Electronic Design

Bob's Mailbox

Hi Bob:
I don't know if you can count on five more years of service on your low-mileage camcorder. We have one engineer here who had several intermittent problems with his camcorder and took it to his fix-it buddy. His buddy said that the Sony camcorders typically failed from leaking surface-mount electrolytic caps. His buddy said it wasn't worth having fixed. Well, this engineer, seeing the possibility of saving some money and fixing it himself, took his camcorder apart and replaced all of the surface-mount electrolytics with tantalums. There were about 100 caps on various boards, under shields, and in some hard-to-get-at places. When replacing them, he found that at least 50% of the caps had visible signs of leakage. As I was saying, he replaced them all and put his camcorder back together and now it works again. He has been using it for about two months (new baby) and it is working fine.

Well, he mentioned it to me, and I have a Sony that is eight years old. Mine had failed about a year ago, after increasing problems. So, I brought mine in and took it apart. Sure enough, same thing: 50% of the electrolytics on the outer board had visible signs of leakage. We did the same for a third engineer who had a five-year-old camera that had failed—same cap problem.

We are in the process now of scrounging up samples of tantalums to try to fix the other camcorders. Hopefully, we will get long life out of the repaired camcorders with the tantalum caps. I don't hold much hope for you getting five years out of your "like new" five-year-old camcorder. Hopefully you will see; time will tell. KEVIN CAWLEY
Keithley Instruments
via e-mail

Hi, Kevin. YOU could be right. Replacing electrolytics, two by two, is not my idea of fun. Maybe keeping it COOL will help. Here in California, in SF, our house runs pretty cool. Thanks for the caution.—RAP

Dear Bob:
Thank you for pointing out the hoaxers who promote the "alternative energy" theory. I find those promoting "scalar-potential electromagnetics" to be especially offensive. I have yet to see a paper on this subject that would be acceptable for publication in a physics journal.

I also agree that "inventions that produce power from the heat in the air" are complete and utter nonsense. However, there is a toy that does indeed derive its energy from "heat in the air." I'm referring to the familiar "drinking bird."

The drinking bird is actually a glass tube with bulbs on both ends. The tube is mounted on a stand so that it can swing freely between a vertical position and a horizontal position. The tube contains freon so that the bottom bulb is filled with freon when the "bird" is in the vertical position.

The upper bulb (the bird's "head") is enclosed in a sponge material. An attachment to the upper bulb forms the bird's "beak" and is enclosed by the sponge. If the sponge on the bird's head is wet, the upper bulb is cooled, which causes the freon in the bottom bulb to rise in the tube. This, in turn, causes the tube to tip over into its horizontal position.

Two things happen when the bird is in the horizontal position. First, the bird's "beak" dips into a cup of water placed next to the toy. This serves to keep the sponge wet. Second, the freon flows back into the lower bulb, causing the bird to return to its vertical position.

This entire process repeats itself indefinitely, as long as the cup of water is refilled regularly. I have kept a drinking bird going for several weeks at a time (until I forgot to refill the cup).

The energy to keep the bird swinging and drinking comes from the air. It is through collisions between air molecules and the moisture on the bird's head that the upper bulb is cooled. Therefore, there does exist a device that derives its energy from the "heat in the air."
via e-mail

Hello, Joe. One MIGHT say this runs on the heat in the air. But if you put a big glass bell jar over the engine, the water vapor under the cover will soon be at equilibrium. Then it will poop out. It only runs—should I say—by the "coolth" in the air. Or, if you brought it to a warm or humid climate, it might quit. Right?

I'm amused that people say this runs on the energy or heat in the air, because one could just as logically say it is an engine that runs with water for fuel. Of course, the energy you could pry out of it is comparable to the energy that it takes you to fetch the water!!! Eh? Most of those papers are not just unsuitable for publication in a refereed journal. They're useless—except in comic books and science fiction.—RAP

Dear Bob:
There is a lot of difference between mouse switches in the amount of push resistance and "ping" on contact and release. I've noticed these characteristics can vary even with the same make and part number of switch, so I suspect it is from manufacturing tolerances. The "ping" is so bad on some mice that they have made my finger numb with a lot of use. I've tried out whole series of display samples in computer outlets and I found no correlation between expensive or cheap units.

When I find a mouse on display that I like, I then try the boxed unit. There is no correlation there, either. I guess the manufacturers either don't know/care or aren't capable of making consistent switch/damping designs.
via e-mail

I'm not a big fan of mice. I sure believe what you say; thanks for the warning.—RAP

All for now. / Comments invited!
RAP / Robert A. Pease / Engineer
[email protected]—or:

Mail Stop D2597A
National Semiconductor
P.O. Box 58090
Santa Clara, CA 95052-8090

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