Voltage lower than expected with Nema 17 stepper motor and L298N

Question

I am using an L298N motor driver with a Nema 17 stepper motor. I am trying to use the motor to turn a valve, but there is not enough torque so the motor is skipping steps.

I am controlling the motor driver with an Arduino and am powering the motor driver with a variable DC power supply.

In attempt to supply more voltage to the motor, I have now removed the 5V_EN jumper and am inputting 5 volts from the Arduino to power to driver circuit.

I have set the variable power supply to 18 volts. Before turning on the motor, the variable power supply is outputting (based on the display) 18 volts and 0.01 amps. When turning on the motor, the power supply is outputting around 6 volts and 2 amps. After turning the motor on once, the power supply continues to output 6 volts and 2 amps even when the motor is off.

How can I increase the voltage to increase the torque of the stepper motor?

If this is not possible, what motor controller drivers (compatible with Arduino) would be appropriate for this task?

Answer 1

If the motor is still drawing 2 amps after it has stopped moving, then it is not off. Your code is telling the motor to hold position, which draws current, and will heat the motor up fast.

Unless you need torque to hold the position, change your code to power off all of the coils to the stepper.

Answer 2

If you are getting 2A then you are already at the rated current of the motor. Increasing it much beyond that will likely burn out the motor. So perhaps the poor performance of the ancient L298 (as Andy mentions) has saved your bacon.

Increasing supply voltage is useful on chopper drives because it limits the torque reduction with fast stepping. It does not change the torque for slow steps. Not sure if yours is of that type- the documentation is inadequate- but I don't see the parts I would expect to be there for current sensing.

You may need a larger stepper or reduction gearing (or belt etc.).