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False alarm on boat

jenevers

By jenevers
in Boat Equipment

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Alan de Enfield Veteran II

Alan de Enfield

Posted
Posted (edited)
6 minutes ago, jenevers said:

Oh dear.

any way to reduce the PIR  sensitivity?

You can get 'double-knock' PIRs, that may be the simplest solution. 

(Double knock require the detector to be triggered twice before it goes into alarm),

 

Alternatively you can get 'pet-friendly PIRs that don't react to anything under (about) 80lbs

 

Alternatively get rid of the spider(s).

 

Found this by Googling :

 

PIR Detector False Alarms
PIR detectors can initiate false alarms due to several causes, the most common are as follows.

  • Spurious heat sources - PIRs detect alarm conditions by a change in the heat pattern 'seen' by the detector. Obviously, some heat sources seen by the detector may cause a false alarm. Common heat sources are central heating systems where the detector is fitted above a radiator or boiler or hot air duct. Note that PIRs pointing at a central heating radiator or boiler do not usually suffer from false alarms as the temperature rate-of-rise is low. Sunlight can also cause false alarms. PIR detectors should not be fitted in direct sunlight - this is actually rare in normal rooms as the detector is usually fitted above the top height of the window, but reflected sunlight (e.g. from glass tables, glass vases, mirrors) can cause false alarms. The event log can be useful in determining the cause of false alarms caused by heat sources. For example if the time of the false alarm coincides with the central heating system coming on or the sun being in a particular declination then this may give a clue as to the cause of the false alarm. Conservatories should never be fitted with a standard PIR for two reasons - firstly, the PIR will almost certainly produce a large amount of false alarms due to temperature fluctuations, and secondly, even if false alarms do not occur, the PIR is unlikely to detect an intruder as the ambient temperature approaches human body temperature. Dual Technology detectors should be fitted in conservatories.
  •  
  • Insects - Flying or crawling insects are often the cause of false alarms. Small insects crawling or flying in front of the external lens of a PIR do not normally cause an alarm condition but large moths may. More serious are insects inside the PIR - the actual size of the internal detection element is small and as such even a small ant crawling across it is almost certain to cause an alarm. It is thus important that when fitting PIR detectors to seal all holes in the casing to prevent insects entering. Also note that some PIRs are described as having 'sealed optics'. These PIRs have the detection element and the inside of the lens sealed from the rest of the unit.
Edited by Alan de Enfield
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jenevers Rising Star

jenevers

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Posted
30 minutes ago, Alan de Enfield said:

You can get 'double-knock' PIRs, that may be the simplest solution. 

(Double knock require the detector to be triggered twice before it goes into alarm),

 

Alternatively you can get 'pet-friendly PIRs that don't react to anything under (about) 80lbs

 

Alternatively get rid of the spider(s).

 

Found this by Googling :

 

PIR Detector False Alarms
PIR detectors can initiate false alarms due to several causes, the most common are as follows.

  • Spurious heat sources - PIRs detect alarm conditions by a change in the heat pattern 'seen' by the detector. Obviously, some heat sources seen by the detector may cause a false alarm. Common heat sources are central heating systems where the detector is fitted above a radiator or boiler or hot air duct. Note that PIRs pointing at a central heating radiator or boiler do not usually suffer from false alarms as the temperature rate-of-rise is low. Sunlight can also cause false alarms. PIR detectors should not be fitted in direct sunlight - this is actually rare in normal rooms as the detector is usually fitted above the top height of the window, but reflected sunlight (e.g. from glass tables, glass vases, mirrors) can cause false alarms. The event log can be useful in determining the cause of false alarms caused by heat sources. For example if the time of the false alarm coincides with the central heating system coming on or the sun being in a particular declination then this may give a clue as to the cause of the false alarm. Conservatories should never be fitted with a standard PIR for two reasons - firstly, the PIR will almost certainly produce a large amount of false alarms due to temperature fluctuations, and secondly, even if false alarms do not occur, the PIR is unlikely to detect an intruder as the ambient temperature approaches human body temperature. Dual Technology detectors should be fitted in conservatories.
  •  
  • Insects - Flying or crawling insects are often the cause of false alarms. Small insects crawling or flying in front of the external lens of a PIR do not normally cause an alarm condition but large moths may. More serious are insects inside the PIR - the actual size of the internal detection element is small and as such even a small ant crawling across it is almost certain to cause an alarm. It is thus important that when fitting PIR detectors to seal all holes in the casing to prevent insects entering. Also note that some PIRs are described as having 'sealed optics'. These PIRs have the detection element and the inside of the lens sealed from the rest of the unit.

Pity they  don’t automatically supply all PIR’s as  “double knock” in that case?

 

31 minutes ago, eightacre said:

I have known a PIR to be triggered by convection currents moving drapes etc. Are you sure it is not just a result of the sunshine warming the boat?

Not at 4 o’clock in the morning!?

 

I wonder if sticking a  thick transparent sheet of plastic over the lens might reduce sensitivity to spiders.

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Posted
Posted
5 hours ago, jenevers said:

Pity they  don’t automatically supply all PIR’s as  “double knock” in that case?

 

Effectively they do as far as i know.

 

The 'double knock' on our alarm at home is actually set at the alarm panel. So basically any PIR could be set to need a double knock to trigger the alarm.

 

We had to do it after getting repeated false alarms from a bay window after we changed from roller to Venetian blinds, no idea why but it stopped them.

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WotEver Veteran II

WotEverDonate to Canal World

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Posted
20 hours ago, dor said:

Smoke detectors can also give false alarms when spiders take up residence.  They can also moult and leave their skin behind which can also interfere.

What does a smoke detector skin look like...?

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