Go Unwired
When choosing wireless dimmers, it’s important to know what type of components you’ll need.
By Ian Phillips and James David Smith
June 2005The wireless dimming products on the market today use digital radio and special encoding/decoding that virtually eliminates false triggering, sluggish response, drop-outs, and other anomalies that plagued the wireless of yore. The best place (besides a running theatre) to see all this in action is a major tradeshow: every wireless product you might have in your space is running, including microphones, intercoms, cellphones and pagers, Bluetooth, and wireless dimmers. If all this stuff works in a show without interference, it just might work anywhere. And it usually does.
Today, there are two different wireless dimming architectures available to you: component, and integrated. A component system is a collection of devices you piece together to fit your needs – various receivers and dimmers you wire together with batteries and other bits and pieces. Integrated systems provide complete receiver/dimmers, ready to drive an electrical load with very little setup required. As always, there are pros and cons to both.The core of the most popular component systems is a wireless DMX link. Add small DC dimmers and you have wireless DC lighting anywhere you need it. Pros: a complete universe of DMX data is available anywhere; purchase only as many dimmers as you need; you can add a dimmer without necessarily adding a receiver. Cons: you have to connect the components together yourself; multiple dimmers can take up quite a bit of space; getting high-current battery power safely to multiple dimmers can be a challenge. A popular component system is the City Theatrical WDS, a 2.4GHz system used in numerous high-profile shows. And, since rules are made to be broken, one piece of the WDS system – the WDS Personal Dimmer – is integrated.
Integrated systems offer a range of receiver/dimmers, basically from small to large. Pros: to dim a lamp or control a motor there’s nothing simpler – just hook it up; smaller packages; multiple dimmers are usually provided. Cons: usually strictly a dimmer system with few or limited options for DMX output. The RC4 Wireless Dimming System operates at 914Mhz and is used by repertory theatres, operas, ballets, and others across North America and around the world. Each RC4 receiver provides four built-in dimmers, except (you guessed it) their DMX receiver which outputs 32 or 64 channels of DMX data.
Although there is a lot of opinion about what frequencies are better, this is just one small part of the equation. Also important are the rf techniques used, the gain of the antennas, other activity in the same band (including other equipment in your show), and the quality of the product design. In our opinion, the newest generation of commercial systems all work well. The 2.4Ghz band has the advantage of being allocated worldwide, making it the best choice for international tours. Surprisingly, the 900Mhz band is less cluttered at the time of this writing, and range is often better.
Pay attention to antennas. Some units have the antenna built into the box, which is good for simplicity of installation. The external or “rubber duck” type might get better range (there are other factors as well) but it’s one more thing sticking out of the box.
So, after weighing the pros and cons – and maybe sweating a bit more than you’d like – you have your new wireless dimming system. Now you need batteries! This is an area where there is a lot of flexibility. This really deserves an article of it’s own, but here are some of the main points:
The type of battery you need will depend on (a) the specifications of your wireless receivers and dimmers, (b) how much room you have to hide everything, and (c) how much power you need to get through the show. Sealed lead-acid batteries (SLAs) are the tried-and-true workhorses of wireless dimming. There are many sizes (amperage directly correlates to physical size) in 6V and 12V models. These batteries like to be charged a lot – you can top them up anytime. With a good quality charger and care to avoid discharging them too much they can last four years.
Batteries are a great way to support a local business. We’ve found the best resource for batteries are local tire and battery shops. They can get just about any type and size. And they’ll often have a good laugh when you tell them what they’re for.
You can get more complicated by making up battery packs of AAA, AA, C, or D cells. The final physical dimensions might be similar to SLA, but the weight will be lower and you can arrange the individual batteries in the space. In a top-hat prop, for instance, a few AA batteries work better than a lead-acid battery.
The rising star of batteries is Nickel Metal-Hydride (NiMH). Performance is great and prices are falling. NiMH batteries have a comparable Amp-hour (A/h) capacity to SLAs in a 1.2 Volt AA-size. Hook up 10 in series for 12 volts and away you go. This is especially handy in costumes or very small props.
Until recently, wireless dimming was used almost exclusively with MR16 12V lamps. In a range of wattages, narrow and wide beams, and familiar to designers, they do the job. There are hundreds of halogen and incandescent variations also available. The downside is they draw a lot of power, and output a lot of that power as heat. In other words, they aren’t very efficient, and efficiency becomes much more important when your power source is a battery.
LEDs – particularly the newest high-output white ones – have begun to steal the show. Smaller batteries can be used, and they’ll last longer. There are two issues that must be considered when using LEDs: they can be operated at lower voltages, and they look best when dimmed with a square-law rather than a linear dimmer. So, if you want to use LEDs with your wireless dimming system there are two questions to ask: “How low a voltage will the wireless receivers and dimmers operate on?” and, “Is a square-law dimmer curve available?” When using NiMH batteries, lower operating voltage means fewer batteries in a pack and less space required for them.
On stage with wireless dimming, rehearsals aren’t the same as shows. “I can’t count the number of times I get a note that there’s a problem with the RF system only to find that the lamp was on for 3 hours and the battery gave out. Most theatre acts/scenes will usually max out at 45 minutes. Unless told differently, that is what I spec to,” remarks Phillips. You’ll want to have a spare battery (or two, or three) for rehearsals. And be prepared to explain that this will not be happening in front of an audience. Smile. Again.
What else can you do with wireless besides lighting? Anything your wireless dimmers are rated for. The RC4 system at Shaw Festival is normally operated at 12V but will work down to 8V. Some wireless dimmers can be used with inductive loads like motors, others cannot – check the specifications of your system carefully and avoid blowing up a perfectly good lamp dimmer.
Lamps for your wireless system: Anything automotive; RV A-type bulbs (you can also operate 12V fluorescents but they won’t dim); LEDs with appropriate current-limiting resistors; all those 12V variations on the MR16 and other architectural 12V lighting.
Relays / solenoids / motors / misc.: 12V coil relays; air solenoids (there’s a lot of this kind of thing at Shaw Festival – air brake pads, actuators, etc., that integrate with stage automation); trucker accessories – coffee pots, stoves, those nifty mug warmers; DC brush motors of various sizes; DC brakes; inverters (make AC in the middle of the stage!).
The main thing to remember is that wireless dimming is just another tool for the stage. The more you use it the better you’ll do with it. And the more you use it, the more you’ll trust it and grow to love it!
Ian Phillips is the Assistance Head of Electrics at Shaw Festival, Niagara-on-the-Lake. Ian can be reached at ian.phillips@sympatico.ca. James David Smith is the designer of the RC4 Wireless Dimming system. Jim can be reached at www.theatrewireless.com or 1-866-258-4577. Ian and Jim will be presenting a seminar on Wireless Dimming at LDI-2005 in Orlando, FL.