Monday, October 16, 2017

Is it Time for AC to Go Away?

You know about AC and DC, but have you heard of IAC?

Probably not, since I just made it up to describe how we are increasingly relying on wind and solar power to generate electricity. In the process, it's stored in batteries in the form of DC before passing through inverters to convert to AC and then converted back to DC again to be used by the computer chips that ultimately drive our LEDs, consoles, video projectors, and almost everything else we connect to electrical power. Each of those conversions comes with an energy cost, which is why I believe that we might one day return to a DC grid.

In the meanwhile, we'll continue to use that intermediate step using AC.

The only reason that we use AC today is because 125 years ago when Edison began building and selling DC generators, we didn't know how to change the voltage of DC, so the voltage produced by a DC generator was the voltage that had to be used by the consumer.

And when it comes to distributing electricity, there's a trade-off between safety and economy; the higher the voltage, the more dangerous but the more economical, and the lower the voltage, the safer but the more it costs to distribute. That's because of the relationship between power, voltage, and current. To transmit the same amount of power at low voltage requires bigger conductors, which cost more money.

That problem left the door wide open for George Westinghouse to walk through with his newly purchased patent on the transformer, which allowed him to build and sell AC generators. That, in turn, allowed consumers of electricity to remove their very loud and smelly generators from their property and tie into the electrical grid, which was supplied by very large generators located far from the premises, and that's mostly how it's done today.

I was reminded of this recently when I checked into my hotel in Shanghai and I found a variety of electrical connectors, including USB, which provide low-voltage DC to charge batteries in all of our devices. That's not unusual these days, but if it becomes more commonplace and expands to include higher current DC outlets, it could alleviate some issues having to do with electrical power distribution. For example, with AC, we now have to think about power factor and harmonics, which can cause overloads and overheating of electrical apparatus. Neither of those exists in the DC domain. And low-voltage DC is much safer than the 100VAC to 240VAC that we currently use around the world.

Converting to DC won't happen any time soon and there are no guarantees that it will happen at all. But imagine having universal voltage at the connection point (5VDC?), universal connectors, and universal frequency (0 Hz!). In the meanwhile, watch out for the effects of low power factor and harmonics.

Sunday, July 23, 2017

Watch This!

When I worked at High End Systems, we used to sell a strobe light called Dataflash. It had an 8-inch diameter clear plastic dome, and the first versions of it were made of breakable plastic. But in the second version, the dome was made of Lexan, which is virtually unbreakable. In the demo room at High End we had an 8 x 8 matrix of Dataflash mounted on the wall and it was programmed to play patterns and effects. Richard Belliveau, one of the owners of the company at the time, used to bring customers into the demo room and tell them how tough Lexan is. It's used for bulletproof glass and for the windshields of helicopters, he would say. And then to demonstrate how indestructible the domes were, he would walk up to the display, remove one at random by spinning it off of the fixture, and then he would slam it down on the floor as hard as he could. The floor was concrete and it was covered by a thin layer of colorful carpet, so it was very hard. The Lexan dome would bounce around but it wouldn't break.

Richard taught me everything I knew about lighting when I worked at High End, including how to sell customers on the features of our products. Soon I was emulating his demonstration of how durable the domes are.

One day, I brought a customer into the demo room and I said, "Watch this." I spun a dome off of one of the fixtures and walked to the middle of the demo room. With all the flare I could muster, I slammed it to the ground as hard as I could. Much to my dismay, it shattered in a thousand pieces.

Apparently, someone had replaced one of the Lexan domes with one of the older style domes and that happened to be the one I randomly picked. When it broke, I was embarrassed and I waited with baited breath for the customer's reaction. Would he laugh, cringe, or walk out in disgust? None of the above. He said, "Wow, that fantastic!" He loved it.

Wednesday, June 7, 2017

More Books, Less Guns


"What does labor want? We want more school houses and less jails. More books and less guns. More learning and less vice. More leisure and less greed. More justice and less revenge. We want more...opportunities to cultivate our better nature." - Samuel Gompers, founding President of The American Federation of Labor

I was very fortunate that to very important people in my life emphasized the importance of education - my mother and father. My education has afforded me opportunities that other people didn't have, and I'm grateful for that. As political tensions around the world elevate, it's increasingly important to educate our children to give them the opportunity to make the most of their lives and give them the tools to better themselves by applying what they've learned about the world. Education levels the playing field. Teach the children well.

Tuesday, November 22, 2016

What's the difference between a stagehand and a tech?

Stagehand Versus Tech

Being a stagehand is an honorable way to earn a living. And it's hard work. Loading and unloading trucks, hauling heavy gear, and working long, hard hours can be a physical challenge, but plenty of decent human beings do it for a living. And as long as you take care not to hurt yourself, you can make it a career. But maybe you want more of a mental challenge. Maybe you want better pay, or better working conditions. Maybe you want to be a tech.

A tech is a skilled craftsperson. It's also an honorable way to earn a living, and it can also be hard work, but it's more mental than physical. While a stagehand works with their hands, a tech works with their head and their hands. A stagehand works against gravity while a tech works with technology. 

A stage hand can see their work - sections of truss, spigots, bolts, wrenches...It's not hard to figure out how to properly assemble sections of truss. A tech, on the other hand, knows how to calculate how much dynamic force can be applied to a truss before it's too much. 

A stage hand can look at a male and a female Edison connector and see that they can be mated. A tech understands how to calculate the load current and knows whether or not the cable can supply enough ampacity for the connected load.

How do you become a tech? You read, study, learn, and put into practice what you have learned. There are plenty of options to chart your career, whether it involves university or the school of hard knocks. Either way, it can be challenging, rewarding, and fun.

If you need help deciding which route to take, drop a line.

What's Your Vector Victor?

Remember the cockpit scene from Airport! when they are taking off?

Roger Murdock: We have clearance, Clarence.

Captain Oveur: Roger, Roger. What's our vector, Victor?

Tower voice: Tower's radio clearance, over!

Captain Oveur: That's Clarence Oveur. Over.

Tower voice: Over.

Captain Oveur: Roger.

Roger Murdock: Huh?

Tower voice: Roger, over!

Roger Murdock: What?

Captain Oveur: Huh?

Victor Basta: Who?

It makes more sense if you know that a vector is an arrow that represents the size and direction of a value. For example, if I say I flew 240 miles, I’ve only given you a distance. But if I say I flew 240 miles in the direction of north by northwest, then that can be graphically represented as a vector by drawing an arrow 240 miles long in the direction of travel, which is north by northwest. (Okay, it doesn’t really have to be 240 miles long because we can scale it down.)

Why would anyone use vectors? Because they make it easier to figure out complex problems. For example, suppose we take off from Austin and fly due east for 120 miles. Then we change course and fly north by northwest for 240 miles. Where would we end up? We can use vectors, as shown below, to find out.

The black arrow represents the first leg of the flight, and it’s 120 miles long in the easterly direction. The red arrow represents the second leg of the flight, and it’s 240 miles long in the north by northwest direction. The orange arrow represents where we end up, and it goes from the tail of the black arrow to the head of the red arrow. We can use the Pythagorean theorem to calculate the length of the orange vector. The Pythagorean theorem says that a2 + b2 = c2, where a is 120 and c is 240.

1202 + b2 = 2402

b2 = 2402 - 1202

b2 = 57,600 – 14,400

b = √(43,200)

b = 208

According to our vectors, we ended up 208 miles due north of where we started, so we would be somewhere around Dallas.

How does all of this apply to power distribution? I thought you’d never ask. The answer is right under your nose. Look at the illustration again (below), this time with the values for all three vectors included.

Do those numbers look familiar? They should if you know how a delta-delta connected feeder transformer works. In North America, the phase-to-neutral voltage (represented by the black vector) is 120V, the phase-to-phase voltage (represented by the red vector) is 240V, and the wild leg or high leg (represented by the orange vector) is 208V.


This is but one example of how vectors can be used to help make complex relationships easier to understand. There are many more. For example, why is it that, in North America, the voltage from phase A to neutral is 120V, the voltage from phase B to neutral is 120V, but the voltage from phase A to phase B is 208V and not 240V? You can use vectors to see why. The key is the phase relationship between phase A and B, which are 120° out of phase with each other. Try it, and if you get stuck, send me an email and I’ll send you an illustration.

Wednesday, October 26, 2016

The Best Product at LDI 2016?

by Richard Cadena

What was the most interesting product at LDI this year?

That’s often the first question you get when you bump into your friends on the trade show floor at LDI or any other industry trade show. Everyone is looking for that one new light or video idea that, above all the others, really blows your doors off. Everyone is certain that it’s there, but we just haven’t found it yet. Have you seen it?

LDI 2016
LDI 2016 just ended a few days ago, and I didn’t see one thing that amazed me, but almost everything there is truly amazing. What’s happening on trade show floors these days is mind-blowing. Think about it. This industry is taking miniscule diodes that emit enormous amounts of colored light with a tolerance of a few wavelengths. Precision-cut high-tech glass or plastic lenses gather and redirect that light through an impressive train of optics with high-resolution treated glass or stainless-steel gobos and color filters made with incredibly strong glass, and an assortment of effects like precision-controlled framing shutters. The light that comes out of the fixture is actually pulsing hundreds or thousands of times per second—so fast that you’re brain can’t even perceive it—and those pulses are varied in width with such precision that they can fool you into thinking that they can dim as smoothly as the sun rises and sets. Then the whole luminaire assembly is robotically moved with stepper motors or servomotors so accurately that they can target a subject to within a few millimeters at a 30-meter throw. All of this is under the control of extremely small and powerful microcomputers that are programmed to respond to highly sophisticated consoles with hundreds of thousands of lines of computer code that is designed to appease the whims of any user who steps up to the keyboard. These controllers are actually spitting out pulses of voltage every four millionth of a second, and the fixtures can not only distinguish between these voltage pulses, but they can make sense of them and decode their intended meaning. In some cases we’re controlling hundreds of thousands of attributes using a single pair of copper wires, or, even more astonishing, over thin air using wireless control. Then very creative people take dozens and dozens of these devices and hang them on brilliantly designed aluminum structures that can support thousands of pounds, power them using application-specific power and data distribution systems, interconnect them and make them all work correctly in an incredibly short amount of time, and then they make them dance to the music of their imagination, all to the delight of anyone who happens by the aisle. These people come from all corners of the world and they transverse the planet in a matter of hours.


Do you really want to know what I think was the most interesting product at LDI? All of it. Every last bit. It all boggles the mind.

Training Opportunities for Live Event Production Professionals

Sunday, May 22, 2016

Heads!

Your head is worth protecting. Any time there are people working overhead, you should be wearing head protection. You don’t want to catch a shackle or a C-wrench on the cranium dropped from a catwalk or the steel without a good helmet. Any head protection is better than none, but there are certain types of helmets for certain jobs. How do you know which helmet is the right one for the job?
If you’re an electrician, then you should use a helmet that will protect you against the hazard of shock and arc flash. Climbing helmets are often vented, but those vents that make them more comfortable in hot weather make you vulnerable to arc flash. In the event of an arc flash, should you be in the arc flash zone, then those vents could allow your to get second-degree burns on your scalp.
Helmets are classified according to national an international standards, and those designed for electricians should be class E or class G according to ANSI/ISEA Z89.1 and CSA Z94.1. A class G provides dielectric protection for up to 2,200 volts and a class E up to 20,000 volts. For the type of work that you and I typically do, a class G is fine.

I just got a new Petzl Vertex Best for $115 with free shipping on Amazon. It’s complaint with ANSI/ISEA Z89.1-2009 type 1 class E. Type 1 means that it is designed to withstand impact from above, but not from the side. I don’t often find myself in environments where I need head protection with class E compliance, but now I’m prepared just in case.