hobbit@pyrite.rutgers.edu (*Hobbit*) (02/14/90)
Thoughts on Brian Hurley's rehacked LDV-1000... My parallel to this a couple of years ago was to take a pair of galvos I'd bought from some local for entirely too much and create a fancy waveform generator for it. This takes the shape of an old modem box [back when high-speed modems were in *big* aluminum cases] with some boards mounted inside, its original power supply, and eight joysticks on the top. The sticks control a bunch of XR2206-based VCO chips that mix and modulate together in various ways, and the result goes to a little driver amp for X and Y. I was really disappointed after getting it all together, because I couldn't make it do anything neat. But then I learned how to "play" it. Later additions consist of a BBD delay line between channels, with which one can create very nice radial rosette patterns, and some channel cross- modulation things, and "fine tune" ten-turn pots for the frequencies. [The original joysticks alone turned out to be way to squirrelly.] It works quite well, is reasonably versatile even within the limited bandwidth that the heavy and slow galvos can provide, and you can save images out on to audio tape. Future plans include a multiplier-based rotator, perhaps some phase-locking techniques for the oscillators, and an FM-modulated audio output so I can save images with very slow DC offsets. Tape decks wimp out anywhere below about 30 Hz. I have given the digital realm some vague amount of thought, but so far this is *completely* analog and I'm somewhat proud of this. If I come up with a pair of D/A's for a computer, I can always just pipe the voltages in through the audio inputs anyway. I think I also have something similar to the galvo pair in the LDV-1000, although it may have come out of something else. HeNe coated mirrors mounted on little flexible rubber things, with attached magnets and a surrounding coil to move them -- sound familiar? They can only go about 60Hz with a fairly limited sweep and I'll bet the linearity sucks, but they were probably fine for tracking laser disks. I haven't tried to integrate these into any other equipment yet, especially since their coatings are optimized for red and I want broadband... Apparently LDV-1000s are hitting the surplus market in a big way these days. Did Pioneer just dump their entire back stock of the things, or what? _H*