I cut the power from the psu and only use the computers usb. During normal operation I switch back on the psu power and run it to the teensy's usb.

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    So, it gets hot when you are running normally and NOT connected to USB? And, the trace is cut?

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    Trace is not cut. I have the teensy powered from the 5v psu via the teensy usb port, not the Vin pin. I have been just unplugging the psu usb and plugging in the computers usb to program.
    It get hot while running normally. I'm trying to upload my schematic but it keeps failing...

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    Heres my schematic.

    Click image for larger version. 

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    I will probably update the wiring and wire the 5v to the Vin pin and cut the trace on the board so I don't need the 5v disconnect.
    The heating is my main issue though

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    I found nothing obviously wrong looking at the schematic.

    I suggest to start scrutinizing the wiring. Most import are the high current paths, long paths, and long high current paths

    Please post a picture of your wiring.

    Have you had a chance to read:

    LED Video Panel at Maker Faire 2014: Concept and Development. Specifically, scroll down to "Power Supplies".

    and

    Teensy 3.2 OctoWS2811 Adaptor (Of course you've read this one. Just including it here for reference)

    Disclaimer: I have not built an LED display even approaching this many LEDs. My biggest is 12x12 so far, so power still has to be managed but is much less of a problem.

    I had to look at pictures from both articles to piece this together.




    But, assuming these are of the same project, you can see that the +5v and GND wires are perhaps only 12" long. Paul didn't use a large capacitor; just ensured that the +5v and GND wires from PSU to LED strip were as short as possible (or practical) and that they tie together at a single point at the PSU. I believe the overall goal is to minimize and voltage drop in the +5v and GND wires due to high current flow through those wires. Thicker wires helps, as you have done. Also, shorter length helps. As does parallel paths. I suspect that the large capacitors are unnecessary.

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    I've seen both of these projects and a few more. I've designed mine mostly based off this one since its close to my pixel count:https://learn.adafruit.com/1500-neop...power-topology
    I put the caps in as a voltage spike buffer per the common practice in the Adafruit neopixel uber guide. The lower led strips have a much shorter run than the upper. I have the lower wired strait to the cat6 cable about 18" from the teensy. The upper however are around 80" away from the teensy. I'm using 22ga wire to power the uppers but I have two strips in parallel for their power and ground. So one 22ga 5v wire and one 22ga ground wire for two strips of 161 pixels. I can't really loop the power and ground back at the end of the strips due to the design of my piece.

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    Wiring inside the piece:
    Click image for larger version. 

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    Wiring going to the upper strips:
    Click image for larger version. 

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    There is about 6" of cat6 connected to the 22ga bundle from the upper strips. No matter how thick the wires are after it still has to go through the 24ga cat6...

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    I'm at the limit of my ability to help.

    I suspect that the core issue is voltage drops in the high current wires and misplacement of the capacitors - these should be at the noise source (LED strip inputs, Teensy Vin). Also, if I understand correctly, Paul advises to take power for the Teensy from one of the power points near the LEDs.

    I'm hoping that someone with far more experience with large LED displays will notice this thread and chime in.

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    Thank you for all your time and help!
    For some strange reason when I switched from the neopixel library to the FastLED the boards are dramatically cooler! I had it powered up for hours yesterday tweaking the fastLED code and both the teensy and the Octo are room temp. I guess the larger ground wires plus the new code helped with power consumption enough to cool everything down.
    I think I'm good... for now. Still running more tests.
    Thank you markonian again

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    Quote Originally Posted by Zeropoint42 View Post
    ... when I switched from the neopixel library to the FastLED the boards are dramatically cooler!
    That's really strange. I have no explanation for this. If you ever figure it out, I'd love to hear about it.

    Paul's OctoWS2811 LED Library is also available and written specifically for the OctoWS2811 Adaptor. It's interesting because it supports
    [...] simultaneous update to 8 LED strips using efficient DMA-based data transfer [...]. Minimal CPU impact and double buffering allows complex animation
    .

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