Choosing a stepper motor driver over a servo has certain advantages, namely price. Where a stepper will do the job, consider using one — but not until you’ve read these expert tips and tactics for choosing wisely.
Know The Four Most Common Microstepping Myths.
Myth 1: A high microstep count will result in evenly spaced steps at that count. Microstepping is good for smooth motion. However, having a 256 microstep/step driver does not automatically mean that you will get 256 evenly spaced increments of motion from the motor for those microsteps.
Determine Joad Requirements.
First, determine the load type. Is it an inertial or frictional load? If purely inertial, use some type of transmission to match load torque to motor torque. Use a device to measure the force required to move the load at the desired speed and acceleration. For example, you can use a spring scale to measure the force on a linear axis or a torque watch to measure rotary force.
Be Aware Of Torque Issues.
Torque is often at the root of many stepper-related issues. Two relatively common occurrences include:
Not enough torque at speed: Most step motors are wound and built to perform at their optimal level at a certain speed range. If a high-speed motor is used in a low-speed application, you will more than likely be pumping in lots of power and yet the motor will still stall due to lack of torque. Using a low-speed motor for a high-speed application will yield similar results.
Consider Voltage And Current Needs.
A simple way to choose a stepper drive is to look for four things — voltage, current, microstepping, and maximum step pulse rate. Ensure that the drive can handle a wide range of current so that you can test the system at different voltage levels to fit your application. The driver should output at least 1.4 times the motor’s rated current.
Apply Correct Voltage.
Microstepping can increase the resolution of a system, which smoothes rotation and prevents vibration and noise. However, problems will arise if incorrect voltage is applied to a PWM (pulse width modulation) or chopper drive. We receive many questions about these drivers. For example, if a motor is rated at 5 V, many users wonder why they need to apply larger voltages.
Correctly Match Motor And Drive.
Don’t believe that a stepper motor (linear actuator stepper motor) will achieve the data sheet’s rated speed and torque when it is matched to just any driver. Like a servo, the motor’s stall torque, rated torque, and rated speed all depend as much on the drive and motor being correctly matched as they do on available voltage and current.