Looking to build a simple circuit that will fire a relay if an insect gets
across the input terminals. I'm thinking a simple Op Amp Comparator would
work.. The end result is to release the shutter on a 35mm canera. Need to
keep the camera from taking to many pictures so a delay between shutter
releases would be a plus...

Ideas or suggestions?


Pat Ziegler
Wholesale Electronics Inc.

In article , Pat Ziegler wrote:
Looking to build a simple circuit that will fire a relay if an insect gets
across the input terminals. I'm thinking a simple Op Amp Comparator would
work.. The end result is to release the shutter on a 35mm canera. Need to
keep the camera from taking to many pictures so a delay between shutter
releases would be a plus...

You're asking a lot. Insect exoskelatons don't conduct real well, and if you
up the voltage I doubt the insect would respond well.

You may have to go with some form of optical motion detector.
(PIR is no good insects are cold blooded,
"Radar" (microwave) is no good insects are too small)

Something with two sensors near the centre of the image
(attached somehow to the viewfinder?) that compares their
output and triggers on sudden changes might be the go.

otoh a sensitive pressure pad could possibly be built using aluminium foil,
it'd miss small ants, but medium sized cockroaches would probably set it off.
if you use gold leaf instead it could be made more sensitive.

Bye.
Jasen

On Sat, 30 Jul 2005 12:04:32 +1200, Jasen Betts
wrote:



You may have to go with some form of optical motion detector.
(PIR is no good insects are cold blooded,

---
PIR _is_ optical, and could work if a focussed, or tightly
collimated IR beam were played upon the IR detectors and interrupted
by the insect, since what a PIR detects is a _difference_ in
temperature.

--
John Fields
Professional Circuit Designer