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2017, which makes more of the adjustment potentiometer's range useful. The
following picture shows how to identify which current sense resistors your board has:
Identification of original 50 mΩ sense resistors (left) and 68 mΩ
sense resistors (right) introduced in January 2017.
So, for example, if you want to set the current limit to 1 A and you have a board with
68 mΩ sense resistors, you would set VREF to 540 mV. Doing this ensures that even
though the current through each coil changes from step to step, the magnitude of the
current vector in the stepper motor stays constant at 1 A:
If you instead want the current through each coil to be 1 A in full-step mode, you would
need to set the current limit to be 40% higher, or 1.4 A, since the coils are limited to
approximately 70% of the set current limit in full-step mode (the equation above shows
why this is the case). To do this with a board with 68 mΩ sense resistors, you would set
VREF to 770 mV.
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