richard Posted November 10, 2003 Share Posted November 10, 2003 I was talking to someone the other day who was saying that his central heatings control system 'piggy backs' the mains cable - ie the data runs along the same cables as the mains voltage (sine waves I expect - I don't understand) so I was wondering why we can't do that with DMX (or some kind of control voltage) Just think - you could have switch packs somewhere, with an add on that pipes in your data, the you just plug in your moving lights and address them and they pick up their data straight away, no more data cables or termination!! I think it would be nice! Link to comment Share on other sites More sharing options...
dominicgross Posted November 10, 2003 Share Posted November 10, 2003 That technology is being used in the 'X10' automation gear, it would have drawbacks for movers though, For example, all the fixtures would need to be on the same mains ring as the desk.And also, we complain about twiching heads with normal DMX, think about it with mains... Link to comment Share on other sites More sharing options...
Andrew C Posted November 10, 2003 Share Posted November 10, 2003 Data integrity shouldn't be such a problem, if implimented correctly. Two areas in the country are being trialed for WWW over mains. It's Scotland and Winchester, but no real evidence of a roll out here (Winchester) yet. But it is true that you'd have to be on the same phase, or devise some method of "connecting" to all three. Link to comment Share on other sites More sharing options...
richard Posted November 10, 2003 Author Share Posted November 10, 2003 As it is most moving lights on big shows are run from switch packs or similar (so that they can be turned off if they start playing up), this being so it shouldn't be too hard to add something to that. If www over mains works then in theory that technology could be used to pass ethernet type stuff down it and then the new lamps with the RJ45 connectors would be almost ready already! Link to comment Share on other sites More sharing options...
Brian Posted November 10, 2003 Share Posted November 10, 2003 devise some method of "connecting" to all threeFor X10 systems you can buy filters/bridges which allow the data to cross-over to a different phase. Link to comment Share on other sites More sharing options...
Guest lightnix Posted November 27, 2003 Share Posted November 27, 2003 Vari-lite Series 200 / 300 does exactly that (and solidly patented the idea to boot), mains and data are fed down the same cable. The data lines are shielded with some kind of foil wrapping which went down to earth. Problems arose when the shielding became damaged (which happened quite often in Series 200 lamp cables), allowing Mains / RF interference to corrupt the data. This wasn't usually a problem when playing shows back, but try to save to disk and... :blink: Link to comment Share on other sites More sharing options...
Tomo Posted November 27, 2003 Share Posted November 27, 2003 If I remember correctly, the IEE was distinctly unhappy with the idea of WWW over power lines due to RF interference. The Scotland trials had some extra stuff to reduce this - it's introduced at the local substation, so only goes in the underground armoured cables giving a reasonable shield. The same would go for a DMX-over-power system - DMX is a nearly square wave, and so has a fine selection of relatively powerful harmonics. In a proper DMX line there is a shield grounded at the desk/DMX splitter to prevent these harmonics from being transmitted into the environment and playing silly devils with the sound equipment and local radio stations. A mains cable doesn't have that shield, although they are mostly twisted triplet, so the RF can get out - and in! The shield is VERY important! The show we're putting on now had a dodgy earth in the DMX splitter, and it pretty much killed the DMX signal to the rig. Link to comment Share on other sites More sharing options...
Brian Posted November 28, 2003 Share Posted November 28, 2003 A mains cable doesn't have that shield, although they are mostly twisted tripletI don't think they are twisted, certainly not in the way that a CAT5 or other data cable is. Link to comment Share on other sites More sharing options...
Knut Posted November 28, 2003 Share Posted November 28, 2003 Uh-oh seemed that anybody like this way of data transfer. I thougt about diagnosis on a "live event" and it would drive you crazy when anything is wrong i.e.: Voltage is wrong.Your data signal goes to a wrong phase. (It must be possib. to send data on all 3 phases)Your currency is wrong about 55Hz (Does anybody know about currency in the UK? - Sorry I don¥t - but in Germany it is 50 Hz) My opinion on that: If your light was installed temporaly than Hands off What about you ? Greets Knut Link to comment Share on other sites More sharing options...
Mars Posted November 28, 2003 Share Posted November 28, 2003 Europe = 50 cycles/second 230/240 V; North America = 60 c/s 110Vfurther search on "main - supply - world" to find good sites. Another way of transmitting data over power lines is the other way around: transmitting power over datalines: amplify the data up to the desired voltage and back up with sufficient current. If the squarewave is rectified, a nice dc supply is available. I would recommend a local dimmer at the load, to prevent dataloss at black outs !What kind of cable ? Phiew... Link to comment Share on other sites More sharing options...
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