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.