An Introduction To DMX Lighting Control – Take Your Lighting To A Whole New Level
Intelligent lighting systems used to be an expensive domain for professionals only; but with the proliferation of cheaper electronics and computer control systems, incredible lighting effects are now firmly within the reach of the hobbyist. Whether you’re planning the most awesome house party ever, or want to take your Christmas or Halloween lighting to a whole new level, it might be time to invest in some DMX systems.
What Is Intelligent Lighting?
Put simply, intelligent lighting contains elements which can be controlled remotely. At the most complex level, this may involve a moving head (pan and tilt), patterns, and colours. On the simplest level, you might just control the colour (a strip of RGB LEDs, perhaps) or a dimmer. Put even more simply – intelligent lighting is awesome.
Combined with a controller, you can simultaneously send a signal to hundreds of devices, sequencing them programatically with a pre-determined show, or live operating the effects on-the-fly. This is basically how I spent my nights at university – sitting in front of a lighting board – moving, flashing, and changing the color of club or concert lighting in time to the music. At most concerts though, the lighting will be pre-recorded, and simply played back at the right time; this ensures a consistent experience.
If you’ve seen the viral video of Halloween house lights set to Thriller, you ought to know that it uses DMX intelligent lighting control.
What Is DMX?
DMX is a serial protocol, digital, unidirectional, and with no error checking. It’s reliable, but is subject to interference which makes it unsuitable for hazardous effects such as pyrotechnics (a stray signal or electrical interference could accidently set off a flame tower, for instance). Like most digital cables, the signal quality degrades over long distances, and repeaters can be used to increase the distance, or split the signal with the equivalent of ethernet switches.
The cable itself consists of two shielded twisted pairs (though only one is pair is used). Technically, 5-pin DMX cabling should be used, but some manufacturers have implemented 3-pin versions which can run over traditional microphone XLR cabling.
Devices are daisy chained together in a single cable and terminated with a special plug; a single DMX master is used to control, while every other device is known as a slave.
At a data level, the DMX512 controllers sends asyncronous data at 250 kbaud; 1 start bit, 8 data bits, 2 stop bits and no parity checking. Notice that although the data part is limited to 8-bit, some devices will combine two channels, giving a multiplexed 16-bit data packet if needed.
DMX512 is so called because it allows up to 512 channels of control. Each device on the DMX “universe” must have a start address set on the device itself; most devices will take up more than one channel. Some of the more complicated lights might have up 12 different channels; a combination of which controls various effects. Identical devices can be set with the same address; these will both react to those instructions.
Of course, this only works if the devices are identical, as each device will use its control channels to do something different. Because of this, your control system needs a “profile” for each device – kind of a like a device driver – which tells it what the device is capable of and what signals to send for each effect.
Here’s a basic introduction in video form to revise what you just learnt; be sure to watch parts 2–4 also.
DMX isn’t limited to just lighting though; you can get smoke machines that are controlled over DMX, and you can even emulate a DMX device with an Arduino, incorporating your own electronic hackery into your show. Basically, DMX is the glue that holds everything together and lets it all talk to each other.
To learn more on the technical side, I suggest reading the[PDF link].
So What Do You Need To Get Started?
First off, you’ll need intelligent lights and devices. These cost a little more than your standard Christmas lights, but they also tend to be built for more demanding usage. To give you an idea of cost, I bought myself an off-the-shelf green laser with DMX control for around $150. You need not necessarily buy new equipment though. If you can control your existing lights or devices by Arduino (like using a relay for a smoke machine), you can also adjust the Arduino to act as a DMX slave device (that is, one that receives DMX signals).
Second, you’ll need a controller: your PC or laptop is fine, but you’ll need a USB to DMX converter. The cheapest I could find is.
There is a surprisingly large range of software available on which to program your shows. DMXControl is widely considered the best free option.
If you don’t mind paying a bit more, DasLight offers a superb software and controller with advanced 3D visualization to plan your show. For simple testing, Virtual Lightdesk is an easy $5 Mac app that’s compatible with all controllers. I’ll be looking more at the software side of things in a later article.
Lastly, you’ll need some cabling; making it yourself is the cheapest option.
Are you ready to get into the world of intelligent lighting? Let us know if you’ve already built some DMX projects and show us a video link. It’s a dangerous and expensive hobby, thats for sure – but it’s also one of the coolest hobbies in the world. Lasers, smoke machine and strobes await you, sir!