Introduction: 14band Graphical Equalizer

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Here comes a simple Graphic Equalizer showing 14 audio bands from 60Hz up to 16kHz. It consist of a PCB based on MSGEQ7 and ESP dev board. Since a MSGEQ7 chip recognizes 7 bands only and an ESP dev board gives us a chance to read a single analog input only, there was a trick used to make it working for 2x7 bands at the same time.

I am sure this trick could be used as an inspiration for another projects as well, the same way as the project could be extended to show different animations or further modified to a stereo input instances relative simply.

Step 1: PCB and Display

A PCB was designed based on a circuit above and the final gerber files for production of a PCB can be found here https://github.com/radimkeseg/RKG_14_BAND/tree/mas... .

It is important to mention there is an analog demultiplexer SN74LVC1G3157DBVR which was selected however its soldering is not that simple due to SOT-23 package which was too small. (I would probably use another one later for this hobby projects). Anyway this demultiplexer does the first trick with a single analog input provided by used ESP module. The way how it reads both inputs is achieved by swapping 2 used MSGEQ7 chips regularly in every reading takt to read one and then the other one. Also by using the PPL oscillator the bands of MSGEQ7 are shifted a bit, therefore it covers the 14 different bands instead of 7 bands twice the same.

The list of elements used in the PCB can be found here: https://github.com/radimkeseg/RKG_14_BAND/blob/mas...

Used breakouts ADMP-401 (microphone), WCMCU-5351 (PPL oscillator), NODE-MCU (ESP devboard).

There is also necessary to complete the "display" which is composed by NEOPIXEL (WS2812B) strips cut to 14 pieces by 8 segments. As seen in the picture above, they are soldered together the way they create a single zigzag line.

First element goes up, soldered together with second elements which goes down, and the third one again up, next down, till the end. Be careful don't make a mistake, the software which is supporting this kind of NEOPIXEL organization. If soldered differently, the code would need to be adjusted accordingly.

Step 2:

Once the NEOPIXEL display is completed, there is necessary to print a mesh that makes the end effect of a light pixel glowing as a small square.

Place the NEOPIXEL stripe into all prepared holes and fix with a fast glue or a hot glue. BTW the 3D model and gcode for 3D printing is designed for stripes that contain 60 pixels per meter. If any other clearance used the model needs to be adjusted.

The 3D model and gcode for 3D printing can be found here https://github.com/radimkeseg/RKG_14_BAND/tree/mas...

Step 3: Wooden Box

The box can be designed several ways. 3D printed or made of concrete or what ever option you could imagine and carry out. I have decided to use a simple plywood sheet and cut the proper sizes using modeler's knife and glue them together.

To make it a bit more robust I have placed small 8x8 wooden sticks into corners.

Then I have placed the prepared display and the PCB in as shown in the picture above and fixed by a hot glue.

At the end I used a sheet of paper and placed that on top of the display and covered by a acrylic glass sheet of 4mm thickness.

The paper causes the light being dissolved and filling the full square in the printed mesh.

Step 4: Software Upload

Last step is to upload software for graphical equalizer which can be found here https://github.com/radimkeseg/RKG_14_BAND

Easiest way is to upload to Arduino IDE, import the files and then compile and upload into the ESP dev board.

Once uploaded the graphical equalizer starts working immediately listening to sound by a small microphone module.

The final result can then work like this for instance.