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Native Californian, biologist, wildlife conservation consultant, retired Smithsonian scientist, father of two daughters, grandfather of 4 small primates. INTJ. Believes nature is infinitely more interesting than shopping malls. Born 100 years too late.

Monday, January 19, 2009

On aquariums and PIR sensors

Will a PIR sensor respond to infrared energy underwater?

I attempted to answer this question today by holding a camera trap against an aquarium, and submerging my arm into the water.

The water was room temperature, considerably less than a codger's body temperature.

The sensor light did NOT respond to my submerged moving arm.

This tells me that a submersible camera trap will have to rely on a trigger based on something other than infrared detection.

The only aquatic mammals we have out here are beavers, muskrats, the water vole, two species of water shrews, otter and mink. There are a pile of diving ducks, waders, and the water ouzel.

I am assuming that even with well insulated coats and plumages, all of these warm-blooded creatures would still give off infrared energy.

If only there were a controller board that allowed alternative trigger mechanisms -- like photoelectric beams.

It looks like I won't be making a cheap submersible camera trap very soon.

But I'm not ready to give up the idea.


Anonymous said...

Is that a set of digital drums in the background there?

Camera Trap Codger said...

Indeed it is. Every camera trapper should have a set.

Ike said...

It seems likely that the colder water would absorb the body heat first, dispersing any infrared signal that would normally set it off.

If you can find another way to make it work, a submersible camera trap sounds like a very cool idea!

Camera Trap Codger said...

Thanks, Ike. I knew there was a simple answer -- just couldn't think it out myself. I think a photoelectric beam would be workable, but all controller boards currently on the market are wired for PIR sensor only. So the controller board is the next obstacle.

Amazingly Average said...

I'm not sure that your test is definitive. Isn't it possible that the aquarium wall interrupted the signal?