Scottydntno said:
Thank you all for your advise, but I was successful at running the bipolar stepper motor with a 12v transformer, capacitor, and a 3 way momentary switch in both directions flawlessly.
Yes. You were successful running it. That's good.
Choosing the right capacitor so that one coil is 90 degrees out of phase, or nearly, with the other coil does the trick. So now the motor runs somewhat like a regular motor, but IIR, not as efficiently.
But with the capacitor circuit, moving the table to a particular position is quite near impossible. The motor will run back or forth, but getting it to an exact position requires a keen eye and some luck, which when moving your table may not be satisfactorily reproducible each and every time.
Stopping and holding it at a particular position requires additional circuitry.
To count the number of rotations of a motor or shaft, have an external counter - ie magnetic pickup, photo diode,... One doesn't need a stepper motor. You could count the number of AC cycles, but the acceleration of the motor and ( changing) torque upon it, makes that problematic.
But you have a stepper and should make use of its features.
The thing about a stepper is that you can set the amount of rotation of the motor by energizing the coils in a certain way. See post #7. The motor "steps" into the next "degree" of rotation.
You need a counter to count the steps, either up or down from some zero position, some transistors( relays ) connected to each coil, and some logic circuitry to turn the transistors on and off in a particular fashion.
You can make your own circuitry, or a use package on a chip.
I have always like this page.
http://homepage.divms.uiowa.edu/~jones/step/circuits.html
