mattW· Premium Member
Ok i have no idea whether this works or not but could you use the voltage across the motor to work out it's rpm? According to my old physics textbook as the rpm increases so does the back emf, so could you just whack a voltage gauge across the motor and use it like a tacho? (i am assuming it doesn't change with load). If you knew the voltage drop at max rpm then you could just change up then, maybe even work out a gear change light. Kiwi i think i remember you talking about playing with the tacho somewhere but i cant find the thread atm. Anyone know whether this would work?