I am trying to build a stepper motor driver, based on the A4989 chip, to control NEMA 17 and NEMA 23 stepper motors.
Stepper motor specifications:
NEMA 17: 0.4 Nm, 1.5 A/phase, 2.1 ohms.
NEMA 23: 1 Nm, 2.4 A/phase, 1.2 ohms.
I made some calculations and found the requirements of this circuit as follows:
For NEMA 17: U = 3.15 V/phase and power is P = 4.725 W.
For NEMA 23: U = 2.88 V/phase and power P = 6.9 W.
The external MOSFETs are IRFZ44N
I have some questions:
Firstly, for choosing proper PSU, if I am half-stepping or micro-stepping, both windings will be energized so the power will be multiplying x2, meaning the current drawn is x2. Is that correct?
If I power the dual H-bridge from 12 V or above (as per the datasheet) with a resistor in series with the drain, will my stepper motor still work and how will it be affected? Also, this chip is specified for 30..500 W steppers so should I dissipate power through a resistor?
Is the MOSFET suitable for such a small coil current, compared to its ID(max)?
The MOSFET has a much higher max. drain voltage than needed but the current is important and I can limit it with Rsense (ITRIP(max) = VREF/(8×RSENSE)), can't I?
Another thought on this was if I could power the chip with 12..50 V, as per the datasheet, but power the H-bridge from a lower voltage.