I have a vintage mechanical speedometer, &tach. I want to drive them with stepper motors.Impulse sensors can be hall effect,magnets, or opto. by a chopper disc, or flywheel teeth. I need a circuit for driving the stepper motors, that I can also caibrate IE. the speedometer.My electronics is in Audio only.Digital I,m totally bereft of.I.m very good at laying out circuit bds, so once I get a complete circuit, I'm O.K. Any help would be greatly appreciated.... Joe

 

Most steppers have a rather low upper limit of how fast they can turn. Say the limit is 5000 steps/second. If the stepper is 200 steps/revolution, that's only 1500 RPM. Will that be enough for your gauges? If not, a PWM controlled DC motor may work better - you could get 6000 RPM that way, depending on the motor. You only need to go one way, so a single FET can control the motor speed.

 

Thank you; Your answer is extremely helpful, I will try your suggested approach. A plus, is that it might be a simpler overall design.....Joe