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Author Topic: How to connect C14 and UK AC mains to relay?  (Read 526 times)
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I'm planning to start using the arduino to control AC appliances.

I plan to use a opto-isolated relay within a sealed plastic box.  From the mains will be a C14 cable socket connecting to a C14 plug shown below: -



This will then connect to the relay and on the other side of the box a normal AC appliance will be connected (UK mains 13A): -



Hopefully that's right.  What I'm wondering now is how these pins should be connected to the relay?  
I was planning to solder a wire to each pin and then screw them into the appropriate connection on the relay -- is that ok?  
After a lot of googling I see they look like "spade terminals" -- is that what they are?  If so do I need to order the right size female terminal (what size would that be?) and "crimp" it to wire?

Also I'm assuming the ground wire skips the relay altogether and goes right across from the C14 ground pin to the 13A ground pin?  What about neutral?

Thanks

« Last Edit: May 14, 2013, 01:44:31 pm by Combo » Logged

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You can use female Quick Connects* which crimp onto the wire, or you can solder wires directly to the contacts.  If you solder I recommend insulating with heat-shrink tubing and if you use quick-connects, I resommend the insulated type. 

You can get quick-connects at from places that sell electrical ro electronic parts, hardware stores, home improvement stores, or auto parts stores.   There are a couple of popular sizes, so make sure you get the right one.

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Also I'm assuming the ground wire skips the relay altogether and goes right across from the C14 ground pin to the 13A ground pin?  What about neutral?
The ground & neutral are connected directly.   The hot wire is switched through the relay.  If you have a double-pole mechanical relay, there's no harm in switching the neutral also, but the ground should be "permanently" connected.

In order for current flow, you need a complete circuit.   You can "break" the circuit and turn-off power with a switch in either the hot or neutral side.    But for safety reasons, the switch/relay normally cuts the hot connection.



* "Quick-connect" or "Quick disonnect" mioght be Americqan slang/jargon, and they might have a different proper name..

This is a Spade Terminal and this is a Ring Terminal.
« Last Edit: May 14, 2013, 02:33:08 pm by DVDdoug » Logged

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I was planning to solder a wire to each pin and then screw them into the appropriate connection on the relay -- is that ok?  
Yes, but see below.
Quote
After a lot of googling I see they look like "spade terminals" -- is that what they are?  If so do I need to order the right size female terminal (what size would that be?)
Measure the width of the terminal. The standard sizes are 3/16", 1/4" and 3/8". There are also some larger sizes but these are rare. Halfords sell insulated spade connectors in those sizes.
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and "crimp" it to wire?
Yes. Or you could use uninsulated ones and solder the wires in place with some heat-shrink over the connection.
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Also I'm assuming the ground wire skips the relay altogether and goes right across from the C14 ground pin to the 13A ground pin?  What about neutral?

Connect that directly too. Only switch (with the relay) the live wire.
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Thanks that helps a lot.

I ordered all the stuff from ebay and it's coming from China so could take a few weeks.  Instead of waiting for them to arrive and then measuring them, any guesses as to what size these pins usually are?

These are the exact items I ordered: -
http://www.ebay.co.uk/itm/190837172752?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2648
http://www.ebay.co.uk/itm/190837163885?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

I looked up quick connects and found some in these sizes: -

Red Connectors: 0.4mm to 1mm² / 22-16awg cable

Blue Connectors: 1.1mm to 2.6mm² / 16-14awg cable

Yellow Connectors: 2.5mm to 6.5mm² / 12-10 awg cable



Do those look right?  Can anyone hazard a guess as to which size/colour I need?

Thanks again.

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If you are still wondering how to connect to the relay, here is a schema I made some time ago:


You see on the relay there are 3 screws but only 2 used, the middle screw is always used, and the side screws depends if you want:

Normally Open: connection is closed when relay is powered or
Normally Closed: connection is closed when relay is not powered
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Get down to Maplin / Halfords / Screwfix and buy yourself a pack which contains an assortment of terminals and a basic crimping tool.
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Leighton Buzzard, UK
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should you really be fiddling with mains if you have to ask questions like these?
I hope your "significant other" has lots of insurance smiley
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Thanks that schematic does help.  That's a two-channel but I can see it's connected in the same way I expected.

And yes this is the first time I'm playing with AC mains.  Have to start somewhere.  I'm taking all the precautions I can think of, including keeping the whole thing within an isolated plastic box.  I see so many videos on youtube of these relays connected bare and sat on a wooden floor or desk!
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