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Krampf #472 Spotting LEDs
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KRA-@aol.com
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Dec 13, 2006 22:36 PST
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Robert Krampf's Experiment of the Week
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This Week's Experiment - #472 Spotting LEDs
Greetings from Miami. Many of you sent emails, saying that you missed last
week's experiment, so I am sending it again with this one. I am staying at a
wonderful campground, surrounded with avocado trees (and yummy avocados),
beautiful sunsets, and VERY bad wireless internet. I am sending these though my
Verizon card instead, so hopefully, you will get this one. If you do not
get this email, please let me know. <grin>
This week's experiment got me scolded by my wife, Nancy. We were driving at
night, when I noticed something strange about the tail lights of the car
ahead of us. As I began to get the idea for an Experiment of the Week, I was
experimenting by shaking my head quickly from side to side. Nancy informed me
that this was not a wise thing to do while driving, and asked that in the
future I warn her before I do strange things for experiments, so she won't think
that I am having some sort of strange medical problem. To see what got me in
trouble, you will need:
to walk around, shaking your head
to warn the people that you love that you are going to be walking around,
shaking your head.
OK, so why are you going to walk around, shaking your head? You will be
looking for LEDs, light emitting diodes. These are small lights that have been
around since the 1960's, but recently have found many new uses. New, very
bright LEDs, and new colors (blue and "almost white") have allowed them to show
up in all sorts of places, from turn signals on new cars to Holiday lights.
What caught my interest is that LEDs will only allow electricity to pass in
one direction. That means that if you power the LED with alternating current,
electricity that goes first one way and then another, the LED will blink on
and off each time the electricity alternates. Household current in the United
States alternates 60 cycles per second, which is why I can see our new, LED
holiday lights blink off and on when I shake my head or move the strand of
lights.
The strange thing about the car is that the electrical system in a car runs
on DC, direct current, since it comes from the battery. Even so, by moving my
head, I could see that the LEDs in the tail lights of the car were blinking
on and off very quickly. I am still researching the "why", but from what I
have found so far, it seems that the LEDs need a different voltage from the car
battery. They are probably converting the direct current to alternating
current, which allows them to use a transformer to change the voltage.
I have also noticed the same thing with some traffic lights and some of the
yellow, warning lights at road construction. Around the house, I have seen
the same flicker in the indicator lights on various appliances, and the clock on
the microwave oven. Check your house, and watch for LEDs, but be sure to
warn your friends, or they may think you are very strange.
Have a wonder filled week!
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From Robert Krampf's Science Education Company
PO Box 60982
Jacksonville, FL 32236-0982
904-388-6381
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