Monthly Archives: June 2006

Simple DMX Signal Locator

If you spend much time involved with lighting in a production environment you can understand how useful it can be simply to know if DMX signaling is present at any given location. Luckily, on the internet you can find instructions for building your very own simple DMX tester. As desribed this “keychain DMX tester” will test for the existance of DMX signal voltage and signal polarity. While not especially complex, this simple pocket tool is bound to come in handy if you spend much time troubleshooting DMX lighting control.

Controlled Lighting

Last year I made a post about some of the options for inexpensive DMX control. For those not familiar, DMX is a serial control protocol used in most modern professional lighting systems for theaters, concert halls, rock tours, etc. I continue to receive feedback on my original posting, some of which I still plan to respond to. In the meantime I would like to pose a few more ideas for you to think about and resources to investigate.

One of the interesting aspects of professional sound and lighting work is that, over time, it has become more and more integrated with computers and more recently, computer networks. Modern sound consoles can use “digital snake” technology and digital control technology which allows for much more flexible installations. In the lighting arena it is incresingly popular to run DMX over (relatively inexpensive) ethernet networks instead of dedicated serial cabling.

As with much of the technology found in production environments DMX over ethernet has been way overpriced. Be it the small demand for the technology compared with “consumer” technology or just the long track record of paying a premium for production technology DMX over ethernet has been out of a reasonable price range for most schools and non-profit theaters.

While poking around on the internet one day updating myself on current production technology I stumbled across the work of Simon Newton. Simon has created an open source driver for ArtNet (one of the popular and standardized protocols for DMX over ethernet). His project, called libartnet is specific to POSIX based systems, including both Linux and Mac OS X.

But what can you do with it, you might ask. Right now if you wanted to control some lights with a PC (using Martin’s LightJockey for instance) you would run a program which would output DMX on some kind of hardware interface (either proprietary or open source) which you would run into an ArtNet converter box and convert to ethernet. That seems kind of silly to me. After all, most PCs already have an ethernet port so why buy two more pieces of hardware? (Remember what I said about production technology being too expensive…) Anyway, with libartnet (assuming your control software recognized it) you could output DMX straight from your ethernet interface. But what software has libartnet support? Well, DMX4Linux does for sure and that means almost any lighting control software that runs on Linux will. Specifically, the GUI based Q Light Controller will. See how useful having a driver abstraction layer such as DMX4Linux is, but I digress. Another benefit of coming directly out of an ethernet port is the support for wireless.

Wireless ethernet is increasingly prevalent and compared with exisiting wireless DMX products it is downright cheap. Now we have solved the problem of wanting wireless control, after all with technology like this you could focus lights using your PDA with it’s built in 802.11x capability. But what about the other applications for wireless DMX? Simply routing the DMX signal between trusses or pipes in a large theater can present a problem. As I mentioned traditional wireless DMX is incredibly expensive and not all that great a technology. It turns out I have a solution for this as well. A few weeks ago I suggested to a hardware engineer I work with that he look into the possibility of using a pre-certified 802.11x transmitter (such as those from Digi International) to create an inexpensive wireless DMX product. After looking around on the internet a couple of weeks later I discovered that wireless ArtNet tranceivers already exist, but as can be expected with production technology, are wildly overpriced.

One of the most interesting solutions I found came from the same Simon Newton who developed libartnet. Simon was able to replace the OS on a Netgear router with a version of Linux and libartnet. Then, using the USB port on the router he was able to connect up some USB-DMX adapters and create an extremely inexpensive wireless ArtNet node. See this page for more information and specifics. The solution isn’t esxpecially elegant but it does show how inexpensively this could be done and gives some hope for future inexpensive ethernet to DMX adapters based on embedded system technology.

Who’s afraid of the big bad record companies?

If you’re an artist you should be! In a time not so long ago pretty much all local bands wanted to get “signed” by one of the big record companies. They seemed to feal these “deals” would get them notoriety and/or make them wealthy performers. All to many of those that did get “deals” ended up poor and unknown while the record executives wallpapered their offices with money.

Thanks to the internet independant artists can have a fighting chance on their own. The possibility of making it big without one of the record companies, if you have talent anyway, is not all that remote. Today one of the best things that could happen to a local band that is good, at least in my opinion, is to be turned down for a record contract and have to go it alone. I’m just waiting for the first wildly successful “viral” marketed band to sweep the nation. I feel we are now on the verge of this great accomplishment. The first few bands to make it big this way are likely to be picked up by one of the big companies which is too bad for them. Eventually someone will be smart enough not to let this happen and know that they have enough marketing capital to go it alone and in the process become much more wealthy. I wait paitently for that day and will not morn the passing of the record companies into the annals of history.

For more on the atrocities committed by the recording industry see “Courtney Love Does The Math” by Cournet Love and “The Problem With Music” by Steve Albini. These two provocative essays written by music industry insiders will give you a deeper understanding of how the present music industry works and a new appreciation for the hardships faced by artists once they make a deal with a record company.