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21 Band Audio Spectrum Analyzer

Adding the final touches.

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21-Band Audio Spectrum Analyzer using ESP32 controller together with a set of three MSGEQ7 ICs for the 21 frequencies and 21 strips of 20 LEDs WS2812B. Audio Amp and Bluetooth are optional.

I call this the PANDEMIC project and it was started from a generic 14-bands spectrum analyzer based on Arduino Mega, and converting it to a 21-bands audio spectrum analyzer now running on ESP32 with more memory for additional color patterns and features. New hardware includes the low cost 6wats Audio Amp and Bluetooth connectivity. After 3 separate revisions I got the parts to fit just right, and included the option to power the board and 420 LEDs on 2 x 18650 3.7v batteries (mounted on bottom side). Adding the batteries is overkill, and is not worth the hassle, since a full charge only last 2 hours at the lowest brightness. 

The biggest challenge was making the LED bezel / 20x 21 LED array. I ordered separate vertical columns for the LED strips to stick on, and then solder the two ends to 3-pin terminals. I also ordered the 2 horizontal PCBs that holds the 21 columns and distributes power to all 420 LEDs .. Using the LED Strips with the PCB was the easiest way I could think of without having jumper wires between the 21 columns .. 

A second variant, which I will try in the upcoming weeks, is to hand solder the 420 LEDs individually which will save me about $40 and will look much nicer. I will try and use low temperature solder paste (138degC) and a heat gun to blow hot air from below the PCB. I'm not sure is going to work, but using a hot-plate will be even more challenging.

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Assembly Drawing

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  • 1 × ESP32 38pin Type-C Dev-board Expressif
  • 1 × SI5251 Skyworks Clock generator - SparkFun
  • 3 × MSGEQ7 7 Band Audio Spectrum Analyzer IC
  • 1 × M18-HX8 Bluetooth - OPTIONAL
  • 1 × PAM8403 Audio ICs / Audio Amplifiers - OPTIONAL

View all 22 components

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  • 1
    Order your parts and wait 3-4 weeks.

    1. Order boards JLCPCB.com (black soldermask finish).

    2. Order parts AliExpress or Amazon and for MSGEQ7 go to Mouser.com to avoid fake ICs.

    3. Order LED strips from BFT-Lighting.com or whatever works for you but be consistent. Do not mix and match or you get some weird colors from different suppliers. (I got 5 rolls of the 74/m black IP30 for about $65).

  • 2
    Solder components to the board top side.

    Solder smaller components first such as the ceramic caps and resistors. Resistors R5, R6, R7 and R8 are only needed if you plan on adding buttons for the Bluetooth such as next / previous. 

    Also don't solder C17 and R9 (only needed for internal clock single 7 channel mode). Next solder the larger electrolytic caps with polarity markings (C12, C13, C14, C15 will be soldered axially on a 90 degree angle). Mount and solder Jacks J1 and J2, will come handy if using a 3.5mm audio line input.  For U0, U1, U2 it's up to you if you want to use an 8-pin DIP socket for mounting the MSGEQ7 ICs. Complete by soldering the rest of the parts.

    Here is the Assembly Drawing (top side).

  • 3
    Ignore the parts on the board bottom side.

    The bottom side components are intended for advanced players. Mainly if you intend to mount everything in a housing resembling a portable speaker, in which case having the extra batteries might come in handy. Use a 2-pin jumper on header Bypass the charging circuit and power directly from 12v. Also make sure header 'ON' gets a jumper if you want the LEDs to come on.

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Sebastian.Anantham wrote 10/31/2023 at 13:51 point

Very nice and hypnotic spectrum analyser 

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