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Topic: Detecting "Physical" Resistance from Stepper Motor (Read 9336 times) previous topic - next topic

sbright33

Just hook a stepper motor winding thru a 10k resistor to Analog input 0.  Couldn't be simpler.  Try my code, or write your own to view that value while it's spinning.

PeterH

So you're measuring current through a winding, then? I suppose that if you average it this gives you an indication of back EMF and hence speed. I don't see how it gives you any information about torque, but if the demanded speed is constant I can see how it would give you an indication of slip, especially if you only need to differentiate between the 0% and 100% cases.

sbright33

No, I'm measuring voltage.  The resistor is only there to protect the Uno, it works without it.  I don't know how it works.  It just does!  Try it!  It does not only measure slip.  It measures a change in TORQUE when you lightly hold or release the shaft while it is spinning at a constant speed.  It does this even before there is any slip.  It is so sensitive, with the proper code, you can just barely touch a 1" radius disc mounted on the shaft which already has a constant torque applied.  It will detect this touch.  It takes a small bit of force to detect the torque of touching a thin shaft because the radius is much smaller.  Keep in mind there is a ULN2003 driver wired up the normal way.  The timing of the measurement may also be important, see my code. 

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