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What is Electronics?

The concept electronics is used for electronic components, integrated circuits, and electrical systems. Main areas of usage are modern information technology and telecommunications, tools for recording and playing sound and picture, sensors and steering systems, instrumentation and measurement devices. Electronics, information technology and communication technology have undergone immense growth during the past 30 years. Our new technology-based lives are run by the development of miniaturized electrical circuits (microchips) and broadband phone and internet through optical fibers or across wireless channels.

Within transportation we have advanced electrical navigation systems, landing systems for planes, and anti-collision systems for ships and cars. Automatic toll stations across the biggest cities provide money for new roads and environmental friendly traffic. Modern cars are provided with constantly advancing electronics, such as airbag systems, ABS breaks, anti-spin systems and theft alarms.

Modern electronics has revolutionized medical diagnosis by introducing new techniques like CT (computer tomography), MR (magnetic resonance), and ultrasound imaging devices. The industry applies electronics for controlling and supervising production processes and developing new technologies.

Centrally in this picture we also have sensors that can “feel” sound, light, pressure, temperature acceleration, etc., and actuators that can “act”, i.e. perform specific operation such as turning on a switch or transmit sound signals. This advancement in technology and electronics will continue with increasing speed in times to come.

Finally, computers have become common facilities in offices and at home. Through systematic miniaturization of electrical components and circuits, computers and other advanced electronics today are now available for ordinary users for moderate prices.

Our Electronic Future

Do you want to revolutionize the world with new and useful technology? Do you want to make new computers that are more effective and creative? Do you want to make new intelligent materials and components by creating them atom by atom? Do you want to construct small nano-robots that can take away cholesterol from the veins, molecule y molecule? Do you want to make new communication paths between electronics and nervs so that deaf people can hear and blind people can see? This may all be possible in the future.

The photo shows spectroscopy-measurements of skin. Optical tecniques are of great interest in medicine.

Everyone agrees that the domain of electronics has revolutionized the world the past decades. Only 50 years ago, the thought of being surrounded by computers, microprocessors, Internet, and cell phones was unheard of. The performance of computers is approximately doubled every other year. This development is due to the fact that we now can place more components closer to each other on microchips. We are approaching the atomic border where each component on the microchip is only a few atom-lengths long. It is therefore necessary to think along new paths in order to bring about the development of the future.

Components in a radiosystem can be measured in the Microwave-lab.

Everyone agrees that the domain of electronics has revolutionized the world the past decades. Only 50 years ago, the thought of being surrounded by computers, microprocessors, Internet, and cell phones was unheard of. The performance of computers is approximately doubled every other year. This development is due to the fact that we now can place more components closer to each other on microchips. We are approaching the atomic border where each component on the microchip is only a few atom-lengths long. It is therefore necessary to think along new paths in order to bring about the development of the future.

Antennas are an omportant part of a radio system. We can measure all antenna-characteristics in the echo-free chamber. The photo shows antenna-element measurements of a georadar (a georadar is a radar used to detect objects underground, like pipes, cables and mines)

The use of new technologies gives unimaginable possibilities. Already today we see how electrical networks allow us to search among incredible amount of information, the CD shelves disappear and you can watch TV programs whenever it suits you. Flat screens with network connections replace clumsy TVs. Microprocessors and electrical sensors make cars, ships, trains, and planes more practical, environmental friendly, and secure.

The field of study of electronics at NTNU provides you with a general knowledge that will allow you to follow on and contribute to the future of electronics. Rather than learning the details of how e.g. a TV is built up of, in this field you will learn about the principles behind the technology of today and tomorrow.

Electronics

- Programme components

The study of electronics at NTNU covers an extensive field, which means that our students specialize gradually and acquire a broad specter of knowledge. The first two years consist of the same basis classes for all students, while in the third year of the study program, students may choose among four main fields of concentration, each of which split further into ten main profiles in the fourth and fifth years of the study program of Electronics.

Electronics

- Job Prospects

During the study of electronics, you will obtain a broad qualification in the fields of electronics and information- and communication technology (ICT). You can get exciting job opportunities in large and small technology companies within product development, research, leadership, sale and marketing both in Norway and abroad.

You are qualified for teaching and researching at the universities and research institutes, or working within consultancy and consulting engineering.

Some job opportunities:

• Radio electronics for use in communication, radar, remote measurements, localization and navigation

• Mobile- and satellite communication systems

• Medical technology based on ultrasonic- and laser technology

• Radar equipment for military and civil surveillance- and navigation purpose

• Ultrasound in medical diagnostics, seismology, sonar, echo sounder, noise and vibrations

• Remedies for handicapped and new telecommunication service based on human-machine communication

• Space Technology

• Fiber-optical telecommunications

• Measuring instruments and measuring technique

• Internet applications

• Micro Controllers and Micro Processors

• Large scale integrated circuits for different applications

• Development of micro sensors and other Micro-Electro-Mechanical Systems (MEMS)

• Digital communication in wireless and wire networks

• Multimedia signal- and image processing damping of noise-pollution, audio technology, music technology

Principles of operation

In any electric motor, operation is based on simple electromagnetism. A current-carrying conductor generates a magnetic field; when this is then placed in an external magnetic field, it will experience a force proportional to the current in the conductor, and to the strength of the external magnetic field. As you are well aware of from playing with magnets as a kid, opposite (North and South) polarities attract, while like polarities (North and North, South and South) repel. The internal configuration of a DC motor is designed to harness the magnetic interaction between a current-carrying conductor and an external magnetic field to generate rotational motion.

Let's start by looking at a simple 2-pole DC electric motor (here red represents a magnet or winding with a "North" polarization, while green represents a magnet or winding with a "South" polarization).

Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator, commutator, field magnet(s), and brushes. In most common DC motors (and all thatBEAMers will see), the external magnetic field is produced by high-strength permanent magnets1. The stator is the stationary part of the motor -- this includes the motor casing, as well as two or more permanent magnet pole pieces. The rotor (together with the axle and attached commutator) rotate with respect to the stator. The rotor consists of windings (generally on a core), the windings being electrically connected to the commutator. The above diagram shows a common motor layout -- with the rotor inside the stator (field) magnets.

The geometry of the brushes, commutator contacts, and rotor windings are such that when power is applied, the polarities of the energized winding and the stator magnet(s) are misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets. As the rotor reaches alignment, the brushes move to the next commutator contacts, and energize the next winding. Given our example two-pole motor, the rotation reverses the direction of current through the rotor winding, leading to a "flip" of the rotor's magnetic field, driving it to continue rotating.

In real life, though, DC motors will always have more than two poles (three is a very common number). In particular, this avoids "dead spots" in the commutator. You can imagine how with our example two-pole motor, if the rotor is exactly at the middle of its rotation (perfectly aligned with the field magnets), it will get "stuck" there. Meanwhile, with a two-pole motor, there is a moment where the commutator shorts out the power supply (i.e., both brushes touch both commutator contacts simultaneously). This would be bad for the power supply, waste energy, and damage motor components as well. Yet another disadvantage of such a simple motor is that it would exhibit a high amount of torque "ripple" (the amount of torque it could produce is cyclic with the position of the rotor).

So since most small DC motors are of a three-pole design, let's tinker with the workings of one via an interactive animation (JavaScript required):

You'll notice a few things from this -- namely, one pole is fully energized at a time (but two others are "partially" energized). As each brush transitions from one commutator contact to the next, one coil's field will rapidly collapse, as the next coil's field will rapidly charge up (this occurs within a few microsecond). We'll see more about the effects of this later, but in the meantime you can see that this is a direct result of the coil windings' series wiring:

There's probably no better way to see how an average DC motor is put together, than by just opening one up. Unfortunately this is tedious work, as well as requiring the destruction of a perfectly good motor.

Luckily for you, I've gone ahead and done this in your stead. The guts of a disassembled Mabuchi FF-030-PN motor (the same model that Solarbotics sells) are available for you to see here (on 10 lines / cm graph paper). This is a basic 3-pole DC motor, with 2 brushes and three commutator contacts.

The use of an iron core armature (as in the Mabuchi, above) is quite common, and has a number of advantages2. First off, the iron core provides a strong, rigid support for the windings -- a particularly important consideration for high-torque motors. The core also conducts heat away from the rotor windings, allowing the motor to be driven harder than might otherwise be the case. Iron core construction is also relatively inexpensive compared with other construction types.

But iron core construction also has several disadvantages. The iron armature has a relatively high inertia which limits motor acceleration. This construction also results in high winding inductances which limit brush and commutator life.

In small motors, an alternative design is often used which features a 'coreless' armature winding. This design depends upon the coil wire itself for structural integrity. As a result, the armature is hollow, and the permanent magnet can be mounted inside the rotor coil. Coreless DC motors have much lower armature inductancethan iron-core motors of comparable size, extending brush and commutator life.

Diagram courtesy of MicroMo

The coreless design also allows manufacturers to build smaller motors; meanwhile, due to the lack of iron in their rotors, coreless motors are somewhat prone to overheating. As a result, this design is generally used just in small, low-power motors. BEAMers will most often see coreless DC motors in the form of pager motors.

Again, disassembling a coreless motor can be instructive -- in this case, my hapless victim was a cheap pager vibrator motor. The guts of this disassembled motor are available for you to see here (on 10 lines / cm graph paper). This is (or more accurately, was) a 3-pole coreless DC motor.

I disembowel 'em so you don't have to...

To get the best from DC motors in BEAMbots, we'll need to take a closer look at DC motor behaviors -- both obvious and not.

For more information

You might also want to check out the "HowStuffWorks" pages on electric motors, as well as the Motorola page on DC motors, and the MicroMo page on thedevelopment of electromotive force.

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Notes:

1. Other (generally either very large, or fairly old) DC motors use windings to produce the external field as well. By using permanent magnets, modern DC motors are more efficient, have reduced internal heating, and use less power.

2. The following 3 paragraphs borrow fairly liberally from material on a number of pages of the MicroMo web site. This is an excellent site, and goes into much greater detail on the ins and outs of coreless motor construction and performance. Particular attention should be given to their pages on Motor Construction , and on the Development of Electromotive Force .

History and background

Principles of operation DC motor behavior

Parameterizing performance

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Home Legalities Feedback

Page author: Eric Seale

This page was last updated on July 9, 2003

This work is licensed under a Creative Commons License.

The Ampere's rule (the right-hand screw rule)

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It is Frenchman Andre-Marie Ampere (1775–1836), a mathematician and physicist, who discovered what happens to a wire winded in a coil when current flows within. The current will generate a magnetic field around the coil, as shown in the following drawing:

The "right-hand screw rule"

Using your right hand, you can find out the direction of the magnetic lines as well as the North pole orientation. Close your fist and hold your thumb upwards, like thumbs-up. If you had the coil inside your hand and your fingers (except the thumb) was showing the direction of the current, then the thumb shows the direction of the magnetic lines as well as the orientation of the North pole. This is called "the right-hand screw rule".

The basic DC motor has actually two windings and two permanent magnets. The coils are powered from the commutator and the brushes. We will see these two later on. For now, you only need to know that during a full cycle of the rotor, the current that runs through each winding change direction once. Thus, each electromagnet will change its magnetic polarity. Moreover, the windings of the two magnets are winded in reversed direction. Thus, when one electromagnet is North, the other is South and vice versa. Look at the following drawing of the basic DC motor:

The following animation indicates how the two electromagnets changes magnetic polarity during a full rotation:

I have with RED color the North pole and with BLUE the South pole. If you watch this animation, you will see that there is one moment that both electromagnets are turned off. This is the time that the basic DC motor provides no torque at all. In all other occasions, the magnets are either PULLED from the opposite pole or PUSHED from the same pole and therefore the mechanical power is generated.

The commutator and the brushes of a DC motor

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This kind of DC motor is called "Brushed DC motor". Why? Because it uses brushes... The brushes are the way that the motor provides the coils with power, and the geometrical characteristics and position of the brushes (and the commutator of course) will be responsible for changing the magnetic field of the two electromagnets according to the position of the rotor. So, how this is done? The brushes are two metallic pieces that act like springs. On one side, they have a piece of conductive material, usually made of carbon to stand against friction. On the other side, they have the pin that the power supply is applied to the motor. The brushes are pushed (by the spring action of the metallic part) against the commutator. The commutator is a metallic ring, also conductive and able to stand friction, that is divided in two parts. The following drawing explains how these parts are:

The commutator is fixed on the shaft of the motor. Each semi-ring has one pole of each coil. Giving thus power to both half-rings, is like giving power to the coils. But while the shaft of the motor rotates, the commutator rotates as well. This causes the poles of the power supply provided to the coils to change. This change of the electric poles, has an affect on the magnetic poles as well. The current direction is changed and - due to the rule of the right-hand screw - the poles of the electromagnets will also change. The following two animations indicates this procedure. The left one shows the brushes and the commutator from above, while the right one shows how the electric and magnetic polarity is changed.

Notice how each part of the commutator changes polarity as it rotates. This is the basic operation of the DC motor. Notice also, that there is one moment that the commutator is short-circuited. During this time, the motor produces no power at all, and also the short-circuit can cause several damages due to over current. This of course does not happen in real life. Later on, i will explain how this is avoided. Now, its worth to see this video that explains exactly how the DC motor is made:

The Ampere's rule (the right-hand screw rule)

________________________________________

It is Frenchman Andre-Marie Ampere (1775–1836), a mathematician and physicist, who discovered what happens to a wire winded in a coil when current flows within. The current will generate a magnetic field around the coil, as shown in the following drawing:

The "right-hand screw rule"

Using your right hand, you can find out the direction of the magnetic lines as well as the North pole orientation. Close your fist and hold your thumb upwards, like thumbs-up. If you had the coil inside your hand and your fingers (except the thumb) was showing the direction of the current, then the thumb shows the direction of the magnetic lines as well as the orientation of the North pole. This is called "the right-hand screw rule".

The basic DC motor has actually two windings and two permanent magnets. The coils are powered from the commutator and the brushes. We will see these two later on. For now, you only need to know that during a full cycle of the rotor, the current that runs through each winding change direction once. Thus, each electromagnet will change its magnetic polarity. Moreover, the windings of the two magnets are winded in reversed direction. Thus, when one electromagnet is North, the other is South and vice versa. Look at the following drawing of the basic DC motor:

The following animation indicates how the two electromagnets changes magnetic polarity during a full rotation:

I have with RED color the North pole and with BLUE the South pole. If you watch this animation, you will see that there is one moment that both electromagnets are turned off. This is the time that the basic DC motor provides no torque at all. In all other occasions, the magnets are either PULLED from the opposite pole or PUSHED from the same pole and therefore the mechanical power is generated.

The commutator and the brushes of a DC motor

________________________________________

This kind of DC motor is called "Brushed DC motor". Why? Because it uses brushes... The brushes are the way that the motor provides the coils with power, and the geometrical characteristics and position of the brushes (and the commutator of course) will be responsible for changing the magnetic field of the two electromagnets according to the position of the rotor. So, how this is done? The brushes are two metallic pieces that act like springs. On one side, they have a piece of conductive material, usually made of carbon to stand against friction. On the other side, they have the pin that the power supply is applied to the motor. The brushes are pushed (by the spring action of the metallic part) against the commutator. The commutator is a metallic ring, also conductive and able to stand friction, that is divided in two parts. The following drawing explains how these parts are:

The commutator is fixed on the shaft of the motor. Each semi-ring has one pole of each coil. Giving thus power to both half-rings, is like giving power to the coils. But while the shaft of the motor rotates, the commutator rotates as well. This causes the poles of the power supply provided to the coils to change. This change of the electric poles, has an affect on the magnetic poles as well. The current direction is changed and - due to the rule of the right-hand screw - the poles of the electromagnets will also change. The following two animations indicates this procedure. The left one shows the brushes and the commutator from above, while the right one shows how the electric and magnetic polarity is changed.

Notice how each part of the commutator changes polarity as it rotates. This is the basic operation of the DC motor. Notice also, that there is one moment that the commutator is short-circuited. During this time, the motor produces no power at all, and also the short-circuit can cause several damages due to over current. This of course does not happen in real life. Later on, i will explain how this is avoided. Now, its worth to see this video that explains exactly how the DC motor is made: