What does the future hold for the live event production industry? What are the job prospects and what can you realistically expect to earn over the next decade in our fascinating little corner of the world?
Every year for the past few years I have driven 30 miles down the road from Austin to speak to the advanced stagecraft classes at Texas State University in San Marcos. Each time I do my best to utter the right words to those college kids as they stand on the precipice of their formal education looking down into the waters of a career in the live event production industry. From where they stand it can seem like a very long way down, and most welcome any pearls of wisdom that might mean the difference between landing a dream gig or living a nightmare. Fortunately, I have a very good relationship with Swami Candela of the Third Millennium, a small medium of large proportion who sees all, knows all, and tells all, except that which cannot be seen, known, or told.
The message that the Swami delivered is one of hope and optimism, even in the face of worldwide economic uncertainty. The last few years have been even more challenging than most for job seekers, and recent college graduates are just as likely to go to New York to occupy Wall Street as they are to find an occupation on Broadway. The Occupy protests are a stark reminder that finding a good job today is not necessarily a given, and that looms large not only for college kids but also for those of us who are concerned about our wages and the growing gap between the rich and the poor.
Most of us in this industry have no delusions about joining the 1%, at least not by pushing road cases and unloading trucks, but we should, at the very least, be able to feed, house, and clothe ourselves and our family and have access to quality health care. Sometimes it seems as if access to those basic needs is slipping away.
The good news is that there is always a demand for the best. The other side of that coin is that if you want to be in the top 10% of your field, you have to be willing to work harder than 90% of your colleagues. But every one of us has that ability to succeed as long as we have the desire. And right now there are a lot of emerging opportunities, courtesy of newly emerging technologies, to find fascinating work in automation, animation, sustainable design, networking, and more.
Some of the best opportunities in the near future will be in the area of automation. Do you remember the scene in “Cowboys and Aliens” where the space craft came flying down the middle of the main street of the western town? That was done by mounting automated lights on an automated winch. (Josh Thatcher, automated lighting programmer in the movie, will conduct a presentation about the experience at PLASA Focus: Austin on February 22.) Automation also plays a big part in “Spider-man: Turn Off the Dark” on Broadway. I was fortunate enough to get a backstage tour and the rigging is incredible. There are so many projects going on that are incorporating automation, like the kinetic sculpture at the BMW Museum and City of Dreams in Macau, China. And these projects require the services of riggers, programmers, networking techs, electronics techs, mechanical engineers, electrical engineers, and more.
Most shows today also incorporate video, and that calls for the services of video directors, video engineers, camera operators, video techs, media server programmers, content designers, scenic designers, LED and projector manufacturers, riggers, automation techs (lots of video displays move on automated winches or trolleys), and more. There will be jobs for a long time to come for people who are good at 3DS Max, Cinema 4D, After Effects, Final Cut Pro, Photoshop, Illustrator, and other software that can be used to generate video content.
Other technologies like wireless, batteries, LEDs, stereoscopic video (3D), media servers, and networking are redefining the landscape of the live event production industry. And that spells O-P-P-O-R-T-U-N-I-T-Y for those who are willing to invest the time and effort to keep up and get ahead.
But being employed is no guarantee of success. As Albert Schweitzer once said, “Success if not the key to happiness; happiness is the key to success.” So if the Swami had only one thing to say to the graduating class of 2012 and to the entire workforce, it would be this: Love what you do and do what you love. If you can make that the central tenant of your belief system then you will be among the best in your field.
|We received a phone call from a former seminar attendee who was in a bit of a jam. He was setting up a stage for an outdoor show when the local authority having jurisdiction (AHJ) was giving him a hard time about some of his gear. It seems that not all of it was listed for outdoor use. If the AHJ didn't allow the use of the gear, the show could not go on.|
Fortunately for those of us in the live event production industry in the U.S., there is an article in the National Electrical Code that allows the use of portable stage and studio lighting equipment and portable power distribution equipment that is not listed for outdoor use under certain circumstances.
"Article 520.10 Portable Equipment Used Outdoors. Portable stage and studio lighting equipment and portable power distribution equipment not identified for outdoor use shall be permitted for temporary use outdoors, provided the equipment is supervised by qualified personnel while energized and barriered from the general public."
Notice that it says "qualified personnel. Who is considered qualified personnel? According to the NEC, it's "One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved." If you've ever taken an APT Entertainment Electricity class, then it could be argued that you are qualified personnel. If not, then check out the upcoming classes at www.APTxl.com.
When the production crew politely pointed out Article 520.10 to the AHJ, he allowed the use of the gear under supervision. The show went off on time and disaster was narrowly avoided.
Video Matters: Thinking Out Loud About Video - Lighting & Sound America, March 2011
Video Matters: From Low End to High End, Video Cams Amaze - Lighting & Sound America, June 2011
Imminent Danger—OSHA Fact Sheet: What is "immenent danger" and why is it important to know? This fact sheet from the U.S. Department of Labor Occupational Safety and Health Administration points out what you should know.
Power Line Distances: One of the most common electrical fatalities involves accidental contact with energized overhead power lines. This safety bulletin from the Contract Services Administration Trust Fund provides minimum required clearances from overhead conductors based on voltage.
Basic Electical Safety Precautions for the Motion Picture and Television Off-Studio Lot Location Productions: Safety bulletin from City of Los Angeles Chief Electrical Inspector Robert England covering grounding requirements, methods, and recommendations, overcurrent protection, and general equipment requirements for location shooting and production.
Working with 480-Volt Systems: Working with 480 volts increases the risk of arc flash, arc blast, and lethal shock compared to working with lower voltage systems. This safety bulletin from the Contract Services Administration Trust Fund provides helpful information about safe working methods, color coding, grounding procedures, and more.
Guidelines for Working with Lighting Systems and Other Electrical Equipment: General safety measures for working with electrical equipment, replacing fuses and circuit breakers, working with power tools, rigging, connecting power systems, color coding, guarding of live parts, working with portable and vehicle-mounted generators, grounding practices, and more. Safety bulletin issued by the Contract Services Administration Trust Fund.
Ontario Television, Film, Live Performance and Event Electrical Guidelines: From the Canadian Electrical Safety Authority (ESA), this 37-page document includes definitions, general practices, power sources, temporary power distribution, Ontario electrical safety code references, glossary, rating of generator sets, acceptable certification and field approval marks, and more. Topics include permits, reporting serious electrical accidents, personnel, equipment and operations, generator sources, utility sources, film and television main and load distribution boxes, minimum size of grounding conductor, and more.
Electrical Safety—Safety and Health for Electrical Trades: This student manual is part of a safety and health curriculum for secondary and post-secondary electrical trades courses. The manual is designed to engage the learner in recognizing, evaluating, and controlling hazards associated with electrical work. It was developed through extensive research with vocational instructors, and it is published by the U.S. Department of Health and Human Services, The Centers for Disease Control and Prevention, and the National Institute for Occupational Safety and Health.
10 Dumb Things People Do When Testing Electricity: Anyone who makes their living by working with electricity quickly develops a healthy respect for anything with even a remote chance of being "live." Yet the pressures of getting a job done on time or getting a mission-critical piece of equipment back on line can result in carelessness and uncharacteristic mistakes by even the most seasoned electrician. The list
below was developed as a quick reminder of what not to do when taking electrical measurements. Published by the Fluke Corporation.
Lockout/Tagout: Lockout is when a padlock is placed on a disconnect switch, circuit breaker, valve handle or other energy- isolating device that is in the off or closed position and tagout iis when a warning tag is placed on the energy-isolating device that is in the closed position. This document from Theatre Safety Programs spells out the procedures for proper lockout and tagout of an electrical service for maintenance and troubleshooting.
Aerial Lifts: Various types of aerial lifts are used every day in our jobs. As use of these lifts becomes routine it is easy to overlook the things which must be done to safely use these very effective tools. This short guide published by Theatre Safety Programs provides important information for the safe operation of aerial lifts.
Personnel Lifts: Personnel lifts are extremely useful machines. However, if not operated in accordance with the manufacturer’s instructions and accepted practice they can become extremely dangerous. This document covers inspection, operation, and a useful check list for the safe operation of a personnel lift. Published by Theatre Safety Programs.
Fall Arresting (Protection) Systems: This helpful document summarizes the requirements for fall protection requirement including OSHA requirements, controlled access zones, safety monitoring, types of fall protection systems, parts of a fall arrest system, 10 critical requirements for an anchorage point, recommendations, requirements, and more. Published by Theatre Safety Programs.
Ladder Safety: Thirteen-percent of workplace deaths and over 16% of the workplace injuries are falls, and ladders are involved in many of these accidents. This handy document from Theatre Safety Programs covers relevant standards, inspection, storage, ratings, setup, procedures for use, and provides a safety check list for working with ladders.
Manual Rigging System Operation: Counterweight rigging systems should only be operated by trained, authorized personnel. This guide offers practical information about the safe operation of manually operated counterweighted rigging systems. Published by Theatre Safety Programs
When I was in college, a friend of mine wrote a song called Maintenance Man, in which he was trying to convince the woman of his dreams that he was the right man to maintain her heart. The lyrics included the line; “Well I’m certified, licensed, bonded, and guaranteed...” It was the most soulful song that never went anywhere.
I thought of that music when someone recently had a question about the difference between certification and licensing. The question stemmed not from a song, but a meeting in which a licensed electrician said that an entertainment electrician is not qualified to tie in power, only to “twist cams together.”
What is the difference between a licensed commercial electrician and an ETCP Certified Entertainment Electrician? It’s a legitimate question: Who is qualified to
perform which tasks? After all, we don't want unqualified people walking in off the street and doing live tie-ins. But is assertion that only licensed electricians are qualified to do live tie-ins correct?
According to the NEC, a qualified person is defined as:
“One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved.”
And then there's an informational note:
“Informational Note: Refer to NFPA 70E-2009, Standard for Electrical
Safety in the Workplace, for electrical safety training requirements.”
NFPA 70E covers electric shock, arc flash, arc blast, and PPE. If you have
been trained to recognize the hazards involved in tying in live, then it
can be argued that you are qualified personnel. Of course, it's up to the
AHJ* to decide whether or not a license is required.
*Informational Note: The phrase “authority having jurisdiction,” or its
acronym AHJ, is used in NFPA documents in a broad manner, since
jurisdictions and approval agencies vary, as do their responsibilities.
Where public safety is primary, the authority having jurisdiction may be a
federal, state, local, or other regional department or individual such as
a fire chief; fire marshal; chief of a fire prevention bureau, labor
department, or health department; building official; electrical inspector;
or others having statutory authority. For insurance purposes, an insurance
inspection department, rating bureau, or other insurance company
representative may be the authority having jurisdiction. In many
circumstances, the property owner or his or her designated agent assumes
the role of the authority having jurisdiction; at government
installations, the commanding officer or departmental official may be the
authority having jurisdiction.
There has always been tension between commercial electricians and entertainment electricians, and as the economy worsens and jobs become more scare, so does the friction. The best defense against hostility is to educate yourself about the rules and regulations, understand your craft and your trade, and secure your position with knowledge and charm.
Ultimately, it's up to the local authority to decide who is qualified for a job, but it’s up to you to decide who is competent to do your own job.
Luminology: The Ellipsoidal Reflector Spotlight
by Richard Cadena
One of the workhorses of theatrical lighting is the ellipsoidal fixture, sometimes known in the United States as an ellipsoidal reflector spotlight (ERS) or in Europe as a profile fixture. The term “ellipsoidal” comes from the shape of its reflector; take a circle, squash it into an ellipse (be careful not to break it, because, by and by, we want the circle to be unbroken!), rotate it 360° about its axis, cut it in half, and there you have it - two ellipsoids (ellipsii?).
Why an Ellipsoidal Reflector?
The ellipsoidal reflector is a relatively efficient way of gathering as much light from the light source as is practical and redirecting it towards the output of the luminaire. It’s not perfect, but it’s better in that regard than some of the other designs. The field an ERS fixture produces - or the cone of light it produces - in combination with the lenses in the fixture tends to be a bit peaked in the center and it falls off near the edges of the field. How peaked it is and how much it falls off is a matter of how the light source sits is positioned inside of the reflector. When it’s properly centered in the focus of the ellipse then the field is as uniform as it gets. When it’s closer to the reflector than to the center of focus then the field has a noticeable hotspot and when it’s too far away from the reflector then it has a noticeable dark spot.
Many of the reflectors that you’ll find in ERS fixtures are fabricated from aluminum. Aluminum reflectors are either highly polished or electroplated to get as much reflectivity as possible in order to increase the efficiency of the luminaire. The higher the specular quality of the reflector the less light is lost to stray reflections and absorption.
Some ellipsoidal fixtures have reflectors made of glass that has been treated with a dichroic coating. The coating is designed to reflect most of the visible light out of the instrument while filtering out the infrared (IR) and ultraviolet (UV) light. It works by allowing IR and UV light from the source to pass through the dichroic coating and the glass reflector towards the back of the instrument where a big metal heat sink absorbs the heat it produces. If you’ve ever tried to change a lamp in a hot ERS fixture (not recommended!) then this needs no explanation.
Fixtures with dichroic glass reflectors are generally more efficient than those with aluminum reflectors - all else being equal - and everything in the path of the light is slightly cooler since a lot of the heat is deflected away from the optical path. However, these improvements come at a higher dollar cost, so they’re not for every application. When budget is a factor - and honestly, when is it not? - then the lower cost fixture with an aluminum reflector typically ends up on the plot, assuming that is an option.
Fun With Form Factors
Ellipsoidals come in a variety of form factors. The earliest ERS theatrical fixtures were conventional tungsten luminaires made by Century Lighting (Lekolite) and Kleigl Brothers (Kleiglight). Today, the ETC Source Four ERS, which was patented by David Cunningham and Gregory Esakoff in 1995, is the most commonly used ERS fixture in the theatre. It has a faceted “near-elliptical” reflector and it is designed to work with an HPL lamp. This arrangement has been licensed to other manufacturers who build ERS fixtures that look and perform in a similar fashion.
There are also many automated lights with ellipsoidal reflectors designed to project images and hard edged beams of light. The term “profile” comes from the fact that the fixture is very good at projecting an outline or contour of a pattern inserted into the gate of the fixture. The gate and the gobo that is put in it, is the plane of focus of the light path, so it projects a sharp image of the gobo pattern, provided the lens is adjusted properly.
And just to complicate matters, we should mention that not all profile fixtures have an ellipsoidal reflector. In fact, some of the sharpest projections can be produced from fixtures like the Robert Juliat SX range of profile fixtures. They use a spherical reflector and condenser optics with four lens elements and these fixtures are known for their uniformity of field and their high quality projection capability.
The Future of the ERS
Ellipsoidals and profile fixtures have been around for a long time, and they’re “bigger” and far more plentiful than other creatures in the theatrical lighting landscape. But that’s exactly what the dinosaurs said to the apes just before they became fuel for our automobiles. Are today’s ERS and profile fixtures on their way to becoming museum pieces?
They certainly are under assault by LED fixture manufacturers. A theatrical-grade LED profile spot is one of the Holy Grails of the theatrical lighting world. But until recently, no one had the courage to charge a conventional incandescent luminaire wielding an LED fixture.
The reasons that LED fixtures were considered inferior to incandescent fixtures were many, starting with the color rendering. (Never mind the reflector type, that goes for all incandescent fixtures.) An LED fixture doesn’t produce the same full spectrum as an incandescent fixture, therefore the way they render colors doesn’t match anything with a filament.
The earliest LED fixtures designed for use in the live event production industry had three very narrow bands of color: red, blue, and green. The human eye perceives white light when all three are on but the fact is that there are a lot of in between colors missing from that “white light.” Consequently, when it strikes an object, unless that object has only those colors produced by the LED fixture then it will not look exactly the same color as it does under incandescent light.
A lot people people recognized that, but it took some smart people named Novella Smith and Rob Gerlach to do something about it. In 2001 they were awarded a research grant from USITT to study human color perception in theatrical lighting and develop an LED solution to satisfy the requirements. Two years later Gerlach wrote a white paper detailing the use of a seven-color LED luminaire with color rendering approaching an incandescent source. In 2007, Gerlach and Smith launched a company called Selador to manufacture and sell LED fixtures.
And then in 2009, ETC, arguably the world’s largest conventional luminaire and dimmer manufacturer, bought Selador. Was it their tacit acknowledgement of things to come or simply another plank in the ETC platform?
ETC has much to lose should LED technology ever overcome all of the obstacles that keep it from replacing incandescent fixtures altogether. Not only would the sales of conventional ERS fixtures suffer but so would the sales of conventional dimmers because LED fixtures typically have built-in pulse-width modulated dimming.
It could be that ETC is hedging its bet and covering all of the bases, just in case. In the history of theatrical lighting, no light source has ever been totally abandoned in favor of new technology; we simply get a bigger tool box and use more tools. And today our lighting tool box is filling fast with a variety of LED fixtures, including ERS and profile spot fixtures, both in a conventional form factor and an automated moving yoke form factor.
Other manufacturers are following suit and adding more colors to their formerly RGB fixtures in order to fill in the color spectrum and raise the color rendering index (CRI). LED fixtures with red, green, blue, white, and sometimes amber are becoming more common.
There are still obstacles to overcome and LED dragons to slay. In order to compete on an equal basis with conventional ERS and profile fixtures, LEDs must have incandescent-like dimming from full all the way down to black, the color rendering needs to be virtually indistinguishable from incandescents, and they need to compete on a pricing level, all of which are very important factors in theatrical lighting, and all of which are very close to becoming a reality.
by Richard Cadena
In 1965, Intel co-founder Gordon Moore predicted that computers would double in power approximately every two years. His prediction became known as Moore’s law. Later on, Intel CEO Andy Grove coined his own law, with his tongue planted firmly in cheek, predicting that networking speed would double every 100 years. Grove was lamenting the fact that, at the time, networking speed had not kept up with computer power.
That was then.
Today, computer network technology has improved to the point where we are able to transport huge amounts of data over copper, wire, and fiber. That’s why we can stream videos to our laptops using Netflix and Hulu, and why new televisions can connect to the internet. It’s also why the live event production industry is being inundated with network technology. You can hardly swing a disconnect switch by its feeder tails without hitting a network-connected console, media server, or computer. If we’re going to be in this business for long we had better get comfy with the technology.
The Ubiquitous Computer Network
The first time I ever heard the term “DMX universe” was in the early 1990s. Until then, 512 slots of DMX was plenty. Then things got more interesting.
As automated lighting grew more complex and full-featured it started chewing up more DMX slots. At the same time, lighting rigs were expanding. What was once considered a “large” lighting rig was dwarfed by the Michael Jacksons and Britney Spears rigs of the world. Then along came media servers and LEDs, and suddenly the industry realized that if we didn’t want to be running wads of DMX cables from FOH to dimmer beach or to the dimmer closet then we had better come up with a better solution. That solution was right under our collective noses, in our homes and offices, courtesy of the computer industry, and it was the computer network.
Now when you go to a show, you need only sniff the air and you’ll find it’s teeming with 802.11, 802.3, TCP/IP, and Ethernet. But what does it all mean?
1. TCP/IP: TCP/IP is a suite of communications protocols including transmission control protocol and internet protocol that is commonly used for computer networking. Most entertainment networks, including the ones used with most lighting and automation consoles like Art-Net, ETCNet, StrandNet, etc., are TCP/IP-based networks.
2. Ethernet and Wifi: Ethernet is one of the physical embodiments of TCP/IP networks and Wifi is another. These are standards that describe the infrastructure of a network, like the cable type or the transmission frequency. Ethernet and Wifi are two of the most common types of networks in the live event production industry. They are borrowed from the computer industry so that we can use the same hardware we use with our networks at home and in our offices.
3. IEEE 802.3 and 802.11: Technically, Ethernet is a standard called IEEE 802.3. It was originally developed by Xerox, Digital Equipment Corporation (DEC), and Intel from 1973 to 1975 and it was formally standardized in 1985 by the Institute of Electrical and Electronic Engineers. Wifi is IEEE 802.11, which is the standard for wirelessly transmitting TCP/IP-based networks.
4. Ethernet, Fast Ethernet, Gigabit Ethernet: Several different flavors of Ethernet have been developed over the years based on the speed of transmission. The earliest has a transmission rate or “baud” rate of 10 megabits per second (Mbps). Later on when cabling and networking techniques were improved another standard was developed called “Fast Ethernet,” which runs at 100 Mbps. Still later, a standard called “Gigabit Ethernet” came along, which runs at 1000 Mbps or 1 Gbps, and today we have 10 Gbps and 40 Gpbs Ethernet. Someday we’ll have 100 Gpbs and 1000 Gbps, or Terrabit Ethernet. (Did I really just say that? Terrabit per second? Wow!)
5. 8-Pin 8-Conductor, a.k.a. RJ45 Connectors: These different types of Ethernet use the same connectors and similar cable. The connectors are technically 8-pin 8-conductor (8P8C) connectors but you know them as RJ45 connectors, those clear plastic connectors with the little plastic tab that breaks off at the mere thought of taking one on any touring show. I was once on a tour where the production company sent these to connect a laptop at the front of house to DL2s on stage. They lasted exactly one load out and then it was run the cable, connect to the DL2s, gaff tape it in place. For that reason, manufacturers have developed “ruggedized” connectors that look like a regular 8P8C connector with an XLR outer shell and ruggedized cable, which looks much like DMX cable. Much better.
6. Cat 5, Cat 5e, Cat 6, and Beyond: The cables are standardized according to categories. You may have heard of Cat 5 cable, which used to be the most common type of twisted pair networking cable around. Today, Cat 5 is hard to find and it has being replaced by Cat 5e and Cat 6 cable. These are different categories of cable as defined by the Telecommunications Industry Association. Cat 5 cable can be used for Fast Ethernet networks while Cat 5e and Cat 6 cable can be used for Gigabit Ethernet.
7. Collision Domains: Networks run fastest when there is little traffic on the wires; that’s why the internet slows down at your house when everyone in your neighborhood comes home from work and jumps online. Limiting traffic on a network helps maintain its maximum speed and there are devices that help accomplish this feat. It’s done by physically segmenting networks with routers, switches, and bridges.
8. Routers, Switches, and Bridges: A bridge is a single input, single output device that filters data on a network to reduce traffic. It does this by only passing data intended for a computer in the network as indicated by the media access control (MAC) address, which is a sort of electronic serial number programmed into each computer. A bridge divides a network in two parts; the part before the bridge and the part after the bridge. A switch also filters data according to the destination MAC address, except it is a single input, multiple output device. It only sends data to the output link on which the matching computer is located by physically connecting the input and the output port. A router also filters data on a network except there is no physical switching. Instead, data is routed to the correct computer with software using the IP address of the destination computer.
9. IP Address: Since you asked, an IP address is kind of like a street address on an envelope; it’s a number that helps data find its intended destination, except an IP address is usually temporary. Most computers currently use version 4 IP addressing, which is a 32-bit number, but there are so many internet appliances today that we are quickly running out of addresses. Version 6 IP addressing uses 128 bits and it will soon be more common than IPv4.
The more astute among you will note that mention was made of 10 things that every stagehand should know about computer networks, yet only nine of them appear in this list. The last thing, and perhaps most important thing that every stagehand should know about computer networks is...drum roll please...where to find more information about them. One of my favorite networking primers is “Rock Solid Ethernet” by Wayne Howell.
I don’t watch much television, but I usually catch 15 or 20 minutes at night when I’m getting ready for bed. At the beginning of an episode of “King of Queens,” the delivery truck driver Doug Heffernan, played by Kevin James, was told by his boss to read a booklet to prepare for a competency test at his place of employment. “I got in this business so I wouldn’t have to read,” he said.
Like Doug Heffernan, a lot of us got into this industry so we wouldn’t have to read. And a lot of us have been displaced from this industry because we don’t read much. Don’t be a Heffernan.
When Remote Device Management Speaks...Consoles Listen by Richard Cadena
What does it take to put a man on the moon? A rocket, some fuel, and lots of computer power. What does it take to change the DMX address on a lighting fixture that’s flown in a rig? A person on a ladder. Houston, we have a problem.
It’s been over 40 years since we landed a man on the moon, so why can’t we change the DMX start address remotely from a lighting console? It’s not rocket science!
DMX has been used successfully for almost 25 years. It’s a uni-directional protocol, meaning that the controller spits out data packets to the receiving devices without regard for whether or not the data was received properly. It works because the data for each of the 512 control channels or “slots” is constantly being refreshed. If one of those packets doesn’t reach its intended destination then another one will come along soon enough and the value for the device under control will be corrected in less than the blink of an eye.
But DMX has its limits.
RDM to the Rescue
As a one-way or “uni-directional” language, DMX has no ability to handle seemingly simple tasks that should be as easy as pushing a button on a radio to ask the lighting tech to climb the truss and change the DMX address. And as of December 2006 there is another way to accomplish the same task faster and easier than finding a free stagehand. It’s called Remote Device Management or RDM.
RDM is a protocol that is separate from DMX although it works seamlessly with DMX on the same wires. It’s intended to replace a person on a ladder with keystrokes on a controller and it allows a lighting operator to perform all of the functions that can be performed through the menu of functions, and possibly more, on a typical automated light or other device, like a dimmer racks.
In most cases RDM doesn’t change how we use DMX; it uses the same consoles, the same output ports, the same DMX cables, and the same devices. The difference is that the manufacturer can add a few lines of computer code to the operating systems of the console and devices under control to allow two-way, or “bi-directional” communication on the same DMX network using the RDM protocol. That’s because the chip in the console and in the receiving device that outputs DMX has always been capable of bi-directional communication; RDM simply takes advantage of both the transmitting and receiving functions of the transceiver chip. But it can only operate in half duplex mode, meaning that a console or receiving device can transmit or receive data, but never at the same time.
Faster Than a Speeding Man on Ladder
A typical implementation of RDM in a fixture might allow you to do such things as change the DMX address, the mode of operation, swap pan and tilt, and perform other housekeeping chores you normally take care of during setup and pre-production. It might also allow you to monitor the devices on the network once the show is underway. It could, for example, allow you to keep tabs on the lamp status (on or off?), the operating temperature, and the operating voltage and current draw (if the device has such sensors). All of this would be possible from the relative comfort of FOH.
It also allows you to “discover” RDM-enabled devices on the network by systematically searching for a type of electronic serial number programmed into RDM-enabled devices called a Unique Identifier (UID). When the controller is prompted to discover RDM devices, it sends a command to the complete range of CIDs - and there are a lot of them...281,474,976,710,656 to be exact! - and listens for a response. If there is more than one on the network then they will all respond at the same time, resulting in data collisions. The controller can detect when there has been such a collision, in which case it narrows the range of UIDs to which it is sending a command and it tries again. It repeats this process until it locates a single UID and then it can have a private conversation with this device. It asks the device exactly what it is, what it does, and how it does it. The device might respond with something like, “I’m a holographic image generator, I have 232 control parameters, and they are intensity, resolution, image size, color...” The controller stores the information in memory and know it knows how to control this device. It then goes on to discover all of the rest of the devices on the network.
It took almost 25 years for RDM to come around, and with 281,474,976,710,656 unique combinations of UIDs you might think that it will take another 25 years for a controller to discover all of the devices on the network in a large rig. You’d be wrong. It actually takes a relatively short amount of time, and it’s far less time consuming than your typical tech on a ladder.
Small Thrill for Man...
RDM-enabled fixtures have been on the market now for about two or three years. Today you can buy automated lights from Barco/High End Systems, Martin Professional, PR Lighting, PR Lighting, and Robe with functioning RDM capabilities. But RDM-enabled consoles are still lagging behind, and an RDM fixture without an RDM console still requires ladder and labor technology to configure the fixture. There are, however, a few lighting consoles - and the list is growing - with RDM capabilities including ETC Eos, Ion, and Element, LSC Clarity, Martin M1, and Zero 88 Jester lighting consoles.
The Jester was one of the first lighting consoles to implement RDM. In the process of setting up the console and patching the fixtures, it gives you the option to discover and configure them automatically using RDM. It works like this.
One of the first steps in the setup of the console is to establish the type of fixtures to be controlled, their DMX parameter assignments (or personality), and to assign a button on the console to each fixture with which to select them. To get started you go into the setup menu and select <Assign Fixtures>, and then <Add Fixtures>. The console will then prompt you for the source of the fixture personality information. To use RDM for this purpose you simply choose the RDM button. The then starts an RDM discovery.
Once a fixture has been discovered, the console asks if you would like to identify it so that you know where the fixture is in the rig. If you choose to identify it, the console sends an RDM identify command and the fixture will respond according to how the manufacturer chose to implement the response. If it’s a lighting fixture it might blink or strobe, if it’s a fog machine it might emit a puff of fog, etc. Next, you can also configure the personality of the fixture by setting its operating mode, its lamp response, etc. Once its configured properly then you can assign that fixture to a button on the console by pressing the <Assign> soft key in the setup window and the button on the console. The fixture personality will then be loaded into the console.
Once the fixture has been loaded, the console asks if you wish to load another fixture. This process repeats until all RDM fixtures have been discovered.
Next, the console prompts you to set the DMX addresses of all the fixtures. If you select <Yes> then it will take you to the <DMX Patch> menu. Then you can select each fixture and set the DMX address manually, or you can have the console automatically patch all of the fixtures without operator intervention. When the DMX address is changed on the console, it also changes on the fixture using RDM. If you have pre-programmed the show using a visualizer then you will probably need to configure the DMX addresses manually to match your plot. Otherwise you will have to make sure you know where each fixture is located before you start programming.
...Big Thrill for Mankind
The first time I had the opportunity to configure a DMX address remotely using RDM was several months ago when I was testing a Wybron Cygnus LED fixture using their Infogate software and gateway. The gateway processes RDM signals and the software paints the screen with information. By changing the DMX address in the software, you could actually watch the display change on the fixture. Watching that happen for the first time was a small thrill for man, and a big thrill for mankind.
Richard Cadena is an ETCP Certified Entertainment Electrician and an ETCP Recognized Trainer. For information about classes and seminars for the entertainment production industry, visit www.APTxl.com.
by Richard Cadena
Suppose that you are a high ranking U.S. naval officer just before World War II. Germany has successfully controlled the seas by using superior numbers of submarines, Winston Churchill is getting very nervous about it, and the United States is beginning to feel threatened. Along comes someone with an idea for some new technology that could provide an edge in the undeclared war to keep shipping lanes open, thus insuring the survival of the Allied countries. The only problem is that the idea comes from a glamorous Hollywood actress and an avante-garde concert pianist and composer. To make matters worse, this new technology relies on a punched paper roll similar to that found in a player piano.
This isn’t a fictitious Hollywood script but a real life scenario. Hedy Lamarr was a glamorous Hollywood movie star in the 1930s and ‘40s and her neighbor was George Antheil. Lamarr learned that, in addition to being a film composer, Antheil also wrote an advice column to the lovelorn in Esquire magazine and had a syndicated column in the Chicago Sun about endocrinology - the study of human glands. She sought his advice about enlarging her breasts, and as you might expect, talk turned from breast enhancement to technological advancement. One thing led to another, and before you could say “endocrinology” they were discussing how they could control torpedoes by radio in a manner that would make it difficult for the enemy to detect and defeat.
What they came up with was a version of frequency hopping whereby the frequency of the control signal would constantly change to avoid detection. This would lessen the impact of interference and lessen the chance of communications being intercepted and jammed.
Today, this technology is commonly used in cordless telephones, WiFi hot spots, and wireless DMX transmitters and receivers. It has been improved significantly over the years to take advantage of increasingly powerful hardware and software, and in the process it has become much more robust. As a result, it is being used much more for wireless DMX transmission and reception. To understand how wireless DMX technology works it helps to understand a little bit about frequency hopping and radio communication.
Imagine that, in addition to your job as a naval officer, you also moonlight as a mad scientist. One of your first mad projects is to build a Jacob’s ladder, which is a high voltage arc gap generator that makes an arc rise between two diverging lengths of bare copper wire, because no self-respecting mad scientist would be without one. When you first turn it on you notice that the arc discharge produces a large amount of electromagnetic radiation, and you think that is s-o-o-o-o cool. So you decide to try to harness its power and use it to communicate a message to the entire world.
If you could somehow connect your voice to the flow of the current in the high voltage generator you think you can make the electromagnetic radiation pulse with the voice signal, thus radiating an electromagnetic version of your message. You have no problem converting your voice to an electronic signal with a microphone, so that part is easy. After much trial and error, you finally succeed in connecting the output of the microphone to the voltage generator, at which point you have an uncontrollable desire to toss your head back, fling your arms towards the heavens and exclaim, “It’s alive!” But upon further examination, you decide that such celebration is unwarranted because the signal can only travel a very limited distance. In order to be a world class mad scientist it is required to broadcast this message a respectable distance. So back to the drawing board you go.
What you eventually discover is that your voice has a limited range of frequencies. If you try really hard to deepen your voice you might be able to get it down into the hundreds of hertz and if you inhale helium gas - which, by the way, is very unbecoming a mad scientist - then you might be able to squeak out tens of thousands of hertz. But through a series of mad experiments you discover that the higher the frequency the farther the travel of the electromagnetic radiation. You reason that if tens of thousands of hertz can travel a very limited distance then a few million hertz should carry it a very respectable distance. So you decide to use the higher frequency as the “carrier” signal. Now all you have to do is to figure out how to make the message ride on top of that high frequency carrier signal.
Late one night in the laboratory, you’re feeling pretty good because there is a full moon and you’ve been inspired by reading Mary Shelley. You’re in the zone and almost by accident you realize that if you changed the frequency of the carrier signal at the same rate as the frequency of your voice that you can encode your message onto the carrier signal. Then all you have to do is to build a receiver that strips out the carrier signal and you will be left with the original voice message. For a world class mad scientist like yourself it was a no-brainer. You figured out how to “modulate” the frequency of the carrier signal, which is called “frequency modulation” or FM for short. Years later a rock band named Steely Dan would write a song about it.
In the process you also learn that you can modulate the voltage level, or amplitude, while keeping the frequency constant. That’s what is known as “amplitude modulation” or AM. Alternatively, you can modulate the phase or the starting time of the carrier signal, which is “phase modulation.” Radio communications typically use one of these modulation techniques, except instead of using a Jacob’s ladder, a very tall and powerful antenna works too.
Now when you take off your mad scientist hat and put on your naval officer hat you have the problem that when you try to communicate with your people using the radio, the enemy has just as much access to the radio waves as you do. So they can easily tune in and pick up your broadcast, thus spoiling the surprise you worked so hard to spring on them. And if that surprise happens to be a radio guided torpedo heading for their U-boat then all they have to do is to send their own radio broadcast at the same carrier frequency in order to jam the transmission. What you end up with is a coyote-roadrunner cartoon scene where the torpedo turns around and chases the coyote. There has to be a better way.
One better way is to change the carrier frequency several times during the broadcast to throw off anyone who might be trying to listen in. That’s what Lamarr and Antheil figured out and eventually patented in 1942. Their scheme was to change the carrier frequency periodically and synch the receiver at the same time using long rolls of paper with rows of perforations which would change the tuning frequency. They proposed using 88 rows of perforations, just like a player piano, which would allow them to make use of 88 different carrier frequencies. They would synchronize the changes in the carrier frequency with the changes in the tuning frequency by using “calibrated constant-speed spring motors, such as are employed for driving clocks and chronometers.” And to insure further accuracy they suggested the use of a synchronizing pulse which would be transmitted periodically to signal the receiver when to start the clock.
The use of frequency hopping would effectively spread the carrier signal among a wider spectrum of electromagnetic radiation. This a technique known as frequency-hopping spread spectrum (FHSS) transmission. It differs from fixed-frequency transmission in that the transmitter and receiver are not set to a single frequency, as is sometimes the case with wireless microphones. Instead, the carrier signal ranges from 2.4 GHz to 2.4835 GHz, which is known as the ISM band (industrial, scientific, and medical), or from 5.47 GHz to 5.725 GHz, which is known as the U-NII band (unlicensed national information infrastructure).
The bandwidth of transmission is less than 1 MHz, so several hops can be made inside each range of frequencies. Depending on the manufacturer, the number of hops can vary from tens to thousands of hops each second. The maximum refresh rate of DMX is 43 Hz, which means that most wireless DMX systems are easily capable of transmitting the maximum number of data packets with plenty of room to spare. If there is any loss of data or data corruption, the data will be refreshed quickly enough that the error will most likely go undetected by the user.
If any of the frequencies in the transmission band have interference, then some FHSS technologies will adapt by hopping over those frequencies. This is a technique known as adaptive frequency-hopping. This helps improve the reliability of transmission. For example, if someone in the production office decides to pop some popcorn in the microwave oven while you’re trying to control the lighting system, then the wireless transmitter will detect interference at a certain frequency and hop over that frequency in the course of sending a data transmission.
Microwave ovens, cordless telephones, and Bluetooth devices all operate in the ISM band, which can potentially cause interference. For that reason, many of the new wireless DMX devices operate in both the 2.4 GHz and the 5 GHz bands. When you see the term “dual band,” that’s what it means.
FHSS offers a variety of advantages over fixed frequency radio transmission. It helps make it more immune to interference by spreading the energy over a range of frequencies so that any narrowband interference has less of an impact on the entire transmission signal. It also allows a transmission to coexist with other devices in the same transmission band and still operate effectively.
Wireless DMX transmission has been around for several years and it keeps getting better by taking advantage of improvements in wireless technology. In the last five years it has become more reliable, easier to implement, and less nerve-wracking than ever before. In my experience, those who argue that wireless DMX is unreliable are typically reflecting on a bad experience they had with it several years ago. If you give the current technology a try, chances are you will not be disappointed.
These advances owe a debt of gratitude to a number of people who have contributed to the technology dating back to the early 20th century, including Hedy Lamarr and Geore Antheil. Lamarr and Antheil were never successful in selling their idea to the Navy. The mad scientist in the Naval officer who reviewed the patent might have impressed with the resourcefulness of the duo but the officer in him likely choked on the idea of using a low tech solution in their high tech, high dollar submarines. FHSS technology was eventually used by the Navy but not until the Cuban missile crisis in 1962, three years or so after the Lamarr-Antheil patent had expired.
Not long ago I was conducting an information session about the industry testing and certification program known as ETCP (Entertainment Technician Certification Program - www.ETCP.ESTA.org). Midway through the session an individual raised his hand and asked a simple question: "Why should I become certified?"
Actually, it was a question from his colleagues and he was just the surrogate questioner. Still, the straightforward question took me a bit by surprise. I was under the impression that the attendees would be people who were already convinced of the value of becoming certified and I wasn't prepared to argue the merits of the program. If only I had seen the link to the EC&M article about a deadly arc flash before the information session I might have been able to say something intelligible without stammering and stuttering.
The article to which I am referring if a forensic analysis of electrical troubleshooting gone wrong. It cost the electrician and an electrical inspector their lives and it was attributed to a lack of training and education.
To read the EC&M article about the deadly arc flashclick here.
When I was a kid, my two older brothers were standing in the front door watching a massive electrical storm through the screen door. I was afraid to get too close to the doors or windows because of what sounded to me like earschplittenloudenboomers. Each bolt of lightning shook the house and rocked the neighborhood. They were both leaning against the door jam with their hands resting on the aluminum weather stripping when suddenly, a bolt of lightning struck the power line in the alley behind our house. Both brothers howled like wolves and nearly jumped out of their fur. The energy of the lightning strike enveloped the house and they got a good shock. As far as we know, it wasn’t severe enough to cause any damage, but they were always a bit goofy so it’s hard to tell.
Can that happen if you’re standing on a metal catwalk and lightning strikes the building?
That was the question on the mind of a reader, “a sound technician with over 35 years of experience, but with limited electrical engineering knowledge,” who wrote: “I have a contract to provide theatrical sound, stage-lighting and video services at a university. Recently, the university allowed multiple cell phone companies to install equipment on the roof of the theatre. The cell phone tower equipment installed by one company includes a conduit from the roof to the stage area catwalks on the inside of the building. The conduit is bonded via a decent gauge wire to the exposed steel of the building. (The cell phone company) also installed a heavy wire from inside the same conduit to the exposed steel of the building. My concern is, what happens in the event of a lightning strike or other electrical issue from their equipment? The building's steel is exposed throughout the catwalk area above the stage and the steel most likely is also connected to our double-purchase rigging system steel. Are we at risk for a shock in this situation? Does it matter if the heavy wire is for lightning suppression versus just a heavy ground wire for their installation?”
You might want to turn off the SpongeBob SquarePants episode and think about this. After all, the voltage between clouds and the earth can reach as high as 10 MV to 1000 MV and the current from a lightning strike can range from a few thousand amps to 200 thousand amps. Get it right and standing on the catwalk during a thunderstorm is not likely to present a problem; get it wrong and it can ruin your whole day.
The short answer to his question is that it should be safe to stand on the catwalk during a thunderstorm because the cell phone tower is bonded to the building. The reason for bonding them is to do our best to make sure all of the metal in the building structure, the cell tower, and the electrical system remain at the same voltage potential regardless of what might happen. Otherwise a lightning strike or ground fault could create a difference in potential that could be very dangerous.
Depending on how tall the cell tower is and how often lightning occurs in the area, there may or may not be a lightning protection system on the building. In either case, there is an electrical grounding system which is separate from the lightning protection system. The general idea behind both is to provide a low impedance path for fault current or lightning discharges. In the case of lightning, the low impedance path keeps the current away from non-conductive parts of the building which would sustain more damage than does the low impedance path. Without it, the lightning discharge could potentially damage materials, start a fire, and/or electrocute anyone with the misfortune of touching two objects at different potentials.
The electrical grounding system keeps all of the bonded parts at the same voltage potential during a ground fault or a lightning strike. This is what generally makes it safe by making sure that one part of the structure becomes energized while another part doesn’t. It also causes a massive amount of current to flow in the event of a ground fault, which insures that the circuit breaker will trip very quickly and remove the voltage from the grounding conductors.
Standing on the catwalk while fault current or lightning discharge current is flowing isn’t enough to hurt you. Much like a bird sitting on an electrical power line that is conducting massive amounts of current, you won’t be injured because there is no 0V reference relative to you. A high voltage has no significance unless it is referenced to another voltage point. That’s why you can’t measure any voltage with one test lead; you can only measure voltage between two points. If, on the other hand, the bird were to straddle the power line and a grounded transmission tower it would be cooked because the tower is connected to the earth, making it a solid 0V reference. Now the high voltage has real meaning.
Bonding the cell tower to the building steel is part of the NFPA 70 (National Electrical Code) requirements for radio and television equipment. Article 810.21 says that masts and structures supporting antennas have to be grounded to an electrode or other suitable grounding connection point. In many cases that means the building steel, provided it has a solid connection (meaning low impedance) to earth. Otherwise the electrode could be a water pipe within five feet of its point of entrance into the building or a grounding rod. The Code also says that the grounding conductor should be protected from physical damage (thus the conduit) and that both ends of the raceway should be bonded to the grounding conductor or to the same electrode to which the grounding conductor is connected.
If there is a lightning protection system then the game changes a bit. A lightning protection system has four main parts: (1) a system of strike termination devices (called air terminals) on the roof and other elevated locations; (2) a system of grounding electrodes; (3) a system of conductors connecting the air terminals to the grounding electrodes; and (4) transient voltage surge suppressors (TVSS). The air terminals are mounted at the highest point on a building in intervals of no more than 20 feet. If it does its job right then the lightning protection conductors will be the preferred path for current due to lightning strikes and it will conduct it through the grounding electrodes and into the earth.
The NFPA 780-2008 Standard for the Installation of Lightning Protection Systems spells out specific requirements for lightning protection systems. One of the requirements is that the lightning protection system, electric service, communications, antenna system grounds, and underground metallic pipe systems all to be interconnected, again, so that they will all stay at the same voltage potential. NFPA 780 also requires that the building is bonded to the lightning protection system for the same reason.
Ideally, the resistance of the grounding system or lighting protection system to the earth should be 0 ohms; however, in practice that just not possible because even the largest conductors have some resistance, even if it is small. So we do the best we can to make the resistance as low as possible.
The NEC says that if the resistance to the grounding electrode is more than 25 ohms it has to be supplemented with another grounding electrode that is bonded to the first. The combination of the two will lower the resistance to ground. In many instances we try to make the resistance to ground less than 25 ohms. The NFPA and IEEE recommend a ground resistance value of 5 ohms or less.
Lightning protection systems are supposed to be inspected every year although there is no enforcement. But you can perform a visual inspection of the grounding and bonding to ease your mind. Things to check for are loose or broken connections in the lightning protection system and the electrical grounding system. Check for corrosion or burned conductors. Pull on components to make sure they are well connected and tighten clamps and splices with a wrench. Check the transient voltage surge suppression units to see if the indicator lights warn of a failure.
Also, grounding rods have a limited life due to corrosion. Moisture, salt, and high temperatures contribute to the degradation of electrodes. The life expectancy of a driven rod or a grounding plate is only five to 10 years. A concrete encased electrode is expected to last 15 to 20 years while a building foundation electrode is expected to last 20 to 30 years. There are also specially engineered electrodes such as an advanced driven rod, which looks a bit like a masonry drill bit, and an electrolytic electrode, which is a hollow copper shaft filled with natural earth salts and desiccants to draw moisture from the air, forming an electrolytic solution that seeps into the soil and keeps it moist and conductive. The life expectancy of the advanced driven rod is 15 to 20 years and that of an electrolytic electrode is 30 to 50 years.
A formal inspection of the lightning protection system is more time consuming and involves specialized test equipment. The 3-point test requires two auxiliary grounding rods to be driven into the ground. Voltage is then applied between the grounding electrode under test and the second grounding rod. An ammeter reads the current generated between them while a volt meter reads the voltage between the electrode under test and the third grounding rod. The result is the resistance in ohms between the ground electrode and the surrounding earth.
There are also ground resistance meters, such as the Fluke 1630 Earth Ground Clamp meter. It allows you to test the integrity of a grounding electrode by clamping the meter around the electrode or grounding conductor instead of using auxiliary stakes.
The main idea behind a lightning protection system is that we want to be able to control where the current from a lightning strike is flowing and it shouldn’t be through you or anyone else. If the lightning protection system, electrical grounding system, and bond are all installed and working properly then more than likely there will be no problems.
There is a lot to know about grounding and lightning protection systems. A good book to read about grounding is called “Soares Book on Grounding” which is published by the International Association of Electrical Inspectors. In the meanwhile, keep your eye out for air terminals (you’ll see plenty of them at the highest point in any outdoor electrical substation) and watch for ways in which electrical grounding systems and lightning protection systems are bonded to electrodes.
A reader writes:
"I worked on a movie set last week with an arena set up of theater lights using a ETC Sensor dimmer (96 channel). There were 4 racks at various location all with their own 200- or 400-amp feeder transformers. We ran feeder with double neutral. They said it was to carry excess voltage back. Can you explain this to me? This is not the norm in theaters in my experience."
A: Dimmers like Sensor dimmers and the vast majority of dimmers we work with in theatre and live event production take a sinewave voltage input and switch the current to the load on and off several times every second. When it does this it changes the waveform from a sinewave to what is known as a complex waveform (anything other than a sinewave). In the process, it generates harmonics (whole number multiples of the supply frequency), which causes current to flow in the neutral of the feeder (the conductor with the white Camlock connector or white markings). Under certain conditions the current flowing in the neutral due to harmonics can exceed the phase current, and since the neutral is the only conductor that is not protected by a circuit breaker, it could burn or melt. Therefore, we sometimes run two neutral feeders to handle the extra current.
If you have worked in the theatre before you may or may not noticed whether or not the neutral is oversized. Rather than run two neutrals in a permanent installation like a theatre or performing arts center, often the neutral is sized larger than the phase conductors for the same reason that we run double neutrals in a portable power distribution system feeding a large number of dimmers.
By the same token, the feeder transformers also have to be able to handle more current in the neutral; therefore we sometimes see K-rated feeder transformers or harmonic mitigating transformers (HMTs). Either way, the idea is to make sure that not only the feeder cable is protected from excess current in the neutral but also the feeder transformer as well.
Do you have a question? Email info@APTxl.com.
by Jacob Coakley
OK, so I’m diving into EEET but I figured first week and all, I’d give you guys a bonus, too. Not only will we do Chapter One – we’ll also do the Introduction! :-)
Biggest thing to take away from the intro is the warning, which I’ll (kinda) repeat here:
“Make no mistake about it: Electricity can kill. It takes as little as 60 milliamps (a milliamp is one thousandth of an amp) passing through the heart to make it fibrillate or stop, causing death within a few minutes. And that’s not the only way it can kill you.”
And then later…
“If you understand how electricity behaves and respect its potential for danger, then you can minimize the dangers and work in relative safety.”
So, two things and then I’ll stop with all the colons for a while: 1.) We’re going to be TALKING about electricity. We are not going to be guiding anyone to open up a dimmer, play with a circuit panel, or in any other way mess with live voltage. Electricity can kill. And while this book, and blog, are meant to educate people about electricity, they are not comprehensive. 2.) Safety first. Never let your guard down when dealing with electricity.
So, without further ado, Chapter 1!
After a brief list of the major players who shaped our understanding of electricity (Volta, Ampere, Edison, Tesla, Westinghouse and others) Richard starts to hit the basics. The REAL basics—a pure base definition of electricity: “the transfer of energy through the motion of charge-carrying electrons.”
And to understand that, you need to know what electrons are. So Swami follows that up with a quick discussion of atoms and subatomic particles. Namely: proton (positive charge), neutron (So THAT’S why the character is named Jimmy Neutron…and, uh, oh yeah, no charge), electron (negatively charged). Plus, there’s an electrostatic attraction between opposite charges—positive attracts negative and vice versa—and a repelling force between like charges, i.e., two positives repel each other. Which makes no sense then how those perky morning news anchors do it. Well, they certainly repel me.
And then Richard follows all that up with our first bona fide equation, guaranteed to send up red flags for theatre folk (techie or not) everywhere. The formula describes the strength of the charges between particles, whether positive or negative, and it reads:
To truly understand electricity, we’ll need to understand some basic concepts, so we know how it works. These are: voltage, current, resistance, power and energy. And, oh yeah, we’ll also need to know about the units of measure for each of these concepts.
I’d say “bring it on” except I still have problems with the metric system—so I’m just hoping to get out of this chapter with my asbestos underwear unscorched.
Voltage—or electromotive force (EMF) is what causes electrons to flow through a conductor. It’s a potential to cause the electron drift, the wave upon which electricity rides. (Yes, I’m now thinking of Metallica’s Ride the Lightning, which I totally owned on cassette, thank you very much.)
Voltage is potential energy—it can make electricity flow, but only if there’s a closed path along a conductive surface. Cadena compares it to gravity. Hold a ball above the earth, it has the potential to fall, turning into kinetic energy. Voltage is gravity. There’s the potential to turn into electricity, but before it can do that, it needs a closed conductive path (it needs you to let go of the ball).
No, we really don’t need to make a joke about the fact I just told you to hold your balls. Get your minds out of the gutter.
A battery can be a source of voltage, and the electrical grid is another source. The specific voltage coming from the power plant varies by where you are in the world.
Current is “the flow of electrons or the flow of electrical charges. It is what we understand to be electricity.”
So voltage gets applied to a conductor, electrons drift, carrying the energy from source to “sink” in the form of electric current.
Ready for some conditionals?
A voltage can exist without inducing current. (Richard gives the example of a battery not connected to anything.) If a path isn’t closed, current can’t flow. A closed path that can conduct electricity is a “complete” or “closed” circuit. One that doesn’t conduct electricity is called an “open” circuit.
Resistance is the opposition to the flow of electric current. Insert your own joke about a high school dance here. I think resistance is easy for me to get because there are—quite obviously—materials that don’t conduct well, so I can understand that different materials have greater and lesser degrees of conductivity/resistance. Also important: There is no such thing as a perfect resistor—every material has some resistance, even in wires. The longer the wire, the more resistance increases.
[WARNING: On my own first trip through this section, I didn’t understand this AT ALL. I am striking out my text to let you know that it’s probably horrendously wrong, but if you want to read it to get a sense of HOW I was getting confused you can do that. You’re probably better off, though, just jumping down to Cadena’s explanation…-Jacob]
Physics definition alert! “Power is the rate at which work is being done. In physics, work is done when a force is applied over a distance. The rate at which it is applied, that is, the magnitude of the force and the speed at which the distance is covered, determines the amount of power involved.” Wow. Talk about clarifying absolutely nothing. Sorry, getting a little bitter. I have read and re-read this section, a grand total of 3 paragraphs, over and over for the past 45 minutes and I still have NO IDEA what the hell is going on. When I originally started taking my notes on this I said I’d try not to get snarky. That’s all gone now. I’m in full-on snark mode. OK, once more with feeling, and then I leave it to the Swami… So, OK, so if power is the rate at which work is being done, it includes a time element. It is not an instantaneous thing. So what is work? Work is force applied over a distance. Pushing a box from point A to point B is work. When you add in speed—or how FAST you’re pushing the box—that is power. (Cadena uses an example of picking up a piece of truss. I use pushing a box because I’m trying to also visualize electricity moving linearly…) For electricity, the EMF (Voltage) applies force on the negatively charged electrons and moves them a distance. That’s work. Voltage is pushing electrons along like you pushing a box, resulting in a current. Except later Swami says that power is voltage multiplied by current—and in my understanding of this voltage RESULTS in current… So where does power come from? Is power simply voltage times current? And if so – well then what does this mean to my understanding of everything above? I’m lost. Swami, come on in. The next morning… Yeah, no kidding. Between that last paragraph and this one, I went to bed. I’m coming at this fresh, and I think I might know what my problem was. I was considering the definition of power nesting formulas. I.e., Work=force (or voltage) over distance, Power=Work multiplied by something. BUT – what I’m thinking now is that power is the exact same formula for work, just with added variables. Namely: How POWERFUL is the force? (Magnitude.) How FAR is the distance? (I have no idea.) But I think that makes the formula make a bit more sense to me. Except Cadena says that voltage would be magnitude, and current would be the amount of work done—which means I don’t understand how voltage also figures into the power formula, if it’s already been used. Oy. I’m going to lay out all my terms here, and let Cadena sort it all out. Work=Force * Distance Power=Work/Time OK, now to plug in some terms from the text: Force = Voltage, which I’m getting from Richard’s statement “Electromotive Force (EMF/voltage) does work on the negatively charged electrons.” Wait – Am I confusing terms here? Is EMF the force, or the work? I don’t think it is b/c of the following statement Work = Current “Current is the indicator of how much work is being done.”
So there you have it. Swami, I’m dying here. Let me know what I’m doing wrong.
I don’t know that I should be moving on without having a good grasp of what I just read, but I gotta.
So, definition time: “Energy is a quantity of work done over time, or the capacity to do work. Electricity is a form of energy that can be converted to and from mechanical energy, safely transported over large distances, harnessed, and used for specific purposes.”
Cadena makes sure we all know that Energy is distinct from Power. Energy is product of power and time. (Which means my formulas above were very wrong…)
He gives the example of a 25kg and a 50kg road case. It takes twice the power to lift a 50kg 1 meter, but it takes the same amount of energy to lift the 25kg case twice as high.
Sigh. I’m going to assume that will make more sense when I understand power better.
SI UNITS OF MEASURE
Now that we understand all those concepts (cough, cough) it’s time to know how to measure them all.
SI Units (from the French Systeme International d’Unites, or International System of Units in English) have seven base units, standardized by agreement. The base units are: the meter, the kilogram, the second, the amp, the Kelvin, the mole, and the candela.
We can derive (calculate) other units from those base units.
The ampere measures current, one of the seven base units in SI. It’s named after Andre-Marie Ampere, a French mathematician and physicist who codified the relationship between electricity and magnetism.
1 Amp is defined as “the amount current it takes to generate a certain amount of force between two current-carrying conductors laid side by side at a specific distance.
Ready for why? I knew you were.
When current flows, it creates a magnetic force around a conductor. When two conductors are next to each other in the same orientation, they will repel each other. The strength of this force of repulsion is how we measure 1 ampere.
Richard then gets into some MAJOR numbers about this is derived and original definitions – but that’s what you really need to know. Amperage is a measure of the force of repulsion from 2 conductors. This is also how a clamp meter works, by the way, by measuring the magnetic fields around a cable.
In electrical formulas, Amperage is represented by the letter “I” (Hey, Swami, why is that? More French?)
In a schematic diagram current is indicated by an arrow in the direction of the current.
A volt is a derived measurement. It’s defined as (wait for it…) “the potential difference across a 1-watt load with a current of 1 amp.” So voltage depends on wattage and current.
Represented by the letter “V” in formulas.
The Ohm measures resistance and is also a derived measurement. It is abbreviated by the Greek symbol Omega (W). It’s defined as “the amount of resistance that will produce a voltage drop of 1 volt given a current of 1 amp.” In a formula, Resistance is written as “R.”
Conductance is the opposite of resistance. It measures how easily current flows through a conductor. It’s measured by the Siemens. (Which I had never heard of before this…) The Siemens is represented by a “G.” The Siemens is a relatively new term—if you’re looking at electricity books before 1971, you might see it referred to as mho. (The opposite of ohm, get it? Wow, those wacky physicists…)
Again, energy is different from power. (Which would mean a lot more if I understood power…) Energy is power applied over time, and is measured by the joule.
Ready for the joule definition? Here it is: “the work required to move 1 coulomb of charge through a potential difference of 1 volt.”
Not happy with that definition? There’s an alternate one! A joule is also “1 watt-second, or the amount of energy expended by using 1 watt for 1 second.”
Because the joule or watt-second is MUCH too small a number to be useful in the production industry, you’ll often hear the term “watt-hour,” which is the equivalent of 3600 joules. (OK, even I could figure out how they figured that one out. J )
HVAC tech’s use still a DIFFERENT measurement of energy, called BTU’s (British Thermal Units). You’ll need to know how to work with those when you measure the impact of lighting on the energy it takes to cool a room.
Again, power is not energy. And power is measured in watts. One watt is defined as 1 joule per 1 second.
In formulas, power is represented by the letter “P.”
Cadena then includes a handy table that lists all the info I just gave you in a very easy-to-read chart—these are the benefits of getting the book, folks. J
At the end of the chapter Richard closes with a quick recap of the law of conservation of energy—which states that energy cannot be created or destroyed, just changed from one form to another. You can change hydraulic energy to electricity to light and heat, but you don’t actually create or lose any energy.
And then he gives his chapter review questions. For me, I only have one—WTF is power? And hopefully Richard’s already answered that question up above…
I’m laughing, but I’m laughing with you Jacob. The good news is that this chapter made you think. The other good news is that you’re really not too far off in most of your conclusions. To clear up the confusion, I’m going to take my magic mind eraser and erase all of those confusing thoughts from your mind and start over again. You already have mastered the concepts of voltage, current, and resistance. (And by the way, the reason we use the letter “I” for current is because they used to call it “intensity” of current.) Now think of an electrical system as a hydraulic system.
Yesterday, I ran into a friend of mine who said he bought stock in a “re-charge” company. He explained that they install re-charge pumps in oil fields so that they can increase the pressure in order to pump twice as much oil through the same sized pipes. Since it costs millions of dollars to install and maintain hundreds of miles of steel pipe, it saves a ton of money. Now think of the pump as a transformer that doubles the voltage and think of the pipeline as a conductor. By doubling the voltage you can supply twice the current using the same size conductor. You’ve just doubled the power delivered to the customer because power is the product of voltage and current. Now think back on the oil pipeline for a moment. The customer receiving the oil can refine it and burn it for fuel, releasing the potential energy in the oil and converting it to useable energy. If the customer siphons off the oil for two hours, then he will have twice as much useable energy as he will if he siphons it off for one hour. That means that energy is time-dependent. The same holds true of electricity. If you hook up a 1000-watt lamp and turn it on for two hours it uses twice as much energy as if you turn it on for one hour. It too is time dependent. And energy is energy, whether it’s in the form of heat (as in burning oil or coal), electricity, or movement (lifting a truss through a distance).
Now think about your electricity bill. Do you know how the electric utility charges you? They charge by the units of kilowatt-hours, meaning they take the number of kilowatts you’ve used and multiply it by the amount of time you’ve used them. That’s the unit of energy.
I hope that helps to clear that mystery up for you.
Random notes and answers to your questions:
The description of the definition of an ampere is the formal definition and it is a bit “involved.” The easier way to describe it, which was the old definition before the international weights and measurements committees got hold of it and “cleared it up,” is that one ampere is the amount of current required to make 6,241,000,000,000,000,000 electrons pass a given point in one second. I could have said that one amp is the amount of current that would cause 6.241x1018 electrons to flow past a given point in one second, but exponents freak out some people.
“…voltage depends on wattage and current” might better be expressed by saying that voltage, wattage, and current (as well as resistance) are all interrelated; change one of them and they all change.
Siemens is not a common term and the reason you probably have never heard of it is because we have ohm meters, amp meters, and volt meters but I’ve never seen a Siemens meter. The only reason I included it is because it might help to understand how current divides in a network. People often say that current takes the path of least resistance but a more accurate expression is that current takes all available paths in inverse proportion to the resistance of the path. So, for example, if there are two paths, one of which has 10 times the resistance of the other, then 10 times as much current will flow through the alternate path as the one with 10 times the resistance. And the inverse of the resistance is the conductance, which is measured in Siemens. Why is this important? What happens when a live conductor is grounded against the chassis of a piece of gear and you come along and touch it? The extent to which you receive a shock depends on the relative resistance of the two paths – the one through the chassis and back to the source through the grounding conductor, and the one through you and back to the source through the earth. The same is true of a lightning strike to the building when you’re standing on the catwalk. The discharge current passes through the lightning protection system, which is bonded to the building steel, which is bonded to the catwalk. Are you safe? What are the two values of the Siemens for the two paths? I'll bet you're looking for a Siemens meter now!
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(AUSTIN, TX - June 8, 2010) The Academy of Production Technology announces pre-sales of a new training DVD designed to instruct lighting programmers on punting, which is the process of running a show “on the fly.”
Industry lighting designer/programmer Richard “Nook” Schoenfeld guides viewers through the process of a universal punting method - step by visual step - in a two-hour DVD tutorial, “Nook’s Ultimate Punt Pages.”
Special pre-release pricing with a 33% discount is in effect for a limited time until the DVD’s release in October.
“I specialize in designing festivals and festival-type tours where punting on consoles as opposed to programming the entire show ahead of time has become an art form,” Schoenfeld says. “I hate to toot my own horn, but the concerts on which I punt the lighting cues usually look much better than most shows that have fully programmed sets of songs.”
The universal art of punting involves setting up one page of the console with as many stage lighting looks as possible before the show. This allows the designer to then choose focus positions or movement cues, color schemes, gobo patterns and intensity levels through a variety of faders and push buttons on the fly, Schoenfeld explains.
“Every lighting professional eventually finds themselves in a situation where they have to improvise the lighting looks,” says Richard Cadena, founder of the Academy of Production Technology, producer of training tools for professionals in the live event production industry. “Unless they know how to set up the console to easily and effectively do so, they will have trouble. Nook’s method of punting is helpful in many kinds of live situations, be it concerts, festivals, corporate events, TV one-offs and other productions.”
Let me just get this out there right off the bat – I’m not a rigger.
So what am I doing in an automation and control class? I’m glad you asked.
I’ve been involved in the production industry in one form or another for over twenty years and I’ve successfully dodged learning much about rigging and automation. Until now.
Some people have an aversion to math, some people have an aversion to heights; I have an aversion to taking responsibility for hanging things over people’s heads. But I received an intriguing email about the Navigator classoffered at Fisher Technology Services, Inc (FTSI). The more I thought about it the more appealing it sounded. Take some motors, a bunch of hardware, some electronics, and a bunch of software, put it all in one pot, simmer, stir, and viola, instant automation.
Okay, it turns out there’s a little more to it than that, but that’s kind of what goes into it.
So this Monday morning I found myself driving far north of downtown Las Vegas in search of FTSI. The GPS on my iPhone pretty much guided me into the front door of the 56,000 square foot facility across the street from the Las Vegas Motor Speedway.
I was directed to a smaller 5,000 facility behind the building where four Disney employees (Chuck Brandt, Christine Chan, and Brian McGuire), a freelance rigger (Mark O’Brien), and an employee of FTSI (Randy deCelle) were waiting to take the class.
The class was led by Dana Bartholomew, VP of FTSI and an affable, very knowledgeable guy with lots of interesting stories about automation. We started by touring the facilities and walking through the rental, fabrication, R&D, and tech areas. It didn’t look much different than the dozens of production facilities I’ve seen around the world except instead of lights and trussing there were lots of winches, controllers, and peripheral gear. And since they fabricate practically everything in house, there was also CNC machines and a huge water jet cutter. The very high ceiling in the warehouse space was an indication of the kind of testing that goes on in there, and indeed there was a 3D automated camera rig set up temporarily.
Back in the class, we got a brief history lesson on the company. Scott Fisher and Joe Champelli both worked for Siegfried and Roy and the company’s first job was the “Big Freakin’ Roller” curtain in Cirque du Soleil’s “O.” Today they have systems installed or are installing systems in Hyperion Theatre, Le Rev, World of Color, Spiderman on Broadway, and they have contributed to movies such as “Green Goblin,” “Avatar,” and “Vacancy.” They also supplied automation systems to Tait Towers and Show Rig.
Navigator is their control software and it was specifically designed to fly people. Therefore, it has many levels of safety, redundancy, and security, which is the key to making it work safely and reliably. In this class we’ll spend three days learning the software before we go out in the warehouse and play with the hardware.
The hardware is made up of a variety of components. The muscle of the system is provided by a gear motor, which is the combination of a servo motor and a gear box. Coupled to the motor are two brakes – one motor brake and one secondary brake. The motor brake is rated for three times the output of the motor while the secondary brake is rated the same as the motor. On the back side of the motor is an absolute encoder and another encoder, an incremental encoder, is coupled to the winch drum. Both are used to track movement and when they get out of synch or they detect travel beyond the safe zones then it signals the controller which then stops the system. The drum is helically grooved and moves the load by taking up or letting out cable.
The system has a 10:1 safety factor, or as some people call it, a 10:1 factor of ignorance. That means that the brake can hold 10 times the rated load of the gear motor. Part of the safety of the system includes a series of stops that signal the console when the load travels beyond the normal limits as tracked by the encoders. There’s a soft stop, a hard stop, and an emergency stop. Each is tracked by the encoders but they all react differently. The soft stop is normal end of travel and when it is reached it causes the controller to slow down and stop the motor. The hard stop just beyond the normal limits of travel and when it’s tripped it stops the motor and trips the hard stop relay, which disables the system. It can be reset from the console. The emergency stop is set to the point at which damage may occur if the load travels beyond that point. When the emergency stop is triggered it opens the e-stop relay which removes power to the system and applies the brakes.
The stops work because the encoders are monitored by the Navigator software, which communicates with the axis control unit (ACU), and that, in turn, communicates with the motor interface board (MIB). The MIB converts the digital information to motor control signals and directly controls the motor. This feedback loop from the motor to the encoders to the software to the controls and back to the motor is what makes the system work.
Automating and motorizing machinery is nothing new. It’s been going on since the beginning of the distribution of electricity. What has allowed it to progress to this level of sophistication is the speed and power of computer hardware and the capabilities of the software. Combine that with a feedback loop and multiple points of monitoring and it becomes incredibly fast, accurate, and safe.
The beauty of this system is that it draws from every corner of the entertainment industry: designers, riggers, electricians, technicians, programmers, operators, and carpenters. It employs the services of machinists, mechanical engineers, electrical engineers, software and hardware designers, consultants, and CAD operators. It represents the culmination of the sum total of much of the body of knowledge in the industry. It sits at the intersection of a range of disciplines and applies them in unique and creative ways. For example, imagine a rig with automated lights on RSC Lightlocks, each of which is on a carrier controlled by a Navigator system. Not only would the lights pan and tilt, but they could also move up and down the length of the truss while adjusting trim in real time. Or what if some automated lights were mounted on articulating robotic arms? Or what about putting automated lighting on a single motorized cart controlled by the automation system? The possibilities are practically limitless and the industry has only scratched its surface. That’s what makes me think that automation just might be the most exciting area of the industry today.
For more information about FTSI and Navigator classes visit www.fishertechnical.com.
One of the most common questions I’m asked is, “How can I get into the lighting industry as a top lighting designer?” or something similar. It always reminds me of the punch line, “I don’t have to outrun the lion; I only have to outrun you.” (Oh, come on! Don’t tell me you’ve never heard that joke.http://jokesbaskets.blogspot.com/2010/03/outrunning-lion-best-jokes.html)
But in this industry it’s not a lion that’s chasing us; rather, we’re chasing the lion and we have to outrun everyone else in the industry if we’re going to catch the prized position. If you want to be the one that chases down the king of all lighting positions, you’ve got to be prepared to put in some extra effort to prepare for a long chase. Here are some of the things you need to know.
Richard Cadena has been in the lighting industry since the time of the bag phone. He is the author of “Electricity for the Entertainment Electrician” and “Automated Lighting: The Art and Science of Moving Light” (now in its 2nd edition). As an ETCP Certified Entertainment Electrician and an ETCP Recognized Trainer he conducts seminars about electricity, power distribution, and controls. He is also the editor of PLSN magazine and he has missed his share of weddings and funerals due to circumstances beyond his lighting control.