Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!cwjcc!gatech!rutgers!topaz.rutgers.edu!hobbit From: hobbit@topaz.rutgers.edu ($ *Hobbit*) Newsgroups: sci.electronics Subject: deflection systems Message-ID:Date: 6 Dec 88 11:33:56 GMT References: <1372@cseg.uucp> Organization: LCS Expert gang, Rutgers Lines: 26 Well, by "light show" you apparently mean oscillators-talking-to-some-kind- of-deflection-system. This is really only part of a decent full-blow show.. anyway, the canonical [albeit expensive] route is to find General Scanning galvanometers and drive them with some kind of amplifier. I don't know about the commercial unit you mentioned [if you have more info on it, could you send it along? The price seemed awfully low] but I do know about the "Laser F/X" thing being marketed by your local yuppie stores -- it isn't a laser, they're using *one* bouncing mirror for deflection, and you could throw one together for about $5. Don't buy it. Anyway, speaker-based kludges will work but will never give you the linearity and repeatibility that real galvos will. An alternative is small stepper motors, 90-degree if you can get 'em, with a holding voltage on one coil and your signal going to the other. [You also might want some form of mechanical restraint so it doesn't "wrap around" on strong pulses.] Check for loose bearings... Professional shows use multiple x-y pairs of GS's better positional-feedback galvos -- they're not only fast as hell, they provide exact feedback about where they are, and you can build your driver accordingly. They also cost something like $700 per. Since GS is apparently still the only company making these things [someone please correct me if I'm wrong] they can get away with this pricing scheme. I've always been generally irked at the prices these manufacturers are getting for laser equipment. They *can't* cost that much to build... _H*