[smalljoshua]

It's completely possible, but if you had DMX1 at 255, DMX 2 at 0 and DMX 3 at 255, removing the 0 at DMX 2 would mean the fixtures would read it as DMX 1 at 255, DMX 2 at 255.

DMX isn't smart enough to know something is "missing". It would screw up all the timings.

Josh

This post has been edited by smalljoshua: 08 February 2012 - 01:26 PM

[jono9691]

Not if the data was replaced specifically replaced by another source.

Why would you ever need to change DMX unless merging?

This post has been edited by jono9691: 08 February 2012 - 01:30 PM

[hadyn.williams]

Maybe I'm not following this properly Jono,

Are you suggesting that you could take part of one universe and a second part of another universe and send them down a single data string?

[jono9691]

No, I am suggesting that it should be possible to have 1 universe of DMX data and be able to allocate specific DMX channels to 2 different control systems and merge that data into a single DMX streem without any possibility of crossover.

[alistermorton]

jono9691, on 08 February 2012 - 01:47 PM, said:

No, I am suggesting that it should be possible to have 1 universe of DMX data and be able to allocate specific DMX channels to 2 different control systems and merge that data into a single DMX streem without any possibility of crossover.

That would indeed be possible so long as there was no crossover between the two sources, so source 1 might send chaneels 1-64 source 2 75-100 and source 3 128-256 say, but the combiner would have to pad out the final DMX stream with zeroes to cover the gaps between the sourves. What isn't possible is to remove the "unneeded" zeroes to reduce the packet size.

[jono9691]

Yep, what he said. The concept is there.

[alistermorton]

jono9691, on 08 February 2012 - 02:33 PM, said:

Yep, what he said. The concept is there.

In fact, in theory, with a clever enough merge controller, you could have crossover, and apply a last takes precedence or highest takes precedence rule (which obviously would give different end results) so whenever any of the sources changes the entrire universe is rebuilt and resent. I'm not sure how useful it would be to allow sources to overlap, though, and you still couldn't remove "redundant" intervening zeroes.

[timsabre]

jono9691, on 08 February 2012 - 01:11 PM, said:

Are you saying something can't be done with software? As far as I know anything can be manipulated via binary.

You cannot "remove" an unused section of the DMX packet, if that's what you were suggesting.

[jono9691]

The idea I originally had was to use with small lasers adding another safeguard. I was suggesting it might be possible though far beyond me to figure out how.

Cheers.

[alistermorton]

jono9691, on 08 February 2012 - 11:58 PM, said:

The idea I originally had was to use with small lasers adding another safeguard. I was suggesting it might be possible though far beyond me to figure out how.

Cheers.

Are you suggesting having two controller systems sending the same data and having a merge system use system "a" unless it stops sending data in which case swap to system "b"? A sort of failover?

[boatman]

I think we should remember that the OP is a student at the University of Sheffield, studying Electrical and Electronic Engineering and, incidentally, hasn't posted in this thread for a week. He asked for guidance on some simple DMX modules which he could build and the latest suggestions, although undoubtedly worthy, are very possibly beyond his abilities.

[deranged-angel]

Getting back on topic, Can I second (Or third or wherever we're up to) this idea

Quote

A really small wireless DMX link, to get DMX into a battery powered special without the need for a cable. If they were cheap enough I bet the market would be large - I haven't researched whether such units already exist.

I've seen too many pantos with the familiar "Click" on a practical with the light being on or off, no fades. I made a glowing apple for this year's panto - One switch turned the red LED on, a secondary switch in HIGH position made the LED "throb" then once in LOW, faded the LED out smoothly. This was pretty easy to make, just used a PIC but not everyone has the time to do it. I think a really small wireless DMX link, maybe 6 channels or similar would be really useful. I would probably buy one for the times I dont have time to make something.

Cheers,

[cedd]

And whatever deranged-angel seconded or thirded, can I fourth it please! Life would suddenly get an awful lot easier with such an item!

To have had all my recent projects (Beauty and the Beast rose, Producers pigeons) controlable wirelessly and having them battery powered would have saved the stage crew loads of work.

For my needs, it would be eaiser if it was a DMX controlled wireless device that controlled a set of TTL outputs, or solid state relays, rather than a DMX link. That needs another device strapped to it to decode the DMX stream.

[dirkenstein]

cedd, on 09 February 2012 - 01:45 PM, said:

For my needs, it would be eaiser if it was a DMX controlled wireless device that controlled a set of TTL outputs, or solid state relays, rather than a DMX link. That needs another device strapped to it to decode the DMX stream.

True. It also nees some LV PWM dimmed outputs suitable for small 6-24v halogens and LEDs, too, for the kinds of things I could see it being used for.

[timd]

dirkenstein, on 09 February 2012 - 05:54 PM, said:

cedd, on 09 February 2012 - 01:45 PM, said:

For my needs, it would be eaiser if it was a DMX controlled wireless device that controlled a set of TTL outputs, or solid state relays, rather than a DMX link. That needs another device strapped to it to decode the DMX stream.

True. It also nees some LV PWM dimmed outputs suitable for small 6-24v halogens and LEDs, too, for the kinds of things I could see it being used for.

A PWM output maybe, if you want to get into powering big stuff you're better driving a separate FET or the like with a TTL PWM output. Keeping things modular is definitely the way to go, but being able to provide analogue values is handy. Maybe designing a wireless board with a few headers on it for shield boards for various purposes would be the way forwards.

Tim