Wiring up a power switch between mains and PSU

  • I've been asking friends and social media connections, but for some reason I can't get a definitive answer.

    I just want a simple block diagram and recommendation of a switch on Amazon to use.

    Maybe some education would be nice too. I don't understand why switches aren't just a gate on one lead.


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  • I had this issue just recently, it's not very clear what goes where...

    Anyway I found this guide

  • Just a word of caution: It's wise to try and ensure it is a switch that cuts the live and neutral. This is because there can be a slight voltage on the neutral due to down stream connections/resistance and you may have the misfortune to be in a building where some numbnuts has got live and neutral swapped. Manythings will work fine, but there will still be a large AC potential between the electronics and earth with only the 'live' leg cut.

    Edit: ...buy yourself a socket tester (£8 from b&q for me in the UK) and run the machine though a plug in RCD breaker.

    Edit 2:Socket tester will check for a good earth and ensure live and neutral are not swapped. The plug in one I got could not check if neutral and earth are swapped.

  • Oh I should point out, in case you didn't realise. That silver strip on the back is an exposed live cable... Even when the switch is off... Huge safety issue... Be super careful when handling that side of things. Get it enclosed as soon as you can.

  • @phaedrux yes, exactly

  • @mangy_dog yeah, what do they mean by ...

    Always connect the ground between your two sockets. If you're using a metal enclosure for this project (which is safer than plastic), make sure connect it directly to ground.

    What two sockets?

  • @mangy_dog I plan on printing an enclosure, like the ones on the prusa

  • @gnydick said in Wiring up a power switch between mains and PSU:

    Always connect the ground between your two sockets. If you're using a metal enclosure for this project (which is safer than plastic), make sure connect it directly to ground.

    What I understand there is that you should ensure that the socket where you will plug the unit into (usually a wall socket) and this IEC socket's ground/earth are connected (and the wall socket's ground/earth need to be correctly wired - if in doubt, get a socket tester and make sure). In addition to that, the ground/earth towards your power supply, also needs to be connected, and as said, if you have a metal enclosure, it should also be connected to the ground/earth.

    The idea for all of these having to be connected is simply that in the event of a rogue wire (sometimes wires go loose), that the machine is safe. Here in South Africa, all houses have to be equipped with "earth leakage" trip switches in our DB box (as I understand in other countries it is called something else). The idea of that switch is simple, if any power leak to earth (typically around 10mA), it will trip. The way it works to detect this is a bit more complicated.

    In essence any appliance that is not double insulated (illustrated as a square in another square), should have an earth connection to make it safe.

    A while back, Angus from the Maker's Muse YouTube channel received a shock while operating a printer. Luckily he had no lasting effects, but upon inspection he found that one of his extension cables/leads had a disconnected earth - this along with a Y-capacitor configuration in one of the printer's power supplies, caused a little bit of power to leak into the metal frame of a different printer, which is where he touched when he shocked.

    Having a 3D printed frame is good, though I would still ground the frame's metallic structure parts, if there are any.

  • Yeah you should connect the earth to the metal frame of your printer and any other expose metal parts I case something causes to short...

    Of course it won't help if your extension cakes earth was buggered as mentioned above with Anguses printer...

  • Thanks all, worked perfectly.0_1543726827401_IMG_20181128_195943.jpg

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