Outsight light PIR effected by moths

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Guys, as an additional deterrent to my alarm system I've got a 500w security light with inbuilt PIR looking directly at a very small area a step away from a pair of patio doors being the most likely danger point on the premises. It's also where one of the CCTV cameras is looking at. The light also triggers a loud fire alarm bell running off the light and normally it is very effective and has very few false triggers.

Suddenly it is being triggered several times each night which I think is due to moths. We are very remote here so no neighbour problems but it is less than satisfactory! Can anyone suggest a economical solution please?

Many thanks

Richard
 
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If it's moths being attracted to the area where the light is fitted why not fit a remote pir away from the lamp? Worth checking it is not a spider or other insect inside the unit.
To the pir that close a spider looks like an elephant flying around your house!
I had that problem with my hall pir, spider that is, an elephant would not have fitted through the door ;)
 
If it's moths being attracted to the area where the light is fitted why not fit a remote pir away from the lamp? Worth checking it is not a spider or other insect inside the unit.

Thanks for responding. You may be right in that of course the light will attract moths but only when lit, and it only comes on if something sets it off. Then you have a situation where there are moths flying around and after resetting it's little wonder that the whole thing then repeats itself. Given that would it help putting in an independent PIR do you think?

I wondered if there was any way to make the PIR less sensitive. There is not a sensitivity control available on the unit (supplied by Screwfix). Any ideas very much welcome!

Cheers

Richard
 
You could try masking some of the fresnel lenses ('fingerprints') with something opaque to infra-red (not ordinary tape!). Have you considered that the false activation might be down to larger mammals like cats, dogs, hedgehogs, foxes, badgers...? I guess that the CCTV would show you! It might not be worth having the fire bell connected.
 
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You could try masking some of the fresnel lenses ('fingerprints') with something opaque to infra-red (not ordinary tape!). Have you considered that the false activation might be down to larger mammals like cats, dogs, hedgehogs, foxes, badgers...? I guess that the CCTV would show you! It might not be worth having the fire bell connected.

Thanks for your reply. I've checked the CCTV and nothing is showing up like that and any of the above certainly would. Even if the bell were disconnected I do not want the light activating frequently, and I feel that if it is a potential intruder a bell may help to put off an attempt at a break-in. The surprise element should help in that and get them to look straight at one of the two cameras trained on the area.

Can you explain your thinking on the infra red filter please.

Cheers

Richard
 
Regarding the remote pir, if it was placed say 5 or 6 metres away but covering the area you wish to monitor, it might be out of the line of flight of the moths or vampire bats triggering it. Remember vampires do not have reflections so may not show up on CCTV either ;) Perhaps a few cloves of garlic might help :D
 
Regarding the remote pir, if it was placed say 5 or 6 metres away but covering the area you wish to monitor, it might be out of the line of flight of the moths or vampire bats triggering it. Remember vampires do not have reflections so may not show up on CCTV either ;) Perhaps a few cloves of garlic might help :D

Thanks for that. I might first try some fine steel mesh as a cage for the PIR to look through in the hope that it may keep the little blighters sufficiently far away to not be such an issue. This must be an issue for many who have security lighting triggered by some sort of PIR surely?

Cheers

Richard
 
I've been thinking about the moth problem today and wonder if the following has legs.

Has anyone here tried using a decoy light to attract moths away from a critical PIR. A 3w LED light would surely be sufficient to do the job?

Cheers

Richard
 
How about a second pir some few metres away, covering the same area, wired in series with the one fitted to the lamp ? Both would have to close the circuit for the light and bell to operate, offering greater stability. The moths would hopefully stay around the detector at the lamp unit and leave the other unaffected.
 
How about a second pir some few metres away, covering the same area, wired in series with the one fitted to the lamp ? Both would have to close the circuit for the light and bell to operate, offering greater stability. The moths would hopefully stay around the detector at the lamp unit and leave the other unaffected.

Thanks for your suggestion. Sounds good to me, what do others with more knowledge than me think?

Cheers

Richard
 
Most people don't use the cheapo PIRs found on security lights as perimeter detection on intruder alarms or CCTV! There are much better (and more expensive) devices for these applications. If we were quoting for the job, we'd use one of these to trigger the camera and fire a relay for the light. The Redwall detectors are pukka gear and I think that Optex make a cheaper unit (but I can't remember the model - sorry).

PIRs work by focussing heat/infra red onto a pyroelectric sensor. This is usually done by a number of lenses in the translucent plasic "window" on the front. The IR is focused from a series of "looking-lines" or "beams" and, as a warm thing moves across one of these, it makes a flash on the sensor and an electrical pulse. The electronics then counts these pulses and triggers the alarm/relay/light/cat scarer... The degree of intellegence and signal processing that goes on inside will define the quality and price of the unit. Good PIRs will be better at rejecting false alarms and will have a degree of sensitivity adjustment (like choosing the pulse count).

You may be able to do something with your 'security' light PIR by masking/covering some of the lenses to reduce the number of looking-lines/beams and reduce the sensitivity.

As for the decoy light - if you really think it's moths - I think that they are more attracted to UV light than visible light. But I do alarms, not biology! ;)

The second PIR in series sounds like a good plan... You'll need to make sure that it has voltage free (clean) contacts if you're going to wire it in series. Most lighting pirs just have a single switched live connection. You may need to add a relay.
 
Many thanks for the comprehensive and useful post. I will follow up on your suggestions. At present the PIR that controls the security light and triggers the fire alarm bell has its sensor constricted to a very well defined and very small area. Obviously something is setting it off rather easily on some nights and as the two cameras looking at this small area do not see cats, bats or anything so I'm assuming it is moths. Last night no false triggers...obviously not a good moth night...for moths that is<G>

Cheers

Richard
 
Most people don't use the cheapo PIRs found on security lights as perimeter detection on intruder alarms or CCTV! There are much better (and more expensive) devices for these applications. If we were quoting for the job, we'd use one of these to trigger the camera and fire a relay for the light. The Redwall detectors are pukka gear and I think that Optex make a cheaper unit (but I can't remember the model - sorry).

Yikes, I've just seen the price of these units! I only want to turn on a light, bell and now the VoiceOff and whilst I am quite prepared to pay more than a bog standard cheepo PIR, surely there must be something half decent at a less eye watering price? Hope springs and all that!

Cheers

Richard
 
I did warn you... ;)

Check for spiders on the PIR. I use a spider deterrent ("No More Spiders")...

I think that jonm01's suggestion of a second lighting PIR mounted a few metres away (at 90 degrees?) and wired in series (with a relay?) should sort you out.
 
I did warn you... ;)

Check for spiders on the PIR. I use a spider deterrent ("No More Spiders")...

I think that jonm01's suggestion of a second lighting PIR mounted a few metres away (at 90 degrees?) and wired in series (with a relay?) should sort you out.

Thanks. Sounds like a sensible precaution. I was aware that they could cause problems with the cameras but not the PIRs.

Cheers

Richard
 

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