where should i place the main switch???

hello, im making a 10x10 led matrix and thankfully its working fine. now its time to place it on a proper case. But i cant decide where in the circuit i should place the main switch. The matrix needs a power supply so i dont know if i should place the switch between the wall outlet and the power supply OR between the power supply and the matrix.

if i do the first i will have to mess with 220v which im affraid of since im a newbee at this. If i do otherwise, the power supply is going to be ON ALWAYS and drawing power even when the switch is off, am i right???

what do you recommend?

im attaching some pics of my project.

thanks!!




Normally you'd switch the power line.

if i do the first i will have to mess with 220v which im affraid of since im a newbee at this.

Use heat-shrink tubing and/or insulated terminals, etc., so it's difficult or impossible to touch the 240V wiring. Switch the hot-side (or if you're using a DPST or DPDT switch) you can switch both sides). The ground should be "permanently" connected and not switched.)

Do some research to find-out which is the hot in your country. If you're using a pre-made power cable and if you have a multimeter, check the connection (by measuring resistance) because the color codes vary.

It's reasonably safe if you do your work when it's not plugged-in and insulate everything. Worse case, you create a short and blow the circuit breaker in your house when you plug it in or turn it on.

DVDdoug:
It's reasonably safe if you do your work when it's not plugged-in and insulate everything. Worse case, you create a short and blow the circuit breaker in your house when you plug it in or turn it on.

In addition to this, do your testing with the device plugged into a surge protector that has a disconnect switch. This gives you a way to quickly shut off power to the device without having to grab and pull a plug.

Also get a non-contact voltage tester. Any hardware store should have them for under $10. You can use this to make sure that power is truly disconnected before you start touching things.

I do notice you only have L/N hooked up to the mains. The earth ground next to the N lug should be wired into the mains earth as well. A grounded 14ga pigtail will ensure polarity cannot be reversed(unless house wiring is bad).

I have a few items that don't have power switches on them. I typically plug them into a switched GFCI strip, along with a desk light, that way I never forget to turn everything off. If the light is off, everything is off.

thank you very much for your answers!!

it helped a lot, now i know how to proceed with the switch. Didn't know a lot of stuff you mentioned but some fast google research did the job.

Ill get this done first thing in the morning then ill let you know how it goes.

Thanks again!

tinman13kup:
I do notice you only have L/N hooked up to the mains. The earth ground next to the N lug should be wired into the mains earth as well. A grounded 14ga pigtail will ensure polarity cannot be reversed(unless house wiring is bad).

i looked for the 14ga pigtail on google and i see it is a cable with a screw on one side. if i screw it on the wooden case, will it work as a ground?

DVDdoug:
Do some research to find-out which is the hot in your country. If you're using a pre-made power cable and if you have a multimeter, check the connection (by measuring resistance) because the color codes vary.

i did the research and my conclusion is that here in Peru we don't use hot and neutral cables since the wall outlets here only have 2 holes in it. we can plug the power plugs either way, unlike the US for example, that has 3 holes sockets which will take in count this "polarity".

so switching any of the 2 cables would work for me, right?

thanks in advance

You can't go wrong with a switch that breaks (disconnects) both 220V wires. You might also wish to put a fuse inside your case. Theoretically if you keep all the 220V wires isolated breaking both lines is not needed but it won't hurt.

When wiring your project you need to be sure any 220V connections and anything that gets hot is not directly against the wood. If the power supply needs cooling air you might have to put some openings in the case (perhaps covered with a screen or perforated aluminum).

When you start to layout the case make a special effort to keep the 220V wires / switches / fuse as far away from the power supply output and low voltage wiring as possible. You should have high voltage on one side and low voltage on the other side.

You might want to look for a "chassis power receptacle with switch" I've seen them for the US plugs. They contain a power cord receptacle, a fuse and a switch in one housing (meant to be chassis mounted).

i looked for the 14ga pigtail on google and i see it is a cable with a screw on one side. if i screw it on the wooden case, will it work as a ground?

No, wood does not conduct electricity (except when its wet). And from your description you don't have the 3rd wire "equipment" ground (which in the US would be connected to a metal case/chassis etc. Your best bet is to keep all the 220V wiring isolated as much as possible. Neither 220v wires should be connected to anything except the power supply input, the switch, a fuse and of course the incoming power cable.

Good luck with your project.

tinman13kup:
If the light is off, everything is off.

Exactly what I do in my shack. The push button switch on my 45 year old lamp failed years ago, so I by-passed it and the lamp is on when plugged into the strip, if the strip is powered. So if the lamp's off, the radios are off.

Two additions: That power supply has a metal housing. The fact that you cannot connect protective earth, as it seems, makes that potentially dangerous. You should act as if the case was under power. I am not sure how your country deals with this in general.

I think nobody mentioned strain relief yet. You have to make sure that your power cable is tightly connected in the box, not only soldered a screwed in. Imagine you trip over the wire, then it has to be impossible that the cable connections comes loose and dangle around in your device, or potentially even worse, the cable comes out completely and you have blank, hot cables lying around in your house.