About the size of a deck of cards ... has made one which is light years ahead of the toy kits, using a Raspberry Pi Pico, a 100 MHz ADC, and an effort to design a better input circuit.

The Raspberry Pi Pico is a $4 microcontroller ... on your switches to its corresponding pin on the Pico. This is where it helps to have that schematic of your wiring on hand to keep you from ...