Thanks for your comments. I will try to answer what I have done and have tried most of your comments.
I have a Intel Pentium Dual CPU; 1.80 GHz and 1 GB of RAM. I use Windows XP SP 2.
I try to capture at 3 fps.(The projector has a gear at the back that can change the speed- so the actual pull is from the back)
I could not find a "trimpot" at our closest electronic shop and replaced R2 with 100k; R1 as mentioned with 68 Ohm. If I remove R2 and connect the 2 wires, it does not trigger the switch, but with the 100k resistor it does.
I have set the double click speed to "slow" when Duffy suggested it.
Distance from an object: it only gets triggered approximately 1mm from the receiver. If I bring it close to the stationary blade, it triggers/captures. It does not trigger the switch even very close to the rotating blade.
It gets easily triggered by the silver carton less than a mm from the receiver. I capture every frame up to approximately 2000 frames, then it becomes erratic and will only capture say every 5th frame. (James stated the same problem- called it the mouse goes to sleep- he installed a switch between the mouse and the USB port )
My problem therefore is that it starts off well and then starts to capture erratically. (One can see with the mouse pointer how it clicks on the "capture" button.)
I just need to mention that the quality of the captured frames are excellent.
(As the shop is a distance from me, I decided to buy the interrupter at the same time, as the price was only app 4 USD.)
Thanks for your interest in my project and your comments
Regards
Albie
(I stayed in Melbourne from 1997-1999)