- Arduino Beetle (AtMega32u4) with 3 analogue pins

- ground down potentiometer tracks to 0.2mm

- 2mm rails, overall height is 5mm

- carbon resistor tracks can't be soldered, had to mechanically fasten them with M1 screws. If someone knows a PCB service that will make 0.2mm PCBs with printed carbon resistors, let me know.     

- the tracks are very heat sensitive with weird failure state (partially working)

- make one hole of the wiper carriage square and oversized, as done on commercially faders with linear rails, to make them more tolerant against misalignment of the rails.

- soldering enameled copper wire is a pain, I butchered the prototype until I discovered headphone cables

- made an USB cable from 4 core headphone cable (1.5mm) too, nice for such a light device. 

- first layer typo is generated and exported as gcode via Sverchok, a Blender addon for parametric design

- arduino sketch has a multi-map function that allows you to remap the analogue readout in a non-linear way, to recalibrate 'linear' potentiometers or even convert logscale potentiometers to linear.