I have a project which includes 16 stepper motors 17HS4401, each connected to a separate DM542 driver. From datasheet of the stepper: Rated current: 1.7 A Rated voltage: 3.6 V Phase Inductance: 2,8 mH The drivers are powered with 36 V DC. Power setting set on the driver: 1.46 A (current halving disabled). The steppers are moving belts with a very lightweight gantry, at 1000 rpm max. I'm using accelstepper library, never experienced any stalls / missing steps, no issue here. For now, I connected just one stepper to measure current draw between power supply and the driver. The stepper was performing a real use scenario, was connected to the belts with the gantry. The measurement was performed with a multimeter. Results: Current draw at idle: 0,23 A Current draw at max speed: 0,7 A Am I missing something here? I never come remotely close to the rated current (1.7 A) or current limit set on the driver (1.46 A). Is the measurement inaccurate? The whole point of this is to find out what power supply I need for 16 of these steppers. If I go by rated current we are talking 27 A power supply (16 x 1,7 A), if however I go by measured values it is only 11.2 A (16 x 0.7 A). When adding a 10% current draw margin it is decision between 30 A and 13 A power supply. To be on the safe side, let's assume that it is possible that at some point all steppers are in move at the same time.
vs Combined with overhead from losses on the drivers etc Drivers have heatsinks for a reason, burns off some of the power there in switching losses in the mosfets 1.46A at 3.6v = 5.2w per coil * 2 coils = 10w per motor (now factor in some losses on top of that, lets call it 50% and double up to be safe, 20w per motor) I(A) = P(W)V(V) where P=20w, V=36 - I=0.55A (close to your 0.7A measurement, so maybe a little more lossy than estimated) PS: You should see most current used during Braking - not during moving PS2: Back-EMF from the motor may affect multimeter readings PS3: Really need a scope to check peak currents, with steppers that can be as high as 100khz or more - multimeter not quick enough Taking our earlier 20w per motor sum * 10 motors, needs at least a 200w PSU.
