PIR detectors in Parallel

Ignoring voltage and load considerations; is there any reason that prevents connection of burglar alarm PIR detectors in parallel? There are no spare 'zones' in my alarm and I wish to add a detector. Being unable to differentiate between the location of triggering events is not a problem.
TIA Richard
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wired in series. This cos they are normally closed and break on an alarm condition. If you parallel them you will only get an alarm when BOTH detectors are triggered.
If you use the tamper contacts they need to be series connected too.
--
fred

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Thanks Fred,
fred wrote:

I knew that there would be a catch. If I'd bothered to think before applying digit to keyboard I hope that I would have worked that one out!
Actually thinking slightly more (as opposed to not at all!), I can achieve the series connection in the control box - duh! I think I'll go and have a lie down in a dark room!
The bizzare thing is that the detector that I will parallel is in a room whose window faces the main road and is very visible, whereas the other room has a rear garden window that can be reached with ease. And this is a professionally (?) installed alarm system

No tamper contacts present - the system is only just young enough to use electrickery rather than caged Geese!

On a slightly different tack; do you know of any DIY wireless systems that permit more than one entry/exit door? Currently back and front doors are entry/exit and I would like to replace the ancient wired system with a wireless system with this feature.
Many thanks
Richard
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<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html> Thanks Fred, <p>fred wrote:<blockquote TYPE=CITE>&nbsp; <br>No problem, just parallel up the power, but the alarm contacts needto be <br>wired in series.</blockquote>I knew that there would be a catch.&nbsp; If I'd bothered to think before applying digit to keyboard I <i>hope</i> that I would have worked that one out! <p>Actually thinking slightly more (as opposed to not at all!), I can achievethe series connection in the control box - duh!&nbsp; I think I'll go and have a lie down in a dark room! <p>The bizzare thing is that the detector that I will parallel is in aroom whose window faces the main road and is very visible, whereas the other room has a rear garden window that can be reached with ease.&nbsp;&nbsp; And this is a professionally (?) installed alarm system <blockquote TYPE=CITE>This cos they are normally closed and break on an alarm <br>condition. If you parallel them you will only get an alarm when BOTH <br>detectors are triggered. <p>If you use the tamper contacts they need to be series connected too.<br>&nbsp;</blockquote> No tamper contacts present - the system is only just young enough to use electrickery rather than caged Geese! <br>&nbsp; <blockquote TYPE=CITE>-- <br>fred</blockquote>
<p><br>On a slightly different tack; do you know of any DIY wireless systemsthat permit more than one entry/exit door?&nbsp; Currently back and front doors are entry/exit and I would like to replace the ancient wired system with a wireless system with this feature. <p>Many thanks<br>&nbsp; <p>Richard <br>&nbsp;</html>
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You can achieve a series connection within the space behind the first PIR - but you'll have to make the connection as there probably won't be a spare terminal to do so. But twisting and taping is fine if done correctly.
--
*Why is 'abbreviation' such a long word?

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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Dave Plowman wrote:

Hi Dave,
I suspect that the 'twist and taping' solution will be easier in the control box as the PIRs will be at opposite ends of the house.
Cheers Richard
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Its just the norm now that if you are wiring in series its just to save time running it back to the main panel. How many zones has this panel got? You can get an 8 zone C&K 800L for 50 - An hour to change over the panel - much cheaper than a wireless system.
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SantaUK
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Right. I've got a mixture with mine, although if every sensor can be wired direct to the panel and all connections made there it makes fault finding a bit easier.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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I can't speak for all systems, but this works just fine on mine.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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to go in series, so that the normally-closed detection loop is broken open by triggering *either* of the PIRs. The 12V supply to the PIRs needs to be wired in parallel, while the contacts, and tamper loop if you're using it, go in series.
(This is for a "normal" cheapie home-install panel; for slightly more exotic stuff like the "Galaxy" panels widely used for small commercial and higher-end domestic setups, you need a fresh zone for each detector (though there are zone-splitters and zone expanders available), as these work on a change between two resistance values to signal triggering, rather than a simple open-circuit vs. closed-circuit; the detectors get fitted with "end-of-line" resistors (sold at a ridiculous price) to turn them from open/closed circuit to different-resistance (typically 1k vs 2k ohms, if I remember aright). I presume the idea is to increase the difficulty of bypassing a sensor - shorting the wires to the contact will cause a resistance change and trigger the alarm/tamper, whereas for a simple closed-circuit system your Italian Job alarm-bypassers will lift the jewels undetected ;-)
No doubt Big will Wallop me if I've got this badly wrong...
Stefek
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Not quite correct - but won't split hairs over it. You can have up to ten detectors on one zone in a Galaxy. Each with its own 1k resistor is the best way to go.

Do I get a prize for betting him?
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M Millar
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With the use of zone nodes on the Galaxy panel, you can have up to thirty detectors on the one zone terminal connections in the panel, using the method you describe.
But if Richard S, is taking two detectors off one zone, but the detectors are at opposite ends of the house, then you need to make note of which zone has been doubled, mainly for your own convenience if a repair is needed in the future.
Connections would be:
Red and Black to the normal power out take.
One wire of the alarm loop on one detector is connected to one wire of the alarm loop on another detector. Then the two wires you have left go across the alarm connections in the panel.
The same way with the tamper loop.
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Thanks to All.
I've just found a booklet that claims to relate to the alarm. It's labelled Scantronic 9449, but the actual number pad says 9427. It was installed in 1987 So your guess is as good as mine as to the number of zones etc. But it is of some considerable antiquity - I would not consider upgrading simply because of the appallingly bad wiring - wires trapped over carpet grippers and draped over CH pipework.
The proposed new PIR location is nearer the control box than the zone that will be paralleled and it will be only the second upstairs detector, thus easy to identify.
One further question: is it complex to replace the current 'ring until someone knocks it off the wall' bell with a 20 minute siren and strobe?
Cheers Richard
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The 9449 panel has the bell timer feature built in. The 9449 is still one of the best control panels you can buy and has a lot features to make dfferent types of install easy. If it was fitted and zoned off properly, it would last for hundreds (slight exageration), so take care of it and don't let anyone else touch it unless they know exactly what they're doing.
If you need an engineers manual, then gives a shout.
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BigWallop wrote:

Oh yes please.
What details/funds etc do you require from me? Off list perhaps?.
Thanks
Richard
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scanned as pdf files, there is a listing for Scantronic under "Cooper Security-Menvier - Scantronic" at: http://www.thesecurityinstaller.co.uk/manuals.shtml but I can't open the directory, perhaps he wants to restrict casual access perhaps an email: http://www.thesecurityinstaller.co.uk /
--
fred

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Just to check Richard. Is the e-mail address you use here a genuine one ?
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Hi Richard,
Did both literature sets get to you OK ?
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The terminals which correspond to the reed relay (or switch etc) CAN be paralleled. The supply terminals can also be paralleled, BUT - the 24 hour loop (if you have one) should be daisychained (serial). HTH
Paul
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I think you will find the alarm contacts will also have to be wired in SERIES
All alarm systems I have seen work with a normally closed circuit, therefore if this is true of the OP, then they will have to wire both the tamper and the alarm circuits in series, only the power should be in paralell.
Sparks...
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You are, of course, correct. I was assuming NO contacts, which would need to be wired in parallel. NC contacts should be wired in series.
Paul
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