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Control systems Electrical circuits, digital signal processors and microcontrollers can all be used to implement control systems. Control engineering has a wide range of applications from the flight and propulsion systems of commercial airliners to the cruise control present in many modern automobiles. Control engineers often utilize feedback when designing control systems. For example, in an automobile with cruise control the vehicle's speed is continuously monitored and fed back to the system which adjusts the motor's speed accordingly. Where there is regular feedback, control theory can be used to determine how the system responds to such feedback. In practically all such systems stability is important and control theory can help ensure stability is achieved. Although feedback is an important aspect of control engineering, control engineers may also work on the control of systems without feedback. This is known as open loop control. A classic example of open loop control is a washing machine that runs through a pre-determined cycle without the use of sensors. Control engineers may also play an important part in determining how human users will interact with their systems.
Electronics is often considered to have begun when Lee De Forest invented the audion in 1907 (also known as a triode vacuum tube). Within 10 years, the audion was used by radio transmitters and receivers as well as systems for long distance telephone calls. Vacuum tubes remained the preferred amplifying device for 40 years, until researchers working for William Shockley at Bell Labs invented the transistor in 1947. In the following years, transistors made small portable radios or transistor radios possible, as well as allowing more powerful mainframe computers to be built. Transistors were cooler, smaller and required lower voltages than vacuum tubes. Before the invention of the integrated circuit in 1959, electronic circuits were constructed from discrete components that could be manipulated by hand. These non-integrated circuits consumed much space and electrical power, were prone to failure and were limited in speed although they are still common in simple applications. By contrast, integrated circuits packed a large number - often millions - of tiny electrical components, mainly transistors, into a small chip around the size of a coin. This allowed for the powerful computers and other electrical devices we see today. In designing an integrated circuit, electrical engineers first construct circuit schematics that specify electrical components and describe the interconnections among them. When the schematics are completed, VLSI engineers convert the schematics into actual layouts, which map the layers of various conductor and semiconductor materials on a scale of micrometres and nanometres. The conversion from schematics to layouts can be done by computer programs, although very often human fine-tuning is desirable to decrease space and power consumption. The physical fabrication of integrated circuits is itself a huge subfield of electrical engineering, on which circuit designers must rely. As transistors become smaller microelectronic circuit designers must involve themselves more and more in the fabrication process (see photolithography). Today, software simulation is essential in the design process of electronic circuits, especially integrated circuits (see SPICE or Cadence Design Systems). Models of semiconductor materials and electrical components are constructed by fabrication plants and manufacturers of electrical components for the purpose of computer simulation. Integrated circuits and other electrical components are then combined onto printed circuit boards (PCBs). Today, PCBs are found in most electronic devices including televisions, computers and audio players. See Electronics and Communication engineering. Main Roll1 Roll2 electric1electric2 electric3 electric4 electric5 |