Actuators & Control · Study deck
Stepper Motors: Drivers and Motion
This first route builds counted motion from motor fundamentals through drivers, current, and acceleration.
Motor Max is your guide for this deck.
After studying this chapter
Learning objectives
You will be able to:
- Explain: The useful design question is whether the physical job needs counted position, continuous speed, integrated feedback, or a simple angle command, then whether the motor, driver, supply, wiring, and software can carry the required torque.
- Explain: Those features establish the mechanical interface and two-phase connection, but not a universal current limit; the actual winding current and driver cooling requirements must come from the motor and driver data.
- Explain: The driver board is not optional decoration; it translates low-power controller signals into the coil current sequence that makes the rotor align one step at a time.
Major section
Start With the Story
An actuator is a part that turns an electrical command into physical action.
- Here the action is counted rotation, but a count sent by the controller is not proof that the shaft or label moved.
- The local machine must stop safely even when its dashboard or wider network is late.
- This opening does not choose a motor size or promise that open-loop counting is always enough.
- Stepper motors fit that story when discrete movement and repeatability matter.
Major section
How It Works: Stepper Motor Step-by-Step Operation
Think of a stepper motor like a clock's second hand that can only move to specific tick marks.
- Step-by-step movement (can be jerky at low speeds).
- The useful design question is whether the physical job needs counted position, continuous speed, integrated feedback, or a simple angle command, then whether the motor, driver, supply, wiring, and software can carry the required torque.
- The driver board is not optional decoration; it translates low-power controller signals into the coil current sequence that makes the rotor align one step at a time.
Major section
Checkpoint: Counted Motion
The counting math is only useful if the electronics can reverse and limit coil current correctly.
- The next section makes that driver boundary explicit.
- A stepper driver is the power spine between the microcontroller and the motor coils.
- The controller pins are only logic signals; the driver contains transistor switches that route real coil current from the motor supply.
Major section
Checkpoint: Counted Motion (continued)
Current through a coil creates a magnetic field, and changing the current path changes the field that pulls the rotor toward the next aligned position.
- Driving one diagonal switch pair sends current through a coil in one direction; driving the opposite diagonal pair reverses that current and swaps the coil's north/south polarity.
- Older dual H-bridge chips make that boundary visible.
- You have now seen the coil sequence directly.
Major section
28BYJ-48 with ULN2003
The 28BYJ-48 is a popular small stepper for hobby projects.
- Sequencing the windings creates steps, while the gearbox trades speed for torque and changes the effective steps per output revolution used in the code.
Major section
NEMA 17 with A4988/DRV8825
For higher performance, NEMA 17 steppers with A4988 or DRV8825 drivers are a common choice.
- Those features establish the mechanical interface and two-phase connection, but not a universal current limit; the actual winding current and driver cooling requirements must come from the motor and driver data.
- Current limit adjustment.
Deck summary
Key takeaways
An actuator is a part that turns an electrical command into physical action.
- Think of a stepper motor like a clock's second hand that can only move to specific tick marks.
- The counting math is only useful if the electronics can reverse and limit coil current correctly.
- Current through a coil creates a magnetic field, and changing the current path changes the field that pulls the rotor toward the next aligned position.
- The 28BYJ-48 is a popular small stepper for hobby projects.
Retrieval practice
Recall check
Motor Max says: answer from memory, then check your reasoning.
Q1A 28BYJ-48 stepper motor has 2048 steps per revolution. How many steps are needed to rotate exactly 90 degrees?
Show answer
Answer: C To calculate the steps for any target angle: steps = (angle / 360) x steps_per_revolution.
Print reference
Answers
Answer key.
- C · To calculate the steps for any target angle: steps = (angle / 360) x steps_per_revolution.