PIR Sensors

[matt80]

Hi all,

I want to fit an outside light which comes on when you walk up the drive. The actual light that I want does not have PIR built in, but I believe you can buy a separate PIR sensor and fit it to the light.

Is this correct?
Is it hard to do?

I already have the wiring in place for the light, and it is operated by a switch. Presumably this doesn't affect whether or not I can fix a PIR sensor?

Thanks!
Matt

 

[breezer]

the switch will affect it, seeing as it will stop it from working if off.
yes you can get mains operated pirs and yes they are eay so wire in.

The incoming supply goes to the pir first, then a switched live to the light, they come eith instrcutions, get them from any electrical wholesaler, shed or online versions of previously mentioned

 

[Big_Spark]

Matt, yes you can but seperate PIR's and not they are not hard to fit..you simply need to read the instructions if you have never done this before and double check all connections BEFORE powering up..

 

[matt80]

Thanks for the quick replies!

It is currently wired as: Fuse box -> switch -> light

Can I make it like this: Fuse box -> switch -> pir -> light

Or does it have to be: Fuse box -> pir -> switch -> light

Thanks again!
Matt

 

[breezer]

this one

CU > switch > pir > light

its less hassle for you to wire it that way. if you wnat your switch to override the pir, you will haveto run in another cable

that said some (not all) pirs will stay on 24 /7 if you switch mains off then on (untill you switch it off again)

 

[matt80]

But surely if the switch is wired before the PIR as you suggest, then turning off the switch will cut the supply to the PIR? So the switch does actually turn off the PIR? Is that correct??

 

[breezer]

that is correct. i only suggested this way since:

it is almost what you have

little additional wiring required

some pirs will latch on if swicthed off and on quick

 

[matt80]

Been to Homebase/B+Q today and all the PIRs seem very bulky and quite ugly (8cm x 10cm ish). Is it possible to get smaller ones, or are they all like this?

 

[breezer]

well dont to to those places then.

you also forget.

you have to have room for your cables, it will be up on a wall

 

[Darkness]

Sorry for jumping in on your post Matt80 but can someone tell me if it is ok to use the cpc earth core of t&e as the switched live if I sleeve it?

It's just I have an operational light going and I was going to wire a PIR to it today. I have no 4-core cable and the only alternative is to run 2 lengths of T&E to the sensor from the light having the 2nd length returning the switched live.

A simple solution would be to use one length of t&e and sleeve the earth cpc acting as the switched live which would save the hassle of running 2-lengths of cable especially when the PIR doesn't require an Earth.

(t&e becomes Brown, Blue and Black cores)

Can I do this or is the cpc restricted to Earth only, use it for earth or don't use it at all?

 

[Big_Spark]

Sorry for jumping in on your post Matt80 but can someone tell me if it is ok to use the cpc earth core of t&e as the switched live if I sleeve it?

NEVER DO THIS, IT IS DANGEROUS

 

[Darkness]

Sorry for jumping in on your post Matt80 but can someone tell me if it is ok to use the cpc earth core of t&e as the switched live if I sleeve it?

NEVER DO THIS, IT IS DANGEROUS

So basically its like what I said, use it for earth or don't use it at all.

 

[plugwash]

really i would say it should always be earthed even if the fitting at the other end doesn't need an earth

 

[Lectrician]

The schematic CU>switch>pir>light is fine, but the circuit diag could be altered.

Simply take a 3core+EARTH from the original light to the PIR.

In the PIR, connect RED to live in, BLUE to neutral, YELLOW to switched live out.

In the original light, connect RED of supply directly to the RED of the 3 core in a seperate terminal block. Connected Black of supply, and BLUE of 3 core to the lights neutral. Connect the YELLOW of the 3 core to the lights live.

Use red sleeve at both ends of the yellow.

Not that RED YELLOW BLUE......may be.....BROWN BLACK GREY if wired with new colours.