107_06 - 1 Electrical Engineering Technology EET 107...

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Unformatted text preview: 1 Electrical Engineering Technology EET 107 Introduction to Circuit Analysis Lecture # 6 Professor Robert Herrick Purdue University © EET 107 - 6 Introduction to Circuit Analysis 2 Summary Wire Table Wire Fuses & Circuit Breakers Fuses Potentiometers & Rheostats Potentiometers Temperature Effects Temperature Sensors Sensors Purdue University © EET 107 - 6 Introduction to Circuit Analysis 3 AWG - Wire Table American American Wire Wire Gauge Gauge ( Appendix 3 ) Appendix Purdue University © EET 107 - 6 Introduction to Circuit Analysis 4 AWG - Wire Table AWG Diamete r Size 0000 or 4/0 000 or 3/0 00 or 2/0 0 or 1/0 2 4 6 8 10 12 14 16 18 20 22 24 Purdue University © mm 11.7 10.4 9.27 8.25 6.54 5.19 4.12 3.26 2.59 2.05 1.63 1.29 1.02 0.813 0.643 0.511 Crosssection Area mm2 107 85.0 67.4 53.5 33.6 21.2 13.3 8.37 5.26 3.31 2.08 1.30 0.823 0.519 0.324 0.205 Crosssection Area CM* 211 000 168 000 133 000 105 000 66 400 41 700 26 200 16 500 10 400 6 530 4 110 2 580 1 620 1 020 640 404 EET 107 - 6 Resistance Ω/1000 feet 0.0490 0.0618 0.0780 0.0983 0.156 0.249 0.395 0.628 0.999 1.59 2.53 4.02 6.39 10.2 16.1 25.7 Safe Current Capacity Amps 230 200 175 150 115 85 65 50 30 20 15 10 5 3 2 1.3 Introduction to Circuit Analysis 5 Wire Resistance American Wire Gauge (AWG) - see Appendix 3 in text u AWG # u Area u Ω per 1000 ft u Maximum allowable current Purdue University © EET 107 - 6 Introduction to Circuit Analysis 6 AWG # Observations AWG # é Area (smaller) ê Ω per 1000 ft é Maximum allowable current Purdue University © EET 107 - 6 ê Introduction to Circuit Analysis 7 AWG House Wiring Examples Fire Protection Ratings Prevent Overheating of Wire u AWG #10 30A max current u AWG # 12 20A max current u AWG # 14 15A max current u Smaller wires handle less current Purdue University © EET 107 - 6 Introduction to Circuit Analysis 8 AWG Observation uAWG u AWG #0000 # 40 Purdue University © LARGE like strand of hair EET 107 - 6 Introduction to Circuit Analysis 9 Wire Resistance Example u Resistance of 500 feet of AWG #12 wire u 1.59 Ω per 1000 feet 1.59Ω R =500 ft 1000 ft =0.795Ω Purdue University © EET 107 - 6 Introduction to Circuit Analysis 10 Solid Wire AWG 22 Jumpers for your wiring board! Careful, breaks easily, bend only once! Vibrating environment, bad news! Purdue University © EET 107 - 6 Introduction to Circuit Analysis 11 Stranded Wire Flexible ! Good for test leads ! Vibrating environment, OKAY ! Purdue University © EET 107 - 6 Introduction to Circuit Analysis 12 Circuit Board Traces Eq. 3-1 l R=ρ A m 3c 100 µm 2 mm R = resistance in ohms (Ω) ρ= resistivity of electrical material in Ω -m l = length of material in meters (m) A = cross-sectional area in square meters (m2) Purdue University © EET 107 - 6 Introduction to Circuit Analysis 13 Fuses Fuses & Circuit Breakers Circuit Purdue University © EET 107 - 6 Introduction to Circuit Analysis 14 Fuse u Metal conductors that melt at a prescribed temperature u Current produces heat – more current creates more heat u Fuses are rated for a maximum current 30 A fuse can handle up to 30 A then it melts ! Purdue University © EET 107 - 6 Introduction to Circuit Analysis 15 Fuse slow blow fuse element fuse element Fuse Schematic Symbol Purdue University © EET 107 - 6 Introduction to Circuit Analysis 16 Fused Circuit 1A fuse E 6V I sw closed Fuse Opens L blown fuse E 6V Purdue University © EET 107 - 6 sw I=0A closed L Introduction to Circuit Analysis 17 Circuit Breaker u Fuses – once blown must replace u Circuit Breakers – can reset and reuse Circuit Breaker Symbol Purdue University © EET 107 - 6 Introduction to Circuit Analysis 18 Rheostats Rheostats & Potentiometers Potentiometers Purdue University © EET 107 - 6 Introduction to Circuit Analysis 19 Two Basic Resistor Types ufixed uvariable rheostat potentiometer Purdue University © EET 107 - 6 2 terminals 3 terminals Introduction to Circuit Analysis 20 Rheostat u 2-terminal uR device value between outside terminal and wiper shaft Purdue University © resistance terminal b a connected to b wiper arm contact wiper arm EET 107 - 6 Introduction to Circuit Analysis 21 Rheostat Schematic Symbols a a R R b b 10 kΩ Rheostat Varies from 0 Ω to 10 k Ω Purdue University © EET 107 - 6 Introduction to Circuit Analysis 22 Potentiometer – 3 Terminals resistance terminal b a connected to b wiper arm c contact shaft (a) Potentiometer Purdue University © a b c (b) Schematic symbol EET 107 - 6 Introduction to Circuit Analysis 23 100 kΩ Potentiometer – ¼ turn a b a b c c (a) Rac = 100 kΩ Purdue University © (b) Rab = 25 kΩ EET 107 - 6 (c) Rbc = 75 kΩ Introduction to Circuit Analysis 24 Potentiometer – Resistor Model a c 100 k Ω Ω b 75 k c 100 k Ω b 25 kΩ Ω 100 kΩ a k 25 a b 75 kΩ c Purdue University © EET 107 - 6 Introduction to Circuit Analysis 25 Using Pot As 2-terminal Device u u Rac = Rab Rbc short or 0Ω short u Prevents unused terminal acting like an antenna a Rab c Purdue University © b short b to c EET 107 - 6 Introduction to Circuit Analysis 26 Temperature Temperature Effects Effects Purdue University © EET 107 - 6 Introduction to Circuit Analysis 27 Temperature Effects As temperature increases u Conductor’s resistance - increases u Insulator’s resistance - decreases u Semiconductor’s resistance - decreases Purdue University © EET 107 - 6 Introduction to Circuit Analysis 28 Temperature Coefficient R (Ω ) + slope R (Ω ) − slope 0 T(°C) 0 (a) Positive temperature coefficient Purdue University © T(°C) (b) Negative temperature coefficient EET 107 - 6 Introduction to Circuit Analysis 29 Transducers Transducers Sensors Sensors Purdue University © EET 107 - 6 Introduction to Circuit Analysis 30 Transducer Transforms from one form of energy to another u Speaker – electrical to sound u Microphone – sound to electrical u LED – electrical to light Purdue University © EET 107 - 6 Introduction to Circuit Analysis 31 Sensor – Special Transducer Sense external environment and translate external measurable quantity into electrical voltage, current, or resistance. −tº Thermistor – detects heat Photoconductive cell – detects light Photodiode – detects light Strain Gauge – detects stress or strain Purdue University © EET 107 - 6 Introduction to Circuit Analysis 32 Varistor A diode like device that senses voltage across it and responds in both the forward and reverse bias modes. I (mA) on 2 1 -100 0 V (V) 100 -1 on -2 off (b) Characteristic curve (a) Schematic symbol Purdue University © EET 107 - 6 Introduction to Circuit Analysis 33 Summary Wire Table Wire Fuses & Circuit Breakers Fuses Potentiometers & Rheostats Potentiometers Temperature Effects Temperature Sensors Sensors Purdue University © EET 107 - 6 Introduction to Circuit Analysis ...
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This note was uploaded on 02/22/2012 for the course ECET 107 taught by Professor Staff during the Fall '08 term at Purdue.

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