Lighting System Basics
Boards,
Dimmers, and DMX
Churches often contract out the design and integration of a lighting system. It can be complicated, expensive, and primarily requires electricians to do the installation. An understanding of the basic components and terms can take some of the mystery out of the job: you will know what you are paying for, raise good questions, and, if you are non-technical, help you to better understand your technical production department.
A basic lighting system is made up of three system parts: a lighting board
(to control the dimmers), dimmers (to power the lights), and the lights. These
components are interconnected with power and data cables. Let’s look
at some of the basics of the first two parts: control and dimming, and the
interconnection between them.
DMX
Before talking about system components, we’ll step through the current
lighting system control standard, “DMX-512” (called “DMX”
for short). This standard was established in 1990. There are newer (and very
needed!) protocols in development, which are finding their way into the market.
DMX-512 is a “digital multiplex” data type specifically for the lighting industry. This standard was created to provide a new, fast, flexible way to control lighting dimmers, eliminating the need to have a separate analog wire for every dimmer. DMX is a serial data protocol that provides 8-bits of level information for up to 512 dimmers, and sends all of this information (a frame) about 44 times a second (called a frame-rate or refresh-rate) over a shielded pair of wires. 8- bits accommodate 256 distinct “levels” of dimming from 0% to 100% (or “off” to “full”). All the system components on a single data line would be called a “DMX universe”. If more than 512 “things” need to be controlled, than a second DMX universe would be used to expand the number of system-wide DMX channels to 1024. I say “things,” because DMX is being used for so much more than simple dimmers. Large touring concerts and installations can use eight universes or more. “Eight thousand, one hundred and ninety-two” sounds impossible to use at one time, but DMX channels are quickly eaten up.
The number of DMX channels can also range from 48- 2,048 (or more) depending on the number of DMX universes (groups of 512) the board is designed to control. DMX channels are also called “DMX dimmers” because the primary function of the DMX- 512 standard involves the control of dimmers. (DMX is used for hundreds of things besides dimmers, however.) For clarity I prefer calling them “DMX channels” to specify data on the DMX line (that may or may not be used to control an actual dimmer). A “DMX universe” output from the board would be called a “DMX port,” typically capable of outputting all 512 DMX-channels. Therefore, a “two-port” board would capable of outputting 1,024 DMXchannels on two DMX universes.
Lighting Boards
Also sometimes referred to as the lighting “desk”, “surface”
or “console,” some popular brands of lighting boards include ETC,
Strand, Leprecon, NSI, Lightronics, Avolites, Electronics Diversified (EDI),
Chauvet, MA Lighting, Flying Pig Systems, Compulite, Martin, and Colortran.
The lighting board is the control surface for the system. It is important to select a board of good quality, value, capability, and room for future growth. Boards can range widely in price, from $350 to $35,000. The number of control channels and DMX channels, and moving light capability, are a few attributes that make a big difference in the cost of the board. The number of control channels can range from 1 to 2,048 or more. The more control channels, the more things that can be controlled individually.
Control channels are available in the form of sliders, dials (encoders), numeric keypads, or a combination of all three. A “manual” board has sliders that need to be moved to change the settings. A “memory” board has sliders as well, to allow users to capture “snapshots” of the settings to be stored for later recall. (A snapshot is referred to as a “Cue” or “Q”.) Typically, both manual and memory boards have some “submaster” sliders that can be used to control a group of channels.
Control channels within the board are “softpatched” to DMX channels that are on the data line coming out of the board. A “soft-patch” electronically attaches a DMX-channel to the control channel on a lighting board. A “one-toone” patch would have a DMX channel patched to every channel in sequence. Channel 1 controls DMX Channel 1.
Thanks to soft-patching, it is possible to patch all 512 DMX channels to Control Channel One. This gives you the idea, but not one you should try: assigning the entire rig to one channel will get that power meter spinning and could cause a “peak load” with your power company, raising the entire electrical bill!
Dimmers
Dimmers are the breaker panel of the lighting system that dims the lights according
to the control signals from the light board. Dimmers are available in different
packages. A dimmer pack is a portable box that typically consists of four to
12 dimmers. A dimmer stick, usually featuring three to six dimmers, is like
a pack, but configured in a longer bar shape that can be mounted to a pipe.
This distributes the connectors along a distance, reducing the cabling from
the lights to the dimmers. A rack is a larger housing, either in a road case
for portable use, or a metal frame for permanent installation, with 12 to 96
dimmers.
Dimmers take an incoming power source and distribute it to the separate lighting fixtures. A dimming system will have a maximum power capacity. A dimmer draws a bit more than the power of the lights connected to it. However, the dimmer should be wired to a power service that can provide the maximum needed power (as if all the dimmers have lights plugged in and they are on at full). Assuming they are operating at 120-volts, typical dimmer wattage ratings are 300W, 600W, 1.2kW, 1.8kW, 2.4kW, and 6kW. “k” means x1000, so 1.2kW = 1,200 watts, and could drive a 1kW lamp w/ 200 watts of headroom before the dimmer breaker might pop. Keep in mind this headroom is typically required; quickly turning on a light causes an inrush current that can be momentarily larger than the actual load of the light.
A dimmer pack, stick, or portable rack has output connectors for the dimmers, so you are able to plug lights (or extension cables) right into it. An installed rack has terminals (similar to breaker panels) inside; the wiring for the dimmer circuits is installed in the building through conduit.
Power
Lighting requires a lot of power. You can determine the amount of total needed
power by deciding how many separate dimmers are required and the total wattage
of all the lights connected to them. For example: If you had ten 1000-watt
lights on five 2.4kW dimmers, the total actual load (if all ten lights are
at full) is 10kW (10,000 watts). The five 2.4kW dimmers would be wired for
a maximum power capacity of 12kW. Since the smallest dimmer rack for this application
is a rack or pack of six dimmers, a six 2.4kW rack would be installed, requiring
a power service of 14.4kW (6x2.4kW).
For larger systems (of 96 or more), a “power factor” or “practical load factor” might be applied. This factor would be an agreedupon figure between the electrician and the lighting system designer, based upon the electrical code for your area. This “factor” allows for a larger dimming system to be fed with slightly less power than the maximum dimming capability of the system, taking into account that each dimmer will not ever be fully loaded by the lights plugged into it, and that the system should not be used with all lights at full at any one time.
For example: A 2.4kW dimmer might have two 1kW par cans plugged into it. Those 400 watts of headroom times 96 dimmers in a full rack is 38.4kW (enough to drive another rack or 12 dimmers or more). This would be using a practical use factor of about 80% (the dimmers typically only have a load on them that is about 80% of their max capacity). Again, this may only be applied (if applicable) at the engineering level, where certified electricians and theatrical lighting system designers are involved.
Because of content, room size, shape, and creativity, lighting systems are finding their way into thousands of churches. Lighting systems are electrical, but the lighting locations, types, angles, quantities, and applications are all design choices. A lighting designer will consider these needs first; then they will run the electrical numbers and confirm the electrical plan with an electrician. If you are involved in a new building project, confirm right away the size of the electrical service that determines your maximum lighting wattage capability. A lighting system design is valuable before the concrete dries, because changing electrical services after they are installed is usually far too expensive.
Chris Gille works in the technical department at Willow Creek
Community Church in South Barrington, Illinois.
