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Electronics Blog

Motorboating?

Q. I have a book on tube-type amplifiers that talks about “motorboating.” What is this?

A. In tube-type amplifiers, when the filter capacitors get old they lose some of their capacitance and develop leakage between their plates. They no longer do as good a job of bypassing AC on the positive side of the power supply to ground. As a result, the supply voltage can sag when the output stages draw current. When they stop conducting the power supply voltage comes back up.

These changes in supply voltage are coupled back to the sensitive voltage amplifiers in the input stages of the amplifier. The result is a kind of oscillation that comes in bursts. In a speaker connected to the amplifier these bursts make a “putt-putt” noise that sounds very much like an old-time motorboat.

Magnet Mistery

Magnet Mistery
Q. There is something I don’t understand about magnets. If you wrap a length of wire around a piece of steel and pass current through the coil, the steel will become magnetized. But with a permanent magnet, there is no coil or current. How can this be?

A. Iron atoms, and those of a few other chemical elements, act as little permanent magnets. This is due to the particular arrangement of protons in the nuclei and electrons going around the nuclei. Normally, the little atom-magnets are not aligned with each other. They point in random directions, so their magnetic fields cancel each other out. But when the iron (or steel) is magnetized, some of these atom-magnets become aligned, and point in the same direction. Then their magnetic fields aid, and together they form a magnet.

Repairing Auto Electronics

Repairing Auto Electronics

Q. I work in an automotive garage. A car came in one day with an electrical problem; a fuse kept popping. My supervisor put a pair of needle-nose pliers into the fuse slot. When the smoke from the wires came out of the car he said, “There is the short.” It took days of replacing burned wire inside the car what a mess! I wouldn’t want to own it. When a fuse does blow is there a reasonable way to or trace it?

A. One thing you can do is solder a couple of wires to a single filament tail light. Then connect the tail light across the empty fuse receptacle. If the short exists the lamp will light. The lamp will limit the current to about one Amp, which will not harm the wires in the harness. Since any current-carrying conductor produces a magnetic field, you can sometimes use a compass to trace the wire through body panels, etc. One amp of current should give a strong enough magnetic field.

There are also pulse generators called “buzz boxes” that can be used to trace wires through bundles and harnesses. The buzz box produces pulses coming at an audible frequency. A detector consisting of a pickup loop, audio amplifier, and speaker or headphones is used to "sniff" or trace out the wire. When you’re on the wire itself you’ll hear a loud tone. If you’re farther away or on another wire, you’ll hear a fainter tone. Telephone techs have used these for years.

One word of caution is in order, though. First, don’t try to use an auto buzz box on AC power lines. Secondly, other devices are often called “buzz boxes,” too. For example, l2VDC-to-120VAC inverters are often called “buzz boxes,” too. If you decide to buy one, make sure that the person you buy it from understands what you want.

PINning it Down

Q. I was reading a magazine article the other day and it mentioned PIN diodes. What are PIN Diodes?

A. PIN diodes have a P-type semiconductor and an N-type semiconductor, as do ordinary diodes. But between the P and N material, there is a very thin layer of undoped, or intrinsic semiconductor. This is what the letter I stands for in "PIN". Undoped semiconductor is a good insulator. The I layer is put between the P and N layers to reduce the capacitance of the diode. The reduced capacitance makes the diode start to conduct and stop conducting faster than regular diodes.

PIN diodes are used in circuits that handle radio-frequency and high speed digital signals.

How long should it take me to complete a lesson?

On average, for a typical CIE Bookstore certificate course, most students complete a lesson in 10 to 14 days.

This is an average, though, and completion times for different lessons vary quite a bit. The introductory lessons at the beginning of most of our courses do not take much time to complete. But the calculus lessons in the math courses and other advanced electronics formulas take a little longer.

Accordingly, we expect students to need more time to complete them than they do for the introductory lessons.

The Need for Electronics Training

When Carl E. Smith founded the Smith Practical Radio Institute in Cleveland in 1934, radio was king. But other electrical goods were also growing in popularity. Things like electric stoves, clothes washers, toasters and coffee percolators.

Time travel ahead 79 years. The need for electronics has never been more demanding! But today, the revolution is led by computers and information technology and a host of consumer products and services ranging from wireless devices and GPS navigators to appliance repair and satellite dish set-up.

What Mr. Smith started eventually became the Cleveland Institute of Electronics - a distance learning school that offers diploma and associate degree courses in Electronics Technology and Computer Information. His first class started with 16 students and consisted of courses in radio and electronics engineering. Since 1956, when the CIE patented its "Auto-Programmed" self-study method, more than 350,000 students in the U.S. and some 70 foreign countries have gotten their start in electronics through the institute. Its curriculum has grown to include computer IT and systems management, conducted through online assignments and testing.

The relevance of electronics remains strong around the world. It manifests itself in many ways and regularly enters forums of economic and social import. Here are a few examples:

  • Green energy. The push for green energy is no longer just about wind and solar power generation. It has expanded to other areas of conservation, and now has its own rack of political footballs including climate change and “cap and trade” legislation in various nations.
  • Smart electric grid. The nation’s electricity distribution system is set to enter the digital age. The revamping includes advanced metering, two-way communication between consumers and utilities, and the ability to more efficiently regulate energy usage with thermostats, washers, dryers and refrigerators – the major electricity users in the home – with home energy dashboards.
  • Computer hardware and software are always being updated or upgraded. For instance, Windows 8 is Microsoft’s new 2014 baby and operating system. It comes in six different versions: Starter, Home Premium, Professional, Ultimate, OEM and Enterprise.
  • New products and services. Things like cellular phones and access to the Internet are truly bringing more people and cultures together around the planet. What will happen next?

Consumer electronics

Headquartered in Arlington, Virginia, the Consumers Electronics Association (CEA) keeps its finger on the pulse of the of the $172 billion American consumer electronics industry. The group is about to host the 2014 International Consumers Electronics Show in Las Vegas, January 2014. It is the world’s largest consumer technology tradeshow. The show is expecting some 110,000 attendees and more than 2,500 exhibitors.

Some of the most anticipated exhibits will showcase mobile devices, green trends in design and packaging, the use of LED, e-ink for electronic paper displays and a large assortment of new computer applications.

The CEA also monitors sales of consumer electronics products across the land. In its 19th Annual Consumer Electronics Holiday Purchase Patterns Study, it estimated consumer electronics sales will increase 6% this holiday season, as compared to 2012. The CEA also reported that 80% of adults intended to purchase technology merchandise as a gift for the holidays, the highest figure in the history of the study. The most purchased products will be computer notebooks, portable mp3 players and flat-panel TVs. Other popular technology-related items that are expected to sell well are digital cameras, Blu-ray players, smartphones and eBook readers.

“Consumer enthusiasm for technology has been building,” explained Gary Shapiro, CEA’s president and CEO, at the end of November. “Results from the Thanksgiving weekend suggest consumer technology will be the must-have gift this holiday and will lead economic recovery in 2014.” Technicians and salesmen with expertise or proficiency for high-tech items may find prospects in this market.

Online shopping, like online training, is also growing. Based on new estimates from a variety of research groups, e-commerce sales should also be stronger for the 2013 holiday season.

Cyber Monday online sales were 5% higher this year than last, at an estimated $887 million, reported comScore, Inc., a Reston, Virginia-based company that measures digital sales.

“We’ve seen an encouraging start to the online holiday shopping season and it would appear that retailers’ aggressive and early marketing efforts have so far succeeded in persuading consumers to open their wallets online,” said comScore chairman Gian Fulgoni. That means that more people are shopping from home, or work, than ever before. An estimated 8.7 million Americans made a purchase on Cyber Monday this year, spending an average $102, comScore said.

Some of the largest e-commerce firms include Amazon.com, Apple, Best Buy, Target and Walmart. Likewise, some of the best selling products through Cyberspace are books, clothing, footware, computer hardware and software, autos and auto parts, home furnishings, iPods and iTunes, and travel arrangements made for airline flights and lodging accommodations.

Of course, just about everything has pros and cons! Some of the advantages of online shopping include convenience, selection and fast price comparison. Disadvantages center around fraud and security issues. And anyone who has received the wrong item or a broken product delivered by FedEx or UPS knows what a hassle it can be to return it.

Training

How does all this relate to electronics training? Think about it. The digital world is expanding. And even more high-tech items are entering the marketplace in a variety of fields. Anyone with an understanding of basic computer IT and electronics will have an advantage over someone who lacks the training.

The sky’s the limit, regarding applications. However, the fields most often mentioned occur under the umbrella of education, lifestyle, entertainment, productivity and IT. But many more disciplines, and employment opportunities, take advantage of high tech tools or concepts.

Government agencies and the U.S. military probably lead the way in shear numbers. But auto mechanics must understand how microprocessors and digital modules work. Farmers are using high-tech equipment to plan, plow, harvest and market their crops or livestock. Medical and healthcare workers use their instruments everyday. Butchers, bakers, candle stick makers – and other retail clerks - will all be better prepared to do their jobs with a little computer savvy.

This brings us back to the CIE. The CIE is waiting to assist you, with beginning instruction or more advanced training. You can earn an Associate Degree in Electronics or Computer Technology, graduate from a career course, or go on to earn a Bachelor's Degree though CIE’s subsidiary, World College. CIE Bookstore offers many professional certificate programs as well.

Graduates leave CIE as skilled technicians or engineers equipped to better tackle the complexities of business and industry, whether it's in computer programming, microprocessor technology, manufacturing, appliance repair or in new fields related to green energy, the smart electric grid, cellular or satellite services and consumer electronics.

The CIE has a strong pedigree of instruction. It traces its roots back 79 years. Obviously, a great deal of water has gone under the bridge during this period, electronically speaking. “Email machines” have largely replaced letters sent via the U.S. Postal Service. Apple’s iPod is a much fancier version of the Victor Victrola. TVs and computers are used more than radios for home entertainment, but radio wave propagation is still very important for cellular and wireless data transmission.

Nowadays, just about everything has a digital or electronics connection to it.

High-tech choices abound. If you are passonate about something – even better. Embrace it. Find a match. But ludites should not apply!

Special Cases

Q. In our lab parts, the MPS-A20's come in plastic cases, but the 2N3431's come in metal ones. Why is this?

A. The 2N3431 is an older transistor type, and at first all transistors were produced with metal cases. After awhile, plastic cases were developed. They are less expensive and much easier to manufacture.

The same is true for integrated circuits. High-quality ICs come in ceramic packages, while less expensive ones come in plastic.

Mask Production

Q. I have been working in electronics for about a year. I have noticed that some printed circuit boards have a kind of plastic coating on them, with holes for the solder joints. What is the coating for?

A. This is called a "solder mask". It helps keep solder off the copper foil traces when the board is made. Most manufacturers use "wave soldering". In this process, molten solder is pumped over a sort of dam which produces a stationary wave in the solder. The board is passed over this wave so that all the solder joints are formed at the same time. A solder mask is often placed on the board before the solder is applied.

Iron Mike

Q. In my job, I work with microphones a lot. How does a microphone work?

A. There are three types: dynamic, crystal and electret. In the dynamic type, there is a thin diaphragm which vibrates along with the sound waves in the air. The diaphragm is attached to a coil suspended in the field of a permanent magnet. When the coil vibrates, a voltage is induced in it that varies along with the sound vibrations.

This voltage is the output signal of the microphone. Dynamic mikes are designed to operate into a low impedance, such as 600 ohms. Typical signal levels are about 50mV.

Crystal microphones use a piezoelectric crystal in place of the coil and magnet. In these types of crystals, mechanical pressure produces a voltage. Crystal mikes are of poorer quality than dynamic mikes, and are used in applications where an inexpensive microphone is acceptable.

They operate into a high impedance, usually 100 K to 1 Megohm, and have a high output voltage level, typically 1 volt.

Electret microphones use a capacitor with a special dielectric which holds a charge indefinitely. The plates of the capacitor vibrate along with the sound vibrations, which changes the value of the capacitor. This makes the voltage across it vary, and it is this voltage that becomes the microphone's output signal.

These microphones have excellent frequency response, and are generally used where small size and a high-quality signal are important. Electret mikes usually require a small battery. They are designed to operate into a high impedance.

An older type of microphone used a container full of carbon particles. The diaphragm was attached to the container so that the vibrations would change the pressure on the carbon particles. Thus their resistance varied along with the sound vibrations. The resistance element was connected in series with a fixed resistor and driven by a source of DC. Thus, the voltage across the resistance element served as the microphone's output signal.

Carbon mikes tended to be unreliable. The carbon particles would become compacted, and the mike had to be tapped a few times to loosen them. They have become obsolete, and are rarely used nowadays.

Dopple Duty

Q. I have seen doppler radar in weather reports. What is the difference between regular radar and doppler radar?

A. Basically, radar emits a burst of radio waves. The radio waves reflects off an object and the radar antenna receives the reflection. Since radio energy travels at the speed of light, if in the time between the transmission and reception of the burst is measured, the distance to the object can be determined. The greater the distance, the longer it takes for the burst to reach the object and be reflected back to the radar unit.

If the object, such as a cloud, is not moving, the frequency of the reflected burst will be the same as the transmitted one. But if the object is moving toward the radar unit, the reflected frequency will be higher. If it is moving away from the radar unit, the frequency will be lower.

This is known as the "Doppler shift" after the name of its discoverer. The faster the object is moving toward or away from the radar unit, the greater will be the doppler shift. A doppler radar can thus display the position of a cloud, and it can indicate how the cloud is moving.