Two PIRs to one set of lights.

cpocal · 13 Sep 2007

Hi all,

I have a PIR that switches on the lights to my property when someone comes through the gate. It is great because I have awkward steps that are dangerous in the dark and so it powers several lights at strategic points.

My problem is that I would like to have the same lights come on when someone exits my front door but I cannot get the two PIRs to work without creating a loop that by-passes the others timer and so they stay on for varying lengths of time. Someone suggested that I fit a relay but I haven't a clue what they mean. Can someone on here please give the right advice?

With thanks, Chris

jj4091 · 13 Sep 2007

Sorry but cannot really understand what the problem is, the on time for most pir's is adjustable so why do you need to start faffing around with relays?

cpocal · 13 Sep 2007

Hi JJ, I do not wish to faff around with relays as I'm not sure what one is.

The problem I have is that I would like to have two PIRs supplying the lights from two different approaches, one at the gate and one at the front door. The problem that arose from adding the second PIR is that electricity is looping to the other PIR via the lights and so is affecting the way they work so I have power going to the non-movement activated PIR receiving a supply from the activated PIR via the lights.

Someone told me that having the two PIRs wired to a relay and then on to the lights would resolve the problem because the relay would direct the power to the lights while not being directly connected to the other PIR. What he said made sense at the time but I don't know what I would ask for.

Someone on here who had the problem before suggests using master and slave PIRs but I can't seem to find them on sale either.

Taylortwocities · 13 Sep 2007

Is the PIR you already have a stand alone one, or integrated into the security light?

tim west · 13 Sep 2007

As they would be on the same phase there should be no problems whether internal relay or triac switching, all that's happening is that one or other pir is overiding the timings you expect, put both pirs to the shortest time setting and then gradually take both of them up in equal steps till you achieve the desired time.

cpocal · 13 Sep 2007

Hi Taylor, they are both stand alone PIRs as they provide power to three 100w lights.

Hi Tim, I tried that but once the power has looped it doesn't seem to matter what I do with the timers the lights can be on for a second or two and then once activated again they might stay on for 5 minutes or more even if I set both PIRs' timers to zero.

1974stephen · 13 Sep 2007

You're not feeding the switched live from one PIR to the feed live of the other PIR are you? The switched live from each PIR needs to be wired in parallel to the live of the lamp cirucit.

Also, are they fed from the same curcuit? This wouldn't affect the operation you descrube but is dangerous and bad practice!

bernardgreen · 13 Sep 2007

1974stephen said:
You're not feeding the switched live from one PIR to the feed live of the other PIR are you? The switched live from each PIR needs to be wired in parallel to the live of the lamp cirucit.

Don't you mean The switched live from each PIR needs to be wired in parallel to the switched live of the lamp cirucit.

breezer · 13 Sep 2007

he does, but i also understand what he means

bernardgreen · 13 Sep 2007

breezer said:
he does, but i also understand what he means

But the in-experienced OP may not.

breezer · 13 Sep 2007

true, but i would also guess the Op doesnt know what sithed live is.

even better if i spelt it right

Taylortwocities · 13 Sep 2007

This works for me, how hard can it be?

Space cat · 14 Sep 2007

The strange interaction of the two PIR switches may be down to there internal electronics, about which we know nothing.

Cpocal, have you wired them up according to Taylortwocities' diagram, which is correct? If you have and the PIRs are interacting then a relay won't help; you need two relays. Even this might not work because solid state (triac) switches have a problem with very light loads - like relay coils! Check your PIRs to see if they have a MINIMUM load current.

In its simplest form, a relay is a switch operated by an electromagnet but the range of different types is vast. You can get umpteen different coil voltages (either AC or DC), a multitude of multipole switch combinations, several types of contact material and a choice or screw terminals, plug-in, PCB mount, etc, etc.

But I digress. You need two relays, each with a 240 volt AC coil and a single, normally open pair of contacts (silver cadmium oxide will do nicely). Make sure that the contacts are rated for the voltage and current you want to switch and allow plenty of spare current switching capacity because lamps have a large switch-on surge.

As for the wiring, the switched live out from each PIR feeds a relay coil. The two relay contacts are then connected in parallel to feed the lights.

cpocal · 14 Sep 2007

Hello everyone, thanks so much for your time and help on this.

Stephen, they are fed from the same circuit and they were wired as in Taylor's diagram. Hence I am at a loss. I removed the one when they wouldn't work together.

Bernard, if their being in parallel is the same as Taylor's diagram then yes they were wired in parallel.

Taylor, my PIRs were wired as in your diagram. The problem I was havin is that the current was being directed back at the non-activated PIR (no movement detected) over the switched live and apparently opening up the gateway across the non-activated PIR to disrupt the timer and then looping until the "gateway" closed on one or the other PIR but this could be seconds or minutes depending upon the gateway resistance I suppose.

Spacecat, can I get a relay that will direct the power from whichever PIR is activated 1st and if not what would happen when someone broke the 2nd beam and the 2nd PIR is activated? Where would I buy these relays and what would I ask for?

I am also seriously considering getting an electrician to do what I initially thought was a simple switching job.

Respect and thanks to ALL responders, Chris

breezer · 14 Sep 2007

there are no beams to break with a pir.

you can get relays from maplins

relay (socket part No N36AW)

how ever, there is no g'tee this will work

Theory states it will / should work, but it may be the load of the realy coil is too little and it may not switch off, or (but unlikely) the back emf will eventualy fry the pir switching device.

only real wa is to try it and see, but then you have the expense of a wether proof box to mount the relays in.

I am curious as to who told you "............and apparently opening up the gateway across the non-activated PIR .............."

I wouldnt get an electrican in, most (house bashers) don't know one end of a relay from another, (that is most, not all)

if you want a diagram how to connect the relays just ask (and yes i know fitting a capacitor will kill the back emf on ac, but value of it i have no idea

)

in words (time to go to earn some dosh)

pir switched live goes to one side of realy coil, other side of coil to neutral, C & NO contacts then swithc lights, you connect Live to NO and swithed Live to C (this way the NC terminal never becomes live)

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Two PIRs to one set of lights.

breezer

breezer

breezer

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