[TheM]

Hi! I am working on a unipolar stepper drive based on a ATMega16. I want the driver to have current limiting and microstepping. For that I need to read the current through the coils. The most common circuit used for that is the one in this figure( attachment ) . When I use the oscilloscope to measure from point A to ground I get what you see in the figure. The current through the coil during the ON period of the MOSFET is as expected, but during the OFF period it drops to zero (which is logical, right? If the FET is off the scope is connected to ground through a 1 ohm resistor). The problem is I want to read the decay current of the coil during the OFF period as well. How do I do this? What circuit do I use?
Thank you.