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PIR lights

:: EPE Chat Zone ≠:: ≠Radio Bygones Message Board :: » EPE Forum Archives 2010 - » Archive through 04 September, 2011 » PIR lights « Previous Next »

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echase
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Username: echase

Post Number: 504
Registered: 07-2007

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Posted on Wednesday, 03 August, 2011 - 06:17 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Do PIRs work through a glass window? Double glazed I think. I have a feeling that it is not very well, as on my house the PIR alarm sensor in our conservatory does not seem to react to people walking outside even though they are sort of in the beam.

The lead thieves keep coming back to try to steal the bit of church lead roof we replaced after the last theft. Personally Iíd just connect the sheet to the live mains or a powerful electric fence device and let them fry, but I have been overruled. Instead someone has suggested that we put a 500W PIR controlled security light up there to blind them/frighten them when they climb up at night. There is a window nearby and the easiest thing is just to shine it through the window. Only 2m from light to thief. It wonít be triggered from movement at ground level as the roof shields the PIR from there.

Might also wire a loud bell across the PIR.

A while back thieves raided many garages in our street. Although they opened our garage door they fled as I had one of these lights inside. It was there just to provide lighting that came on automatically for my benefit. I had not considered the security aspect.
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alec_t
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Username: alec_t

Post Number: 713
Registered: 03-2009

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Posted on Wednesday, 03 August, 2011 - 06:32 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I share your doubts. Double-glazing is designed to be a heat barrier, so unless the PIR is exceptionally sensitive it will need to be external.
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ant
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Username: ant

Post Number: 813
Registered: 05-2006

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Posted on Wednesday, 03 August, 2011 - 06:36 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hello Edward,

No they don't; this is why a dual (radar and PIR) detector exists as radar will detect outside events. I think, not certain, that they can be set up to react to those outside events - certainly it could be done by sniffing at the indicator LED...

Bear in mind the possibility of the heat cracking the window!

There's also this "magic water" or something but it depends on the police managing to find it first!

Regards Ant

(Message edited by Ant on 03 August, 2011)
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arw
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Username: arw

Post Number: 1074
Registered: 04-2005

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Posted on Wednesday, 03 August, 2011 - 07:18 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Think you mean SmartWater -- highly effective and the warning signs alone will deter many thieves:
http://www.smartwater.com/Business/Products/Churches-and-Heritage.aspx

This wireless PIR system is designed for church roofs but costs £500 (a snip, considering). The PIRs can be camouflaged with special webbing tape:

http://www.alarmsforfarms.com/wireless-church-roof-alarm-121-p.asp
Alan Winstanley -- EPE Magazine Online Editor
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www.EPEmag.net - hobby electronics and more
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echase
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Username: echase

Post Number: 505
Registered: 07-2007

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Posted on Wednesday, 03 August, 2011 - 10:22 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Useful alarm idea.

We have a spare microwave sensor so could try it.

We think Smartwater is pretty useless as our insurer insists we use it, itís expensive and no scrapyard seems to check for it when the thief sells it to them. So it's no deterrence at all. Plus I guess that if the thief melts down the lead and sells it as ingots it destroys the Smartwater and melting lead is easy.
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echase
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Username: echase

Post Number: 507
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Posted on Thursday, 04 August, 2011 - 10:57 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Although, having said that, the last time they climbed up to both our's and the local school's rooves and they went away again without removing the lead (but causing lots of tile damage). Was that because they could see the Smartwater and thought better of removing the lead? I donít know if Smartwater is visible. They also bent back some mock lead we have and abandoned removing that, we assume after realising itís just galvanised steel.
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arw
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Post Number: 1075
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Posted on Thursday, 04 August, 2011 - 12:46 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Smartwater is invisible unless fluoresced by UV light. It's like DNA, and the tiniest traces of it on eg clothing or skin would be enough to link the culprit or anyone handling it with (stolen) property. I understand traces can last for weeks.

Police stations are already automatically scanning for it on arrested people. Even if scrapyards are ignoring the threat for now, they'll be contaminated with traces too as will anyone handling it. I can't think of anything better.
Alan Winstanley -- EPE Magazine Online Editor
Subscribe now at www.epemag.com!

www.EPEmag.net - hobby electronics and more

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