If you want to fill your life and home with gadgets and gimmicks, electronics offers opportunities galore. In this chapter, you’ll learn about some common ways that electronics can improve and enrich your life. You’ll also get a chance to build a simple wet cell and then do a couple of experiments on your own body!
Fluorescent lamps offer better efficiency than incandescent light bulbs do, but you can’t remove an incandescent bulb from its socket and put a conventional fluorescent “tube” in its place. Engineers invented the compact fluorescent lamp (CFL) to satisfy people’s desire for a direct-replacement fluorescent counterpart to the incandescent bulb.
Fluorescent and incandescent lamps differ in several ways. One of the most obvious, but also most easily overlooked, differences lies in the amount of light that the device produces per unit surface area. An incandescent lamp has a brilliant filament with a tiny surface area that emits all of the light, but the light from a fluorescent lamp comes off uniformly from a surface with considerable area. This difference presented the inventors of the CFL with a major challenge: How could they make a fluorescent light bulb physically small without sacrificing overall brilliance?
A typical “old-fashioned” fluorescent tube has the shape of a long, thin cylinder. If the entire assembly is coiled up into a helix, the overall size of the lamp can be reduced. However, the amount of light emitted per square millimeter of bulb surface must increase if the lamp is to maintain its overall brilliance. The phosphor (coating on the inside of the glass that makes the whole thing glow) in a CFL must, therefore, produce far more visible light per unit of area than the phosphor in a conventional fluorescent bulb does. As a result, CFLs burn hotter than conventional fluorescent bulbs do. The CFL phosphor must withstand the high temperatures without rapidly degenerating.
The CFL concept originally came about during the “energy crisis” of the 1970s. Engineers at General Electric produced a working CFL but decided against mass production because of the high startup cost. For consumer use, CFLs didn’t gain traction until the mid-1990s when China began exporting helical fluorescent tubes, which gave off unnatural blue-green light. By around 2005, this problem had been overcome. Today, you can get CFLs that produce light almost indistinguishable from the output of a typical incandescent bulb.
If you see two otherwise identical table lamps with shades, one having a 60-watt “soft-white” incandescent bulb and the other having a CFL that produces the same amount of light output, you probably won’t know which bulb is which until you look inside the shade. But a “60-watt-equivalent” CFL consumes only 10 to 12 watts of actual power. You can expect the CFL to last several times longer than an incandescent bulb does, although the CFL costs more up front. Savings accrue over time as the result of less frequent bulb replacement and reduced overall energy consumption. In the end, a good CFL gives you the better deal.
One of the most significant problems with CFLs arises from the fact that they don’t work very well in cold weather. If you live in a region where the winter temperatures drop below freezing, you won’t like CFLs for outdoor use. They’ll have trouble starting up, and once they do get going, they’ll take awhile to reach full brightness. If the temperature gets much below 0°F (−18°C), as it can in the northern United States and most of Canada, CFLs might not start up at all. If you want to replace outdoor incandescent lamps with more efficient devices, you’ll do better to go with light-emitting-diode (LED) lamps.
Another, less noticeable problem with conventional CFLs is a gradual decline in light output as they age. The newer designs suffer less from this trouble than the earliest ones did; some people don’t even notice it until the old CFL burns out and they install a new one of the same wattage. While you can rely on CFLs to last longer than incandescent lamps do, the lifespan difference is greatest in situations where you don’t turn the lamp on and off very often. Yet another limitation of CFLs is the fact that the basic types won’t work with dimmers. You can buy dimmable CFLs, but they cost more than ordinary ones.
In some situations, CFLs produce high-frequency AC that can interfere with wireless-device reception at close range. Do you have a radio-controlled garage-door opener whose motor box has a light that comes on for a few minutes after you close the door? Is it an incandescent bulb? If so, try replacing that incandescent lamp with a CFL, and see if you still get the same operating range that you did before.
I discovered the radio-frequency interference (RFI) from a CFL by accident. The remote-control box for my garage-door opener transmits a radio signal to the motor. It normally works up to 100 feet away. When I replaced the 60-watt incandescent lamp in the motor box with a “60-watt-equivalent” CFL, the range went down to 20 feet. Because I’m an amateur radio operator, and therefore, have had plenty of experience with RFI issues, I diagnosed the trouble right away. I put a new 60-watt incandescent lamp in the motor box, and the system worked normally again.
One of the oldest, and yet most effective, ways to conserve energy entails installing simple timers or motion-sensing actuators that can keep you from unnecessarily burning electric lights. These devices can, in some cases, also help you keep your home a bit more secure (when you’re gone) than it would otherwise be.
Simple timers comprise small switch-equipped clocks that plug into an electrical wall outlet, and that have one or more outlets on them for use with electric lights and small appliances. You can set the timer to switch a lamp on at sundown, for example, and off at bedtime. Most of them contain simple mechanical clocks, although a few are entirely electronic and contain no moving parts.
If you have several of these devices connected to different lamps around the house, and if you set them to switch the lamps on and off at various times, you can go on a short vacation and uninformed neighbors will never suspect that you’re away from home. You’ll find these timers at nearly all major department stores and good hardware stores.
Here’s a Tip!
You can use timers of the sort described above with small appliances, not only lamps. For example, you might have a timer device turn your TV set on at 7 p.m. and off at 11 p.m. every day when you’re on vacation, and a second timer in another room switch a different TV set on at 8 p.m. and off at 10 p.m.
Motion sensors can detect the presence of moving objects and use the impulse to switch a light or other appliance on and off. The most common devices of this sort are housed in metal boxes with light-bulb sockets attached to them. Figure 8-1 is a photograph of a motion-sensing light switch intended for use with outdoor floodlights. It is housed in a cabinet roughly the size of an electrical switch box, and made from similar rugged metal. The lamp sockets contain rubber grommets to keep water from intruding and causing electrical problems.
FIGURE 8-1 This photograph shows two 50-watt incandescent spot lights with a motion-sensing actuator between them. It’s mounted under a deck, over the back entrance to a residential home.
When a large object comes into the range of the device and moves around, an electrical impulse goes to a delay switch, which actuates the lights for a certain period of time. If no further motion occurs, the lights stay on for just a minute or two; you can adjust the length of time before they automatically switch off. You can also adjust the sensitivity of the device, so it won’t generate false positives when small insects approach it, yet will detect the presence of a moving person or large animal within a few feet. You can obtain switches of this type at most major department stores.
A heat pump transfers thermal energy from one place to another. The term “pump” comes from the fact that the device uses a common external source of power, usually electricity, to move thermal energy rather than generating it directly.
Homogenize This!
All humanmade heating or cooling systems act against the natural process called heat entropy that takes place as temperatures gradually equalize throughout the universe. In a simplistic sense, all of our furnaces and air conditioners impose small-scale order in a gigantic thermodynamic system that relentlessly strives for chaos, a process whose ultimate endpoint some scientists have called the heat death of the cosmos.
Figure 8-2 shows the basic components of an air-exchange heat pump, also called an air-source heat pump, operating to transfer heat energy from the outdoor environment to the indoor environment (heating mode). The fan blows outdoor air through a coil that contains a refrigerant. As the refrigerant passes through the outdoor coil, depressurization and evaporation occur, causing the refrigerant to absorb heat energy. This process can occur even if the outdoor temperature is quite cool. The fluid then passes through pipes (shown as solid lines) to the indoor coil, where the refrigerant undergoes compression and condensation, causing it to release the heat energy it took in from the outside. The indoor coil becomes considerably warmer than ordinary room temperature; in fact, it can warm to as much as +35°C (+95°F) as the refrigerant passes through the indoor coil. The air that has been heated by the indoor coil then flows into the ductwork and circulates throughout the house.
FIGURE 8-2 An air-source heat pump, operating to transfer heat energy from the outdoor environment into a building.
Tip
Air-exchange heat pumps work well in the heating mode as long as the outdoor temperature remains above roughly +39°F (+4°C). If the outdoor air gets colder than that, it doesn’t contain enough thermal energy to allow efficient operation.
Figure 8-3 portrays the same heat pump operating to transfer heat energy from the indoor environment to the outdoor environment (cooling mode). The fan blows indoor air through a coil that contains a refrigerant. As the refrigerant circulates through the indoor coil, depressurization and evaporation occur, so the refrigerant absorbs heat energy, thereby chilling the air that moves past the coil. The cooled air then flows into the ductwork and circulates throughout the house. The chilling process can also remove some water vapor from the indoor air if the humidity is high, causing the indoor coil to “sweat.” The heated fluid passes through pipes (shown as solid lines) to the outdoor coil. In the outdoor coil, the refrigerant undergoes compression and condensation, causing it to give up the heat energy that it acquired from indoors. The outdoor fan blows warm air into the external environment.
FIGURE 8-3 An air-source heat pump, operating to transfer heat energy from inside a building to the outdoor environment.
Some heat pumps extract thermal energy from beneath the earth’s surface rather than from the outside air, and transfer this energy into a house or building. Figure 8-4 illustrates the principle. Basically, it’s a modified air-exchange system. The outdoor coil resides underground, so the system requires no fan. In some arrangements, the outdoor coil can be placed near the bottom of a deep pond or lake. Heat transfer occurs by conduction from the earth to the coils. The system shown in Fig. 8-4 constitutes a ground-source heat pump, also called a geothermal heat pump.
FIGURE 8-4 A ground-source (geothermal) heat pump, operating to transfer heat energy from the earth into a building.
In some locations, the earth temperature rises and remains high even at shallow depths. Saratoga, Wyoming, and Hot Springs, South Dakota, offer locations in the United States with plenty of available geothermal heat despite their severe winters. Iceland is another good example. In locations such as these, a ground-source heat pump can function at much lower outdoor air temperatures than an air-exchange heat pump can.
In locations where subsurface temperatures are high, even quite close to the surface, a network of pipes can replace the outdoor coil, buried just deep enough to allow heating of water that a mechanical pump (similar to the type of pump that brings water up from a well) can circulate through the house. That type of heating system is probably the most efficient design attainable in the real world! The only component that consumes any energy is the water pump, similar to the one in a well. Otherwise, you can literally get your heat for free (until your government finds a way to tax you for using it).
Ground-source heat pumps can cool the indoor environment during the summer in most locations. However, in some places, such as those mentioned above where the subsurface temperature is high, the cooling mode isn’t practical.
Caveat!
Heat pumps, especially deep ground-source systems, cost a lot of money to install. You should expect several years to pass before you recover the up-front expense in terms of the month-to-month savings that you realize, compared with the cost of running the system that the heat pump replaced.
You can assemble an electrochemical wet cell and see how much voltage and current it produces. You’ll need a short, fat, thick glass cup that can hold 12 ounces (about 0.36 liter) when full to the brim. Get some distilled white vinegar and table salt at your local supermarket. You’ll need some bell wire (solid copper insulated wire of 18 to 22 gauge), a wire cutter, some electrical tape, some steel wool or an emery cloth, and two pipe clamps measuring 1/2 to 5/8 inch (1.3 to 1.6 centimeters) wide, one made of copper and the other of galvanized steel, designed to fit pipes 1 inch (2.5 centimeters) in diameter. You should be able to find these items at a hardware store. You’ll also need your multimeter, which you used for applications earlier in this book.
Get rid of the bends in the pipe clamps, and straighten them out into strips. The original clamps should be large enough so that the flattened-out strips measure at least 4 inches (about 10 cm) long. Polish both sides of the strips with steel wool or a fine emery cloth to get rid of any oxidation that might have formed on the metal surfaces.
Cut two lengths of bell wire, each about 1.5 feet (50 centimeters) long. Strip 2 inches (5 centimeters) of insulation from each end of both lengths of wire. Pass one stripped wire end through one of the holes in the copper electrode, and wrap the wire around it two or three times, as shown in Fig. 8-5A. Wrap the other end of the stripped wire from the copper electrode several times around the positive (red) meter probe tip, as shown in Fig. 8-5B. Pass one stripped end of the other length of wire through one of the holes in the galvanized electrode, and wrap the other end of the wire around the negative (black) meter probe tip. Secure all four connections with electrical tape to insulate them and keep the wires from slipping off. Remove both of the meter probe leads from their receptacles on the meter.
FIGURE 8-5 Attachment of wires to electrodes (at A) and meter probes (at B). Wrap the bare wire around the metal. Then secure the connections with electrical tape.
Lay the strips against the inner sides of the cup with their ends resting on the bottom. Be sure that the strips are on opposite sides of the cup so they’re as far away from each other as possible. Bend the strips over the edges of the cup to hold them in place as shown in Fig. 8-6. Be careful not to break the glass! Fill the cup with vinegar until the liquid surface is slightly below the brim.
FIGURE 8-6 A wet cell made from a vinegar-and-salt solution. The glass cup has a brimful capacity of approximately 12 fluid ounces (0.36 liter).
Once you’ve put the parts together, as shown in Figs. 8-5 and 8-6, add a rounded teaspoon of common table salt (sodium chloride). Stir the mixture until the salt completely dissolves in the vinegar. You’ll know that all the salt has dissolved when you don’t see any salt crystals on the bottom of the cup after you allow the liquid to stand still for a minute or two.
Set the meter to measure a low DC voltage. The best meter switch position is the one that indicates the smallest voltage that’s greater than 1 volt. Insert the negative meter probe lead into its receptacle on the meter. Then insert the positive meter probe lead into its receptacle and note the voltage on the meter display. When I conducted this experiment, I got a reading of 515 millivolts (or 0.515 volt). After 60 seconds, the voltage was still 515 millivolts.
Remove the positive meter lead from its receptacle on the meter. Set the meter for a low DC current range. The ideal setting is the lowest one showing a maximum current of 20 milliamps or more. Insert the disconnected meter lead back into its receptacle, and carefully note how the current varies with time. I got a reading of 8.30 milliamps to begin with. The current dropped rapidly at first, then more and more slowly. After 60 seconds, the current stabilized at 7.45 milliamps, as shown by the lowermost (solid) curve in Fig. 8-7.
FIGURE 8-7 Graphs of maximum deliverable currents as functions of time for various amounts of salt dissolved in 12 fluid ounces of vinegar. Lower (solid) curve: 1 rounded teaspoon of salt. Middle (dashed) curve: 2 rounded teaspoons of salt. Upper (dashed-and-dotted) curve: 3 rounded teaspoons of salt.
When you conduct these tests, you’ll probably get more or less voltage or current than I got, depending on how much vinegar you have poured into your cup, how strong the vinegar itself actually is, and how large your electrodes are. In any case, you should find that the open-circuit voltage remains constant as time passes, while the maximum deliverable current decreases.
Warning! If you get a notion to try any of these exercises with an automotive battery or other large commercial wet cell or battery, forget about it! The electrolyte (chemical solution that stores the energy) in that type of battery is a powerful acid that can boil out and burn you severely if you short-circuit the terminals. Some such batteries can even explode if you mistreat them, with obviously disastrous consequences.
Add another rounded teaspoon of salt to the vinegar. As before, stir the solution until the salt has completely dissolved. Repeat the voltage and current experiments. You should observe slightly higher voltages and currents. As before, the open-circuit voltage should remain constant over time, and the maximum deliverable current should fall. I measured a constant 528 millivolts. The current started out at 10.19 milliamps and declined to 8.76 milliamps after 60 seconds, as shown by the middle (dashed) curve in Fig. 8-7.
Add a third rounded teaspoon of salt and fully dissolve it. Once again, measure the open-circuit voltage and the maximum deliverable current. When I carried out this little exercise, I got a constant 540 millivolts. The current began at 11.13 milliamps, diminishing to 9.43 milliamps after 60 seconds passed, as shown by the uppermost (dashed-and-dotted) curve in Fig. 8-7.
When you leave the ammeter connected across the cell terminals for awhile, you’ll notice that bubbles appear on the electrodes, especially with higher salt concentrations. The bubbles comprise gases (mainly hydrogen and oxygen, but also some chlorine) created as the electrolyte solution breaks down into its constituent elements. Although you won’t see it in a short time, the electrodes will eventually become coated with solid material as well.
If you “short out” your wet cell and leave it alone for an extended period, all of the chemical energy in the electrolyte will ultimately get converted into heat. The maximum deliverable current will fall to zero, as will the open-circuit voltage. The cell will have met its demise, killed by its own juice!
Try This Experiment!
When you measure the voltage across the terminals of your wet cell without requiring that the cell deliver any current (other than the tiny amount required to activate the voltmeter), the cell doesn’t have to do any work. You might expect that the voltage will remain constant for hours under those conditions. Let the cell sit idle overnight, with nothing connected to its terminals, and measure its voltage again tomorrow. What happens?
In this experiment, you’ll use a salt-and-vinegar solution to make contact between the electrodes and your hands, but most of the electrolyte will be inside your body! For this experiment, you’ll need all the items left over from the previous experiment.
Remove the galvanized and copper electrodes from the vinegar-and-salt solution. Leave the solution in the cup. Leave the wires connected to the electrodes. Rinse the electrodes with water, dry them off, and get rid of the bends so they both form flat strips with holes in each end. Make sure that the probe leads are plugged into the meter. Then switch the meter to one of its most sensitive DC voltage ranges.
Wet your thumbs, index fingers, and middle fingers up to the first knuckles by sticking both hands into the vinegar-and-salt solution. (Don’t be surprised if this solution stings your fingers a little bit. It’s harmless!) Grasp the electrodes between your thumb and two fingers. Don’t let your hands come into contact with the wires, but only with the metal faces of the electrodes. What does the meter say? When I conducted this experiment, I got a steady 515 millivolts.
Rinse your hands with water and dry them off. Switch the meter to its most sensitive DC current range. Wet your fingers with the vinegar-and-salt solution again, and grasp the electrodes in the same way as you did when you measured the voltage before. Watch the current level for 60 seconds, making sure that you don’t change the way you hold onto the electrodes. The current reading should decline, rapidly at first, and then more slowly. When I did this experiment, the current started out at 122 microamps and declined to 95 microamps after 60 seconds had passed. Beyond 60 seconds, the current remained almost constant. Figure 8-8 illustrates the current graphed against time.
FIGURE 8-8 Graph of maximum deliverable current as a function of time from my “body cell.” I wetted my hands with a solution of 3 rounded teaspoons of salt dissolved in 12 fluid ounces of vinegar.
Set the meter to a different current range and repeat the above experiment. Don’t expect to get the same readings as before. Of course, a small amount of variation is inevitable in any repeated experiment involving material objects. In this case, however, you should see a difference that’s too great to be explained away by imperfections in the physical hardware.
An ideal ammeter would have no internal resistance, so it would have no effect on the behavior of a circuit when connected in series with that circuit. But in the real world, all ammeters have some internal resistance because the wire coils inside them don’t conduct electricity perfectly. Unless it’s specially engineered to exhibit a constant internal resistance, a meter set to measure small currents has a greater internal resistance than it does when set to measure larger currents. Most inexpensive test meters (such as mine) aren’t engineered to get rid of these discrepancies.
When I changed the meter range while measuring my body current, my meter’s internal resistance competed with my body’s internal resistance. When I set the meter to a lower current range, I increased the total resistance in the circuit, reducing the actual flow of current. Conversely, as I set the meter to a higher current range, I decreased the total resistance in the circuit, increasing the actual current.
In the previous experiment, you discovered that your body resistance affects the amount of current that can flow in a circuit when your body forms part of that circuit. In this experiment, you’ll measure your body resistance. You’ll need everything you used in the previous experiment, along with a second copper electrode.
An ohmmeter (resistance-measuring meter) for DC actually comprises a milliammeter or microammeter in series with a set of fixed, switchable resistances and a battery that provides a known, constant voltage, as shown in Fig. 8-9. If the resistances are selected appropriately, the meter gives indications in ohms over any desired range. The device can be set to measure resistances from 0 ohms up to a certain maximum, such as 2 ohms, 20 ohms, 200 ohms, 2 kilohms, 20 kilohms, 200 kilohms, 2 megohms, or 20 megohms. All multimeters, which you learned about earlier in this book, have an ohmmeter function.
FIGURE 8-9 A multirange ohmmeter works by switching various resistors of known values in series with a sensitive DC current meter.
If you want to measure the resistance between two points with an ohmmeter, you must make sure that no voltage exists between the points where you intend to connect the meter. Such a preexisting voltage will add or subtract from the ohmmeter’s internal battery voltage, producing a false reading. Sometimes, in this type of situation, an ohmmeter might say that a component’s resistance is less than 0 ohms or more than “infinity” ohms!
Heads Up!
The measurement of internal body resistance is a tricky business. The results you get will depend on how well the electrodes are connected to your body, and also on where you connect them.
Get a second copper clamp from your local hardware store. Take the bends out of it to make it into a flat strip, and then polish it in the same way as you polished the other two electrodes. Connect one copper strip to each of the meter probe tips using bell wire. Switch the meter to measure a relatively high resistance range, say 0 to 20 kilohms. Dip your fingers into the electrolyte solution left over from the previous experiment. What does the meter say? Repeat the experiment using the next higher resistance range (in my meter, that would be 0 to 200 kilohms).
When I measured my body resistance using the above-described scheme, I got approximately 7.8 kilohms (that is, 7800 ohms) with the meter set for 0 to 20 kilohms, and 4.9 kilohms with the meter set for 0 to 200 kilohms. The difference resulted from internal meter resistance, just as in the previous experiment with the current-measuring apparatus. The higher resistance range required a different series of resistances than the lower range. These resistances appeared in series with the resistance of my body, so the total current flow (which is what the meter actually “sees”) changed as the range switch position changed.
Fact or Myth?
One of my friends tried this experiment. He got 6.3 kilohms at the 0-to-20-kilohm meter range, and 4.5 kilohms at the 0-to-200-kilohm meter range. He wondered if the results of this experiment could serve as an indicator of a person’s overall health. I said that I didn’t think so, but that I really didn’t know. I doubt that anyone can definitively answer that question one way or another!
Try this experiment with a copper electrode and a galvanized electrode, in the same arrangement as you used when you performed the previous experiment. Connect your body to the meter, as shown in Fig. 8-10A. Then reverse the polarity of your “body-electrode-meter” circuit by connecting the red wire to the black meter input, and connecting the black wire to the red meter input, so you get the configuration shown in Fig. 8-10B. You should observe different meter readings. You might even get a “negative” body resistance or a meter indication to the effect that the input is invalid.
FIGURE 8-10 Try to measure your body resistance with the arrangement you used to measure current in the previous experiment, as shown at A. Then try the same test with the meter probe wires reversed, as shown at B.
The range of radio frequencies from 3 to 30 MHz is sometimes called the shortwave band. Technically it’s called the high-frequency (HF) range. The waves are actually long, as they travel through space, compared to the waves in most wireless communications these days. But they’re short compared to the wavelengths that were most commonly used when the term was coined.
In the early 1900s, practically all communication and broadcasting was done at frequencies below 1.5 MHz (wavelengths of more than 200 meters). Engineers thought that the higher frequencies were useless. The vast region of the electromagnetic spectrum comprising wavelengths of “200 meters and down” (frequencies of 1.5 MHz and above) was given to amateur radio operators and experimenters, who became known as hams.
Within a few years, those hams discovered that the shortwave frequencies could support long-distance communications and broadcasting. In fact, the shortwave band worked better than the traditional longwave band did, allowing reliable contacts spanning thousands of miles using transmitters with only a few watts of output power. Soon, commercial entities and governments took keen interest in the shortwave band, and amateurs lost most of it. But the hams did manage to retain exclusive use of small slivers of the shortwave spectrum, and these so-called “HF ham bands” remain popular to this day.
Shortwave radio is still used for international broadcasting, particularly by developing countries. In the more technologically advanced nations, most government and business entities have moved their operations to the very high frequencies (VHF) from 30 to 300 MHz, the ultra high frequencies (UHF) from 300 MHz to 3 GHz, and the microwave frequencies above 3 GHz. This ongoing shift has given rise to talk of letting ham radio operators use more of the shortwave band that they originally discovered.
An HF radio communications receiver, especially one that offers continuous coverage of the HF spectrum, is sometimes called a shortwave receiver. Most general-coverage receivers function at all frequencies from 1.5 MHz through 30 MHz. Some also operate in the standard broadcast band at 535 kHz to 1.605 MHz. A few receivers, called all-wave receivers, can operate below 535 kHz, and into the so-called longwave radio band, as well as in bands at frequencies above 30 MHz.
Anyone can build or obtain a shortwave or general-coverage receiver, install a modest wire antenna in a backyard or even inside a frame house, and listen to signals from all around the world. This hobby is called shortwave listening (SWLing). Millions of people in the world enjoy it. In the United States, the proliferation of computers and online communications has largely overshadowed SWLing since the 1980s, and many young people grow up today ignorant of a realm of broadcasting and communications that still predominates in much of the world.
Various commercially manufactured shortwave receivers exist on the market, ranging in price from under $100 to thousands of dollars. A simple wire receiving antenna, which is all you need to receive the signals, costs practically nothing. Some of the better electronics or hobby stores carry these receivers, along with antenna equipment, for a complete installation. You can also shop around in consumer electronics and amateur radio magazines.
In most countries of the world, people can obtain government-issued licenses to send and receive messages via amateur radio. Hundreds of thousands of people have amateur radio licenses in the United States alone. Radio hams communicate by talking, sending Morse code, or typing on computer terminals. Typing the text on a computer resembles using the Internet. In fact, groups of amateur radio operators have set up their own radio networks, and some have “patched” into the Internet. Some hams, rather than talking or texting or using Morse code (also called “CW” for “continuous waves,” even though technically they aren’t continuous) on the radio, prefer to experiment with electronic circuits, and sometimes they come up with designs that later find their way into commercial equipment.
Some radio hams chat about anything they can think of except business matters, which are illegal to discuss using the ham radio frequencies in the United States. Others like to practice their emergency-communications skills, so they can be of public service during crises, such as hurricanes, earthquakes, or floods. Still others like to go out into the wilderness and talk to people thousands of miles away while sitting out under the stars. Radio hams communicate by radio from cars, trucks, trains, boats, aircraft, and even bicycles.
The simplest ham radio station has a transceiver (transmitter/receiver), a microphone, and an antenna. A small ham-radio station fits on a desk, and is about the size of a home computer or hi-fi stereo system. If you want, you can add accessories until your “rig” takes up an entire room in the house (or the better part of the basement, as in the author’s installation shown in Fig. 8-11). You’ll also need an antenna of some sort, preferably located outdoors. Figure 8-12 shows a simple vertical antenna designed to operate at 14 MHz, one of the most popular ham radio frequencies.
FIGURE 8-11 The author’s amateur radio station including a transceiver, Internet-ready computer, interface for digital radio communications, power meter, hi-fi audio system for big sound, and two displays, one of which is a flat-screen TV set.
FIGURE 8-12 The antenna for the ham radio station shown in Fig. 8-11. It’s made of telescoping sections of aluminum tubing, mounted on a deck railing, and can be taken down or put up in a couple of minutes.
Amateur radio is an electronics-intensive and, increasingly, computer-intensive hobby. Radio hams are more likely to own two or more personal computers than are non-hams. Conversely, computer engineers and “power users” are more likely to be interested in ham radio than people who avoid computers. If you use a computer very much, and especially if you’re interested in hardware design (as opposed to programming), you shouldn’t have trouble obtaining an amateur radio license.
Figure 8-13 is a block diagram of a computerized ham radio station. The computer can be used to network with other hams who own computers, and it also serves as a terminal for the transceivers. The computer can also control the antennas for the station, and can keep a log of all stations that have been contacted. Most modern transceivers can be remotely operated by computer over the radio or using the Internet.
FIGURE 8-13 Block diagram of a sophisticated ham radio station. This design includes more peripherals than the station shown in Fig. 8-11, including a so-called “linear amplifier” for generating high-power signals at shortwave frequencies.
For Aspiring Hams Only
You’ll need to get a license to transmit on the amateur frequencies. The transmission of radio signals without a license is against the law, and can result in fines and/or imprisonment. There are several levels, or classes, of ham radio licenses available in the United States, all of which are issued by the Federal Communications Commission (FCC). For complete information, contact the headquarters of the American Radio Relay League (ARRL), 225 Main Street, Newington, CT 06111. This organization publishes books on all subjects relevant to ham radio, as well as license-exam study materials and a monthly magazine called QST, which means “Calling all radio amateurs.” The people at ARRL headquarters can tell you the location of the nearest amateur radio club, where you can meet local hams and find out if this hobby is right for you. They maintain a website at www.arrl.org.
For centuries, people have imagined having personal robots. Until the explosion of electronic technology, however, people’s attempts at robot-building resulted in clumsy masses of metal that did little or nothing of any real use. But now, personal robots can be practical, affordable devices for many people!
Personal robots can do all kinds of mundane chores around your house. Such robots are sometimes called household robots. Personal robots can be used in the office; these are called service robots. Some personal robots incorporate advanced features, such as speech recognition, speech synthesis, and object recognition. Household robot duties might include:
• Car washing
• Floor cleaning
• Cooking
• Dishwashing
• Laundry
• Lawn mowing
• Maintenance
• Meal serving
• Child’s playmate
• Snow removal
• Window washing
• Companionship
Around the office, a service robot might do things such as:
• Floor cleaning
• Coffee preparation and serving
• Delivery
• Dictation
• Equipment maintenance
• Filing documents
• Greeting visitors
• Meal preparation
• Photocopying
• Toilet cleaning
• Window washing
Homogenize This!
You can enter “personal robot” (as a phrase) into your favorite Internet search engine, and you’ll get some really cool hits. I found one place (as of this writing) called the Robot Shop (www.robotshop.com). Then I hit a link called “Domestic Robots” and got information about all sorts of machines, including vacuum cleaners, sweepers, companions, and even a robot golf caddy!