Servo rotation control

[Soloratov]

First off, not sure if this is really the right way to do this, but the idea popped into my head and I figured I would give it a shot. Here is the situation I am trying to create:

Rotate a shaft at roughly 100rpm for 10 revs. Start and stop point must always be the same. Pushbutton start, automatic stop.

Now the RPM is not as important, but that rate or close to it preferred. I have tried regular DC motors with timers, positioning switches, and I am trying to avoid stepper motors as the motors and controls are not cost effective for my project. I figured I would try to look into servos. Basically I just need to spin something exactly 10 times and have it always start and stop in the same place. My only other option is to get a 10:1 gearbox and rig a sort of dual switch setup to the motor, and hope I can have a finger on the gearbox hit the secondary switch at teh end point, and start all over again when the first switch is pushed again. Kind of like 2 light switches in one hallway. Any help is greatly appreciated.

 

[joemcder]

You have not explained the application. Regular DC motors are designed to run at high RPM. Assuming you need some torque to turn something you need a gear box. 10:1 is unlikely to work. A servo often has a gear ratio of 50:1 to 250:1. A geared AC motor might be more convenient in some cases.

In any event, a latching limit switch can be used for turn off.