A stepper motor can move in accurate, fixed angle increments known as steps. For practical purposes, a stepper motor is a bit like a servo: you can tell it to move to a pre-defined position and can count on getting fairly consistent results with multiple repetitions. Servos though, are usually limited to a 0-180 degree range, while a stepper motor can rotate continuously, similar to a regular DC motor. The advantage of steppers over DC motors is that you can achieve much higher precision and control over the movement. The downside of using steppers is that they are a bit more complex to control than servos and DC motors.
The 28BYJ-48 Stepper Motor
The motor has 4 coils of wire that are powered in a sequence to make the magnetic motor shaft spin. When using the full-step method, 2 of the 4 coils are powered at each step. The default stepper library that comes pre-installed with the Arduino IDE uses this method. The 28BYH-48 datasheet specifies that the preferred method for driving this stepper is using the half-step method, where we first power coil 1 only, then coil 1 and 2 together, then coil 2 only and so on…With 4 coils, this means 8 different signals.
- Motor Type: Unipolar stepper motor
- Connection Type: 5 Wire Connection (to the motor controller)
- Voltage: 5-12 Volts DC
- Frequency: 100 Hz
- Step mode: Half-step mode recommended (8 step control signal sequence)
- Step angle: Half-step mode: 8 step control signal sequence (recommended) 5.625 degrees per step / 64 steps per one revolution of the internal motor shaft. Full Step mode: 4 step control signal sequence 11.25 degrees per step / 32 steps per one revolution of the internal motor shaft
- Gear ratio: Manufacturer specifies 64:1. Some patient and diligent people on the Arduino forums have disassembled the gear train of these little motors and determined that the exact gear ratio is in fact 63.68395:1. These means that in the recommended half-step mode we will have: 64 steps per motor rotation x 63.684 gear ratio = 4076 steps per full revolution (approximately).
- Wiring to the ULN2003 controller: A (Blue), B (Pink), C (Yellow), D (Orange), E (Red, Mid-Point)
- Weight: 30g
The ULN2003 stepper motor driver
The ULN2003 stepper motor driver board allows you to easily control the 28BYJ-48 stepper motor from a microcontroller, like the Arduino Uno. One side of the board side has a 5 wire socket where the cable from the stepper motor hooks up and 4 LEDs to indicate which coil is currently powered. The motor cable only goes in one way, which always helps. On the side you have a motor on / off jumper (keep it on to enable power to the stepper). The two pins below the 4 resistors, is where you provide power to the stepper. Note that powering the stepper from the 5 V rail of the Arduino is not recommended. A separate 5-12 V 1 Amp power supply or battery pack should be used, as the motor may drain more current than the microcontroller can handle and could potentially damage it. In the middle of the board we have the ULN2003 chip. At the bottom are the 4 control inputs that should be connected to four Arduino digital pins.
- Stepper motor driver board with ULN2003.
- A, B, C, D four-phase LED indicates the status of the stepper motor work.
- Stepper motor with a standard interface
- Size: 2.8cm x 2.8cm x 2cm
