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Thread: FFT on LED wall (R Pi + Teensy/Octo + Microphone + WS2812B) : Will this work ?

  1. #1
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    FFT on LED wall (R Pi + Teensy/Octo + Microphone + WS2812B) : Will this work ?

    Hello,
    I'm new to this world and I'd like your help

    I'm a first year student in an engineering school in France and I'd like to make an LED wall.

    The primry objective of this project is to display live the FFT of the sound (speach and music) captured by a microphone.
    Example: https://www.youtube.com/watch?v=IUbECxGWvFw

    The setup would be this one:


    Iíll later also put Glediator on the Rasberry Pi, and my final wishes are to display GIF, and if everything works out great why not add some more strips and use VideoDisplay to have a bit of fun with it.

    Do you think Iíll encounter any major issues with this setup or will it be quite straightforward ?

    Thank you for your help.
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  2. #2
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    What you are trying to do is certainly not impossible, though big LED walls are not simple project and the forum is littered with projects that have run into trouble around the sheer current needed for these things.

    The straightforwardness of this would depend on how familiar you are with the intersection of programing and electronics, since while the octo library has plentiful examples you will need to massage the code a fair bit if you want to make this thing multi purpose and start grafting things together. And there will be a fair bit of mechanical work in making a solid product with all this mounted to it.

    Suggested starting point would be hitting the Teensyduino download page, installing and having a look at the Octo examples, and the audio library->anylisis->fft examples. And see if you can graft them together in a way that will at least compile.

    If that's making sense then go shopping for the microphone, teensy, octo board and a short length of strip (<60 pixels) and get a prototype going. The idea is to build something that can sit on the bench and run off USB power without having unwieldy amounts of strips or large power supplies. And also means that if you let the magic smoke out it hurts less.

    Once the basics are working it's time to suss out the full scale design mechanically and electrically.

  3. #3
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    Thank you for your anwser !

    The idea is to take inspiration from this for the FFT : https://learn.adafruit.com/fft-fun-w...forms/hardware.

    Being able to make a bigger wall is really a bonus for later, as long I'm able to just but an good looking spectrum analysis on 8 strips I'll be really happy
    Last edited by Kevin; 04-16-2016 at 10:44 AM.

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Maybe start with File > Examples > OctoWS2811 > SpectrumAnalyzer.

    https://github.com/PaulStoffregen/Oc...umAnalyzer.ino

    This example reads audio on analog pin A3 and shows a 60 band spectrum analysis on 1920 LEDs (a 60x32 grid). No Raspberry Pi needed.

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    Thank you

    The Raspberry Pi is for later, making it portable, linking to Glediator etc.

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    Hi,

    I tried to test out the teensy with OctoWS2811 > BasicTest :
    I just connected a strip of 30 LED on LED_7 (powerd with +5V of the octo) via the Octo with a CAT6 cable but they just turn RED, that's it.

    Is it because I didn't connect 8 strips ?

    Thanks

    PS : during the soldering work I slipt and lifted off the SMD next to the LED.
    Last edited by Kevin; 05-22-2016 at 10:12 AM.

  7. #7
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    You don't need 8 strips, since the library can't tell if anything is connected. Dull red would often indicate power problems but see below for suggested steps.

    edit - see other post for this bit, think it's actually a decoupling cap

    Will have to check but I think that component is the resistor for the LED so not a critical problem but makes the next step awkward:
    Normally first advice would be to load the blink example and make sure it works, but that's going to be tricky here!
    Do you have the components to wire up a resistor+LED to pin 13?

    Otherwise load up examples->teensy->tutorial3->helloSerialMonitor. Then bring up the serial monitor and make sure it's printing hello world at you
    Next check you have power and ground happening on the strips with a multimeter if you have one, otherwise double check that things are going where they should (and consider getting/borrowing one).
    Then load up the adafruit neopixel library strand test example and point it at the pin with LEDs connected (21 I think). This should be the same as what you are doing but uses a different library and simpler setups.
    If that hasn't found anything it's time to dig into the strip wiring.
    Last edited by GremlinWrangler; 05-22-2016 at 01:07 PM. Reason: Found second post on same topic

  8. #8
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by Kevin View Post
    I just connected a strip of 30 LED on LED_7 (powerd with +5V of the octo) via the Octo with a CAT6 cable but they just turn RED, that's it.
    Check the power supply voltage actually at the LEDs. The red LED needs less voltage than green and blue, so if you've got a low voltage problem, you'll get mostly or all red.

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    I changed computers, now when the strip is not connected to the +5V it's still stay red but when connected it turns white and the test program does nothing but when only the data is connected the red flickers..
    I can't even managed to set a different color on one of the LEDs.

  10. #10
    Senior Member PaulStoffregen's Avatar
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    First, start with File > Examples > OctoWS2811 > BasicTest. That will display different colors, without depending on any PC-based communication. Get that working first!

    If the LEDs don't show the color changes, you'll need to post photos showing your actual wiring. Something is probably not connected properly, but nobody can help with wiring until you post detailed photos that clearly show exactly how you've actually connected everything.

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    I thnik I fried my new teensy

    I added an external power supply and cut the 5V connection under the teensy but just after I loaded the BasicTest onto the Teensy, it died.

    Here is a photo of the wiring (5V output on the power block) :
    I must have done something quite wrong & dumb.

    Thanks for your help

  12. #12
    Senior Member+ Frank B's Avatar
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    The most dumb: YOU DID NOT ISOLATE THE HIGH-VOLTAGE ON THE SUPPLY. DO THIS ASAP.

  13. #13
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    Second the comment on having one, pref two layers of something between you and those AC terminals (so two things have to fall off, break or fail before anything can toast you and/or parts). And electrical tape only qualifies has 0.5 of a layer. At the moment you also have a real risk of the wire flexing enough to break and then ending up loose on the bench so your solution should involve some form of cable support (can be as simple as cable tieing the incoming cable along the side of the PSU frame). Proper cable crimps can help there as well, both shielding you and preventing things coming loose unexpectedly.

    What will also be complicating things here is the ground for the Teensy. It's sharing power with the Octo board but not seeing a ground wire to either at the moment except for the ones looping through the strip.

    And you appear to be connected to the output end of the strip (see little arrows and Din/Dout markings). Have done this myself and it's not garunteed to have blow the pixel and the driver but it certainly will not work like that.

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