SainSmart A4988 Stepper Motor Driver for Arduino Mega2560 Mega1280 RepRap Ramps Simple step and direction control interface Five different step resolutions: full-step, half-step, quarter-step, eighth-step, and sixteenth-step Adjustable current control lets you set the maximum current output with a potentiometer, which lets you use voltages above your stepper motor"s rated voltage to achieve higher step rates Intelligent chopping control that automatically selects the correct current decay mode (fast decay or slow decay) Over-temperature thermal shutdown, under-voltage lockout, and crossover-current protection