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Halderman ch048 lecture

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Halderman ch048 lecture

  1. 1. ELECTRONIC FUNDAMENTALS 48
  2. 2. Objectives <ul><li>The student should be able to: </li></ul><ul><ul><li>Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “A” (General Electrical/Electronic Systems Diagnosis). </li></ul></ul><ul><ul><li>Identify semiconductor components. </li></ul></ul><ul><ul><li>Explain precautions necessary when working with semiconductor circuits. </li></ul></ul><ul><ul><li>Discuss where various electronic and semiconductor devices are used in vehicles. </li></ul></ul>
  3. 3. Objectives <ul><li>The student should be able to: </li></ul><ul><ul><li>Explain how diodes and transistors work. </li></ul></ul><ul><ul><li>Describe how to test diodes and transistors. </li></ul></ul><ul><ul><li>List the precautions that a service technician should follow to avoid damage to electronic components from electrostatic discharge. </li></ul></ul>
  4. 4. SEMICONDUCTORS
  5. 5. Semiconductors <ul><li>Definition </li></ul><ul><ul><li>Flow of electricity in semiconductors is caused by movement of electrons in materials known as conductors </li></ul></ul>
  6. 6. Semiconductors <ul><li>Definition </li></ul><ul><ul><li>Conductors have fewer than four electrons in their outer orbit </li></ul></ul><ul><ul><li>Insulators contain more than four electrons in their outer orbit </li></ul></ul>
  7. 7. Semiconductors <ul><li>Definition </li></ul><ul><ul><li>Semiconductors contain exactly four electrons in their outer orbit </li></ul></ul><ul><ul><li>Semiconductors are neither good conductors nor good insulators </li></ul></ul>
  8. 8. Semiconductors <ul><li>Examples of Semiconductors </li></ul><ul><ul><li>Germanium and silicon </li></ul></ul><ul><ul><li>Each has four electrons in outer orbit, or valance ring </li></ul></ul>
  9. 9. Semiconductors <ul><li>Examples of Semiconductors </li></ul><ul><ul><li>Neither has free electrons to provide current </li></ul></ul><ul><ul><li>They can conduct current if another material is added </li></ul></ul>
  10. 10. Semiconductors <ul><li>Construction </li></ul><ul><ul><li>When a small amount of another material is added to a semiconductor, it’s called doping </li></ul></ul>
  11. 11. Semiconductors <ul><li>Construction </li></ul><ul><ul><li>Doping elements are called impurities </li></ul></ul><ul><ul><li>After germanium and silicon are doped, they are not pure elements </li></ul></ul>
  12. 12. Semiconductors <ul><li>Construction </li></ul><ul><ul><li>Only one atom of impurity for 100 million atoms of germanium or silicon make them conductive </li></ul></ul>
  13. 13. Semiconductors <ul><li>Construction </li></ul><ul><ul><li>Combined materials are classified in two groups </li></ul></ul><ul><ul><ul><li>N-type materials </li></ul></ul></ul><ul><ul><ul><li>P-type materials </li></ul></ul></ul>
  14. 14. Semiconductors <ul><li>N-Type Material </li></ul><ul><ul><li>N-type material is silicon or germanium doped with elements such as phosphorus, arsenic, or antimony </li></ul></ul>
  15. 15. Semiconductors <ul><li>N-Type Material </li></ul><ul><ul><li>These impurities have five electrons in outer orbit </li></ul></ul><ul><ul><li>The five electrons are combined with the four electrons in germanium or silicon </li></ul></ul>
  16. 16. Semiconductors <ul><li>N-Type Material </li></ul><ul><ul><li>There is room for only eight electrons </li></ul></ul><ul><ul><li>The extra electrons repel other electrons outside the material </li></ul></ul>
  17. 17. Figure 48-1 N-type material. Silicon (Si) doped with a material (such as phosphorus) with five electrons in the outer orbit results in an extra free electron.
  18. 18. Semiconductors <ul><li>P-Type Material </li></ul><ul><ul><li>P-type material is produced by doping silicon or germanium with boron or indium </li></ul></ul><ul><ul><li>These impurities have three electrons in outer shell </li></ul></ul>
  19. 19. Semiconductors <ul><li>P-Type Material </li></ul><ul><ul><li>The resulting material has seven electrons </li></ul></ul><ul><ul><li>The lack of one electron enables material to attract electrons </li></ul></ul>
  20. 20. Figure 48-2 P-type material. Silicon (Si) doped with a material, such as boron (B), with three electrons in the outer orbit results in a hole capable of attracting an electron.
  21. 21. SUMMARY OF SEMICONDUCTORS
  22. 22. Summary of Semiconductors <ul><li>Two types of semiconductor materials: N type and P type </li></ul><ul><li>N-type material has extra electron </li></ul>
  23. 23. Summary of Semiconductors <ul><li>P-type material is missing one electron </li></ul><ul><li>Movement of electrons in or out of material is possible to maintain balanced material </li></ul>
  24. 24. Summary of Semiconductors <ul><li>In P-type semiconductors, electrical conduction occurs as a result of holes in the outer orbit </li></ul><ul><li>In N-type semiconductors, electrical conduction occurs as a result of excess electrons </li></ul>
  25. 25. Summary of Semiconductors <ul><li>Hole movement results from electrons jumping into new positions </li></ul><ul><li>Electrons travel toward the positive terminal </li></ul><ul><li>Holes travel toward negative terminal </li></ul>?
  26. 26. Figure 48-3 Unlike charges attract and the current carriers (electrons and holes) move toward the junction.
  27. 27. DIODES
  28. 28. Diodes <ul><li>Construction </li></ul><ul><ul><li>Diode is electrical one-way check valve </li></ul></ul><ul><ul><li>Formed by combining P-type material and N-type material </li></ul></ul>
  29. 29. Diodes <ul><li>Construction </li></ul><ul><ul><li>Diode means “having two electrodes” </li></ul></ul><ul><ul><li>Electrodes are electrical connections </li></ul></ul>
  30. 30. Diodes <ul><li>Construction </li></ul><ul><ul><li>The positive electrode is the anode </li></ul></ul><ul><ul><li>The negative electrode is the cathode </li></ul></ul><ul><ul><li>The point where the materials join is the junction </li></ul></ul>
  31. 31. Figure 48-4 A diode is a component with P-type and N-type materials together. The negative electrode is called the cathode and the positive electrode is called the anode.
  32. 32. Diodes <ul><li>Operation </li></ul><ul><ul><li>Extra electron in N-type material can flow into P-type material </li></ul></ul><ul><ul><li>If battery is connected to diode, electrons that flowed from N-type material to P-type material would be replaced by electrons flowing from battery </li></ul></ul>
  33. 33. Diodes <ul><li>Operation </li></ul><ul><ul><li>Current flows through the diode for these reasons: </li></ul></ul><ul><ul><ul><li>Electrons move toward the holes (P-type material) </li></ul></ul></ul><ul><ul><ul><li>Holes move toward the electrons (N-type material) </li></ul></ul></ul>
  34. 34. Figure 48-5 Diode connected to a battery with correct polarity (battery positive to P type and battery negative to N-type). Current flows through the diode. This condition is called forward bias.
  35. 35. Diodes <ul><li>Operation </li></ul><ul><ul><li>Current flows through diode with low-resistance </li></ul></ul><ul><ul><li>Condition of low resistance is called a forward bias </li></ul></ul><ul><ul><li>If battery connections were reversed, electrons would be pulled toward battery </li></ul></ul>
  36. 36. Diodes <ul><li>Operation </li></ul><ul><ul><li>Because electrical conduction requires flow of electrons across the junction, the diode offers high resistance </li></ul></ul><ul><ul><li>Condition of high resistance is called reverse bias </li></ul></ul>
  37. 37. Figure 48-6 Diode connected with reversed polarity. No current flows across the junction between the P-type and N-type materials. This connection is called reverse bias.
  38. 38. Diodes <ul><li>Operation </li></ul><ul><ul><li>Diodes allow current flow only with current of correct polarity </li></ul></ul><ul><ul><li>Diodes are used in alternators to control current flow </li></ul></ul>
  39. 39. Diodes <ul><li>Operation </li></ul><ul><ul><li>Diodes are used in applications to prevent possible damage due to reverse current flows </li></ul></ul>?
  40. 40. Figure 48-7 Diode symbol and electrode names. The stripe on one end of a diode represents the cathode end of the diode.
  41. 41. ZENER DIODES
  42. 42. Zener Diodes <ul><li>Construction </li></ul><ul><ul><li>Zener diode is designed to operate with reverse-bias current </li></ul></ul>
  43. 43. Zener Diodes <ul><li>Operation </li></ul><ul><ul><li>Zener diode blocks reverse-bias current, but only up to a certain voltage </li></ul></ul><ul><ul><li>Beyond certain voltage (the breakdown voltage or zener region), the zener diode will conduct current in the opposite direction </li></ul></ul>
  44. 44. Zener Diodes <ul><li>Operation </li></ul><ul><ul><li>Zener diodes are heavily doped </li></ul></ul><ul><ul><li>Voltage drop remains the same before and after breakdown voltage </li></ul></ul>
  45. 45. Zener Diodes <ul><li>Operation </li></ul><ul><ul><li>Zener diodes perfect for voltage regulation </li></ul></ul><ul><ul><li>Zener diodes can be constructed for various breakdown voltages </li></ul></ul>
  46. 46. Figure 48-8 A zener diode blocks current flow until a certain voltage is reached, then it permits current to flow.
  47. 47. HIGH-VOLTAGE SPIKE PROTECTION
  48. 48. High-Voltage Spike Protection <ul><li>Clamping Diodes </li></ul><ul><ul><li>Diodes can be used as high-voltage clamping device </li></ul></ul><ul><ul><li>Power connects to cathode </li></ul></ul>
  49. 49. High-Voltage Spike Protection <ul><li>Clamping Diodes </li></ul><ul><ul><li>If coil is pulsed on and off, high-voltage spike is produced </li></ul></ul><ul><ul><li>Diode redirects high-voltage spike back into coil windings </li></ul></ul>
  50. 50. High-Voltage Spike Protection <ul><li>Clamping Diodes </li></ul><ul><ul><li>Prevents damage to rest of electrical and electronic circuits </li></ul></ul><ul><ul><li>Diode connected across terminal of coil to control voltage spikes is a clamping diode (despiking or suppression diode) </li></ul></ul>
  51. 51. Figure 48-9 (a) Notice that when the coil is being energized, the diode is reverse biased and the current is blocked from passing through the diode. The current flows through the coil in the normal direction. (b) When the switch is opened, the magnetic field surrounding the coil collapses, producing a high-voltage surge in the reverse polarity of the applied voltage. This voltage surge forward biases the diode, and the surge is dissipated harmlessly back through the windings of the coil.
  52. 52. High-Voltage Spike Protection <ul><li>Clamping Diode Application </li></ul><ul><ul><li>Diodes first used on A/C compressor clutch coils </li></ul></ul><ul><ul><li>Used to prevent high voltage spike from A/C clutch coil from damaging delicate electronic circuits </li></ul></ul>
  53. 53. Figure 48-10 A diode connected to both terminals of the airconditioning compressor clutch used to reduce the high-voltage spike that results when a coil (compressor clutch coil) is de-energized.
  54. 54. High-Voltage Spike Protection <ul><li>Clamping Diode Application </li></ul><ul><ul><li>Automotive circuits are electrically linked to each other </li></ul></ul><ul><ul><li>High-voltage surge anywhere could damage electronic components in other circuits </li></ul></ul>
  55. 55. High-Voltage Spike Protection <ul><li>Clamping Diode Application </li></ul><ul><ul><li>Many relays have diode to prevent voltage spike </li></ul></ul>
  56. 56. Figure 48-11 Spike protection diodes are commonly used in computer-controlled circuits to prevent damaging high-voltage surges that occur any time current flowing through a coil is stopped.
  57. 57. High-Voltage Spike Protection <ul><li>Despiking Zener Diodes </li></ul><ul><ul><li>Used to control high-voltage spikes </li></ul></ul><ul><ul><li>Commonly used in electronic fuel-injection circuits </li></ul></ul>
  58. 58. Figure 48-12 A zener diode is commonly used inside automotive computers to protect delicate electronic circuits from high-voltage spikes. A 35 volt zener diode will conduct any voltage spike higher than 35 voltage resulting from the discharge of the fuel injector coil safely to ground through a current-limiting resistor in series with the zener diode.
  59. 59. High-Voltage Spike Protection <ul><li>Despiking Resistors </li></ul><ul><ul><li>Coils must have protection from high-voltage spikes </li></ul></ul><ul><ul><li>Resistor called spike protection resistor can be used </li></ul></ul>
  60. 60. Figure 48-13 A despiking resistor is used in many automotive applications to help prevent harmful high-voltage surges from being created when the magnetic field surrounding a coil collapses when the coil circuit is opened.
  61. 61. High-Voltage Spike Protection <ul><li>Despiking Resistors </li></ul><ul><ul><li>Resistors preferred for two reasons </li></ul></ul><ul><ul><ul><li>Reason 1 </li></ul></ul></ul><ul><ul><ul><ul><li>Coils usually fail when shorted rather than open </li></ul></ul></ul></ul>
  62. 62. High-Voltage Spike Protection <ul><li>Despiking Resistors </li></ul><ul><ul><li>Resistors preferred for two reasons </li></ul></ul><ul><ul><ul><li>Reason 1 </li></ul></ul></ul><ul><ul><ul><ul><li>Shorted condition results in greater current flow </li></ul></ul></ul></ul>
  63. 63. High-Voltage Spike Protection <ul><li>Despiking Resistors </li></ul><ul><ul><li>Resistors preferred for two reasons </li></ul></ul><ul><ul><ul><li>Reason 1 </li></ul></ul></ul><ul><ul><ul><ul><li>Diode cannot control this extra current </li></ul></ul></ul></ul>
  64. 64. High-Voltage Spike Protection <ul><li>Despiking Resistors </li></ul><ul><ul><li>Resistors preferred for two reasons </li></ul></ul><ul><ul><ul><li>Reason 1 </li></ul></ul></ul><ul><ul><ul><ul><li>Resistor in parallel can reduce potentially damaging current flow </li></ul></ul></ul></ul>
  65. 65. High-Voltage Spike Protection <ul><li>Despiking Resistors </li></ul><ul><ul><li>Resistors preferred for two reasons </li></ul></ul><ul><ul><ul><li>Reason 2 </li></ul></ul></ul><ul><ul><ul><ul><li>Protective diode can also fail </li></ul></ul></ul></ul>
  66. 66. High-Voltage Spike Protection <ul><li>Despiking Resistors </li></ul><ul><ul><li>Resistors preferred for two reasons </li></ul></ul><ul><ul><ul><li>Reason 2 </li></ul></ul></ul><ul><ul><ul><ul><li>Diodes usually fail by shorting </li></ul></ul></ul></ul>
  67. 67. High-Voltage Spike Protection <ul><li>Despiking Resistors </li></ul><ul><ul><li>Resistors preferred for two reasons </li></ul></ul><ul><ul><ul><li>Reason 2 </li></ul></ul></ul><ul><ul><ul><ul><li>Shorted diode allows excessive current to flow through coil circuit </li></ul></ul></ul></ul>
  68. 68. High-Voltage Spike Protection <ul><li>Despiking Resistors </li></ul><ul><ul><li>Resistors preferred for two reasons </li></ul></ul><ul><ul><ul><li>Reason 2 </li></ul></ul></ul><ul><ul><ul><ul><li>Resistor usually fails open, so failure would not in itself cause a problem </li></ul></ul></ul></ul>
  69. 69. DIODE RATINGS
  70. 70. Diode Ratings <ul><li>Specifications </li></ul><ul><ul><li>Diodes are rated according to the following: </li></ul></ul><ul><ul><li>Maximum current flow in forward-bias direction </li></ul></ul><ul><ul><ul><li>Diodes sized by amount of current they can handle </li></ul></ul></ul>
  71. 71. Diode Ratings <ul><li>Specifications </li></ul><ul><ul><li>Maximum current flow in forward-bias direction </li></ul></ul><ul><ul><ul><li>Rating is normally from 1 to 5 amperes </li></ul></ul></ul>
  72. 72. Diode Ratings <ul><li>Specifications </li></ul><ul><ul><li>Rating of resistance to reverse-bias voltage called peak inverse voltage (PIV), or peak reverse voltage (PRV) </li></ul></ul><ul><ul><ul><li>Technician should use replacement diodes that have the same or higher rating than specified by manufacturer </li></ul></ul></ul>
  73. 73. Diode Ratings <ul><li>Specifications </li></ul><ul><ul><li>Rating of resistance to reverse-bias voltage called peak inverse voltage (PIV), or peak reverse voltage (PRV) </li></ul></ul><ul><ul><ul><li>Industry numbering code indicates PIV rating </li></ul></ul></ul>
  74. 74. Diode Ratings <ul><li>Specifications </li></ul><ul><ul><li>Rating of resistance to reverse-bias voltage called peak inverse voltage (PIV), or peak reverse voltage (PRV) </li></ul></ul><ul><ul><ul><li>Example ratings </li></ul></ul></ul><ul><ul><ul><ul><li>1N 4001-50 V PIV </li></ul></ul></ul></ul>
  75. 75. Diode Ratings <ul><li>Specifications </li></ul><ul><ul><li>Rating of resistance to reverse-bias voltage called peak inverse voltage (PIV), or peak reverse voltage (PRV) </li></ul></ul><ul><ul><ul><li>Example ratings </li></ul></ul></ul><ul><ul><ul><ul><li>1N 4002-100 V PIV </li></ul></ul></ul></ul>
  76. 76. Diode Ratings <ul><li>Specifications </li></ul><ul><ul><li>Rating of resistance to reverse-bias voltage called peak inverse voltage (PIV), or peak reverse voltage (PRV) </li></ul></ul><ul><ul><ul><li>Example ratings </li></ul></ul></ul><ul><ul><ul><ul><li>1 N 4003-200 V PIV </li></ul></ul></ul></ul>
  77. 77. Diode Ratings <ul><li>Specifications </li></ul><ul><ul><li>The “1N” means the diode has one P-N junction </li></ul></ul><ul><ul><ul><li>Higher rating diode can be used with no problems </li></ul></ul></ul>
  78. 78. Diode Ratings <ul><li>Diode Voltage Drop </li></ul><ul><ul><li>Voltage drop across diode about the same as required to forward bias diode </li></ul></ul><ul><ul><li>Germanium diode has forward voltage of 0.3 to 0.5 volt </li></ul></ul>
  79. 79. Diode Ratings <ul><li>Diode Voltage Drop </li></ul><ul><ul><li>Silicon diode has forward voltage of 0.5 to 0.7 volt </li></ul></ul>
  80. 80. Diode Ratings <ul><li>Diode Voltage Drop </li></ul><ul><ul><li>NOTE: When diodes are tested using digital multimeter, the meter will display the voltage drop across the P-N junction (about 0.5 to 0.7 volt) when the meter is set to the diode-check position. </li></ul></ul>
  81. 81. LIGHT-EMITTING DIODES
  82. 82. Light-Emitting Diodes <ul><li>Operation </li></ul><ul><ul><li>All diodes radiate some energy </li></ul></ul><ul><ul><li>Most diodes radiate heat </li></ul></ul>
  83. 83. Light-Emitting Diodes <ul><li>Operation </li></ul><ul><ul><li>Light emitting diode (LED) radiate light when current flows through diode in forward-bias direction </li></ul></ul>
  84. 84. Figure 48-14 A typical light-emitting diode (LED). This particular LED is designed with a built-in resistor so that 12 volts DC may be applied directly to the leads without an external resistor. Normally a 300 to 500 ohm, 0.5 watt resistor is required to be attached in series with the LED, to control current flow to about 0.020 A (20 mA) or damage to the P-N junction may occur.
  85. 85. Light-Emitting Diodes <ul><li>Operation </li></ul><ul><ul><li>Forward-bias voltage required for LED ranges from 1.5 to 2.2 volts </li></ul></ul><ul><ul><li>LED will only light if voltage at anode is at least 1.5 to 2.2 volts higher than voltage at cathode </li></ul></ul>?
  86. 86. Light-Emitting Diodes <ul><li>Need for Current Limiting </li></ul><ul><ul><li>Excessive amperes that flows across P-N junction of electronic device can destroy junction </li></ul></ul>
  87. 87. Light-Emitting Diodes <ul><li>Need for Current Limiting </li></ul><ul><ul><li>Resistor must be connected in series with every diode to control current flow across junction </li></ul></ul>
  88. 88. Light-Emitting Diodes <ul><li>Need for Current Limiting </li></ul><ul><ul><li>Resistor protection should include the following: </li></ul></ul><ul><ul><ul><li>Resistor value should be from 300 to 500 ohms </li></ul></ul></ul>
  89. 89. Light-Emitting Diodes <ul><li>Need for Current Limiting </li></ul><ul><ul><li>Resistor protection should include the following: </li></ul></ul><ul><ul><ul><li>Resistors can be connected to either anode or cathode </li></ul></ul></ul><ul><ul><ul><ul><li>Current flows through LED in series with the resistor </li></ul></ul></ul></ul>
  90. 90. Light-Emitting Diodes <ul><li>Need for Current Limiting </li></ul><ul><ul><li>Resistor protection should include the following: </li></ul></ul><ul><ul><ul><li>Resistors can be connected to either anode or cathode </li></ul></ul></ul><ul><ul><ul><ul><li>Resistor will control current flow regardless of position </li></ul></ul></ul></ul>
  91. 91. Light-Emitting Diodes <ul><li>Need for Current Limiting </li></ul><ul><ul><li>Resistor protection should include the following: </li></ul></ul><ul><ul><ul><li>Resistors protecting diodes can be actual resistors or other current-limiting loads such as lamps or coils </li></ul></ul></ul><ul><ul><ul><ul><li>LED will require about 20 to 30 milliamperes (mA), or 0.020 to 0.030 ampere </li></ul></ul></ul></ul>
  92. 92. PHOTODIODES
  93. 93. Photodiodes <ul><li>Purpose and Function </li></ul><ul><ul><li>All semiconductor P-N junctions emit energy </li></ul></ul><ul><ul><li>When LED is exposed to bright light, voltage potential established between anode and cathode </li></ul></ul>
  94. 94. Photodiodes <ul><li>Purpose and Function </li></ul><ul><ul><li>Photodiodes respond to various wavelengths with a “window” built into housing </li></ul></ul>
  95. 95. Figure 48-15 Typical photodiodes. They are usually built into a plastic housing so that the photodiode itself may not be visible.
  96. 96. Photodiodes <ul><li>Purpose and Function </li></ul><ul><ul><li>Photodiodes are used in steering wheel controls for transmitting information from steering wheel to data link and unit being controlled </li></ul></ul>
  97. 97. Photodiodes <ul><li>Purpose and Function </li></ul><ul><ul><li>Several photodiodes can transmit data between two moving points without physical contact units </li></ul></ul>
  98. 98. Photodiodes <ul><li>Construction </li></ul><ul><ul><li>A photodiode is sensitive to light </li></ul></ul><ul><ul><li>When light strikes diode, electrons are released </li></ul></ul>
  99. 99. Photodiodes <ul><li>Construction </li></ul><ul><ul><li>Diode conducts in forward-bias direction </li></ul></ul><ul><ul><li>Resistance across photodiode decreases as light intensity decreases </li></ul></ul>
  100. 100. Photodiodes <ul><li>Construction </li></ul><ul><ul><li>This characteristic makes photodiode useful for controlling some automotive lighting systems </li></ul></ul>
  101. 101. Figure 48-16 Symbol for a photodiode. The arrows represent light striking the P-N junction of the photodiode.
  102. 102. PHOTORESISTORS
  103. 103. Photoresistors <ul><li>A photoresistor is a semiconductor material (usually cadmium sulfide) that changes resistance with the presence or absence of light </li></ul><ul><ul><li>Dark—high resistance </li></ul></ul>
  104. 104. Photoresistors <ul><li>A photoresistor is a semiconductor material (usually cadmium sulfide) that changes resistance with the presence or absence of light </li></ul><ul><ul><li>Light—low resistance </li></ul></ul>
  105. 105. Photoresistors <ul><li>Photoresistor can be used to control headlight dimmer relays and headlights </li></ul>
  106. 106. Figure 48-17 Either symbol may be used to represent a photoresistor.
  107. 107. SILICON-CONTROLLED RECTIFIERS
  108. 108. Silicon-Controlled Rectifiers <ul><li>Construction </li></ul><ul><ul><li>Silicon-controlled rectifier (SCR) commonly used in electronic circuit </li></ul></ul><ul><ul><li>SCR is semiconductor device that looks like two diodes connected end to end </li></ul></ul>
  109. 109. Figure 48-18 Symbol and terminal identification of an SCR.
  110. 110. Silicon-Controlled Rectifiers <ul><li>Construction </li></ul><ul><ul><li>When anode is connected to higher voltage source than cathode, no current will flow </li></ul></ul>
  111. 111. Silicon-Controlled Rectifiers <ul><li>Construction </li></ul><ul><ul><li>When positive voltage source is connected to SCR, current flows from anode to cathode with 1.2 voltage drop </li></ul></ul>
  112. 112. Silicon-Controlled Rectifiers <ul><li>Construction </li></ul><ul><ul><li>Voltage applied at gate turns SCR on </li></ul></ul><ul><ul><li>If voltage source at gate is shut off, current will continue to flow until source current is stopped </li></ul></ul>
  113. 113. Silicon-Controlled Rectifiers <ul><li>Uses of an SCR </li></ul><ul><ul><li>SCRs used to construct circuit for center high-mounted stoplight (CHMSL) </li></ul></ul><ul><ul><li>If third stoplight is wired to either left or right brake light, it will flash with turn signals </li></ul></ul>
  114. 114. Silicon-Controlled Rectifiers <ul><li>Uses of an SCR </li></ul><ul><ul><li>When two SCRs are used, both brakes lights must be activated to supply current to CHMSL </li></ul></ul><ul><ul><li>Current to CHMSL is shut off when both SCRs lose power source </li></ul></ul>
  115. 115. Figure 48-19 Wiring diagram for a center high-mounted stoplight (CHMSL) using SCRs.
  116. 116. THERMISTORS
  117. 117. Thermistors <ul><li>Construction </li></ul><ul><ul><li>Thermistor is semiconductor that has been doped to provide given resistance </li></ul></ul><ul><ul><li>Thermistor produces small voltage when heated </li></ul></ul>
  118. 118. Thermistors <ul><li>Uses of Thermistors </li></ul><ul><ul><li>Thermistor commonly used as temperature-sensing device for coolant temperature and intake manifold air temperature </li></ul></ul>
  119. 119. Thermistors <ul><li>Uses of Thermistors </li></ul><ul><ul><li>Thermistors operate opposite to typical conductor and are called negative temperature coefficient thermistors </li></ul></ul><ul><ul><li>Resistance decreases as temperature increases </li></ul></ul>
  120. 120. Chart 48-1 The resistance changes opposite that of a copper wire with changes in temperature.
  121. 121. Figure 48-20 Symbols used to represent a thermistor.
  122. 122. RECTIFIER BRIDGES
  123. 123. Rectifier Bridges <ul><li>Definition </li></ul><ul><ul><li>Rectifier means “to set straight” </li></ul></ul><ul><ul><li>Rectifier is electronic device used to convert changing voltage into straight or constant voltage </li></ul></ul>
  124. 124. Rectifier Bridges <ul><li>Definition </li></ul><ul><ul><li>A rectifier bridge is group of diodes used to change alternating current to direct current </li></ul></ul>
  125. 125. Figure 48-21 This rectifier bridge contains six diodes; the three on each side are mounted in an aluminum-finned unit to help keep the diode cool during alternator operation.
  126. 126. TRANSISTORS
  127. 127. Transistors <ul><li>Purpose and Function </li></ul><ul><ul><li>Transistor is semiconductor that performs these electrical functions: </li></ul></ul><ul><ul><ul><li>Electrical switch in circuit </li></ul></ul></ul><ul><ul><ul><li>Amplifier of current in circuit </li></ul></ul></ul><ul><ul><ul><li>Regulator of current in circuit </li></ul></ul></ul>
  128. 128. Transistors <ul><li>Purpose and Function </li></ul><ul><ul><li>A transistor has three layers of P-type and N-type materials </li></ul></ul><ul><ul><li>This type transistor is called bipolar transistor </li></ul></ul>?
  129. 129. (FREQUENTLY ASKED QUESTION, column 2, question 1, page 516)
  130. 130. Chart 48-2 Comparison between the control (low-current) and high-current circuits of a transistor compared to a mechanical relay.
  131. 131. Transistors <ul><li>Construction </li></ul><ul><ul><li>Transistor with P-type material on each end; N-type material in center is called PNP transistor </li></ul></ul>
  132. 132. Transistors <ul><li>Construction </li></ul><ul><ul><li>The opposite arrangement is called NPN transistor </li></ul></ul><ul><ul><li>Material at one end is emitter </li></ul></ul>
  133. 133. Transistors <ul><li>Construction </li></ul><ul><ul><li>Material at opposite end is collector </li></ul></ul><ul><ul><li>Base is in the center </li></ul></ul><ul><ul><li>Voltage applied to base controls current through transistor </li></ul></ul>
  134. 134. Transistors <ul><li>Transistor Symbols </li></ul><ul><ul><li>Transistor symbols contain arrow indicating emitter </li></ul></ul><ul><ul><li>Arrow points in direction of current flow </li></ul></ul>
  135. 135. Transistors <ul><li>Transistor Symbols </li></ul><ul><ul><li>Arrowhead in semiconductor symbol stands for P-N junction and points from P-type material to N-type material </li></ul></ul><ul><ul><li>Arrow on transistor always attached to emitter side of transistor </li></ul></ul>
  136. 136. Figure 48-22 Basic transistor operation. A small current flowing through the base and emitter of the transistor turns on the transistor and permits a higher amperage current to flow from the collector and the emitter.
  137. 137. Transistors <ul><li>How a Transistor Works </li></ul><ul><ul><li>Similar to two back-to-back diodes </li></ul></ul><ul><ul><li>Conducts current in only one direction </li></ul></ul>
  138. 138. Transistors <ul><li>How a Transistor Works </li></ul><ul><ul><li>Transistor allows current to flow if electrical conditions switch it on </li></ul></ul><ul><ul><li>Electrical conditions are determined by means of the base (B) </li></ul></ul>
  139. 139. Transistors <ul><li>How a Transistor Works </li></ul><ul><ul><li>Base will carry current only when proper voltage and polarity are applied </li></ul></ul><ul><ul><li>Main circuit current flows through emitter (E) and collector (C) </li></ul></ul>?
  140. 140. Figure 48-23 Basic transistor operation. A small current flowing through the base and emitter of the transistor turns on the transistor and permits a higher amperage current to flow from the collector and the emitter.
  141. 141. Transistors <ul><li>How a Transistor Works </li></ul><ul><ul><li>Current controlling base is control current </li></ul></ul><ul><ul><li>Control current must be high enough to switch transistor on or off </li></ul></ul>
  142. 142. Transistors <ul><li>How a Transistor Works </li></ul><ul><ul><li>Control voltage (threshold voltage) must be above 0.3 volt for germanium and 0.6 volt for silicone transistors </li></ul></ul><ul><ul><li>Control current also regulates main current </li></ul></ul>
  143. 143. Transistors <ul><li>How a Transistor Amplifies </li></ul><ul><ul><li>Transistor amplifies if signal is strong enough to trigger base </li></ul></ul><ul><ul><li>Current flow can be connected to higher powered electrical circuit </li></ul></ul>
  144. 144. Transistors <ul><li>How a Transistor Amplifies </li></ul><ul><ul><li>Lower-powered circuit controls higher-powered circuit </li></ul></ul><ul><ul><li>Low-powered circuit’s cycling is exactly duplicated in high-powered circuit </li></ul></ul><ul><ul><li>Therefore, transistor can amplify a signal </li></ul></ul>
  145. 145. FIELD-EFFECT TRANSISTORS
  146. 146. Field-Effect Transistors <ul><li>Field-effect transistors (FETs) rely on strength of small voltage signal to control output </li></ul><ul><li>Typical FET includes source, gate, and drain </li></ul>
  147. 147. Figure 48-24 The three terminals of a field-effect transistor (FET) are called the source, gate, and drain.
  148. 148. Field-Effect Transistors <ul><li>Many FETs are constructed of metal oxide semiconductor materials called MOSFETs </li></ul><ul><li>MOSFETs are highly sensitive to static electricity and are easily damaged by excessive or high-voltage surges </li></ul>
  149. 149. Field-Effect Transistors <ul><li>Most automotive electronic circuits use MOSFETs </li></ul><ul><li>Manufacturers often recommend antistatic wristband when working with modules containing MOSFETs </li></ul>?
  150. 150. Figure 48-25 A Darlington pair consists of two transistors wired together, allowing for a very small current to control a larger current flow circuit.
  151. 151. PHOTOTRANSISTORS
  152. 152. Phototransistors <ul><li>Similar to photodiode </li></ul><ul><li>Phototransistor uses light energy to turn on base of transistor </li></ul><ul><li>Phototransistor is NPN transistor with large exposed base area </li></ul>
  153. 153. Phototransistors <ul><li>Base area permits light to control transistor </li></ul><ul><li>Phototransistor may or may not have base lead </li></ul><ul><li>If not it has only collector and emitter leads </li></ul><ul><li>When connected to powered circuit, light intensity is amplified by gain of transistor </li></ul>
  154. 154. Figure 48-26 Symbols for a phototransistor. (a) This symbol uses the line for the base; (b) this symbol does not.
  155. 155. INTEGRATED CIRCUITS
  156. 156. Integrated Circuits <ul><li>Purpose and Function </li></ul><ul><ul><li>Solid state components used in many semiconductors </li></ul></ul><ul><ul><li>Solid state because they have no moving parts </li></ul></ul>
  157. 157. Integrated Circuits <ul><li>Purpose and Function </li></ul><ul><ul><li>Semiconductor devices are solid state </li></ul></ul><ul><ul><li>Semiconductor devices are often combined (integrated) into one group of circuits called integrated circuit (IC) </li></ul></ul>
  158. 158. Integrated Circuits <ul><li>Construction </li></ul><ul><ul><li>ICs are usually encased in plastic hosing called CHIP with two rows of inline pins </li></ul></ul><ul><ul><li>Arrangement called dual inline pins (DIP) </li></ul></ul>
  159. 159. Figure 48-27 A typical automotive computer with the case removed to show all of the various electronic devices and integrated circuits (ICs). The CPU is an example of a DIP chip and the large red and orange devices are ceramic capacitors.
  160. 160. Integrated Circuits <ul><li>Heat Sink </li></ul><ul><ul><li>Heat sink describes any area around electronic component that conducts damaging heat away from electronic parts </li></ul></ul>
  161. 161. Integrated Circuits <ul><li>Heat Sink </li></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>Ribbed electronic ignition control units </li></ul></ul></ul><ul><ul><ul><li>Cooling slits and cooling fan attached to alternator </li></ul></ul></ul>
  162. 162. Integrated Circuits <ul><li>Heat Sink </li></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>Heat-conducting grease under electronic ignition module in GM’s HEI distributor ignition systems </li></ul></ul></ul>
  163. 163. Integrated Circuits <ul><li>Heat Sink </li></ul><ul><ul><li>Heat sinks prevent damage to diodes, transistors, and other electronic components </li></ul></ul><ul><ul><li>Excessive heat can damage junction between N-type and P-type materials </li></ul></ul>?
  164. 164. TRANSISTOR GATES
  165. 165. Transistor Gates <ul><li>Purpose and Function </li></ul><ul><ul><li>Understanding operation of electronic gates is important to understanding how computers work </li></ul></ul>
  166. 166. Transistor Gates <ul><li>Purpose and Function </li></ul><ul><ul><li>Gate is electronic circuit whose output depends on location and voltage of two inputs </li></ul></ul>
  167. 167. Transistor Gates <ul><li>Construction </li></ul><ul><ul><li>Voltage at base of transistor determines whether transistor is on or off </li></ul></ul><ul><ul><li>Voltage at least 0.6 volts different from emitter turns transistor on </li></ul></ul>
  168. 168. Transistor Gates <ul><li>Construction </li></ul><ul><ul><li>Most electronic and computer circuits use 5 volt power source </li></ul></ul><ul><ul><li>Two transistors wired together permit several different outputs depending on transistor wiring </li></ul></ul>
  169. 169. Figure 48-28 Typical transistor AND gate circuit using two transistors. The emitter is always the line with the arrow. Notice that both transistors must be turned on before there will be voltage present at the point labeled “signal out.”
  170. 170. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>Voltage at A is higher than that of emitter; top transistor is turned on </li></ul></ul><ul><ul><li>Bottom transistor is off, however, unless voltage at B is also higher </li></ul></ul>
  171. 171. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>If both transistors are on, output signal voltage is high </li></ul></ul><ul><ul><li>If only one transistor is on, output is zero </li></ul></ul>
  172. 172. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>Because both A and B must be on to provide voltage output, circuit is called AND gate </li></ul></ul>
  173. 173. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>Other gates can be constructed with various connections to two transistors </li></ul></ul><ul><ul><ul><li>AND gate—both transistors must be on to give output </li></ul></ul></ul>
  174. 174. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>Other gates can be constructed with various connections to two transistors </li></ul></ul><ul><ul><ul><li>OR gate—either transistor can be on to produce output </li></ul></ul></ul>
  175. 175. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>Other gates can be constructed with various connections to two transistors </li></ul></ul><ul><ul><ul><li>NAND (NOT-AND)—output is on only when both transistors are on </li></ul></ul></ul>
  176. 176. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>Other gates can be constructed with various connections to two transistors </li></ul></ul><ul><ul><ul><li>NOR (NOT-OR) gate—output is on only when both transistors are off </li></ul></ul></ul>?
  177. 177. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>Gates are logic circuits constructed so output depends on voltage of the inputs </li></ul></ul><ul><ul><li>Inputs come from sensors or other circuits </li></ul></ul>
  178. 178. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>Outputs can operate output device if amplified and controlled </li></ul></ul><ul><ul><li>Example: blower motor is turned on when these events occur: </li></ul></ul><ul><ul><ul><li>Ignition (input) is on </li></ul></ul></ul>
  179. 179. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>Example: blower motor is turned on when these events occur: </li></ul></ul><ul><ul><ul><li>A/C is commanded on </li></ul></ul></ul>
  180. 180. Transistor Gates <ul><li>Operation </li></ul><ul><ul><li>Example: blower motor is turned on when these events occur: </li></ul></ul><ul><ul><ul><li>Engine coolant temperature is within predetermined limits </li></ul></ul></ul><ul><ul><li>If these conditions are met, control module commands blower motor on </li></ul></ul>
  181. 181. OPERATIONAL AMPLIFIERS
  182. 182. Operational Amplifiers <ul><li>Operational amplifiers (op-amps) are used in circuits to control and amplify digital signals </li></ul><ul><li>Op-amps often used for motor control in climate control systems </li></ul><ul><li>Op-amps provide proper voltage polarity and amperes to control direction of permanent magnetic motors </li></ul>
  183. 183. Figure 48-29 Symbol for an operational amplifier (op-amp).
  184. 184. Figure 48-30 Schematic for a blinking LED theft deterrent.
  185. 185. ELECTRONIC COMPONENT FAILURE CAUSES
  186. 186. Electronic Component Failure Causes <ul><li>Frequent causes of premature electronic component failure includes </li></ul><ul><ul><li>Poor connections </li></ul></ul><ul><ul><ul><li>Source of most engine computer failures </li></ul></ul></ul><ul><ul><ul><li>Often intermittent and so hard to find </li></ul></ul></ul>
  187. 187. Electronic Component Failure Causes <ul><li>Frequent causes of premature electronic component failure includes </li></ul><ul><ul><li>Heat </li></ul></ul><ul><ul><ul><li>Electronic components should be kept as cool as possible </li></ul></ul></ul><ul><ul><ul><li>Component temperature should never exceed 260 (127°C) </li></ul></ul></ul>
  188. 188. Electronic Component Failure Causes <ul><li>Frequent causes of premature electronic component failure includes </li></ul><ul><ul><li>Voltage spikes </li></ul></ul><ul><ul><ul><li>High-voltage spike can burn hole through semiconductor material </li></ul></ul></ul><ul><ul><ul><li>Source of spike is often discharge of a coil </li></ul></ul></ul>
  189. 189. Electronic Component Failure Causes <ul><li>Frequent causes of premature electronic component failure includes </li></ul><ul><ul><li>Voltage spikes </li></ul></ul><ul><ul><ul><li>Poor connections at battery or other major electrical connections can cause high-voltage spikes </li></ul></ul></ul>
  190. 190. Electronic Component Failure Causes <ul><li>Frequent causes of premature electronic component failure includes </li></ul><ul><ul><li>Voltage spikes </li></ul></ul><ul><ul><ul><li>Ensure all electrical connections are clean and tight </li></ul></ul></ul>
  191. 191. Electronic Component Failure Causes <ul><li>Frequent causes of premature electronic component failure includes </li></ul><ul><ul><li>CAUTION: One of the major causes of electronic failure occurs during jump starting a vehicle. Always check that the ignition switch is off on both vehicles when making the connection. Always double check that the correct batter polarity (+ to + and – to –) is performed. </li></ul></ul>
  192. 192. Electronic Component Failure Causes <ul><li>Frequent causes of premature electronic component failure includes </li></ul><ul><ul><li>Excessive current </li></ul></ul><ul><ul><ul><li>Electronic circuit designed for designated range of amperes </li></ul></ul></ul>
  193. 193. Electronic Component Failure Causes <ul><li>Frequent causes of premature electronic component failure includes </li></ul><ul><ul><li>Excessive current </li></ul></ul><ul><ul><ul><li>If coil winding in solenoid or relay shorts, excessive current will go through circuit </li></ul></ul></ul>
  194. 194. Electronic Component Failure Causes <ul><li>Frequent causes of premature electronic component failure includes </li></ul><ul><ul><li>Excessive current </li></ul></ul><ul><ul><ul><li>If computer fails, measure resistance across all computer-controlled relays and solenoids </li></ul></ul></ul>
  195. 195. Electronic Component Failure Causes <ul><li>Frequent causes of premature electronic component failure includes </li></ul><ul><ul><li>NOTE: Some computer-controlled solenoids are pulsed on and off rapidly. This type of solenoid is used in many electronically shifted transmissions. Their resistance is usually about half the resistance of a simple on-off solenoid—usually between 10 and 15 ohms. Because the computer controls the on-time of the solenoid, the solenoid and its circuit control are called pulse-width modulated (PWM). </li></ul></ul>
  196. 196. HOW TO TEST DIODES AND TRANSISTORS
  197. 197. How to Test Diodes and Transistors <ul><li>Testers </li></ul><ul><ul><li>Diodes and transistors can be tested with an ohmmeter </li></ul></ul><ul><ul><li>Diode or transistor must be disconnected from circuit </li></ul></ul><ul><ul><ul><li>Use diode-check position on digital multimeter </li></ul></ul></ul>
  198. 198. How to Test Diodes and Transistors <ul><li>Testers </li></ul><ul><ul><li>Diode or transistor must be disconnected from circuit </li></ul></ul><ul><ul><ul><li>In diode-check position, meter applies a higher voltage than when ohms test function is used </li></ul></ul></ul>
  199. 199. How to Test Diodes and Transistors <ul><li>Testers </li></ul><ul><ul><li>Diode or transistor must be disconnected from circuit </li></ul></ul><ul><ul><ul><li>Slightly higher voltage (2 to 3 volts) will forward bias diode or P-N junction </li></ul></ul></ul>
  200. 200. How to Test Diodes and Transistors <ul><li>Diodes </li></ul><ul><ul><li>In diode test position, meter applies voltage </li></ul></ul><ul><ul><li>Display shows voltage drop across P-N junction </li></ul></ul>
  201. 201. How to Test Diodes and Transistors <ul><li>Diodes </li></ul><ul><ul><li>Good diode should give an over limit (OL) reading with test leads attached to each lead in one way and a reading of 0.400 to 0.600 V when leads are reversed </li></ul></ul>
  202. 202. How to Test Diodes and Transistors <ul><li>Diodes </li></ul><ul><ul><li>Low-voltage reading with leads attached both ways means diode is shorted and must be replaced </li></ul></ul>
  203. 203. How to Test Diodes and Transistors <ul><li>Diodes </li></ul><ul><ul><li>OL reading with leads attached both ways means diode is open and must be replaced </li></ul></ul>
  204. 204. Figure 48-31 To check a diode, select “diode check” on a digital multimeter. The display will indicate the voltage drop (difference) between the meter leads. The meter itself applies a low-voltage signal (usually about 3 volts) and displays the difference on the display. (a) When the diode is forward biased, the meter should display a voltage between 0.500 and 0.700 V (500 to 700 mV). (b) When the meter leads are reversed, the meter should read OL (over limit) because the diode is reverse biased and blocking current flow.
  205. 205. How to Test Diodes and Transistors <ul><li>Transistors </li></ul><ul><ul><li>With meter set to diode-check position, a good transistor shows voltage drop of 0.400 to 0.600 between the following: </li></ul></ul><ul><ul><ul><li>Emitter and base and between base and collector with meter connected one way and OL when leads are reversed </li></ul></ul></ul>
  206. 206. How to Test Diodes and Transistors <ul><li>Transistors </li></ul><ul><ul><li>With meter set to diode-check position, a good transistor shows voltage drop of 0.400 to 0.600 between the following: </li></ul></ul><ul><ul><ul><li>OL reading in both directions when transistor tested between emitter and collector </li></ul></ul></ul>
  207. 207. Figure 48-32 If the red (positive) lead of the ohmmeter (or a multimeter set to diode check) is touched to the center and the black (negative lead) touched to either end of the electrode, the meter should forward bias the P-N junction and indicate on the meter as low resistance. If the meter reads high resistance, reverse the meter leads, putting the black on the center lead and the red on either end lead. If the meter indicates low resistance, the transistor is a good PNP type. Check all P-N junctions in the same way.
  208. 208. CONVERTERS AND INVERTERS
  209. 209. Converters and Inverters <ul><li>Converters </li></ul><ul><ul><li>DC-DC converters are electronic devices that transform DC voltage from one level to another higher or lower level </li></ul></ul><ul><ul><li>Used to distribute various levels of DC voltage from single power bus </li></ul></ul>
  210. 210. Converters and Inverters <ul><li>Examples of Use </li></ul><ul><ul><li>Circuit the PCM uses to convert 14 V to 5V </li></ul></ul><ul><ul><ul><li>5 volts is called reference voltage (V-ref) </li></ul></ul></ul><ul><ul><ul><li>5 V-ref powers many sensors </li></ul></ul></ul>
  211. 211. Figure 48-33 A DC to DC converter is built into most powertrain control modules (PCMs) and is used to supply the 5 volt reference called V-ref to many sensors used to control the internal combustion engine.
  212. 212. Converters and Inverters <ul><li>Examples of Use </li></ul><ul><ul><li>PCM operates on 14 volts </li></ul></ul><ul><ul><ul><li>Uses principle of DC conversion to provide constant 5 volts to sensors </li></ul></ul></ul><ul><ul><li>Hybrid electric vehicles use DC-DC converters </li></ul></ul>
  213. 213. Figure 48-34 This DC-DC converter is designed to convert 42 volts to 14 volts, to provide 14 V power to accessories on a hybrid electric vehicle operating with a 42 volt electrical system.
  214. 214. Converters and Inverters <ul><li>Examples of Use </li></ul><ul><ul><li>Central component of converter is transformer that isolates 42 V input from 14 V output </li></ul></ul><ul><ul><li>Power transistor pulses high-voltage coil of transformer </li></ul></ul>
  215. 215. Converters and Inverters <ul><li>Examples of Use </li></ul><ul><ul><li>Resulting changing magnetic field induces voltage in coil windings of lower voltage side </li></ul></ul><ul><ul><li>Diodes and capacitors control and limit voltage </li></ul></ul>
  216. 216. Converters and Inverters <ul><li>DC-DC Converter Circuit Testing </li></ul><ul><ul><li>Usually DC control voltage used </li></ul></ul><ul><ul><ul><li>Supplied by digital logic circuit to shift voltage level to control converter </li></ul></ul></ul>
  217. 217. Converters and Inverters <ul><li>DC-DC Converter Circuit Testing </li></ul><ul><ul><li>Usually DC control voltage used </li></ul></ul><ul><ul><ul><li>Voltage test indicates if correct voltages are present when converter is on and off </li></ul></ul></ul>
  218. 218. Converters and Inverters <ul><li>DC-DC Converter Circuit Testing </li></ul><ul><ul><li>Voltage measurements usually specified to diagnose converter </li></ul></ul><ul><ul><li>Digital multimeter (DMM) that is CAT II rated is used </li></ul></ul>
  219. 219. Converters and Inverters <ul><li>DC-DC Converter Circuit Testing </li></ul><ul><ul><li>Follow manufacturer’s safety precautions </li></ul></ul><ul><ul><ul><li>High-voltage circuits usually indicated by orange wiring </li></ul></ul></ul>
  220. 220. Converters and Inverters <ul><li>DC-DC Converter Circuit Testing </li></ul><ul><ul><li>Never tap into wires in DC-DC converter to access power for another circuit </li></ul></ul><ul><ul><li>Never tap into wires in DC-DC converter to access a ground for another circuit </li></ul></ul>
  221. 221. Converters and Inverters <ul><li>DC-DC Converter Circuit Testing </li></ul><ul><ul><li>Never block airflow to converter heat sink </li></ul></ul><ul><ul><li>Never use heat sink for ground connection for meter, scope, or accessory </li></ul></ul>
  222. 222. Converters and Inverters <ul><li>DC-DC Converter Circuit Testing </li></ul><ul><ul><li>Never connect or disconnect converter while converter is powered up </li></ul></ul><ul><ul><li>Never connect DC-DC converter to larger voltage source than specified </li></ul></ul>
  223. 223. Converters and Inverters <ul><li>Inverters </li></ul><ul><ul><li>Inverter is electronic circuit that changes DC into AC </li></ul></ul><ul><ul><li>In most DC-AC converters switching transistors are turned on alternately in pulses </li></ul></ul><ul><ul><li>Result is modified sine wave output rather than true sine wave </li></ul></ul>
  224. 224. Figure 48-35 A typical circuit for an inverter designed to change direct current from a battery to alternating current for use by the electric motors used in a hybrid electric vehicle.
  225. 225. Coverters and Inverters <ul><li>Examples of Use </li></ul><ul><ul><li>Waveform produced by inverter is not perfect sine wave of household AC </li></ul></ul><ul><ul><li>More like pulsing DC </li></ul></ul>
  226. 226. Figure 48-36 The switching (pulsing) MOSFETs create a waveform called a modified sine wave (solid lines) compared to a true sine wave (dotted lines).
  227. 227. Coverters and Inverters <ul><li>Examples of Use </li></ul><ul><ul><li>Inverters power AC motors </li></ul></ul><ul><ul><li>Inverter consists of three half-bridge units </li></ul></ul>
  228. 228. Coverters and Inverters <ul><li>Examples of Use </li></ul><ul><ul><li>Output is created by pulse-width modulation </li></ul></ul><ul><ul><li>Three-phase voltage waves are shifted 120 degrees to each other </li></ul></ul>
  229. 229. ELECTROSTATIC DISCHARGE
  230. 230. Electrostatic Discharge <ul><li>Definition </li></ul><ul><ul><li>Electrostatic discharge (ESD) is created when static charges build up on human body </li></ul></ul><ul><ul><li>When we touch conductive material, static charge discharges </li></ul></ul><ul><ul><li>ESD can severely damage electronic components </li></ul></ul>
  231. 231. Electrostatic Discharge <ul><li>Definition </li></ul><ul><ul><li>Typical static voltages </li></ul></ul><ul><ul><ul><li>If you feel it—at least 3,000 volts </li></ul></ul></ul><ul><ul><ul><li>If you hear it—at least 5,000 volts </li></ul></ul></ul><ul><ul><ul><li>If you see it—at least 10,000 volts </li></ul></ul></ul>
  232. 232. Electrostatic Discharge <ul><li>Definition </li></ul><ul><ul><li>Typical static voltages </li></ul></ul><ul><ul><li>Voltages seem high, but amperes are low </li></ul></ul><ul><ul><li>Electronic components can be ruined if exposed to just 30 volts </li></ul></ul>
  233. 233. Electrostatic Discharge <ul><li>Avoiding ESD </li></ul><ul><ul><li>Keep replacement electronic component in protective wrapping until installation </li></ul></ul><ul><ul><li>Before handling electronic component, ground yourself </li></ul></ul>
  234. 234. Electrostatic Discharge <ul><li>Avoiding ESD </li></ul><ul><ul><li>Do not touch terminals of electronic components </li></ul></ul><ul><ul><li>If working where touching terminals may occur, wear static electrically grounding wrist strap </li></ul></ul>
  235. 235. FREQUENTLY ASKED QUESTION <ul><li>What Is the Hole Theory? </li></ul><ul><ul><li>Current flow is expressed as the movement of electrons from one atom to another. In semiconductor and electronic terms, the movement of electrons fills the holes of the P-type material. Therefore, as the holes are filled with electrons, the unfilled holes move opposite to the flow of the electrons. </li></ul></ul>? BACK TO PRESENTATION This concept of hole movement is called the hole theory of current flow. The holes move in the direction opposite that of electron flow. For example, think of an egg carton, where if an egg is moved in one direction, the holes created move in the opposite direction. <ul><ul><li>Figure 48-3 Unlike charges attract and the current carriers (electrons and holes) move toward the junction. </li></ul></ul>
  236. 236. FREQUENTLY ASKED QUESTION <ul><li>What Is the Difference Between Electricity and Electronics? </li></ul><ul><ul><li>Electronics usually means that solid-state devices are used in the electrical circuits. Electricity as used in automotive applications usually means electrical current flow through resistance and loads without the use of diodes, transistors, or other electronic devices. </li></ul></ul>? BACK TO PRESENTATION
  237. 237. TECH TIP <ul><li>“ Burn In” to Be Sure </li></ul><ul><ul><li>A common term heard in the electronic and computer industry is burn in, which means to operate an electronic device, such as a computer, for a period from several hours to several days. </li></ul></ul>BACK TO PRESENTATION <ul><li>Most electronic devices fail in infancy, or during the first few hours of operation. This early failure occurs if there is a manufacturing defect, especially at the P-N junction of any semiconductor device. The junction will usually fail after only a few operating cycles. </li></ul><ul><li>What does this information mean to the average person? When purchasing a personal or business computer, have the computer burned in before delivery. This step helps ensure that all of the circuits have survived infancy and that the chances of chip failure are greatly reduced. Purchasing sound or television equipment that has been on display may be a good value, because during its operation as a display model, the burn-in process has been completed. </li></ul><ul><li>The automotive service technician should be aware that if a replacement electronic device fails shortly after installation, the problem may be a case of early electronic failure. </li></ul><ul><li>NOTE: Whenever there is a failure of a replacement part, the technician should always check for excessive voltage or heat to and around the problem component. </li></ul>
  238. 238. FREQUENTLY ASKED QUESTION <ul><li>How Does an LED Emit Light? </li></ul><ul><ul><li>An LED contains a chip that houses P-type and N-type materials. The junction between these regions acts as a barrier to the flow of electrons between the two materials. When a voltage of 1.5 to 2.2 volts of the correct polarity is applied, current will flow across the junction. </li></ul></ul>? BACK TO PRESENTATION <ul><li>As the electrons enter the P-type material, it combines with the holes in the material and releases energy in the form of light (called photons ). The amount and color the light produces depends on materials used in the creation of the semiconductor material. </li></ul><ul><li>LEDs are very efficient compared to conventional incandescent bulbs, which depend on heat to create light. LEDs generate very little heat, with most of the energy consumed converted directly to light. LEDs are reliable and are being used for taillights, brake lights, daytime running lights, and headlights in some vehicles. </li></ul>
  239. 239. FREQUENTLY ASKED QUESTION <ul><li>Is a Transistor Similar to a Relay? </li></ul><ul><ul><li>Yes, in many cases a transistor is similar to a relay. </li></ul></ul><ul><ul><li>Both use a low current to control a higher current circuit. </li></ul></ul>? BACK TO PRESENTATION A relay can only be on or off. A transistor can provide a variable output if the base is supplied a variable current input. <ul><ul><li>Chart 48-2 Comparison between the control (low-current) and high-current circuits of a transistor compared to a mechanical relay. </li></ul></ul>
  240. 240. FREQUENTLY ASKED QUESTION <ul><li>What Does the Arrow Mean on a Transistor Symbol? </li></ul><ul><ul><li>The arrow on a transistor symbol is always on the emitter and points toward the N-type material. The arrow on a diode also points toward the N-type material. </li></ul></ul>? BACK TO PRESENTATION <ul><li>To know which type of transistor is being shown, note which direction the arrow points. </li></ul><ul><ul><ul><li>PNP: pointing in </li></ul></ul></ul><ul><ul><ul><li>NPN: not pointing in </li></ul></ul></ul>
  241. 241. FREQUENTLY ASKED QUESTION <ul><li>What Is a Darlington Pair? </li></ul><ul><ul><li>A Darlington pair consists of two transistors wired together. This arrangement permits a very small current flow to control a large current flow. The Darlington pair is named for Sidney Darlington, an American physicist for Bell Laboratories from 1929 to 1971. </li></ul></ul>? BACK TO PRESENTATION <ul><li>Darlington amplifier circuits are commonly used in electronic ignition systems, computer engine control circuits, and many other electronic applications. </li></ul><ul><ul><li>Figure 48-25 A Darlington pair consists of two transistors wired together, allowing for a very small current to control a larger current flow circuit. </li></ul></ul>
  242. 242. FREQUENTLY ASKED QUESTION <ul><li>What Causes a Transistor or Diode to Blow? </li></ul><ul><ul><li>Every automotive diode and transistor is designed to operate within certain voltage and amperage ranges for individual applications. For example, transistors used for switching are designed and constructed differently from transistors used for amplifying signals. </li></ul></ul>? BACK TO PRESENTATION <ul><li>Because each electronic component is designed to operate satisfactorily for its particular application, any severe change in operating current (amperes), voltage, or heat can destroy the junction. This failure can cause either an open circuit (no current flows) or a short (current flows through the component all the time when the component should be blocking the current flow). </li></ul>
  243. 243. FREQUENTLY ASKED QUESTION <ul><li>What Are Logic Highs and Lows? </li></ul><ul><ul><li>All computer circuits and most electronic circuits (such as gates) use various combinations of high and low voltages. High voltages are typically those above 5 volts, and low is generally considered zero (ground). However, high voltages do not have to begin at 5 volts. </li></ul></ul>? BACK TO PRESENTATION <ul><li>High, or the number 1, to a computer is the presence of voltage above a certain level. For example, a circuit could be constructed where any voltage higher than 3.8 volts would be considered high. Low, or the number 0, to a computer is the absence of voltage or a voltage lower than a certain value. </li></ul><ul><li>For example, a voltage of 0.62 may be considered low. Various associated names and terms can be summarized. </li></ul><ul><ul><li>Logic low = Low voltage = Number 0 = Reference low </li></ul></ul><ul><ul><li>Logic high = Higher voltage = Number 1 = Reference high </li></ul></ul>
  244. 244. TECH TIP <ul><li>Blinking LED Theft Deterrent </li></ul><ul><ul><li>A blinking (flashing) LED consumes only about 5 milliamperes (5/1,000 of 1 ampere or 0.005 A). Most alarm systems use a blinking red LED to indicate that the system is armed. A fake alarm indicator is easy to make and install. </li></ul></ul>BACK TO PRESENTATION <ul><li>A 470 ohm, 0.5 watt resistor limits current flow to prevent battery drain. The positive terminal (anode) of the diode is connected to a fuse that is hot at all times, such as the cigarette lighter. The negative terminal (cathode) of the LED is connected to any ignition-controlled fuse. </li></ul><ul><li>When the ignition is turned off, the power flows through the LED to ground and the LED flashes. To prevent distraction during driving, the LED goes out when the ignition is on. Therefore, this fake theft deterrent is “auto setting” and no other action is required to activate it when you leave your vehicle except to turn off the ignition and remove the key as usual. </li></ul><ul><ul><li>Figure 48-30 Schematic for a blinking LED theft deterrent. </li></ul></ul>
  245. 245. WARNING <ul><li>Always follow the manufacturer’s safety precautions for discharging capacitors in DC-AC converter circuits. </li></ul>BACK TO PRESENTATION
  246. 246. WARNING <ul><li>Do not touch the terminals of a battery that are being used to power an inverter. There is always a risk that those battery terminals could deliver a much greater shock than from batteries alone, if a motor or inverter should develop a fault. </li></ul>BACK TO PRESENTATION

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