(ambitious) DIY MIDI controller + expression pedal + footswitches

[aliteraryhigh]

I'm a full-time software engineer and part-time "everything else" engineer, and I love working on DIY tech projects and generally just tinkering. A vaguely recent project I did was for the xmas tree decorating project at my job. I wired up a Raspberry Pi in ours with some computer speakers, rigged up about 20m of programmable LED strips, and had the lights flash and dance to the intensity of whatever music was playing.

That being said, I'm getting back into guitar a lot more lately and realized I no longer have any pedals, I've just been using various plugins in Cubase for my sound. That's all well and good, and it's no problem at all to automate effects and parameter changes, but I'd love to have the option to do it the "old fashioned" way with stompboxes again. I've got a general idea of how I wanna do the footswitch(es), and have plenty of references/resources for that. I've even got a very vague idea of how I'd put together a basic MIDI controller with an Arduino or Raspberry Pi to connect the footswitch(es). I haven't the slightest idea how I'd go about putting together a DIY expression pedal though, and that's what I mainly want right now.

I know at the end of the day it's just a pedal with a rocker and a potentiometer in it, and I know I could also just get a cheapo pedal online for $20-30, but that's no fun! After all, I work for a manufacturing company and could probably cobble together enclosures/pedals out of the various steel sheet scrap we have every now and then. Anyone have any resources/references for a DIY expression pedal? Or should I go down the fully-custom rabbit hole?

[BertKoor]

3D printing a gear and straight rocker attached to the foot part, sure.

I used to have a pedal which worked with opto-coupling: light source and light-sensitive resistor with a foot-operated thing sliding inbetween having a slit going from narrow to wide. Solves some physical problems regular pots have.

Arduino has analog pins, so no challenge there I guess.

[resynthesis]

Aye, opto (like the massive old Morley pedals) or maybe Hall effect sesnsors were my first thoughts