Does anyone know an easy way to get/make a simple device to determine the direction of a spinning shaft? It must give some logic (5V) signal, NOT encoded in any way. Just +5 if CW or 0 if CCW (or backwards, or 3.3V, or whatever else, it doesn't really matter). However, it must not A) require any digital controller (no arduino, ATtiny, PIC, computer, raspi, etc.) B) have an "encoded" output, or gray code C) have a large "dead band" where it still indicates CW but it's actually spun a tiny bit CW (or vis-versa). Must be under 3-4 degrees D) require the shaft to spin quickly E) be expensive. This is a prototype for an ANALOG mill D.R.O., so I don't want to have to spend ten bucks on one part that I have to buy several of, plus the other parts. Its a 1/4" threaded rod, but can easily be adapted to whatever else it needs to be. The device needn't be small, and I will have a 3D printer avaliable (or at least a mill).