3 electric circuits
- 1. MECHATRONICS ELECTRIC CIRCUITS AND COMPONENTS PUSHPARAJ MANI PATHAK MECHANICAL & INDUSTRIAL ENGINEEING, IIT ROORKEE 1
- 2. Introduction • Electric circuits and components are important in design of discrete circuits for signal conditioning and interfacing. • Electron moves and produce electric current. Useful jobs can be done by energized electrons. • Electron moves because we impose an electric field that imparts energy by doing work on the electrons. • A measure of electric field potential is voltage. • Voltage is also referred as electromotive force or emf. 2
- 3. Electric Circuit Terminology • Current is time rate of flow of charge • 𝐼(𝑡) = 𝑑𝑞 𝑑𝑡 (q=charge) • DC Circuit: Voltage and current in a circuit are constant (independent of time) • AC Circuit: Voltage and current vary with time usually sinusoidally 3
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- 5. • Voltage source adds energy to electron. • Anode: Electrons are attracted. • Cathode: Electrons are released • Electron flow from cathode to anode through the circuit. But standard convention is in opposite direction. • Load: Network of circuit elements that may store (I,C) or dissipate electrical energy (R) • Ground: Indicates a reference point in circuit where the voltage is assumed to be zero. 5
- 6. Electronic components Passive components Resistance (R) Inductance (L) Capacitance (C) Active components Tube devices Vacuum Tubes Gas Tubes Solid state (semi conductor devices) Diodes Transistors 6 Basic Electrical Elements
- 8. • Passive electrical elements: R, L, C • Passive elements require no additional power supply, unlike active devices such as integrated circuits. • These elements are defined by voltage current relationship. • Two types of energy sources • Voltage source (V) • Current sources (I) • Ideal source contains no internal resistance, inductance or capacitance. 8
- 9. Resistor • Dissipative element that converts electrical energy into heat. • Ohms law define V-I characteristics (V=IR) 9 R = 𝜌𝐿 𝐴 𝜌 is resistivity of material
- 11. Wire Lead Resistor Color Bands 11 Resistor value & tolerance are expressed as R = ab×10c± tolerance(%) a band: ten digit b band: one digit c band: power
- 12. • Variable Resistor • Provide range of values controlled by mechanical screws knobs or linear slide • Most common type is potentiometer or pot 12 Potentiometer schematic symbol
- 13. Capacitor • Passive element that stores energy in the form of an electric field. • The filed is the result of separation of charges. • Dielectric material is an insulator that increases the capacitance as a result of permanent or induced electric dipoles in the material. 13 Parallel Plate Capacitor
- 14. • Strictly DC current does not flow through the capacitor • Charges are displaced through circuit. • Displacement current • Capacitance is a property of the dielectric material, plate geometry and plate separation. • Values of typical capacitors range from 1 pF to 1000 µF 14 𝑉 𝑡 = 1 𝐶 න 0 𝑡 𝐼 𝜏 𝑑𝜏 = 𝑄(𝑡) 𝐶 𝐼 𝑡 = 𝐶 𝑑𝑉 𝑑𝑡
- 15. Inductor • A passive element that stores energy in the form of a magnetic field. • Energy storing element that stores energy in the form of magnetic field. • Characteristics are from Faradays law of induction 15 𝜆 is total magnetic flux through coil winding due to current. It is measured in webers(Wb) = = = = t d V L t I dt dI L t V LI dt d t V 0 ) ( 1 ) ( ) ( ) (
- 16. • Current through an inductor cannot change instantaneously because it is integral of voltage. • Motors have large inductance, so it is difficult to start and stop motors instantaneously • Unit of measurement of inductance is Henry • Typical inductance range from 1µH to 100mH 16
- 17. Kirchhoff’s Laws • Kirchhoff’s Voltage Law (KVL) • Sum of the voltages around a closed loop or path is 0. 17 𝑖=1 𝑁 𝑉𝑖 = 0 −𝑉1 − 𝑉2 + 𝑉3+. . . −𝑉𝑁 = 0 Kirchhoff’s Voltage Law
- 18. Kirchhoff’s Current Law (KCL) • Sum of the currents flowing into a closed surface or node is 0. 18 = = = − + N i i I I I I 1 3 2 1 0 0 Kirchhoff’s Current Law 𝐼1 𝐼2 𝐼3 Node Surface 𝐼1 𝐼2 𝐼3 𝐼𝑁 …
- 20. Voltage Dividers 20 s R s R V R R R V V R R R V 2 1 2 2 1 1 2 1 + = + = Series Resistance Circuit
- 21. Parallel Resistance Circuit 21 2 1 2 1 2 1 2 1 2 1 2 1 0 L L L L L C C C R R R R R I I I eq eq eq + = + = + = = − − Using KCL
- 22. Voltage & Current Sources and Meters • An ideal voltage source: has zero output resistance and can supply infinite current • An ideal current source has infinite output resistance and can supply infinite voltage • An ideal voltmeter has infinite input resistance and draws no current. • An ideal ammeter has zero input resistance and no voltage drops across it. 22
- 23. Real Voltage Source with Output Impedance 23 Rout is small
- 24. Real Current Source with Output Impedance 24 Rout of commercially available current source is high. So as to minimise current division effect
- 25. Real Ammeter with Input Impedance 25 Rin of commercially available ammeter is small minimizing the voltage drop VR in the circuit.
- 26. Real Voltmeter with Input Impedance 26 Rin in commercially available voltmeter (an oscilloscope or multimeter) is very large (1 to 10 MΩ.)
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- 28. Thevenin Equivalent Circuit • To simplify the analysis of complex circuits we wish to replace voltage sources and resistance networks with an equivalent voltage source and series resistor. • Thevenin theorem states that given a pair of terminal in a linear network , the network may be replaced by an ideal voltage source Voc in series with a ressitance RTH. • Voc is equal to the open circuit voltageacross the terminals, andRTH is the equivalent resistance across the terminals when independent voltage sources are shorted and independent current sources are replaced with open circuits.. 28
- 30. Norton Equivalent Circuit • Here the linear network is replaced by an ideal current source ISC and the Thevenin resistance RTH in parallel with this source. • ISC is found by calculating the current that would flow through the terminals if they were shorted together having removed the remaining load circuit. • It can be shown that the current ISC flowing through RTH produces the Thevenin voltage. 30 Norton equivalent circuit
- 31. AC Circuit Analysis • Sinusoidal Waveform 31
- 32. • Time shift between the signal and reference. • +ve phase angle-leading waveform. • -ve phase angle lagging waveform. • Frequency of signal 32 t = 2 1 = = T f
- 34. References • W. Bolton, Mechatronics: Electronic Control Systems in Mechanical and Electrical Engineering (6th Edition), Pearson, 2015 • D.G. Alciatore and Michael B. Histand, Introduction to Mechatronics, Tata Mc Graw Hill, 2012. • Mechatronic System Design; Shetty Dedas, Kolk and Richard • Mechatronic Handbook: Bishop; CRC press • R. Merzouki, A. K. Samantaray, P. M. Pathak, B. Ould Bouamama, Intelligent Mechatronic Systems: Modeling, Control and Diagnosis, ISBN 978-1-4471-4627-8, 2013, Springer, London 34
- 35. 35 Thank You