Stepper motors are DC motors that move in discrete steps. They have multiple coils that are organized in groups called “phases”. By energizing each phase in sequence, the motor will rotate, one step at a time.
With a computer controlled stepping you can achieve very precise positioning and/or speed control. For this reason, stepper motors are the motor of choice for many precision motion control applications.
Stepper Motor Operation
In this theory section, we’ll get a quick reminder about how stepper motor works. Stepper motors work in very specific way, a standard stepper motor will have two or more coils that charge and discharge when electricity is allowed to flow through them. The animation below illustrates that.
When the coils are charged and discharged in a specific pattern (usually sequentially), it creates an electromagnetic attraction between the coil and the motor. When this occurs fast enough it makes the stepper motor turn, and we get the movement you see above.
Advantages of Stepper Motor
- Positioning – Since steppers move in precise repeatable steps, they excel in applications requiring precise positioning such as 3D printers, CNC, Camera platforms and X,Y Plotters. Some disk drives also use stepper motors to position the read/write head.
- Speed Control – Precise increments of movement also allow for excellent control of rotational speed for process automation and robotics.
- Low Speed Torque – Normal DC motors don’t have very much torque at low speeds. A Stepper motor has maximum torque at low speeds, so they are a good choice for applications requiring low speed with high precision.
Disadvantages of Stepper Motor
- Low Efficiency – Unlike DC motors, stepper motor current consumption is independent of load. They draw the most current when they are doing no work at all. Because of this, they tend to run hot.
- Limited High Speed Torque – In general, stepper motors have less torque at high speeds than at low speeds. Some steppers are optimized for better high-speed performance, but they need to be paired with an appropriate driver to achieve that performance.
- No Feedback – Unlike servo motors, most steppers do not have integral feedback for position. Although great precision can be achieved running ‘open loop’. Limit switches or ‘home’ detectors are typically required for safety and/or to establish a reference position.