> Is it possible to use a common PIR surveillance sensor to detect
> a warm->cold->warm temperature transition?

Think it might be. I tested some PIR circuits a few years ago and
found that cold outside air blowing through the open door into a
warm room was quite apparent on the 'scope and would have
triggered the following logic/micro. But as I wanted only a people
detector this was filtered out with a comparator
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist