Single Relay Enclosed Case for Power Cord

thingiverse

This case was created to work seamlessly with my Octoprint and Plugin for PSU Control (https://github.com/kantlivelong/OctoPrint-PSUControl) to switch the active line on a 240VAC power cord safely. Other cases were too open and didn't provide a tight cable grip. It uses the skinny single board (usually blue) relays from China, which usually have green and red LEDs and have the contacts terminal very close to the end of the board. Use M3 6mm screws along with brass melt-in nuts. I take no responsibility if you do this yourself without a qualified electrician. 240V/120V AC kills. Don't be dumb! I shouldn't need to say this, but do these next steps with an unplugged power cable! Choose a thick power cord if possible; it will help keep the cable snug. Carefully cut the outer insulation. I found bending the cable tightly and then using a razor to gently cut the outer only. Grip and slide your hands away from the cut to make the insulation slide down to expose the internal wires. In Australia, the brown wire is the 240V active that needs to be switched in the relay (in the USA, it's the black wire). Choosing any wire except the active/phase wire is dangerous. Cut and strip approximately 5mm on both sides of the cut; tin with a soldering iron if you wish. Place two small zip ties around the ends of the outer insulation, but don't fully tighten yet. Screw or terminate the wires into the relay. Choosing which two will depend on whether you want NO or NC; I choose NO (Normally Open). Bend the Earth and Neutral wires into a U shape to squeeze in below the terminated wire; it's really up to you how you fit it in. It worked best for me this way. Once the relay is sitting on its shelves, push the cord down inside with the zip ties on the inside. If you need to reduce the exposed wires, slide a tight-gripped hand down the cord to push the insulation back down. Tighten zip ties and screw on the lid. You might also find it easier putting in the Dupont cable before the lid.