how to ... WIRE AN ON / OFF SWITCH???

[Superully]

ok, here's another one. i have the following on / off switch



from the back: you can see the switch has four terminals to which wires can be attached



let's say i have a "normal" power plug with three wires (phase, neutral and ground), how can i wire this switch "into the circuit" so that the on / off switch can do its job?

[Etienne MacGyver]

Dont know exactly the colors in germany, but here in holland its like this :
Brown fase
black switched fase
blue neutral
green/yellow ground



In this way, both the "fase" as the neutral are switched
the ground is connected continue nomatter what position the switch is..

[level42]

Impossible to answer without knowing more about that switch.

To know more, you need to measure.

But first, some assumptions:

Since it's 4 terminals, I expect that this is a double-pole NO switch. This means it's "two switches in one". By throwing the switch you throw "over" two contacts at once.
This is good for mains in Europe, because with our wall-outlets you never know what lead has phase (dangerous) or neutral (safe).

First measure in Off position. Set your Fluke to diode/continuity test ("beep") and measure between all the pins, all combinations.
I expect that everything should be open (no beeps).

Next throw the switch to ON.

Now, I would expect you to measure shorts (beeps) between pin 2 and 3 and also between 5 and 6 (At least I think those are the numbers).

There should be NO beep between 3 and 6     and    2 and 5 !!!


If this all is correct, you're safe to go:

Wire phase to pin 3. Pin 2 will now carry the phase when switched on, so wire from here to your device to be "fed".
Wire neutral to pin 6. Pin 5 will now carry the neutral when switched on, so wire from here to your device to be "fed".

The ground can be connected straight trough, but since the switch is mounted on a metal plate, this should be wired to ground too...

[level42]

heh-heh, Etienne's solution is also correct of course, but he's assuming the measurements as I mentioned (In which he is VERY likely correct, but I'm always careful with mains stuff )

Of course it doesn't matter which side you choose as "input" or "output", it's still just contacts.

Do think about the grounding though...

[Superully]

thx for your input guys (as always), i'll do the necessary checks tomorrow (because i still have to prepare for school tomorrow )

The ground can be connected straight trough, but since the switch is mounted on a metal plate, this should be wired to ground too...

how would you do that? is it even necessary?

[Etienne MacGyver]

You made a very good point too andre with measuring, i "ASSUMED" from experience, but that is not always the case...

but here i am 99,9999999999%  sure its like this

and yes, it can go otherway around since you never know which pin has the fase here because its possible to plug it in "upsidedown"

Anyway, about your numbers, i dont see more than 1 - 6 ...

3  2  1
6  5  4

 

[level42]

You made a very good point too andre with measuring, i "ASSUMED" from experience, but that is not always the case...

but here i am 99,9999999999%  sure its like this

and yes, it can go otherway around since you never know which pin has the fase here because its possible to plug it in "upsidedown"

Anyway, about your numbers, i dont see more than 1 - 6 ...

3  2  1
6  5  4

 

Mehhh, you're right !! Didn't look properly !!! (Already thought it was a funny numbering....) I corrected the numbers in my posting !!!

Yes, I am as certain about it as you are, but this is not only about this, this is also about learning some stuff to Ully, but don't tell him !



 

Rule-of-thumb: Any metal parts in a device that's carrying mains voltages that can be touched directly should be grounded.

I explained that when it was still 56 degrees Celcius in your home (above 0)

It's like a Control Panel: you will always find a ground wire that runs under a screw or something that is bare (no paint). The reason ?

Well....suppose something goes wrong. Let's assume a washing machine (which is fully metal on the outside)  produces some kind of short, or the wiring gets damaged. Because of this the mains voltage may make contact with the metal of the machine. It may still work OK, but the next time you touch the machine it's ZZZAP time....

[Etienne MacGyver]

Okay, class is open 

Imagine that the inside of the switch is like this :



The "moving part" inside the switch connects the terminals depending on the position.
in this case "off" means that terminal 1 & 2 are connected.
If you move the lever "a" in the direction of the arrow, (the on position) it will move the internal "conductor" to connect terminals 2 and 3.

with this knowledge, you know that the "input" always is the middle terminal.

The switch you have is a double version, wich basicly means what andre says; two switches in one case.
for example a few more pics, because it does not stop at double, there exist also triple and more;






Hope this helps a bit 

Class dismissed 

[Etienne MacGyver]

Also a note on grounding..

Only devices that are marked with the double isolation sign are alowed to be connected without ground :



I get a lot of times the question from customers and friends;

"the pc works fine on a non grounded socket, why i need to use a grounded outlet ?"

i can only say, try your pc on a non grounded socket, take your voltmeter and measure between the metal of the case and some ground point (like your central heater, or waterpipes)

you will be surprised about the voltage you read.... 
ok, the current is low, but you can feel the shock if you touch both

and thats just when its operating in the way it should...
Imagine what happens if there is a loose wire making a short and you are the "conductor" between the device and ground....

[Superully]

thx a lot for the explanations, teacher etienne. may i sit down now?

i just did the measures as instructed and the results where what you nostradamus guys predicted - which means i'm good to go installing the on / off switch.

one question regarding the grounding remains though: would you cut up the ground wire from the plug and attach each end of it with a screw to the metal plate? like this 

[Superully]

one more thing: is it important which terminals lead to the socket and which ones lead to the cabinet's power supply? because in etienne's drawing terminals 3 & 6 are on the cabinet side (going to the power supply), but andré wrote "wire from pins 2 & 5 to the device to be fed" (the power supply). or did i just understand this incorrectly?

[level42]

thx a lot for the explanations, teacher etienne. may i sit down now?

i just did the measures as instructed and the results where what you nostradamus guys predicted - which means i'm good to go installing the on / off switch.

one question regarding the grounding remains though: would you cut up the ground wire from the plug and attach each end of it with a screw to the metal plate? like this 

No, screw both wire under the same terminal (the left one or the right, doesn't matter). The metal plate is probably not the best conductor. This would add a resistance to anything that is connected to the ground wire "behind" it....

[level42]

one more thing: is it important which terminals lead to the socket and which ones lead to the cabinet's power supply? because in etienne's drawing terminals 3 & 6 are on the cabinet side (going to the power supply), but andré wrote "wire from pins 2 & 5 to the device to be fed" (the power supply). or did i just understand this incorrectly?

No, as mentioned before that doesn't matter. As long as both are on one side..

[Superully]

ok, both ground wires will go to the same screw then!

[Etienne MacGyver]

Correct, ground wire on one screw,
i tend to use the "middle" terminals as inputs, but with your switch it does not matter since there is no terminals 1 and 4  
and even if there where, it still works the same in your situation..

the point is that terminals 2-3 and 5-6 are closed in the on position and open in the off position (wich "breaks" the circuit)