Any ideas on how to accomplish this?

[sayzer]

Sayzer,
What is the correct distance between the two laser beams?

I did not know about deer group work!

Since Bart said that they appear standing all together, placing the laser beams at a height low enough somewhere around the tires of vehicle and also around the legs of the deer could be ok. Bart can find the correct height with respect to the ground. And if there is a group work going on, Bart’s code may also detect it! :-)

Also, considering an average vehicle speed and putting a second set of lasers somewhere after the first set (say 20 meters), can provide much much safer detect. Costs $10 extra!

- May use small pieces of mirrors and can control the entire circuit from home. No battery is needed! Remember, the range of cheap (US$2.0) laser pointers is over one mile and if you get a good quality one you get about 10miles.

Also, here is my version of social warning (modified from Melanie's)

<a href="http://img10.picsplace.to/11/warning2.JPG"><img src="http://img10.picsplace.to/11/thumbs/warning2.JPG" alt="Image Hosting by PicsPlace.to" ></a>

[Archilochus]

Don't know if this is what Melanie was referring to with the pressure sensitive cable... but I just remembered something from back when I used to live in an area with 'full-service' gas stations... They had a hose run across the pump area, and when a car ran over the hose the change in air pressure [I think] in the hose triggered a sensor with a bell in the service bay.

Seems like even if a deer did step on the hose, it might not displace enough air to cause a trigger.

Of course it would only work on a hard, fairly smooth surface.
Also would be hard to hide from the trespassers, who will be likely to destroy any sensors they find.

Arch

[Acetronics2]

Seems our friend Sayzer has re-invented the wheel ....

http://www3.telus.net/chemelec/Proje...aser-Alarm.htm

.... no comment, I bought some 2N5777 about 35 Years ago... and they are always here !!!

Alain

[sayzer]

Any progress out there?

[ronsimpson]

You want to cense cars and not animals.
1.)Place a rubber hose across the road. Plug the far end. Close end has a pressure censor. The hose should not be airtight, it needs a small hole [leak]. When a car drives over the hose, the air pressure changes.
2.) I have a commercial device. There is a “coil” in a PVC tube buried under the road. The coil oscillates. The frequency is not stable, it slowly drifts over time. When a car passes over the coil the frequency changes fast. It is built on a ‘metal detector’ idea.
3.) I now am playing with flux-gates for another projects. It appears I can detect large metal objects 20 feet away. Too complex but fun.

I can supply details if you need it.

[Archangel]

Love those bureaucratic words, Traffis lights around town use a large coil of wire under the street to sense the metal vehicles presence. I believe a smaller coil is there too as the tank coil of an oscillator. I remember seeing metal detector circuits over the years that used 2 coils, and you would null out the circuit, when metal appeared it would throw the circuit out of Null and it would oscillate. I believe the coils were supposed to be at right angles to each other.

Another suggestion: Radio Shack sells a cheap / toy metal detector, it might be the basis of what you need.

Last Idea, bury a sheet metal plate,or install overhead or on side, and hook to a darlington transistor switch circuit. the vehicle might induce enough stray capacitance to trigger switch.
Cheap enough to experiment, anyway.

edit : Doe! sorry Ron, I didn't see your mention of metal detector.

Melanie: I like it!
JS
http://www.ssec.honeywell.com/magnet...eets/an218.pdf
http://home.clara.net/saxons/bfo.htm
http://www3.telus.net/chemelec/Projects/Metal/Metal.htm
http://home.skif.net/~yukol/MetalE.htm
http://electronics.howstuffworks.com...-detector3.htm
http://www.absoluteautomation.com/dr...rms/index.html