hi macwarior, nice to see someone liked my circuit. i designed it (with some help) so im sure that id be qualified to help u with it :lol: . In the projects section, i have posted an updated version that works very well, and some more info on it. its called laser or IR beam alarm system.
to make it really simple, id just use a relay. ive never used any relays before but i know wut they do, and i dont have a clue how to draw one on the schematic, but im sure someone else will help u with that. an emitter resistor might be required (i dont know diddly squat about relays and power consumption). i think a relay would be best suited for wut u want to do, but i dont fully understand wut u r looking to do. i dont know wut a cable release is, but are u just aiming to have the camera snap a pic if the beam is crosed or somethin?
As for the resistor that says 300k to 1M, you will have to play with that value to find the sensitivity that you want. also, you can use a voltage other than 9v, 3v would probably work fine also, but you would have to play with that resistor value. i only used 9 volts to make the buzzer loud enuf. the higher that resistance, the less sensitive, and vica versa.
I'm pretty sure that a PNP transistor is the only thing I'm looking for - they open the gate with low voltage (= dark photoresistor) on the base, right?
nope. a PNP transistor turns on wen there is a negative voltage @ the base. and an NPN turns on wen there is a positive voltage @ the base. they're just oposite of each other. and there HAS to be a power source.