OT infrared animal detection
2003-01-18 by Ron Amundson
I noticed a post in the archives concerning the design of a infrared animal detector. Someone had posted something about IR photodiodes. When one needs to measure infrared radiation of objects close to ambient temperature, the spectral response of economical semiconductor detectors really kills the S/N ration. To detect animals you really need a long wave sensor, and the photodiode style units can run a few hundred dollars. A pyroelectirc detector for a dollar or two will work if you can chop the IR signal, which is difficult to do in a handheld unit. Another possibility is the thin film thermopile detector. They tend to be more expensive $20-$100 in low quantities, all you need is an op amp and a comparator to trigger an LED if an animal is within the field of view. In volume they are pretty cheap as well as surplus when you can find them.