Specific module for 28-BYJ48 steppers, on the board, in addition to the ULN2003A chip we find 4 LED diodes with relative limitation resistors, the LEDs A, B, C, D indicate the status of the stepper motor operation. The control signals coming from the control board are supplied to the pintrip J1, the motor is connected to the 5-pin Pinstrip J4. The pin strip J3 is used for power supply, if you connect the 28-BYJ48 motor that must be powered at 5 V you will need to mount a jumper so that the same voltage reaches both the motor and the U1 chip. Given the motor absorption, the motor power supply cannot be derived from the control board, but must be supplied by a special external power supply For more information see https://www.adrirobot.it/driver-stepper-28-byj48-motor-controller-uln2003a Test video: https://youtu.be/LnlwZVwTCUM