Controlling Stepper 28BYJ48 Motor with ESP32

Stepper 28BYJ48 practical reference

A cheap 5V geared stepper motor bundled with the ULN2003 driver board, common in camera sliders and small CNC-style projects.

Key specifications

• Motor type: 5-wire unipolar stepper with internal ~1:64 gear reduction
• Step angle: 5.625°/64 per internal step — roughly 4096 half-steps per output-shaft revolution through the gearbox
• Operating voltage: 5 V DC (matches the bundled ULN2003 driver board; a 12V-coil variant also exists)
• Driver IC: ULN2003 Darlington transistor array, 4 inputs (IN1-IN4)
• Current draw: ~240 mA per phase — low torque, not suited to driving loads heavier than light gears or small pointers

Pinout and connection notes

The motor connects to the driver board via its own keyed JST connector, not loose wires — only IN1-IN4 and the power terminal go to your microcontroller and supply.

• IN1: Coil control input 1 — connect to a digital output pin
• IN2: Coil control input 2 — connect to a digital output pin
• IN3: Coil control input 3 — connect to a digital output pin
• IN4: Coil control input 4 — connect to a digital output pin
• -: Ground, on the driver board's power terminal
• +: Power, 5V DC, on the driver board's power terminal — the motor's 5-pin JST plugs directly into the driver, no separate motor wiring needed

Integration checklist

1. Confirm the exact part number and breakout-board revision.
2. Verify supply voltage, current demand, logic levels, and signal direction against the datasheet.
3. Check controller pin assignments and bus address or interface mode against the example code.
4. Power up with external loads disconnected, then test signals before full integration.
5. If readings or communication fail, check power and ground first, then pin mapping, interface settings, and library initialization.

Troubleshooting and reproducibility

Record the board used, wiring, library/version, supply arrangement, and measured behavior. Use the selected board-specific wiring example as the source of truth. Never assume visually similar modules share identical voltage tolerance or pin order.