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SOLVED (RPi3 + WS2812b + SPI) Flicker at 100% White

Discussion in 'Hardware Support' started by w.ashcroft, 15 August 2017.

  1. w.ashcroft

    w.ashcroft New Member

    Messages:
    5
    Hardware:
    RPi3
    Hello,
    I have a fully working Hyperion Ambilight setup, however when there is a bright image on screen, or the remote app is used to put the LEDs at 100% white, there is lots of flicker/flashing of the whole strip of 312 LEDs as if suddenly hit with lots of interference.

    At first I thought this might be a power supply / voltage drop issue, but a quick test with the Adafruit strand test and an Arduino is rock solid at 100% white (same power supply, just moving data and ground pins from RPi to Arduino [grounds are commoned]).

    I think this proves there is nothing wrong with the power supply, wiring, LEDs or hardware, but something within the RPi or Hyperion is causing this. Any ideas? @penfold42 :)

    Many thanks,
    Warren
     
  2. Akriss

    Akriss Active Member

    Messages:
    567
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    I had that happen once.

    I had thought the 20 amp power supply I bought was adequate for my 244 apa102. Doing the math showed that 20 amps should be more then enough. However, just like you my entire led strip started blinking when at full white. I didn't have a higher amperage power supply to test with but I did have two 10amp power supply's. I had to separate the power supply's so each power supply powers two sides only and only share a ground line. It works though!

    So I guess my labeled 20amp supply was lacking a bit.

    I haven't bought a higher amperage single power supply yet. "I'm thinking Don't fix what isn't broke.":)

    a picture of my setup [​IMG]

    Hope it helps.
     
  3. w.ashcroft

    w.ashcroft New Member

    Messages:
    5
    Hardware:
    RPi3
    Hello,
    Thanks for the input, I immediately thought power supply but it doesn't explain why the Arduino can run the strips at 100% white without any issues, with the same power supply.

    Cheers,
    Warren
     
  4. penfold42

    penfold42 Active Member

    Messages:
    746
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    Level shifter ?
     
  5. w.ashcroft

    w.ashcroft New Member

    Messages:
    5
    Hardware:
    RPi3
    There isn't one in the setup already, are you suggesting I add one? I suppose that explains why it's fine with an Arduino providing the signal, however why would this make a difference on the RPi, when the only difference between good and bad is the actual data? (i.e. blue 0 0 255, vs white 255 255 255).
     
  6. penfold42

    penfold42 Active Member

    Messages:
    746
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    Yup - I suggest adding one.

    Theory says they're always required but of course some people sometime get away with it

    A logical 1 needs a longer pulse time - any marginal voltages will show up the more '1's you have.

    A brighter strip will cause more voltage drop in both the power and ground return wires which will alter the threshold voltage.
     
  7. w.ashcroft

    w.ashcroft New Member

    Messages:
    5
    Hardware:
    RPi3
    Thanks - I've ordered some 74HCT125 chips and will update how I get on.
     
  8. w.ashcroft

    w.ashcroft New Member

    Messages:
    5
    Hardware:
    RPi3
    Using a level shifter sorted the issue - LEDs are now rock solid, no more strobing at full white and no more occasional flicker either.

    Thanks!
     
    • Like Like x 1
  9. wiisos

    wiisos New Member

    Messages:
    1
    Hardware:
    RPi1/Zero
    Hi I have the same problem with SPI (pin19). In my case happens in all colours but if I low voltaje the flickering recudes considerably. Do you have the schematic that you used? Where you bought it?

    Thanks in advance