Equalizer with band-pass filters

Discussion in 'The Projects Forum' started by zoom, Nov 21, 2014.

  1. zoom

    Thread Starter New Member

    Jul 11, 2014
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    I've been playing around with an IC named MSGEQ7 which returns the amplitude of seven different frequency bands. To be able to utilize it, I use arduino.

    Now I want to make the circuit permanent but I realised that I really don't need to use this IC with an Arduino, instead I can build separate band-pass filters to get the amplitude of the desired frequency band.

    So, what I want to do is designing a band-pass filter with a varying capacitor or resistor so that I can shift the center frequency of the band-pass filter. But I really don't need the amplitude of the frequency instead I want to get HIGH or LOW if there is this frequency in the given signal.

    I am planning to connect the output of each filter to base of an NPN transistor to drive some LEDs.

    So, all in all I need help for designing the band-pass filter. I want to use op-amp to make it easier (I think it makes it easier, right ?) But I don't know much about it. Googled it but could not find a proper design, especially with a varying parameter to be able to change the middle frequency.

    Appreciate if you guide me.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Simple filters generally have a limited adjustment range. How wide a range do you want?
     
  3. Veracohr

    Distinguished Member

    Jan 3, 2011
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    Look up state variable filter designs, probably your best bet.
     
  4. zoom

    Thread Starter New Member

    Jul 11, 2014
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  5. crutschow

    Expert

    Mar 14, 2008
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    It's likely you can't get such a wide frequency range with a single filter expect by switching capacitors. Would that be acceptable?
    Why do you want to build you own filters when that MSGEQ7 will do what you want much simpler? :confused:
     
  6. zoom

    Thread Starter New Member

    Jul 11, 2014
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    No, actually I am planning to use 7 different filters for each range, not a single filter for whole range.
    Well, the msgeq7 I have is defective and also I need to spend one arduino nano to use it on a permanent project. That's why I want to achieve this project with my own filters, also it's a good practice :)
     
  7. Jony130

    AAC Fanatic!

    Feb 17, 2009
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  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The msqeq7 is called an "equalizer" but it is really just a set of seven filters with sample/hold to detect the maximum signal in each band - then transmit those levels to the Microcontroller. It does not adjust (equalize) the various bands.

    What is your goal? Build filters to sample and display - or - build filters that adjust and equalize and audio signal?
     
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