GRBL 3 Axis Control Board Output signal: 1: Fan: used for shaft motor cooling 2: Shaft: connect motor shaft, keep the same with power supply voltage, 5A electricity, if the motor power of the spindle is high, can connect external relays such as the switch. G code M3 open, M5 closed, with version 0.9/1.1 of the firmware can adjust PWM, achieve the speed of the axis governing and tunable laser 3: X axis motor signal output, A4988 max 1.5A electric current 4: Y-axis motor signal output, A4988 max 1.5A electric current 5: Z-axis motor signal output, A4988 max 1.5A electric current Input signal: 1: X-axis minimum limit X- 2: Y-axis minimum limit Y- 3: Z-axis minimum limit Z- 4: Reset button: press the button, system will restart, can be used for urgent stoping of machine Package Contents： 1 x GRBL CNC Controller 1 x USB cable 3 x Heat sinks