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Topic: current limit resistors (Read 384 times) previous topic - next topic

oldPGMguy

i have a stepper, I'm driving from a ULN2003 ...the stepper is 12volt with 75 ohm windings and its rated at 0.16A...if i put 75ohm resistors on each ULN2003 outputs for the motor,will it limit the current to 0,16A?
I'm old and started too late with microcontrollers

jackrae

Why would you want to do that.  If the coils are 75ohms and the drive voltage is 12 volts then the maximum current that can flow under steady state (DC) conditions is 12/75 = 0.16amps  which is the rated current of the motor.  Under pulse drive conditions the mean current will be (much) less due to the inductance of the windings and the fact that the on/off effect of the pulsed drive means the effective power (heating) is less.

oldPGMguy

i just thought if the motor is rated for 160ma..it should get that...the motor gets hot after a while..just trying to cool it down
I'm old and started too late with microcontrollers

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