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EEE255. Yrd. Doç. Dr. Mehmet Ali Aktaş. Electronic Systems. In recent years electronic systems have found their way into almost all aspects of our lives .
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EEE255 Yrd. Doç. Dr. Mehmet Ali Aktaş
Electronic Systems • In recent years electronic systems have found their way into almost allaspectsof ourlives. • Such systems wake us in the morning; control theoperation of our cars as we drive to work; maintain a comfortable workingenvironment in our offices and homes; allow us to communicate worldwide;provide access to information at the touch of a button; manage the provisionof power to maintain our high-technology lifestyles; and provide restfulentertainment after a day of ‘electronically controlled’ excitement. • In many cases electronic systems are used in these applications becausethey provide a more cost-effective solution than other available techniques. • However, in many cases electronics provide the only solution, and the applicationwould be impossible without its use.
Electronic Systems • While electronic elements represent essential components of almost allcomplex systems, it should be noted that few, if any, engineering systemsconsist of entirely electronic elements. Even applications such as mobilephones or MP3 players require mechanical elements such as cases and keyboardsin order to make a useable product. • In practice all real engineeringprojects are interdisciplinary in nature and involve a wide range of engineeringskills and techniques coming together to solve what are often quitecomplexproblems.
Electronic Systems • One method is to adopt what might be termed a systematic approach,in which a complex problem or system is simplified by dividing it into anumber of smaller elements. These elements are then themselves subdivided,the process being repeated until the various constituents have beendevolved into elements that are sufficiently simple to be easily understood. • This approach is widely used within engineering in what is termed topdowndesign, where a complex system is progressively divided into simplerandsimplersubsystems. • A problem with the reductionist view is that it ignores characteristics thatare features of the ‘whole’ rather than of individual components. Thesesystemic properties are often complex in nature and may relate to severaldiverse aspects of the system.
Electronic Systems • In recent years, modern engineering practice has evolved a more ‘holistic’approach that combines the best elements of a systematic approach togetherwith considerations of systemic issues. This results in what is called a systemsapproachtoengineering. • The systems approach has its origins back in the 1960s but has gainedfavour within many engineering disciplines only recently.
Electronic Systems • Before looking at the nature of electronic systems, it is perhaps appropriateto make sure that we understand what we mean by the word system. • In an engineering context, a system can be defined as any closed volumefor which all the inputs and outputs are known. This definition allows us toconsider an infinite number of ‘systems’ depending on the volume of spacethat we decide to select. However, in practice, we normally select our ‘closedvolume’ to enclose a component, or group of components, that are of interesttous. • Thus we could select a volume that includes the components thatcontrol the engine of a car and call this an ‘engine management system’.In some situations only particular inputs and outputs to a system areof interest, and others may be completely ignored. For example, one inputto a mobile phone might be air entering or leaving its case. An electronicengineer designing such a system might decide to ignore this form of inputand to concentrate only on those inputs related to the operation of the unit.
Electronic Systems • Figure 10.1 represents a generalised system, together with its inputs andoutputs. This diagram makes no assumptions about the form of any of itscomponents, and this could represent a mechanical or biological systemjust as easily as an electrical or electronic arrangement. Thus the inputs andoutputs in this case could be forces, temperatures, velocities or any otherphysical quantities. Alternatively, they could be electrical quantities such asvoltagesorcurrents.
Electronic Systems • When considering electronic systems, we are concerned with arrangementsthat generate, or manipulate, electrical energy in one form or another. • However, the nature of the inputs and outputs to such systems may dependon where we choose to draw the system’s boundaries.
Electronic Systems • In Figure (a), we have chosen to consider themicrophone and speaker as parts of our system. Here the input and outputare in the form of sound waves. • In Figure (b), we have chosen to consider themicrophone and speaker as parts of our system. Here the input and outputare in the form of sound waves.
Electronic Systems • The vast majority of real-world physical quantities (such as temperature,pressure and humidity) vary in a continuous manner. This means that theychange smoothly from one value to another, taking an infinite number ofvalues. In contrast, discrete quantities do not change smoothly but insteadswitch instantlybetween distinct values. • Having noted that physical quantities may be either continuous or discretein nature, it is not surprising that the electrical signals that representthem may also be either continuous or discrete. • However, there is not necessarily a direct correspondence between these forms, since it may beconvenient to represent a continuous quantity by a discrete signal, or viceversa. For reasons that are largely historical, continuous signals are normallyreferred to as analogue, while discrete signals are described as digital.
Electronic Systems • Both analogue and digital signals can take many forms. Perhaps one of thesimplest is where the voltage of a signal corresponds directly to the magnitudeof the physical quantity being represented. This format is used for boththe input and the output signals in Figure
Electronic Systems • Although it is very common to represent the magnitude of a continuousquantity by the voltage of an electrical signal, many other forms are alsoused. For example, it might be more convenient to represent the value of aphysical quantity by the magnitude of the current flowing in a wire (ratherthan by the voltage on it), or by the frequency of a sinusoidal waveform.These and other formats are used in certain situations, these being chosen tosuittheapplication.
Electronic Systems • It is often convenient to represent a complex arrangement by a simplifieddiagram that shows the system as a set of modules or blocks.Thismodularapproach hides unnecessary detail and often aids comprehension. An exampleof a typical block diagram is shown in Figure
Electronic Systems • Thisshowsa simplified representation of an engine control unit (ECU) that might befound in a car. This diagram shows the major components of the system andindicates the flow of energy or information between the various parts. Thearrows in the diagram indicate the direction of flow. • When energy or information flows from a component we often refer tothat component as the source of that energy or information. Similarly, whenenergy or information flows into a component, we often say that the componentrepresents a load on the arrangement. Thus in Figure we couldconsider the various sensors and the power supply to be sources for the ECUand the ignition coil to be a load.
Electronic Systems • In electrical systems a flow of energy requires an electrical circuit. Figure10.5 shows a simple system with a single source and a single load. In thisfigure the source of energy is some form of sensor, and the load is some form of actuator.
Electronic Systems • We noted earlier that we are free to choose the boundaries of our systemto suit our needs. We might therefore choose to divide the system ofpreviousFigure into a number of subsystems, or modules, as shown in thefollowingFigure.
