UK 240V 3 core switched by Arduino via relay

Hi from an absolute Arduino and (electronics in general) beginner

I'm struggling to find reference through the internet to identify the wiring connections on the 240V side of said relay. I have a 3 core live, neutral and earth on my 240V supply - but where do I connect them with regard to the NC, NO and common connections on the relay? (internet only offers 'lighting' 2 core solutions)

thanks in advance

Is your "3 core live" meaning 3 phase?

Weedpharma

weedpharma: Is your "3 core live" meaning 3 phase?

I think he means 3-core ie, live, neutral and earth; so just a normal single-phase supply.

I'll be the first to say this, since someone always does: if you have to ask about how to do mains wiring, you shouldn't be doing it.

tickustorso:
… but where do I connect them with regard to the NC, NO and common connections on the relay? (internet only offers ‘lighting’ 2 core solutions)

thanks in advance

This depends on what you want to do.

Power supply to Common and load to NO to apply power, IE, to turn something on.

Common and NC if you want to have something running all the time but turn it off occasionally

Neutral and earth are not connected to the relay but go straight through to the load.

As Jimbo said, if you don’t know what you are doing, DON’T DO IT!

Weedpharma

OK weedpharma - thanks for taking time to reply

You'll have to forgive me if I dont use the correct terminology - as I say, I'm absolutely new to arduino, electrics and electronics in general

No, by '3 core' I mean there is a live, neutral, and earth, as in 'L, N and E', as embossed in the actual plug. This plugs into a ring-main socket which also has L, N and E and a switch to turn on or off the supply (sorry if this sounds patronising but I'm trying to clarify my objective as best possible).

My aim is to use the Arduino and relay to switch the power supply on and off dependent on other conditions being met

I've got the Arduino side of the relay sorted (I've had the relay clicking away merrily) but I'm struggling with the 240 side

The relay is a Songle 8 channel 30VDC 250VAC 10A, the pump is 240V 125W

Thanks in advance for any advice offered

OK,

I'm unsure why, but reply #3 (above) didn't appear on my screen until I'd posted reply #4

Firstly - thanks for the reply, but just to confirm; the appliance is plugged into the ring main as normal, then what I would call the 'Live' core goes into the 'common' on the relay, and out of either the NC or NO (dependent on requirements) on the relay, then onward to the pump?

Ok - I get that - so the relay is acting literally like a switch in a lighting circuit - thanks

Secondly - I appreciate the advice, I really do, but I'm a bit disappointed in the 'if you have to ask', or 'if you don't know what you're doing - don't do it' comments.

I know about mains wiring, but I dont know about relay connections - in any case, I would estimate that over 95% of intitial posts on this site are requests for advice regarding problems that posters are struggling to solve - are you really suggesting that they 'shouldnt ask'?

Final comment; disappointed, but grateful (weedpharma) for your advice

You only need to break the “L” core with the relay since “N” is grounded. I always connect L to NO and load to COM, that way there is no voltage on NC when the relay is off. If you connect L to COM, then when the relay is off NC will be “HOT”.

Note:
If you are using a rubber “portable” cable you should use a double pole relay and break both “L” AND “N”, since a rubber cable may get damaged and spliced “backwards” making “N” HOT.

Re the "if you don't know, don't do it".

We have all types of members from school kids to engineers.

We do not want to be responsible for someone with no idea what they are doing, getting hurt or hurting someone else.

Unless we know what experience a new member has (and this was not mentioned in the OP), we need to assume minimal knowledge and respond accordingly.

A basic question such as how to connect a relay in a power lead, does not show a large degree of electrical knowledge so the answers reflected this.

No one is putting you down, just protecting their posteriors.

Weedpharma

tickustorso: so the relay is acting literally like a switch in a lighting circuit

It's not acting like a switch, it is a switch, just operated by a wire not a finger.

tickustorso: I would estimate that over 95% of intitial posts on this site are requests for advice regarding problems that posters are struggling to solve

That's very likely true, and is a large part of the forum's purpose, but very few of them are about a) killing yourself or b) possibly violating a zillion council bye-laws and clauses in your homeowner policy.

Jimbo

Which specific part of my original post directly covered the topic 'killing myself'?

I followed the suggestion in weedpharmas second post, and the suggestion offered by jcallen and i've managed to achieve my objective........... without killing myself

Your two posts however, have offered no advice whatsoever. None. Your second post is, quite frankly, insulting.

Tell me - is answering a question on someone elses behalf a privilege which comes with Tesla status? - as in "I think he means 3-core ie, live, neutral and earth" - how do YOU know what I meant? - wasn't the question put to me?

What was your motive for even replying to the post if you were going to offer no advice whatsoever? I mean please - why?

weedpharma - thank you for your further post - it is a valid point - I wouldn't want you to receive a letter of my widowed wife's solicitor blaming you for my death because "he followed weedpharma instructions" - I take that on board

Again - weedpharma and jcallen - thanks for the advice - its worked - and thanks to your specific detail I now have a clearer understanding of how a relay works - thanks.