28BYJ-48 Stepper Motor 5V DC 4-Phase Unipolar with 1:64 Gear Reduction

The 28BYJ-48 is a small 5V DC 4-phase unipolar stepper motor with a built-in 1:64 gear reduction, widely used in Arduino robotics, automation, and educational projects. Because it is a geared stepper motor, the output shaft turns slowly but with enough torque to move small mechanisms, and the 1:64 reduction means the internal rotor makes 64 turns for every single turn of the output shaft. The motor is driven by energising its four phases in sequence, and it is normally paired with a ULN2003 driver board, which provides the current gain needed by the windings.

Its stride angle is specified as 5.625 degrees divided by 64, and with 64 internal steps per rotor revolution and the 64:1 gearbox, a full output revolution takes approximately 4096 steps. That resolution allows the 28BYJ-48 stepper motor to hold position without a feedback sensor in open-loop control, which is why it appears in camera sliders, small valve actuators, curtain mechanisms, and 3D printer accessories. The 5V 4-phase winding has a DC resistance of 50 ohms with 7 percent tolerance at 25 degrees Celsius, and the motor runs at a 100 Hz base frequency with low acoustic noise. This unipolar stepper motor is a practical entry point for anyone learning step-based motion control with an Arduino.

1. Arduino and microcontroller robotics projects that use a ULN2003 driver board.
2. Small automation mechanisms such as camera sliders and curtain openers.
3. Educational demonstrations of stepper motor and open-loop position control.
4. Valve and damper actuation in light-duty fluid control systems.
5. 3D printer accessories, filament guides, and small linear stages.
6. Industrial equipment and laboratory instruments requiring low-speed geared motion.

1. Model: 28BYJ-48.
2. Rated voltage: 5V DC.
3. Number of phases: 4 (unipolar).
4. Speed variation ratio (gear reduction): 1/64.
5. Stride angle: 5.625° / 64.
6. Base frequency: 100 Hz.
7. DC resistance: 50 Ω ±7% at 25°C.
8. Idle in-traction frequency: greater than 600 Hz.
9. Idle out-traction frequency: greater than 1000 Hz.
10. In-traction torque: greater than 34.3 mN·m at 120 Hz.
11. Self-positioning torque: greater than 34.3 mN·m.
12. Friction torque: 600–1200 gf·cm.
13. Pull-in torque: 300 gf·cm.
14. Insulation resistance: greater than 10 MΩ at 500V.
15. Dielectric strength: 600 VAC, 1 mA, 1 s.
16. Insulation grade: A.
17. Temperature rise: less than 40K at 120 Hz.
18. Noise: less than 35 dB at 120 Hz, no load, 10 cm.
19. Body diameter: 28 mm.
20. Steps per output revolution: approximately 4096 (64 internal steps × 64 gear ratio, per common documentation).