how to control the spindle with the usb controller

To control a spindle using the USB CNC interface, you will need a relay board that contains a transistor that can activate the relay with a power source with enough current that can activate the relay. This video explains all of the information you will need to develop this relay circuit: https://www.youtube.com/watch?v=PJO_XoLL6lQ&index=44&list=PLE72E4CFE73BD1DE1