I built a circuit for this purpose many years ago and it is probably superseded
in terms of capability by new designs put together by people who "really" know
how to design such circuits! Mine is based on the use of 2 555 timer ICs or the
556 dual timer. It can close a switch (and thus operate a flash or a camera if you
devise a suitable interface for the camera) in response to a light turning on (so
acts as as a slave trigger), by the breaking of a light beam (so it is a dark trigger)
or sound. It also has the capability of introducing variable delay and it can be
made to trigger itself and work as an intervalometer.
The circuit was applied to photographing insects in flight by making the dark activated
condition react when two intersecting laser beams were broken simultaneously so in the
"X" detection mode. Breaking just one beam would not diminish the light sufficiently
on the light sensor for it to trigger the sync circuit. I've also used it with
barn swallows which were a lot easier to photograph than tiny insects - well, wasps.
You can read more about this here:
http://people.rit.edu/andpph/text-cross-beam.html
and
http://people.rit.edu/andpph/text-flying-bird.html
There are companies who sell commercial versions of such devices. One was just mentioned
in Popular Photography this month.
andy
rush rouge wrote:
* a two / three beam pulsed infrared camera trigger - so say when the fly
is precisely *here* in the frame (and 2 beams are broken) the camera goes
off or, when something cat height walks through this precise spot the
camera fires, but not if something dog height walks through. (I really
should use this thing more too!)
hmmn , this should be a very useful DIY for me... Is there a possiblity of
having more info on this one ???
Regards
Rush
