Hello,
On Sun, Nov 27, 2005 at 11:51:37PM +0100, Olivier Guilyardi wrote:
> I'm currently planning a live show using Jackbeat and modifying it for this
> purpose. This is about music of course, but I'm also interested by controlling
> lights, to warm the dancefloor up.
>
> The technology in this area seems to be named DMX, and there seem to be some
> Linux driver project called dmx4linux, by the Linux Lighting Group.
>
> I'm not sure that this DMX technology is the solution to my problem.
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
> Here's what I'd like to do :
> - control 16 light sources
> - control the luminosity level of each of these light sources (!= on/off)
> - do this is in C from Linux
> - for less than 400 ? (including light sources)
> - building simple diy hardware is ok
>
> Any idea ?
>
Jacob
Received on Mon Nov 28 04:15:12 2005
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