Using Stepper Motor as an Encoder

[SK0480]

Iam using 4 coil unipolar stepper motor with 48 poles, and I've found that i can use another stepper motor as an encoder. Iam working on an education project--and the equipement I have is NI ELVIS board with DAQ, Labview....... I need to know what steps I will need to take to use another stepper motor as an encoder.

Thanks

[JtotheB · Accepted solution]

Hey SK0480,

You can do this, but it requires building some other circuits. Here is a simpler circuit using 2 comparators. This schematic may also be useful to you. Hope that helps!

[SK0480]

OK so will I need to connect this motor to the shaft of the other stepper motor iam trying to measure the steps. because to run the stepper motor iam using a current driver amplifier, 

[SK0480]

so if iam using a unipolar 5 wire stepper motor, then what kind of stepper motor I will need to use it as an encoder and how would I able to connect both motors together.

Thanks

[JtotheB]

You should be able to use any stepper motor as an encoder. Of course, the step size is going to limit your resolution for measurement, and it may not be reliable. Since the motor is unipolar, theoretically you could use a unipolar motor for the encoder as well. Is there some reason you want to use a stepper motor rather than a quadrature encoder? They aren't expensive, would be much easier to work with, and will give you much more reliable results. I found one here for less than $4.

As for connecting the shafts, you would probably need some kind of gearing. That all depends on your application. You could even use the gear ratios to create a more useful encoder. Hope that helps!

[SK0480]

what you mean by gearing, gear ratio are you talking about coupling

Thanks

[JtotheB]

I mean to use gears to connect the shafts of your motors together.

[SK0480]

Hello

Ok I appreciate your help, I need to know if iam using a quadrature encoder, what do I need to make sure when selecting such encoder, i mean what do I need to make sure so that it gives me the accurate reading--does the encoder need to have same resolution as a stepper motor.

Thanks

[JtotheB]

Almost any quadrature encoder should work for your application. It does not need to have the same resolution as the motor. All you will need to do is determine how many counts on the encoder correspond to a step on your motor and you should be all set.

[SK0480]

Hello John

Ya this helps out a lot..ok iam using an NI elvis board with a built in daq board, it has breadboard attached to it which has DIOs and analog input/outputs...so Iam using a quadrature encoder how will I need to connect it and measure the steps using labview..

Thanks

SK