Making Electronic Calipers
owl writes:
https://kevinlynagh.com/calipertron/
Have you ever wished for a 500 Hz, millimeter-precise linear position sensing system? Well you're in luck - all you need is some circuit board, a basic microcontroller, and a wee bit of maths!
Why make calipers?
Electronic calipers are awesome. This $30 pair has served me well for years, reading far more precision than my skills justify:
Such calipers work via capacitive coupling between a PCB on the powered slidey display and a passive PCB "scale" in the stationary spine.
Back in March, I idly wondered if the same working principle could be used for a cheap and cheerful "maker-friendly" positioning system. E.g., slide some passive PCB scales into an aluminum extrusion rail, add a capacitive pickup to the bottom of whatever carriage you've got riding along, and tada - you've got sub-mm closed-loop positioning. All for the cost of some PCB, a few GPIO pins, and some firmware (so free, basically).
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