Rylan, it occurs to me that we could simply use one LDR as a toggle switch. So fire laser and valve is on, fire laser at same ldr and valve is off. I can think of two solutions, one using a 555 timer and the other using a picaxe 08m. The 08m is cheap, about £2 sterling, but an advantage of using it as a toggle switch, is that it could also provide the scanner drive for the Peachy basic, with few additional components (maybe none). Plus you can change the behaviour of the circuit just by re-programming it (it is therefore more flexible). But I'll try to find time today, to put the circuits into my simulator and get them both working that way. If they work in the sim, they work in real life.