Timer Controlled 1 - 8 Demux? (a audio spectrum analyzer)

Discussion in 'Digital Circuit Design' started by Creative3431, Sep 17, 2016.

  1. Creative3431

    Thread Starter New Member

    Sep 17, 2016
    I am trying to make a audio spectrum analyzer. My plan is to take the audio to a MSGEQ7 seven band graphic equalizer, controlled with a 555 timer, then take the output of the MSGEQ7 to a demux. From there go to 7 LM3916 LED display drivers. The issue I am facing is finding a demux that is just controlled by the timer. The output of the equalizer is separated such that each of the pulses represents a specific frequency. So the first puls will be 63Hz, followed by 160Hz, etc. So what I need is for the demux is to do the opposite of what is going on in the equalizer. So the output of 1 would be high for one pulse, then low for the next 7, while pin 2 would be high on the second pulse etc. Is there a chip for this?
    Thank you
  2. ScottWang


    Aug 23, 2012
    Please show your circuit or block diagram.
  3. Creative3431

    Thread Starter New Member

    Sep 17, 2016
    Certainly. 20160917-110952_p0.jpg
  4. ci139


    Jul 11, 2016
    Quote (datasheet)
    • Only an off chip resistor and capacitor are needed to select the on chip clock oscillator frequency.
      The filter center frequencies track this frequency.
    • The seven frequencies are peak detected and multiplexed to the output to provide a DC representation of the amplitude of each band.
    • Gain AV Peak input to DC output, Vin = 100 mVpp, fin = 1 kHz Min:Typ:Max 20:22:24 (dB)
    ((as i get it)) it outputs analog value of the signal e.g. you need 7 sample and hold (and perhaps regenerate A/D hold D/A out) buffers ((i may get it incorrect - donno the chip))

    your pin7 on MSGEQ7 is floating . . .
    Last edited: Sep 17, 2016
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012

    It would be something like this. My concern (with the schematic posted below) is that the MSG07 reset pin is not held high long enough - you may need a 555 as a single shot to use Q3 of 4-bit counter to trigger the 555 monostable (with an non to invert the 555 signal). Then use that 555 monostable output to keep the MSQ07 AND the 4-bit counter in reset together.

    The outputs 0-6 of the cd4051 go to your seven LM3916.

    Good luck.

    ci139 likes this.