Side-mountable housing for circuit breaker-based appliance switch

WARNING: THE USE OF THIS MODEL INVOLVES WIRING MAINS VOLTAGE CABLES (240 V IN THE UK). DO NOT PROCEED IF YOU'RE NOT COMFORTABLE DOING THIS!

I like to be able to switch on/off electrical equipment in groups that are only ever used together. For instance the keyboards/sound modules, mixer, amplifier, and PC/monitor. Or the CNC machine, dust extractor, and control laptop. Or my entire electronics workbench. This probably even saves me a tiny bit of money as it turns off energy vampires (e.g. AC adaptors that are constantly plugged in).

For this, I use miniature circuit breakers because I like the satisfying and tactile feedback when they're turned on (arming) and turned off (release). Before anybody points out that circuit breakers are not designed for regular use as switches and will wear out quickly, the two that are mounted side by side in one of the photos (an older design of mine, different shape breakers, not this model) have been going strong for nearly 12 years now. So there's that.

I usually don't switch them under load and that probably prolongs their lifetimes (no arcing). They could even be used as emergency shutoff switches, although regular such use under heavy load would likely shorten their lives.

This model fits the following range of breakers: https://cpc.farnell.com/europa-components/euc1p16c/circuit-breaker-1-pole-16a-230vac/dp/MC02696, and 8.1 mm diameter, 16 A, 3-core mains cable such as this: https://cpc.farnell.com/pro-elec/pelb0753/cable-3183y-1-50mm-wht-5m/dp/CB22764. Use of a thinner cable will require either you re-designing the cable clamp tabs, or winding some tape around the cable so it is held securely in the cable clamps.

The housing is not quite symmetrical (there's a bit that sticks out on one side of the breaker so the housing is wider on that side - I should really just make both sides wider so the model is symmetrical) so you need to print the left wall or right wall version depending on where you want to mount it. You will also need four M3 nuts and four M3x14 bolts for the cable clamps/strain reliefs. The nuts slot in near the base of the housing and need to be inserted before the breaker is fitted in. Make sure the clamps hold the mains cables securely!

WARNING (again): do not mess with mains wiring unless you know what you're doing!

I've wired the input (feed) cable to a standard fused UK mains plug and the output to a trailing mains socket (that I then plug a multi-socket extension into), but you can obviously do whatever suits your setup.

The neatest way of routing the wires inside the housing is a bit fiddly and involves carefully stripping the outer insulation in the middle of a length of mains cable (without damaging the inner wires) leaving neutral and earth intact, and only cutting the live wire to connect to the circuit breaker (this approach is not shown in the photos but I've done it for one or two of the switches in my place). This may involve some trial and error with how much outer insulation to remove (there must be enough left for the clamps).

If you're using the switch to connect two separate pieces of cable, you could use screw terminal blocks. Two should fit (offset end-on rather than side-by-side) although I've not checked this. I've simply spliced the neutral and earth wires (with an offset), soldered them together, then covered them with heat shrink and then electrical tape (shown in one of the photos). Again: make sure the cable clamps/strain reliefs hold both cables securely by the outer insulation, not the inner wires!

Finally, you'll need three screws to attach the housing to wherever it's meant to go. Can't remember what size but it will be pretty obvious once you have printed the housing. The entire assembly should be pretty obvious. You'll probably want to recess the switch somewhat from the face of the surface you're mounting it to so as to avoid accidentally turning it off if you hit it with something.