Suggestions on creating a DMX control board

[dpavelko]

Hello,

 

First I am going to write what my idea is, and then what I am thinking.

 

I want to make a DMX512 light control board, that is customized for a community theatre I work in. We just bought a new LED lighting system that has 12 LEDS all feeding from one box (each is addressed individually, so a total of 36 addresses) I want to make a board that has a grand master, and a slider for R,G,&B. AND I want to make a wheel that I can spin to a color and it will automatically make it.

I also want to be able to plug this control board in between our existing 48 channel control board, and our computer system.

 

I am an electrical engineering student (second year) so this is something that I am willing to invest the time to learn now! I have done quite a bit of researching online but have not found the holy grail.

 

Some questions I have:

1) Are their fader/sliders that are already DMX, that don't need a analog -> DMX conversion.

2) How does a grand master work, technically. Is it done on the analog side or after it has been converted into the digital world. (I get what a grand master does... but not HOW it does it)

3) Do you need a DMX transmitter on each channel that all feeds into a microprocessor?

4) If any of you know of any sites or have information yourself of helpful DIY stuff related to making a DMX board I would greatly appreciate it.

 

I am trying to learn the world of digital design/circuits/etc. so I am learning theory but if you know of specific parts that would be helpful too!

 

Thanks! I will keep you updated on my successes! :)

-Dylan

P.S. questions welcomed!

[david.elsbury]

I honestly wouldn't bother. This is going to cost so much compared to the cost of buying some hardware... or software.

Sorry to p1ss on your parade... perhaps look at a PC based solution? What is your existing board? What is your existing PC system?

[dpavelko]

We have a 48 channel DOVE lighting board, that is connected with a STARPORT made by DOVE that runs on DOS... yes DOS. DOVE is a small theatre/church lighting company that is based out of my town.

Do you have any suggestions for a cheap computer control USB -> DMX_OUT ideally something that runs on the (dare I say it) mac?

[david.elsbury]

Plenty of suggestions HOWEVER select your software first before selecting an interface, a lot of programs will only run on their (or specific) interfaces. This is because the software is free and they make their money back on the hardware.

 

Personally I use Lightfactory, and find it an okay program for my needs, (I'm sure our resident sales rep will be along soon enough to plug it...) but as I say look at the software. Use the search function for "USB DMX".

 

Common interfaces are the Enttec USB DMX Open and Pro.

[pritch]

Some questions I have:

1) Are their fader/sliders that are already DMX, that don't need a analog -> DMX conversion.

2) How does a grand master work, technically. Is it done on the analog side or after it has been converted into the digital world. (I get what a grand master does... but not HOW it does it)

3) Do you need a DMX transmitter on each channel that all feeds into a microprocessor?

4) If any of you know of any sites or have information yourself of helpful DIY stuff related to making a DMX board I would greatly appreciate it.

 

1. No; you can only have one transmitting device in a DMX network, so if each fader transmitted by itself, you'd end up in a right mess.

2. Not sure; intuitively, I'd say that it's done on the digital side, seeing as desks these days can tell you what the grand master is set at.

3. No; see number 1.

4. There's some information out there on using an Arduino to send or receive DMX with RS485 transceiver chips, I don't know if that'll be of any good.

 

Because you can only have one transmitter on the network, if this is going to sit between an existing desk and everything else, you'd need to receive the data, and retransmit it.

 

As someone who has to deal with the quirks of a desk that someone long ago thought was a good idea, I'd beg you to reconsider. It may seem like a good idea now, and you may well produce a desk that works well, and is pleasant to use... but go a few years down the line, when you might have moved on to pastures new, consider the poor sod who has to fix it when it goes wrong.

[Wol]

Some questions I have:

1) Are their fader/sliders that are already DMX, that don't need a analog -> DMX conversion.

2) How does a grand master work, technically. Is it done on the analog side or after it has been converted into the digital world. (I get what a grand master does... but not HOW it does it)

3) Do you need a DMX transmitter on each channel that all feeds into a microprocessor?

4) If any of you know of any sites or have information yourself of helpful DIY stuff related to making a DMX board I would greatly appreciate it.

1) A potentiometer (as thats most likely what you'll be using for a 'fader' if building stuff) will give you an analogue voltage. Use a ADC (analogue to digital converter) to convert this signal into a digital one which a microprocessor reads in. Some microprocessors will even have inbuilt ADCs for you to use (have a look at the PIC range from Microchip).

2) In my experience of digitally controlled desks (e.g. something with DMX), the grand master appears as another channel of analogue input to the processor. The microprocessor performs functions based on the value of each channel, and the value of the master. This way you can soft-disable the master on certain channels, map the grand master to other functions etc...

3) Which microprocessor are you talking about here? If its the one in the control surface, then no. Lots of potentiometers give lots of analogue inputs into a microprocessor, which turns these analogue inputs into a DMX packet

4) The Arduino route mentioned above is possibly a tad OTT for the kind of thing you're aiming at (or at least would be considered from my point of view as a fourth year Electronic Engineer). Microchip themselves have released code on how to transmit and receive DMX as an application note on their website and that way you have a system you can build yourself and learn from the bottom up rather than just buying a high level board and programming it.

 

Going the low level route, you'll want to start to learn how to do basic microprocessor design and using the things before deling into an application (although admittedly the first PIC program I wrote was a dinky DMX transmitter!), have a look at how to interface analogue inputs into these, having a look at the DMX protocol (google will help you here) and have a look at RS485 line drivers (They come in their own little package, avaiable for free to sample off maxim-ic.com). Start patching the cumulative knowledge of all these things together a bit. Also, if you want a dial to bring up a different hue for the things, then start looking at rotary encoders and how they interface with the outside world (the datasheet will tell you).

 

I guess a lot of it comes down to how much you wish to learn, but as you say:

I am trying to learn the world of digital design/circuits/etc. so I am learning theory but if you know of specific parts that would be helpful too!

I'm guessing you can be thrown in at the deep end ;-). Also chances are that there are enough people around where you are doing Electronic Engineering who will be able to help you out. Find out who teaches the electronic design modules and get in contact with the lecturer and take it from there.

 

And if all that talk has put you off and you want to go for a prebuilt route, have a look at the MagicQ software from ChamSys. This will let you give out DMX using the Enttec DMX adapters as mentioned above. The software also works on a mac. This is however just a computer based solution, and you have to buy the hardware from ChamSys themselves if you want real faders.

 

edit: One question I do have, what do you mean by "I also want to be able to plug this control board in between our existing 48 channel control board, and our computer system.", in terms of functionality you're expecting from this setup and what you want to be controlled from what?

[springgrove]

This will indeed be a labour of love and a learning experience! Wol has given some very useful information.

 

Here are some other links that give technical background on DMX:

http://www.dmx512-online.com/

http://www.dmx512.com/web/light/dmx512/index.htm

http://www.dmxprojects.com/projects.html

 

Hope these help

Nigel

[dpavelko]

Thank you for all the great info! I still do want to go the low level route if possible (though I am debating about trying to make a software program and then just make a USB -> DMX converter... hmmm, may be even harder I don't know)

 

edit: One question I do have, what do you mean by "I also want to be able to plug this control board in between our existing 48 channel control board, and our computer system.", in terms of functionality you're expecting from this setup and what you want to be controlled from what?

 

Hmm. What I mean is... well let me describe the set up and I think that will explain what I mean/want.

We have 48 dimmers, and a 48 channel board. The theatre (through donations of course) were just able to purchase a new LED light system that has 12 different fixtures that branch off from the one box. So we are setting the start address for this at 49. I want to build a controller that you can change the start address to 49 and then control the LEDS. So it would be connected between the 48 channel board, and our computer which already takes in DMX data from our current board.

Yes I know that I would have to take in the data and the re-output with the new data, but thats what I think would be the most functional, and quite doable (once I can figure everything else out that is)

 

I will look into the info you and others gave me, thanks everyone

[Wol]

Thank you for all the great info! I still do want to go the low level route if possible (though I am debating about trying to make a software program and then just make a USB -> DMX converter... hmmm, may be even harder I don't know)

Depends what you fancy learning; electronic design with low level software design or high level software design :-p.

 

Hmm. What I mean is... well let me describe the set up and I think that will explain what I mean/want.

We have 48 dimmers, and a 48 channel board. The theatre (through donations of course) were just able to purchase a new LED light system that has 12 different fixtures that branch off from the one box. So we are setting the start address for this at 49. I want to build a controller that you can change the start address to 49 and then control the LEDS. So it would be connected between the 48 channel board, and our computer which already takes in DMX data from our current board.

Yes I know that I would have to take in the data and the re-output with the new data, but thats what I think would be the most functional, and quite doable (once I can figure everything else out that is)

Intriguing setup.... What does the computer do in all this? You mention that it takes *in* DMX. What exactly do you do with this DMX input and use it for? From what you've mentioned, what you seem to want from this controller is an amalgamation of a controller and DMX merger and I'm tempted to argue that its going to be easier to just make a DMX controller and run a separate universe to the LED controller box, but if the computer in all this is acting as a DMX recorder or similar, then this might not work with two universes.

 

DMX reception at low level is a bit trickier compared to transmission as you have to do some..... interesting timings of the break signal at the start of the DMX packet which you should really do properly, rather than fudging it by using the framing error part of the UART! If you're using the fairly cheap PIC range, you also have limited RAM ( < 512 bytes), so if trying to receive a full DMX packet, ( which I'd say is worth it, as at some point along the line, theres always a chance that someone might stick something at a higher DMX address going in, which your device might just ignore and not retransmit!) you'll need a RAM block. Have a look at the dmxprojects site that uses a RAM IC.

 

You could even try and separate the two systems out, so make the controller on its own, and build a fairly simple DMX merger. The two things on their own might end up being more useful and flexible rather than combining both systems into one box?

[P. Funk]

It is definitely doable, but getting it to be reliable (including the DMX input buffer arrangement you've mentioned) might be difficult. The approach I would probably take would be to run all of your faders (if you're using faders) into a multi channel ADC chip, and link it up with some kind of central microcontroller. I got a Microchip PIC to do DMX in/out last year using some code adapted off the internet (took about a day's effort) - I may still have the code somewhere if thats something you want to do. Have a big think about User Interface though - when you say you want red/green/blue/master do you mean that all the LEDs will always be set to the same colour? If this is correct, I'd question the use of a dedicated controller - why not address all the units to DMX 45, use your existing board, and leave those dimmer channels free when you use the LEDs? A software based solution will almost certainly be easier if you have the programming ability - you could grab yourself an Enttec Open DMX dongle, and a MIDI fader box, and write a bit of code to translate MIDI fader positions into DMX instructions.

 

Also, whats

our computer which already takes in DMX data from our current board.

then? What does the computer do? What dimmers do you have / what protocol are they running on? Sounds very complicated.

 

Its likely to end up being expensive. Getting decent faders, a chassis, all the hardware, and everything you use/break during development could cost you quite a bit, so be ready!

 

Hope that makes sense, haven't posted here for a while :** laughs out loud **:

Jon

 

edit: Wol got there before me. Agree on the seperate universe idea!

[benash]

Have been doing some reading on the DOVE website, from what I can guess the desk is a dumb (as in not intelligent) 2 scene 24/48 or 48/96 desk that feeds into a computer via the STARPORT. The computer the gives you the ability to do timed crossfades and presets etc so presumably the LED's would be driven by the computer as well so that you can syncronise the whole thing. I may of course be wrong about this whole thing so feel free to shoot me down.

 

There is this awesome photo. I'm starting to think that Americans' much maligned lack of irony is actually a myth.

 

Anyway, to the OP are you wanting to be able to have different LED units running different colours or are they all going to be the same? If they are going to be all the same you might be able to save yourself a pile of time and money and just buy a 4 channel DMX controller and hook it into your system with a DMX merger.

 

You mentioned a wheel selector to choose what colour the LED's are putting out. Colour has more than one dimension (which is what you would be limited to with a wheel), you'd probably want a two dimensional selector (like a track ball) plus an intensity fader (which gives you the three degrees of freedom that a RGB system has by definition). I don't envy you the challenge of turning a bunch of physical inputs into a colour selector but you seem keen enough so go hard and keep us updated.

 

For my money I'd be thinking the colour selection stuff is better handled on the computer even if your inputs are still dedicated physical controls. I appreciate you're an electrical type and I'm pretty sure when I was in second year mech eng I would have tried to do the whole thing mechanically. Sometimes you've just gotta step outside your area. Perhaps if you can hook your physical controls into the PC, have that running a second program that actually handles the conversion from colour to RGB levels and then hook that into your existing PC control package? Or maybe I should give up and stick to levers and gears.

 

One final thought... if the desk that you have is what I've been looking at, you might do well to head down to your local lighting shop and get them to give you a brief rundown on one of the mid-lowrange programmable desks, it'd be worth it to get a sense of their user interface and what they can do onboard without an external computer.

 

Good luck, sounds like fun.

[Wol]

You mentioned a wheel selector to choose what colour the LED's are putting out. Colour has more than one dimension (which is what you would be limited to with a wheel), you'd probably want a two dimensional selector (like a track ball) plus an intensity fader (which gives you the three degrees of freedom that a RGB system has by definition)

 

Were you (the OP) thinking along the lines of a hue selector for this? E.g. have a wheel for hue (as hue is an angle really and can loop around). Then a fader to act as a brightness from off (black) through to fully saturated (e.g only red), through to full brightness (white) so standard would be to have the fader halfway, but can be easily brightened or dimmed if necessary.

 

P.Funk: I like the idea of using the BCF2000 as a direct controller rather than into a computer >.> Tis half tempting to make some dongle to do that with proper parameter feedback!

[P. Funk]

P.Funk: I like the idea of using the BCF2000 as a direct controller rather than into a computer >.> Tis half tempting to make some dongle to do that with proper parameter feedback!

 

At risk of going off topic slightly, interesting idea. It wouldn't be hard to create some kind of (very small) dongle that simply upscaled MIDI control change parameters into a DMX state - may be not so good for big gigs but being able to use a MIDI controller as something to generate some quick looks / focussing could be really useful? Only issue I can see is there's no easy power source - PP3 maybe... Summer job for me I think!

[Tomo]

While this would make a pretty interesting project, I'm not sure it's such a great solution.

Mostly because it's not extensible - if you buy (or hire) any extra DMX-controlled devices like moving lights, how would you control them?

 

Have a look at the various DMX lighting consoles available - you can get some pretty good ones designed for the task of driving dimmers, LEDs and moving lights for not much.

 

You mentioned Mac - SmartFade ML can connect to Mac OS-X computers for a heads-up display, while being quite happy on its own as a full-featured lighting console.