user20421: I am using my uno with gshield for my cnc. I would like to put laser on it. Laser have 3 wires. Red wire to power supply +, Black wire to power supply -, White wire to Arduino digital pin. I need to Connect the Arduino board ground to power supply -, but don't know how... Simple diagram (like child is using painter) would be great. 
Thanks for help,
Urban

user10024: You take a wire, connect one end to the ground on the Arduino board and the other end to the ground on your power supply. Don't forget to strip the insulation. It doesn't get simpler than that.

20421: <p>I am using my uno with gshield for my cnc. I would like to put laser on it. Laser have 3 wires. Red wire to power supply +, Black wire to power supply -, White wire to Arduino digital pin. I need to Connect the Arduino board ground to power supply -, but don't know how... Simple diagram (like child is using painter) would be great. </p>

<p>Thanks for help,
Urban</p>
 10024: <p>You take a wire, connect one end to the ground on the Arduino board and the other end to the ground on your power supply. Don't forget to strip the insulation. It doesn't get simpler than that.</p>
