LEET Control

The Control MIDI unit is part of the LEET Synthesizer project. If you haven’t – It is a good idea to read the main post first before continuing with the details below:

This post describes how the control unit works and what you need to build your own.

Description of the Control unit

Product guide. Click here to download high-resolution PDF.

Part list:

Component cost is around $6 on eBay October 2020 (will depend on shipping and supplier).

  • 1x 3D printed core 3DPCB
  • 4x 3D printed potentiometer knobs
  • 1x Arduino pro micro, or compatible clone (5V version. ATmega32U4) – (~$4)
  • 7x 6x6mm 4pin through hole tact switches – preferably with low activation force (50g / 0.5N) – ($0.2)
  • WS2812 LED-strip with 4 LEDs (60 LEDs/m. I used IP60, white FPC) – ($1.1)
  • 4x 100kohm High-end potentiometer with short shaft (called RK09K, RK09D, RV09 or PTV09A etc. 10k-500kohm will also work)
  • 1x 25cm RK wire (containing 24 strands of 0.3mm copper wires) – ($0.1)


  • 3D printer (FFF/FDM with PLA filament)
  • Solder station with a narrow tip
  • Basic tools: Needle- and cutting pliers, knife, hot-glue
  • Computer to run Arduino IDE and upload firmware (using a Micro USB cable)

Build it

I have not made a step by step building instruction, but if you have built the other devices it should be sufficient to look at the illustration below. The build process is very similar to the step by step instruction for the keyboard.

This model was made a while ago and is not using my latest 3D methods; LED-strip is soldered in place and switches can be a bit difficult to insert.

Please note that the VCC wire (magenta) routing is changing side under the LED-strip (dotted line below). Route the wire first, then LED-strip.

Backside view showing routing of wires.

Future versions

I developed this unit to test both control and arpeggiator functions. If you would like to control more than four variables, take a look at these two concept sketches. The smaller version has eight knobs and is more compact. The full size has seven knobs, and room for a label that describes the function of each knob.

Let me know which version you prefer!

Download project files

All files required for this project are available at this GitHub repository:



This project is open source under MIT License
(Attribution is optional, but appreciated /Johan von Konow ;)

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