Re: [linux-audio-user] Linux Lighting

Hello, On Sun, Nov 27, 2005 at 11:51:37PM +0100, Olivier Guilyardi wrote: DMX512 is just a serial protocol, where a vector of 512 8-bit values is send periodically over the wire (this 512 block is AKA universe). At the sender side you'll need a PC interface (an old ISA card would probably be the cheapest ;) and at the receiver side you'll need your light source (dimmer pack or scanner or ...). The 400 EUR limit seems to be a problem. Either you are really lucky and get a used set of lamps, dimmer packs, cables, ... or you'll have to do some not-so-simple hardware/programming stuff on your own. An important influence on the money you have to spent has the power consumption of the light sources: e.g. if you want 16 PAR64 with 1kW each you'll spent much more than if you used PAR56/300W. The DMX approach is IMO the more professional way, you can extend your equipment easily, you can rent or borrow some special equipment for an event. You can connect your computer to any professional light installation and you have less worries about the audience's security. If I had a project like yours and able to get all of the above for 600 EUR, if would definitely take it. On the other hand, if you really want to spent a lot of time with soldering, hacking and (kernel) programming, you might use the following approach for the electronics (no, I don't have schematics). This is probably more fun but you won't be able to connect any light device to it that ist more 'intelligent' than a simple light bulb. AFAICT this is the cheapest approach if you look at the bill of material only: - Try to get or build cheap (but sufficient) single dimmers (at least consisting of an opto-coupler, a TRIAC, a damper coil and some additional parts), semiconductor relais (without zero point detection) with some damper circuitry might do it as well. - You need 16 on/off (TTL, ...) outputs on your computer (printer port) and connect them to the LEDs of the opto couplers (with Rs please). - You need 1-3 on/off inputs (on for each AC phase you intend to use), best would be, if the inputs are able to raise interrupts. Connect them to a zero point detector or a schmidt-trigger unit that switches around 0V of each used phase. Don't forget the opto coupler. - Write an RTAI-Linux realtime task that is trigerred every time the corresponding AC phase is zero (or changes from + to - or vice versa, depends on your HW), wait between 0ms (100%) and <10ms (~0%) before you switch on the output opto coupler for a short time and fire the TRIAC (all times for 50Hz). This is not trivial, especially if there are inductive loads around and/or the AC frequency is not constant. If you switch off the output to late (>=10ms), you get 100% instead of 0%. The blinkenlight guys had done something like that for the arcade project in Paris some years ago and it worked: http://www.blinkenlights.de/arcade/backstage.en.html Jacob