VK3YE likes to work CW (Morse Code) on the 40-meter band, but doesn’t like the monotony of hand keying CQ endlessly. He devised this simple project using an Arduino to tap out CQ and his call sign automatically at predetermined intervals. The keying was originally accomplished using a reed relay as shown in the video. However, after several days of use it became sticky. So he switched to the circuit described in snarfusmaximus’ video below, consisting of a 4N25 optocoupler and 470 ohm resistor.