Regarding lamp dimming by including only selected full half-cycles, I believe you'll get a lot of flicker on the lamp. This is especially the case if you want a large number of levels. Our Shoebox dimmer (http://www.dovesystems.com) maps the 256 levels of DMX to 33,333 possible turn-on times in each half cycle. If you want ten lamp levels (and don't care about relative lamp intensity or DC component), you could select to send 1 to 10 half-cycles every 83mS, resulting in a flicker rate of only 12 Hz. This would be quite visible. Harold On Fri, 16 Jan 1998 16:13:55 -0500 "Montaigne, Mike" writes: >Tks Andy, I printed that out. >Question: >Simple light dimmers are C/R time from '0' crossover to trigger triac. >Theater (analog) dimmers are 0-10V control & 0-10V ramp into >comparator >to time from '0' xover. >Even if controlled by DMX or other serial link, still electronically >noisy because of A.C turn-on. >Why not (using micro) always start on '0' crossover and leave out 1/2 >cycles. >The more 1/2 cycles you leave out (alternate odd and even so load is >balanced), the dimmer the light. >Would this work? I've never seen it, but I may be re-inventing the >wheel again. >Comments? >Mike > >>---------- >>From: Andrew Warren[SMTP:fastfwd@IX.NETCOM.COM] >>Sent: Wednesday, January 14, 1998 5:45 AM >>To: PICLIST@MITVMA.MIT.EDU >>Subject: Re: Mains lighting control >> >>Montaigne, Mike wrote: >> >>> I am involved with our church's annual Singing Xmas Tree, where we >>> have an choir put on a concert in a 6 level tree shaped pyramid. >>> We use Xmas tree lights in 4 colors and some special channels as >>> well, all on dimmers. .... we now want to remote the control pots >>> and I now need dc control rather than R/C time constant control as >>> we want to run the controls ~200 ft away from the triacs/power >>> boards. .... it seems to me, I could run RS422 signals as well on >>> two wires. Rather than re-inventing the wheel (fun but takes >>> time), can any of you help me. Surely this has been done many times >>> before - theater lighting etc. >> >>Mike: >> >>Yes, it's been done before; take a look at the DMX512 mini-FAQ at: >> >> http://waapa.cowan.edu.au/lx/dmx-faq.htm >> >>-Andy >> >>=== Andrew Warren - fastfwd@ix.netcom.com >>=== Fast Forward Engineering - Vista, California >>=== http://www.geocities.com/SiliconValley/2499 >> >