Pinout
ULN2003 driver board (28BYJ-48 stepper) pinout
Pins
- IN1–IN4 (step sequence inputs — the four LEDs A-D mirror them)
- IN5–IN7 (the Darlington array's three spare inputs, not wired to the motor socket)
- − / + power pins (5–12V motor supply; the 28BYJ-48 is a 5V motor)
- White JST-XH 5-pin socket for the 28BYJ-48 motor (red wire = common +V)
Specifications
| Driver IC | ULN2003A, 7 Darlington channels |
|---|---|
| Channel current | 500 mA max per channel |
| Output voltage | 50 V max |
| Input logic | 5 V TTL/CMOS (3.3 V usually works) |
| Board supply | 5–12 V (match the motor: 5 V for a 5 V 28BYJ-48) |
| Motor | 28BYJ-48, unipolar 4-phase, 5 wires |
| Motor rated voltage | 5 V DC |
| Phase resistance | ≈50 Ω (5 V version) |
| Gear ratio | ≈1:64 |
| Steps per output turn | ≈2048 full steps / 4096 half-steps |
Notes
- The ON/OFF jumper beside the power pins feeds the motor common from +; pull the cap to cut motor power while keeping the logic connected.
- The 28BYJ-48 is unipolar; its gearbox gives ~2048 full steps (4096 half-steps) per output turn.
