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Ask The Editor, He Knows!
Got a question or a problem with a project--ask The Editor. Please remember that The Editors' column is limited to answering specific electronic project questions that you send to him. Personal replies cannot be made. Sorry, he isn't offering a circuit design service. Write to:
C&E HOBBY HANDBOOKS INC. P.O. Box #5148
North Branch, N.J. 08876
Electrical Vs Electronic
I read about "electronics" a lot, and every so often the word "electrical" creeps in. What's the difference? Isn't it all electrons running around inside wires and little parts, anyhow? Please straighten me out.
-D.R. Hawkins, Southport, NY
You're on the right track when you say, "Isn't it all electrons running around inside wires and components?" Electricity is the flow of electrons (through wires and circuit components). Electronics is a special branch of electricity, in which the electrons go through electronic components. Electrical, as encountered in everyday life, is a somewhat simpler discipline, involving mostly lights, motors, generators and so on. In electronics we usually put the electrons through more transformations (or changes). A fairly simple way to decide whether a circuit is just electrical instead of electronic, is whether it involves what we call active components or only passive components. Active components are transistors (or vacuum tubes) for example. Passive components are resistors and capacitors.
Likes Computer Review
Thanks for your informative article on the Atari ST-520 (as compared to the Apple McIntosh). I was about to buy a Mac when I bumped into an Atari, and then I read your article on the Atari ST 520. I am now seriously considering buying (the Atari), but the stores where I've seen it seem to be run by salespeople who don't know much about it, and nothing at all about word processing programs available for it.
Can you help me find retail outlets in the metro New York area where they might know what the Atari can really do?
- M.C. Stone, New York, NY
The problems you've run into are common in the merchandising of home microcomputers in many retail outlets. The Mac is sold only through computer stores, whose salespeople know more and are paid more out of the higher price(s) charged for the Apple McIntosh. Since we ran the article you read on the Atari ST there have been many software pro grams published for it, including Word (for word processing) and Degas (for high-quality graphics), at prices far below competitive programs for the Mac. A list of stores selling the Atari ST and software for it in your area is attached. Thanks for your kind words.
To Socket Or Not to Socket
What's the real story on IC (integrated circuit) sockets? Should I use them in my projects, or shouldn't I? Is it better to solder ICs directly into the project board, or should I go to the extra trouble of first mounting a socket, then plugging the IC into the socket?
-James Winslow, High Point, N.C.
The way I do it is to rig the project up first on a solderless breadboard and get it working the way it's supposed to. Then I hand wire the project on a perforated board, or a home-made printed circuit board (if I'm going to make up several copies of the finished project). I don't usually use sockets because they can cause trouble when a pin on the IC bends or breaks as the IC is inserted into the socket. The only time recommend using sockets is when the circuit is still being designed or debugged, even after the hand wiring stage. Then the use of sockets is recommended. (Or when you're going to reuse the circuit components, as in Ed Noll's new column, Chip-by-Chip.
I often get noise in my car radio (more on AM than on FM) from the windshield wiper when it's working. I have a friend who gets similar noise in his car's CB radio from his car's windshield wiper. How can this be cured?
-Elbert Farouk, Atlanta, Georgia.
Noises in car and CB radios can come from a number of sources in your car's electrical system. Most common, of course, is the windshield wiper, because that's not on very often and if it is, you'll usually have the car radio off, being too much concerned with seeing what's ahead to have the radio (or CB) on anyhow. Other sources of this kind of impulse (AM) noise are the radiator fan, the gas pump, and the ventilation blower motor. Capacitors to by pass the electrical (AM) impulse noises to the car's chassis are needed in the DC supply lines of all these devices to reduce the noise.
Also, the car's alternator, particularly in the low speeds (first, and second) can make lots of noise. Installing by-pass capacitors (0.1, 600 VDC) at each device will by pass most interfering electrical impulses to ground, clearing the hash from the radio.
Sound Goes Up and Down
I have an SW (short wave) radio that acts strange. The sound keeps going up and down, fading in and out, particularly on stations far away at night. Will a better antenna fix that, or what?
-Lester Goodwin, Albuquerque, NM
A little research into shortwave and DX (long distance) AM radio will show that AM signals often fade in and out, causing the kind of sound variations you complain about. All sets have an Automatic Gain Control (AGC) that helps minimize fading, but some radio signals come from so far way that the fading, which is normal at great distances, particularly at night, can't be entirely overcome.
Young But Likes Antiques Radios
I am only 13 years old, but I've already got two antique radios, and want to start a real good collection. I have built and repaired several radios already. But I don't know how to find old time radios. Can you help me locate them?
-Ronnie White, Melvin, South Dakota.
You should advertise, man, advertise. You can do it for free, too. Tell all your friends, relatives and neighbors, first of all. Put up notices in your local supermarkets.
Your parents can put up notices in their plants or offices. And you should visit all possible garage sales, flea markets, tag sales, etc.
Start thinking about where people might have old radios, stashed away in closets, garages, and attics. You'll begin to get results.
Don't offer much money ($1.50 to 2.00) until you know more about the market values involved. Read our Antique Radio articles, and check the list of Antique Radio Sources we ran in the Antique Radio Department in our last issue.
Reader Loves Us
Where have you been all my life? I just bought the latest issue of Electronics Handbook, and it's great. One question, however. I saw an ad in another magazine for a wireless microphone, and they wanted $800 for it? How many parts could there be in it to justify such a high price (most resistors and capacitors only cost a few cents, don't they)? Isn't that just a ripoff? How can they get away with it.
-Thomas Pruit, Newcastle, Delaware
The ad you saw was for a professional microphone system, probably for use in making movies and TV commercials. It's a super high fidelity device, and includes not only the microphone, but a radio transmitter, as well as a precision receiver. It also has to be extremely small so that the actor or singer using it can keep it concealed from the camera.
The receiver picks up sound to be recorded along with the pictures. In addition to being extremely high fidelity (and stereo), it has to work with absolutely no fading or static, and sometimes at considerable distance. Put all these requirements together, and also remember that the market for this system is very small, unlike the market for mass-production radios and TV sets. The price is probably not all that much out of line.
As you guessed, you can get wireless mikes that will work OK for only a few dollars. But they will be mono, will have low fidelity, and won't work reliably for much distance.
Go Another Way
Is there a company that will design printed circuit boards from schematic diagrams? I've tried making PC boards, but they seem to be more trouble than they're worth. Where can I get then custom-built?
-Karl Montrose, Durham, NH
What you need are solderless breadboards. Radio Shack has them in small, medium and large. Solderless breadboards are good because you can build on them, troubleshoot, make design changes, and use the final design. And afterward you can take it all apart quickly to reuse the components and the board(s) all over again. You can often put the PC overlay right on top of the solderless board and trace most of it out there. You can frequently simplify the layout some, but you'll find it much easier to use these boards than PC boards. PC boards were used before solderless board were thought of. They're still good for making several (or many) copies of a project. But for one shots, go with solderless or perf boards.
Light Bulb Resistance is Wrong
One of the basics of electronics I've learned is that more current flows through a low resistance than through high resistance. But when I measure a light bulb's resistance I get only fraction of an ohm. How come the light bulb doesn't draw hundreds of amperes of current (thousands of watts) when it's plugged into 110 (115 or 120) volts AC power in the wall? What's the story?
-Lee Knowles, Paducah, Kentucky
When the filament of an incandescent light (tungsten) is cold, its resistance is very, very low, less than an ohm, as you measured. So you're right (almost). If it stayed low, it should as you've stated use hundreds maybe thousands of watts. Much more, obviously than the power line transformer outside your home could supply. What happens, however, is that the filament heats up fast when current starts flowing through it, increasing its resistance to much higher than when it's cold. This resistance then keeps the flow of current down low so that only 60, 75, or maybe a hundred watts of current flow most of the time. When the lamp is first turned on, a great deal of current does flow, briefly, and this called the initial surge. With light bulbs, as with most other devices, much more current flow briefly, when the device is turned on, than after it gets going normally.
Also see: New Book Reviews
More from EH magazine: Tandy's Radio Shack
Adapted from: Electronics Handbook--Spring 1987
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