I first saw the laser harp during the Jean Michel-Jarre concert 'Rendezvous Houston' in 1985. Ever since then I've told myself that I would build a laser harp, and it would be *just* like the one I saw - it would open and close and be frameless (ie no sensors above the player).
For a long time I was convinced it was impossible, the sensors I used (CDS cells, and photodiodes) just weren't *sensitive* enough, giving at best a 12" range.
Then I made 2 errors in my detector circuit - I wired one Op-amp input to 5v not gnd, and forgot to connect the other op-amps input to anything. Then it started to work incredibly well - detecting pulses over a 20' range. (I still don't know 100% how it works)
I've been meaning to put together a website. I've had so many emails lately that I think I'll start tonight.
I need to make a better movie, I have opening and closing sound effects that *should* have been loaded into a sampler. The noises you hear when the beam opens/closes are not the right ones.
I'll shoot the movie tonight and start the web page.