Reply To: Tin's 1100x900mm Build

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John Wells

Isn’t it easier? For DRV8825, supplied max current is Vref * 2 (from the datasheet).

So for coils rated at 1.2A, max Vref is 0.6V , or 1.2V for 2 motors in parallel. I wouldn’t go that high — about 70% of the values should be enough.

You don’t need to do any complicated calculations.

Proof: V=IR
Resistance of coil = 3 ohms. This doesn’t change (outside of heat effects)
Max current we set at the driver: 1.2A (ideally around 70% of this)
==> V = 3 * 1.2 = 3.6 [which is correct; the rated coil voltage]

No need to worry about 12V anywhere.