DIY Arduino Audio Spectrum Analyzer on VFD Display

A spectrum analyzer is a measurement tool that displays real-time frequency analysis of incoming audio signals. It is usually an integral part of equalizers and audio signal processing devices. The vertical axis shows the amplitude of certain frequencies measured in decibels.

The presented device is very simple to build, and consists of several components:

- Arduino nano microcontroller

- VFM202MDA1-1 type VFD Display wich is slightly modified

- Stereo potentiometer to control the intensity of the input signal

- and two capacitors

This time I will show you how to make such a device on a 20x2 VFD display. In one of my previous videos you could see the making of a VU meter on such a display. The advantage of these displays is that they emit a very bright light with high contrast, and the beautiful retro look. In the video I mentioned earlier (https://www.youtube.com/watch?v=gotUokTuP9U) you can see how to modify such a display, and then you can use the libraries intended for 16x2 character LCD with HD44780 driver chip. Specifically in this case, to control this VFD display is used "LiquidCrystal" library.

In the pictures you can see how the device is made

For analysis and processing of the audio signal is used "fix_fft" library. As for the code, the base is taken from Ray Burnette with some minor tweaks. New code is adapted for 20x2 characters, increased noise sensitivity threshold and some minor visual corrections. The device is built into a suitable box made of PVC material with thicknesses of 3 and 5 mm, coated with self-adhesive wallpaper. A thin transparent filter foil is placed on the front of the display.