Stepper motor running detection

Hi!

I'm looking for a way to use an Arduino ADC port to read directly from a stepper motor phase to see if the motor is running or the motor is stopped. Right now what i found is this simple circuit with a voltage divider a capacitor reading the back EMF.

http://m.eet.com/media/1120246/ststep13.gif ->from this website http://www.eetimes.com/document.asp?doc_id=1279202

The problem with this circuit is that it uses 2 phases (so i'd need 2 ADC pins). Since i have only one ADC channel left i'm looking for a way to detect the stepper motor running/stopped with just one phase information.

PS-i only have access to the motor phases (not the driver DIR, EN pins) otherwise it would be simpler.

I presume, from your last sentence, that the Arduino is not controlling the motor.

What about using something (maybe a hall effect sensor) to generate a pulse on an Arduino digital pin from the pulses going to the motor coil. Then you Arduino could derive information from the time between pulses.

...R

Are you wanting to detect stalls by measuring back-EMF at suitable points in the
decay cycle?

Or are you wanting to see if its being stepped at all?

@Robin2: Yes. That is correct. I am using the Arduino just for measuring the phase information. It is not controlling the stepper motor.
That might also work. I'll try that approach. Tks!

@MarkT: i just want to check whether the stepper motor is rotating or is fixed in a position (stopped).

Is the stepper driver using microsteps?

it might be using. is that relevant for the detection?

Well if its microstepping with a chopper driver you'll have rapidy changing
voltages all the time whether moving or not, rather than relatively simple on/off.

Perhaps investigate with a multimeter?

Today i measured one phase relative to ground with the oscilloscope. I guess microstepping is being used because i saw different pulse widths when printing. When stopped i saw a fixed pulse width.

Have you the option to use some sort of optical detection of the actual moving part?

...R

It might be possible although the end application has the stepper motor enclosed.

electronics_guy3243:
It might be possible although the end application has the stepper motor enclosed.

Perhaps the apparatus it moves may be accessible to an optical detector ?

…R