How to Control Stepper Motors

A stepper motor and drive (motion controller not shown)

A stepper motor is capable of precise positioning, speed and acceleration. To control a stepper motor, you'll need a step motor drive as well as a motion controller or indexer to tell the drive what you want the motor to do.

Things You'll Need

• Stepper motor
• Stepper motor drive
• Power Supply
• Motion Controller

Instructions

1. 

   Connect the power supply and stepper motor to the motor drive. If you are controlling more than one motor, you will need a drive for each one, but you can often connect several drives to the same DC power supply if the current rating is sufficient to supply the combined needs of all the motors.

2. 

   The step motor drive has two inputs, "step" and "direction". When the direction input is low and a pulse is applied to the step input, the drive moves the motor one step (or one microstep). If the direction input is high when the step pulse is received, the motor moves one step in the opposite direction. The total number of pulses determines the distance moved by the motor, but it is not a matter of simply spewing a group of pulses because the driver attempts to move the motor one step at a time in real time with the incoming pulses. In order to smoothly accelerate, travel a specified distance, slow down and stop, the drive needs a step signal source that can output a precisely timed and counted stream of pulses. This is the job of the motion controller.

3. The motion controller can range from a stand alone device that simply indexes the motor a preset distance when a switch contact is closed to a programmable unit that holds a motion routine in memory or even a PC computer running CNC machine control software that follows a G-code program. To move two of more motors in a coordinated manner, you'll need a motion controller capable of multiple axis linear interpolation or "contouring".

4. If all you need is to spin the stepper motor continuously at a constant speed, you can sometimes get away with replacing the motion controller with a fixed frequency pulse generator. This could be a simple as a circuit containing a 555 timer IC and a few resistors and capacitors.

Resources

• Geckodrive motor controls
• Advanced Motion Systems