Use an ATtiny85 to Control a Music Spectrum Analyzer

Spectrum analyzers display the amplitude of frequencies across a range coming from signals varying from RF sources to light waves. But most people know spectrum analyzers as the colorful visualizers for music. Those let you see if your music is hitting mostly in the bass range, treble range, and so on. You can then use that information to adjust your equalizer in order to get a balanced soundstage. It used to be common for stereos to come with built-in spectrum analyzers, but that isn't the case with modern powered speakers. If you miss the visualization, Tuenhidiy has an Instructables tutorial that will walk you through how to build an ATtiny85-controlled music spectrum analyzer.

The Microchip ATtiny85 is one of the most humble microcontrollers on the market today. It isn't very powerful, but it is suitable for many basic projects. It is also affordable and power efficient. In this case, the ATtiny85 needs to perform two tasks. It needs to analyze the audio signal to determine the amplitude of each frequency range and it needs to drive LEDs based on that information. The LED matrix on which the frequency amplitudes are shown has a total of 320 individual RGB LEDs and driving them all is not a trivial task. But this device accomplishes that, despite the ATtiny85's lack of RAM and I/O pins.

To complete this project, you will need a large perfboard. That eliminates the need for a custom PCB, but you should prepare yourself for a lot of wiring and soldering work. The ATtiny85 microcontroller drives the LED matrix through 11 different shift registers and 16 transistors. Those shift registers let the ATtiny85 control all 36 of the matrix's rows and columns through just a few I/O pins. Audio is input through a standard 3.5mm jack, so you can connect this spectrum analyzer to a wide range of music players. An optional sheet of transparent acrylic protects the electronic components. Power comes from a 5V/2A wall wart. All of the code you need to make the spectrum analyzer work is available on the Instructables tutorial page.