The internal PIR sensor on my garage alarm was being constantly triggered by spiders, so I've had to put several layers of duct tape over the "lens" to keep it quiet.

Now I've discovered that spiders are cold-bloodied creatures, so I'm confused how this can happen....

Male, 69, no banana for scale...

 

The general infra-red emission from the garage is being interrupted by the spider, generating a change signal.

 

The spider may be colder than the background it is walking in front of (such as a warm wall), which generates a movement signal in the PIR sensor.

 

The internal PIR sensor on my garage alarm was being constantly triggered by spiders, so I've had to put several layers of duct tape over the "lens" to keep it quiet.

Now I've discovered that spiders are cold-bloodied creatures, so I'm confused how this can happen....

Male, 69, no banana for scale...

They love sensors, don't they.

I've sprayed lavender and peppermint oils on the mounts and backside of cameras and various sensors to keep the bugs away. With limited success.

 

hi daba,
Spider webs glow like fluorescent tubes when the camera IR illuminates them at night, which cause false alarms, especially when there are windy conditions
The only method I have found that works is to brush them off, I have tried various grease compounds, insect repellents to no avail.
E

 

Wow, thanks for the replies guys, I'd sort of forgotten I'd asked this question... My additional thoughts and responses ....

ericgibbs : it's supposed to be a passive IR sensor, not a camera with IR illumination, in that respect I don't believe the sensor radiates IR.

crutschow : there's no heating in the garage where the sensor is installed. Spiders would be the same temperature as the surroundings.

boostbuck : "The general infra-red emission from the garage...." ? What is generating that ? Wish I could harness it and use it to keep me warm when working in it. Any way, there's no car in the garage to radiate any heat, it's more of a workshop that a garage, the only car that would fit it there would be toy car.

Any way, interesting to note that after the "garage" was built in 2014, I put a PIC driven LED above the door, as an added deterrent to wannabe burglars. I worked on the principle that if it's something they don't know about, they'll likely leave alone. The LED gives 3 rapid flashes, every 2 seconds, and I've just calculated out that it has flashed over 473 million times !! Not bad going ...

 

Passive PIR looks at IR background (as the reference to) changes. A very close (that make it relatively large) 'cold' object of a different thermal density (bug to air, etc..) will change the IR background level the same way a 'hot' large distant object will.
Sensors are warmer (electronics generates heat from losses) than the background, that attracts bugs in cold weather so measures to keep bugs away help.

Adjust the sensitivity to detect only the desired targets and use PIR outdoor detectors with bug shields to push the bugs away from the internal sensor so their background changes are below the needed trigger limit.

 

ericgibbs : it's supposed to be a passive IR sensor, not a camera with IR illumination, in that respect I don't believe the sensor radiates IR.

hi daba,
You can use your mobile phone camera to detect IR.
Any IR radiation will show as bright dots/spots on your phone display, just shield the phone camera from any ambient light and hold it in front of the Sensor.

The non IR camera's I have used were never triggered by creepy-crawly insects.

E

 

The general infra-red emission from the garage...." ? What is generating that ?

All objects above absolute zero radiate IR, and the hotter the object is the more IR it radiates, along with the peak wavelength of the IR becoming shorter.
At room temperature (300K) the peak occurs at around 10 micron wavelength, so the IR motion sensor are sensitive to that wavelength.
That is different than a typical LED IR, whose wavelength is close to 1 micron.
Wavelength and relative amplitude vs. temperature shown below:

 

When I had false alarm problems in my shop, I placed two sensors in parallel that solved most of them, then as the dual sensor modules became available, I switched over to them.

Dual sensor=passive IR and microwave.