Tag Archives: Light-emitting diode

Light Bulbury 2014


Crystal AM Radio
(During the Second World War, Prisoners of War used a razor blade and a pencil lead in place of the crystal to make secret  radios.)

Along with the demise of the incandescent light bulb (as mentioned yesterday) there have been other fundamental changes in technology. A century ago a radio receiver could be assembled by virtually anyone using items such as a galena crystal, and some wire wrapped around a toilet paper (or similar) tube. The only component you really needed to purchase was a set of headphones.

A transmitter required a bit more – an ignition coil from a car, a tuning coil wrapped around an oatmeal box. The telegraph key was the main purchase item. Incidentally, the construction was called “breadboarding” since the parts were mounted on a piece of wood, such as the board used to cut bread.

Fifty years ago you could tune your car with a set of basic tools usually twice a year. Oil and filter, set of sparkplugs and ignition points, and every so often a new set of sparkplug wires.

Today most people don’t work on their own cars; they take it to a shop where (for $79) the mechanic hooks a device to the car’s computer and the computer reports what the car needs. If that clunking noise isn’t something that the computer tracks, it must not be important.

Electronics – the same way. As a kid if the television wasn’t working right, I’d take the tubes out, ride my bicycle to the Rexall Drugstore, use their tube tester and purchase a replacement tube right there.

Today’s devices aren’t home-repair or experimenter friendly. First, the manufacturers glue everything shut; second, there’s very little in the way of documentation.

I guess I’d like to point to today’s kids and complain that they spend all their time playing video games and texting, but can’t. If there’s no 21st century equivalent of a mechanical alarm clock begging to be taken apart, just to see how it works, how can we get them excited? Kids are still naturally curious – now we have to figure out how to feed their curiosity.

How Do I See the End of 2013?

It is with some degree of sadness that I mark the passing of the incandescent light bulb.

Actually it is for one reason in particular – you could understand, and therefore teach others how a light bulb work. If you run electricity through a high resistance wire, the electric energy becomes heat and light.

You could tell your kids how Thomas Alva Edison knew he needed the resistance, and a vacuum would keep the filament from burning out immediately. How, as he tried different materials for the filament, he said, “I have not failed. I’ve just found 10,000 ways that won’t work.” How Edison then went on to invent many things – how to record sound, motion pictures, medical fluoroscopy and how these inventions spawned whole industries.

How it was this date in 1879 when Edison first demonstrated the light bulb to the public and that one of those basic light bulbs has been glowing almost continuously for 112 years.

How when you add a second electrode to an incandescent light bulb and you have a diode rectifier; add a third, making a triode that can amplify an electric signal – an important step leading to the proliferation of radio and eventually television.

What a great teaching tool!


Can you clearly explain how an energy efficient compact fluorescent bulb works? How about an LEDs (light emitting diode)?

Didn’t think so – me either.

Lights! Action!

Sorry – it’s been busy around here. As I get older, the medical types seem to find more things they can poke, prod or test.

And to think I used to be on the OTHER side of the examination spectrum.

Poetic justice? Perhaps.


In the meantime, my wife found an idea online on how to convert a regular lamp to a cordless one. They sell LEDs (light emitting diodes) on tape; you just cut off what you need and save the rest for later.

So we took an old table lamp, placed the handy self-sticking led tape to the top and bottom of the lampshade (on the inside, of course), ran it through the lamp to some batteries, and voila! A cordless lamp.

Actually, more of a very bright night light.

However, it fits in with all my hurricane preparation stuff, but does so with style.

And my wife likes it.

The Advance of Technology



1963: “Teacher, how does a light bulb work?”

What an excellent topic for Science class today. Several inventors had built light bulbs, but they didn’t last very long. Thomas Alva Edison figured out how to make the first practical light bulb after years of research. He was a prolific inventor with over 1,000 patents including how to record sound and motion pictures.

For the light bulb he figured out that he’d need a filament – that is something that glows – and it needed to be in a vacuum so it wouldn’t just burn up. A glass bulb would maintain a vacuum and let the light shine through, but the filament was a problem. He tried all types of exotic metals, including silver, gold and platinum, but eventually settles on carbon. One story is that he carbonized a piece of cotton thread for the filament.

Today we use tungsten for the filament, but the rest of the design hasn’t changed much. They’re reliable – in fact there are several bulbs that were installed at the beginning of the twentieth century that are still burning today.

2003: “Teacher, how does a one of those curly light bulbs work?”

Well, let’s Google that. Hmmm, it was invented back in 1976 by George Hammer who worked for GE , but they didn’t want to spend the money to manufacture them. Eventually, the Chinese started making them.

They use less electricity than incandescent bulbs but the light is kind of funny colored. They’re supposed to last for five years, but around my house they seem to last about half as long as the old style light bulbs they replace.

They’ve got mercury in them, which is a hazardous material. The expression “As mad as a hatter” referred to the fact that hat makers used mercury and as they absorbed it through their skin, they exhibited erratic behavior, so if you break one, you have a problem.

There’s a phosphor inside that glows. That’s about the best I can do to explain it.

2013: “Teacher, how do light emitting diode – LED light bulbs work?”

Ooops, we’re out of time for science. Put your science books away and get out your social studies books so we can learn all about how Congress gets things done.


My life is fairly typical. I go to work. I come home.

On weekends I putter around the house.

A ten minute repair job can take me an hour because I spend at least 50 minutes looking for my tools.

I’ve gotten to the point that I freely buy one more pair of pliers, one more screwdriver, or whatever. My friends tell me how their kids borrow their tools and eventually they find a rusted mass of metal that is vaguely pliers shape out in the yard.

Not me.

My tools just disappear for long periods of time then magically re-appear.

Go figure.


Flashlights are even worse. I think my son uses them to find his cat, who likes to play hide-and-seek with him by hiding under my bed. In any case, flashlight after flashlight disappears.

One day my wife suggested that there was a parallel universe and between myself and my alternative counterpart, we had to share things. She indicated it made sense because socks followed the same pattern. They’d disappear in the drier. Weeks later they’d show up. Of course I thought she was crazy.

I stopped at Wally-World and bought a handful of additional flashlights. One by one they began to disappear. I told my wife I was going to use my label maker and mark them with “This is Dad’s flashlight! Do not touch under penalty of death!”

They all disappeared.

This morning there was a flashlight on my nightstand. The side was marked with a label that said, “!htaed fo yltanep rednu hcuot ton oD !thgilhsalf s’daD si sihT”

I thought about it all day.

When I got home, I opened a bottle of wine and brought 2 glasses into the family room. I poured a glass for my wife and said, “Please, tell me about this parallel universe idea of yours.”