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Homework Help: Help designing a music visualizer for a 12x12 LED screen

  1. Nov 23, 2015 #1
    I am working in a group for designing a LED interactive Screen. My part of the project is the design of the music visualization system. I am new in this area, but I know I need to use some op-amps to filter the input signal from the mp3 player.
    Could anyone give me any suggestions on how to continue on the project? I know there are several ways to do it (there are multiple ways to digitize the signal eg. FFT ) but I’m not very sure which one to follow.

    Any help would be appreciated!

    Thank you in advance!
  2. jcsd
  3. Nov 23, 2015 #2
    I'm not sure that I can help without giving you the whole design.
    You would have to go digital early in the circuit to use FFT's.
    What can you do with band-pass filters?
  4. Nov 23, 2015 #3


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    You need to define what you want to visualize. Do you want the spectrum, or the time domain? Or, something else (like patterns based on frequency content)

    If you want the spectrum you need to digitize and run the FFT. If you want time domain, you need to digitize and decide how to trigger.
    You need to anti-alias filter before you digitize.

    Look at winamp visualization plugins and decide EXACTLY what you want to display.
  5. Nov 24, 2015 #4
    Thank you for your reply! I have to display the frequency domain and when this is done I will try and do some other frequency related patterns as well.
    I can't find enough information on how to do that though. Do you know any page that could be of help? Thanks!
  6. Nov 24, 2015 #5
    I guess I will have to go the digital way to use FFT. I am currently researching about filters because it is the first time I will work in this field. If you have any design that could help or know where and how to search for it, it would be very appreciated. Thanks!
  7. Nov 24, 2015 #6
    Since you mentioned FFT and a 12x12 array of LEDs, I was thinking you wanted to show the amplitude of 12 spectral bands on a bar-chart type of display. But now I wonder if you really had any specific display pattern in mind.
    The hardware design for pure digital would be some microprocessor with an A-to-D converter and 24 discrete outputs (DO). Once the wave form has been captured, you can drive the 12x12 array by clocking through each row with 12 DOs any using the other 12 DOs to select which LEDs in that row should be lit. What you code in the microprocessor would be whatever you want (FFT, etc).

    The PIC24 series (below) may work for you - but there are many others. There's more than a trivial amount of design work to do.


    A more analog design might be simpler - but less flexible.
  8. Nov 24, 2015 #7
    Thank you!
  9. Nov 24, 2015 #8


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    Staff: Mentor

    Another option for having a fun visual display with music is to drive the display in an x-y fashion. If you put a continuous sine wave (say at 60 Hz) on the horizontal axis, and drive the music waveform on the vertical axis, you can get some really fun and cool Lissajous patterns. I used to do this with an old oscilloscope and rock music back in college. It was a very popular display.

    You could even adjust the frequency of your horizontal sine wave to give you the best patterns for the particular song that is being played. I don't know if the resolution of a 12x12 display is enough to get good patterns, though.

    https://mbhs.edu/~jeglick/Images/TV/Lissajous Curves.jpg
  10. Nov 24, 2015 #9


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    Gold Member

    A bit Offtopic, but .....
    I set up a dual servo amplifier to drive the deflection coils of a TV. Equalized one channel's bass to get enough phase shift to look cool.
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