Path: utzoo!attcan!utgpu!watmath!watdragon!rose!ccplumb From: ccplumb@rose.waterloo.edu (Colin Plumb) Newsgroups: comp.sys.amiga.tech Subject: Re: Using Amiga to control theater lights (was: Re: Sick, sick idea...) Keywords: DMX512, lighting, MIDI Message-ID: <17271@watdragon.waterloo.edu> Date: 16 Oct 89 16:43:59 GMT References: <17243@watdragon.waterloo.edu> <4369@sugar.hackercorp.com> Sender: daemon@watdragon.waterloo.edu Reply-To: ccplumb@rose.waterloo.edu (Colin Plumb) Organization: U. of Waterloo, Ontario Lines: 33 In article <4369@sugar.hackercorp.com> karl@sugar.hackercorp.com (Karl Lehenbauer) writes: >How about using a MIDI lighting controller? There's this one by J. L. Cooper >that I think outputs the 0-5v standard. It has a bunch of faders and moving >them puts out a MIDI stream of continuous controller messages (I guess) which >you can record with a regular sequencer and play to the MIDI-in on the box, >controlling 16 channels or so per box, multiple boxes were supported. H'm... the discrete (one wire per dimmer) standard, which isn't used much any more, is 0-10v. A lot of people develped various multiplexed analogue and then digital standards, with Strand winning the analogue market-share wars and getting their standard formalised as AMX192 in 1986. This is 0-5v, but merging multiple streams is tricky so multiple controllers isn't a good solution. The one I was looking at is DMX512, which is also difficult to connect multiple controllers to, and I'm not sure if it's the same thing. 16 channels per box seems awfully limiting. 64 is, I'd think, a reasonable minimum. Also, a quick sanity check... when light levels are changing rapidly, you need at least 15-20 updates/sec. 20 updates/sec x 64 dimmers x 10 bits/update = 12,800 baud, within MIDI's range. But wait! How many bytes does it take over the MIDI port to change a light level? 2 is okay, 3 gives problems... (I hope there's a deeper FIFO in the 3000's serial port.) >It looked pretty neat when I checked into it a couple years ago. I don't >even know if J. L. Cooper is still in business, but if so this is one way >to get off the ground with no hardware development whasoever. A differential driver isn't a heck of a lot of work. There are sample schematics in the DMX512 standard. All you need is +5, -5, one chip and about 3 resistors. -- -Colin