Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!udel!haven.umd.edu!umbc3.umbc.edu!gmuvax2!smasters From: smasters@gmuvax2.gmu.edu (Shawn Masters) Newsgroups: sci.electronics Subject: Re: Laser show controllers? Summary: Voice coils Message-ID: <1991Jun9.132425.1667@gmuvax2.gmu.edu> Date: 9 Jun 91 13:24:25 GMT References: <1991Jun9.051036.5366@athena.cs.uga.edu> Sender: smasters@cns01.gmu.edu Organization: George Mason University, Fairfax, Va. Lines: 23 The method of using a speaker to drive a mirror position has been refined into what is known as a voice coil. You mount a mirror on the end of the voice coil, so that when it's extended it has a different angle of reflection. This is used in many models of laser disk players to position the beam on the disc(in fact I got my first x y laser display unit from a friend that tore down a Dragons slayer(sp?) game). Another source is the stepper mechanisms out of some hard drives. The problems you find is that the coil vibrates, and there is a bit of jitter if it's making discrete motions(from point to point). You can get it to make really neat paterns when hooked up to sinusodial source on both x and y, but these tend to be fairly easy on the coils, unlike most animation by laser. The other problem is that I've never seen a voice coil fast enough to draw a diagram that the eye would catch whole. You can get them to do circles, but I think that would die on something more demanding like a square. Of course, what you mentioned about the speaker is great for home stereo systems and certain types of music:-). Shawn Masters smasters@cns01.gmu.edu