Electronic Design

Bob's Mailbox

Dear Bob:
I started reading your article "What's All This Incandescent Stuff, Anyhow?" in the Dec. 7, 1992 issue, when I came to a mention of an old college alumnus "who lives in Lompoc, Calif." I was immediately overcome by a severe attack of Lateral Thinking. Roger Ramjet! An ancient, tongue-in-cheek cartoon series that keeps recycling on our local TV.

I think the last episode I saw featured Roger Ramjet and his All-American Eagles (Padaahh!) rushing to the aid of the Lompoc Opera Company, who were presenting a season of Zucchini's opera 'Madame Butterfat' in between bouts of trouble with a mysterious Phantom.

They are always rushing to the rescue of somebody in Lompoc. The point is: I always imagined Lompoc to be a fictitious location. Surprise, surprise to see it mentioned in your column as a real place. What sort of place is it, I wonder?

Every state seems to have a "bend in the road" town that is lampooned on stage and screen. Ours is Eketahuna, which is actually on the main road from the Big Smoke to the Capitol. Strictly speaking, it was two bends in the road; one North and one South of the Pub. And very little else. How many bends has Lompoc got, I wonder?

Concerning the actual article, the technicalities of incandescent bulbs has always been of interest to me, especially the dramatic difference in cold and hot resistance. With cunning design, this can be put to good use to make the lamp act as an overload protection device for some other item—loud-speaker voice coils, for example. Or heater-current regulation.....
Alan M. Wooler, B.E.,
New Zealand Association of Radio
Transmitters Inc.,
North Shore, New Zealand

Lompoc's a nice quiet town of 36,000, about 860 curves west of L.A. and 3400 curves south of S.F. (details later).—-RAP

Dear Bob:
About a month ago, I wrote an essay on the current state of the art in artificial lighting, and yesterday I read your column about incandescent lighting. Such a coincidence!

After hundreds of years of artificial illumination, and decades of electrified homes, you'd think lighting technology would be a little less primitive.

I sit reading under a 60-W light bulb on a hot summer evening. The air conditioning is on, and the cool breeze keeps me comfortable. But soon the thermostat kicks the A/C off, and almost immediately I am aware of the heat radiating from the lamp. Doesn't this seem just a bit primitive? After all, why produce a lot of heat when what you really want is cool light? The waste is doubled when we must consume power to remove this excess heat from our homes with air conditioning.

The various alternatives to incandescent lights, in my opinion, all fall short of the ideal. Fluorescent lights have been receiving much promotion as energy efficient, long-life alternatives to incandescents. Recently, several styles have been marketed that can be screwed into a regular light socket in place of an ordinary bulb. I tried one in a bedside lamp, but find that I rarely use it. The light (despite advertising claims) is unpleasantly harsh, and up close has an annoying flicker. It also buzzes audibly. It isn't shaped exactly like an ordinary light bulb, either. The shade sits up higher than the lamp designer intended, exposing the unsightly white plastic base of the bulb, and making the entire lamp look odd. Thanks, but I'd rather have a regular light bulb.

Quartz-halogens have a very nice quality of light, and I prefer them to ordinary light bulbs but for two drawbacks. First, most of them operate on 12 V rather than the customary 120 V, and require a lamp with a step-down transformer and a unique socket. Therefore, they are not directly interchangeable with ordinary light bulbs. Second, the bulbs are expensive, and when you add the cost of the unique light fixture, they are also expensive to install. Even if their long-term cost is lower, the up-front cost can be formidable.

Quartz bulbs that CAN directly replace an ordinary bulb have only recently appeared on the market, but these are even more expensive—about $25.00 for one 30-W bulb. The 30-W bulb is claimed to supply as much light (and better quality light) as an ordinary 60-W light bulb. I may try one of these if and when the price comes down a bit.

I currently use a (12 V) quartz reading light, and like it. Even if it gets hot at times, however.* What we really need is a lamp that produces good quality light and burns cool—the efficiency of a fluorescent with the light quality (and silence) of a quartz-halogen. But no one has invented this yet.

Do any fundamental laws of physics preclude the efficient conversion of electricity into light without the generation of copious amounts of unwanted heat? Perhaps we need to find, develop, and perfect another technology that produces light from electricity. I wonder how much research has been done on using electro-chemistry for lighting? The cyalume, more popularly known as the lightstick, produces absolutely cool light when two chemicals are mixed inside a plastic tube. The mixing liberates stored chemical energy in the form of greenish or yellowish light. It lasts for only an hour or so, but could it be possible to have a sustained light-producing reaction within an electro-chemical device? Electrical power would separate the reactants within an electrolytic cell. These would then flow into a transparent reaction chamber where they would recombine and produce cool light. Of course the color and brightness would have to be improved over what is currently produced by a cyalume, but who knows what is possible? Edison had to try hundreds of filament materials before he found a suitable one.

It might turn out that the electrochemical conversion steps cannot be made extremely efficient, and would produce waste heat. Even so, this could be done in a central reactor outside the air-conditioned environment, and the "charged" reactants piped throughout the home, office, or factory to where lighting was required. At the point where light was produced, it would be done without heat production. This would be ergonomically preferable, and still save the expense of pumping the waste heat out of the air-conditioned space. New homes would have central heat and air, and a central lighting generator.

If this idea bears no fruit, how about solid-state devices? The efficiency of LEDs is being increased continually, and recently etched silicon has been made to produce light from electricity, albeit with low efficiency. Perhaps further innovation will lead to a highly efficient semiconductor light source, though I have some reservations about monochromatic lighting. (The worst lights of all, to me, are the sodium-vapor and mercury-vapor lamps used in parking lots and other public places.)

How about producing all of the light in a single highly efficient source, and piping it to wherever it was needed with fiber optics? (A "light" socket would really be a light socket!) Too lossy, I suppose.

If all else fails, we can always begin raising fireflies in enormous numbers. If we can train them to respond to voice command ("light on"), we will have produced the equivalent of a coolburning light fixture with a built-in "clapper."

*The dichroic filter mentioned in your article sounds like just the ticket here.
D. Lee Hornyak,
NASA,
John F. Kennedy Space Center, FL

When new ways to generate light efficiently are found, we'll hear about them. There's no conspiracy of silence there. Note, not all fluorescents hum—electronic ballasts don't. You could shop around more—vote with your dollars! Irecently read about a "concept car" with a single central light source, and light pipes—it looked disastrously stupid! How can it be efficient when you turn off the headlights and run only your brake lights?—RAP

Dear Bob:
Computers can be seductive-they can encourage you to do something unnecessary and time-consuming. Is it because the results look so nice that your audience may just ignore problems with the content? Is it because performing some tasks on a computer is a little like taking a mental vacation? Spending two hours drawing a simple schematic is easier on the brain than actually designing a circuit.

But I really don't want to trash computers—even the ones that make a satisfying crunch after a 30-ft. fall to the pavement. They do lots of things really well. We computer users simply have to learn when and how it's appropriate to use them.

For example, I've had some very good results from using spreadsheets. In the past, they've helped me do a few things faster and with less effort than I could have done with other approaches. If you think about what you want to do before you get started, a spreadsheet can give you a useful presentation of the results of many calculations. If you do something dumb, like using an erroneous equation, you can get wrong answers and not even know it because the equation giving you those wrong answers doesn't appear in the printout. The ideal way to print out your spreadsheet is to show the equations in the boxes right next to the results. That way, you're a lot more likely to catch mistakes than when all you print are the answers.

Do I hate computers? No, I think they're great. But occasionally I have to remind myself that they're tools. And like all tools, they do a good job when you use them appropriately and for a job you understand. You wouldn't try to pound nails all day with a screwdriver, would you? And even if you have a hammer, you might decide to find someone else to help if you can only hit the nail one time out of ten. If we use the same king of guidelines before we decide to use computers, we'll be more productive.

Remember, "computers don't kill time, people kill time—with a little help from their computers."
Kerry Lacanette,
Applications Engineer,
National Semiconductor

Kerry, I sure agree, having the EQUATIONS printed out would help. Somebody says Mathcad is good for that.—RAP

Dear Bob:
...I've got a comment or two to pass along. First, one of my pet peeves that I hear of from time to time is the so-called phenomenon of Engineering half-life or engineering obsolescence. I maintain that if an engineer has been properly educated, he is equipped to solve problems using skills that as yet don't succumb to any real deterioration—mathematics, for example.

If an engineer ONLY accumulated the surface skills and knowledge, such as Univac 1108 programming, without acquiring any underlying problem-solving/knowledge-accumulating skills, both the school and the individual are not properly doing the job of education. I believe this half-life balderdash comes from the accountants and managers who wish to keep a newer (i.e. lower-cost) staff around. They will try to convince anyone who will sign up for it that they will self-destruct in five or eight or ten years if they want to stay in the engineering domain.

It's also a fact of the engineering life that we as designers must keep learning what implementation options exist and how to apply them. Otherwise, our solutions will not fit the real world of the moment, even though they might work. If the old engineer won't progress from his slide rule to a calculator, he may still solve problems he faces, but at what loss of speed and accuracy?
Dean S. Carpenter,
Assoc. Staff Engineer,
Scientific Atlanta
Norcross, Georgia

If an engineer could focus on only one task, and could not keep his eye on other techniques, he might indeed have a "half-life." That's where Electronic Design is very valuable. I agree, education is a lot better than training.—RAP

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