2000rpm from a Stepper @ 12 volts

Hey everyone!

I am trying to drive a speedometer in an older car from an arduino. The new transmission has an electronic speed sensor. The old speedo takes 1000rpm / 60mph mechanical input.

Now i can get the steppers i have (a NEMA17 and a small motor from a printer) can brake 2krpm at 27 volts. Since i don't want to have 3x9 volts under the dash i attempted it again at 12 volts, and got about 400rpm peak.

Is there a stepper that will run at 2krpm at 12 volts? Or should i resort to a DC-DC converter? I don't have a DC motor encoder handy, and i am not interested in waiting for one to ship from China.

Any ideas? Thanks!

12V is highly unlikely (from a 200 step motor). The back-EMF from the motor is one limiting factor and it goes up with speed. High performance steppers normally driven from 48V, 80V, even 120V....

A stepper with fewer steps might be more plausible, especially if bipolar. Ex-printer motor?

Why do you want to use a stepper? A DC motor seems ideal for this task, and it would be much easier to control than a stepper.

A DC motor would do the task, but i would need feedback from an encoder, which i do not have.

Why do you need an encoder? If you need to know exactly how far you have rotated, are you planning on the stepper motor not skipping steps? They do, especially when pushed to the limits.

trum4n: A DC motor would do the task, but i would need feedback from an encoder, which i do not have.

You just need a single hall effect sensor / magnet, a photointerrupter, or photo reflector thingy -- not necessarily a full blown encoder. As long as you can detect a full rotation of the shaft of the motor that should be sufficient to get its rotational speed right.