Electrical Components Chap #3 PDF

Electrical Components Chap #3  Circuit Protection Devices: Fuses Circuit Breakers Fusible Links Why do you think we went from standard fuses to mini fuses?  Why do fuses blow in a vehicle? Too much resistance...

Electrical Components Chap #3  Circuit Protection Devices: Fuses Circuit Breakers Fusible Links Why do you think we went from standard fuses to mini fuses?  Why do fuses blow in a vehicle? Too much resistance? Too much voltage? Too much current?? This is why a fuse blows!! Do they “Blow” or does it get hot and burn or melt? Easiest way to check fuses is to use a test light. Should have power on both sides of the fuse  Checking Fuses Should have power on both side Always check all the fuses Make sure ignition is on so that circuit has voltage applied to it Some fuses will not have power at all, they may be spares Some headlight/taillight fuses will only have voltage with headlights on How about these things Cartridge fuse. May have to pull out for visual inspection to determine if its blown since test light cant be used  Circuit Breaker Trips like a fuse but resets itself after it cools down A good circuit breaker can be checked for resistance. If it is good, will show a small amount of resistance Fusible Link – An insulated piece of wire that is slightly smaller than the wiring in the rest of the circuit. Designed to burn up before circuit wiring Pull on them to test. If they are bad, they will pull apart Not a Fuse!! Switches- Dozens of different types used in the vehicle but they all work the same. Designed to open and close the path that current can flow Single pole single throw (SPST) Switch Most simple form of a switch  SPDT and DPDT Switch Single Pole Double Throw and Double Pole Double Throw  May be used in circuits such Ganged Switch as headlight switch, turn signal switch or wiper switch Multiple sets of contacts move all together at the same time How is switch in the normal position without being acted upon  Switch Operation Open Switch Closed Switch Internal Switch Parts (Contacts) Burnt Switch Contacts  Hood/Trunk Light Switch May use mercury to open and close contacts or use a metal check ball the moves to close switch  Best way to test a switch!! Power to – Power through If 12 volts goes in, 12 volts should come out. Its not a load device, its only a conductor Power on both sides of switch with switch turned on. Power to, power through Can Test Resistance and Voltage Drop Use resistance setting to measure for continuity(open circuit), remember, there is a big difference between a reading of OL and a reading of 0.0 Power To, Power Through – Bad Switch Power to switch Power through switch- these 2 numbers should be If light wont come on when switch is turned on but will illuminate if switch is bypassed with a jumper wire, then switch is faulty  Lets build a circuit Build a simple circuit with a switch and a light bulb. Hook it up to your power board so that it works. Test the switch on your table using your test light and meter. Test it all 4 ways, testlight, resistance, voltage drop and jumper wire  Electromagnets – How Do They Work? Magnet forms when current flows through a coil of wires Magnet strength can be determined by: 1) Amount of current flowing through wire 2) Number of windings in coil 3) Size and length of core material Direction of lines of force Where are they used on the car?  Relays in fuse box Relays are used to operate high current devices such as fuel pump, cooling fans, horns and antilock brake pumps.  What is a relay? An electromagnetic switch used to control a high amp draw device. Designed to protect the switch that turns the relay on Contains a set of electrical contacts, coil of wire and electrical terminals  Standardized Terminals 85 - Low current coil (power or ground 86 – Low current coil (power or ground) 30 – Feed to high current contact (power or ground) 87 – output of high current contact (power or ground) will have continuity with terminal 30 when relay is energized 87 A– output of high current contact (power or ground) will have continuity with terminal 30 when relay is not energized 4 vs 5 Terminal Relay (Physical Difference)  4 Terminal Relays Does not have terminal 87a Whats inside? Electromagnetic coil creates magnetism and pulls switch closed 4 Terminal Relay Circuit How does a relay fail? 4 terminal fuel pump relay Where are the standardized numbers we have been taught?? Can I Just Swap a Relay to figure out if one is faulty? Absolutely!! Jumping Relay Never jump the low current coil terminals!!!! It’s the load Jumper wires can be our best friend Can I flip this relay around in the connector and will it still work?  85 30 86 87 What does test light do with relay installed or with it removed??  Fixed Resistors Used to add resistance to a circuit that will cause a decrease in current flow Where are they used?? Circuit Boards Color Bands – Used to determine resistance value range Google How to use the bands to determine resistance value  Stepped Resistors Most Common Use - Blower Motor Circuits to allow different fan speeds  Wired in The stepped resistor decreases Stepped Resistor series with the blower motor current flow in the circuit which makes the blower motor spin slower Wired in series with the blower motor, so a faulty resistor will affect blower speeds If relay will not energize, what would blower motor do in high speed?  Variable Resistor Rheostat Potentiometer A resistor who’s resistance can Examples: dash light dimmer switch, physically be changed. Usually by radio volume knob, throttle position turning or movement sensor and accelerator pedal position sensor Rheostat (2 Wire) Potentiometer (3 Wire)  Rheostat to dim dash lights  Potentiometer for use as throttle position sensor  Standard Diode One-Way Electrical Check Valve Semi-conductive material that blocks electrical flow in one direction but allows flow in the other direction  If current flows through diode, it is forward biased If diode blocks current, it is reverse biased Turn on voltage is amount of voltage needed to push current through diode  LED – Light Emitting Diode Works like a standard diode. Current only flows one way and blocked the other direction.  Clamping Resistor (Similar to Clamping Diode) Dissipates voltage spikes caused from induction Another job of a diode- AC to DC Rectification Clamping Diode  Transistor High Speed Electrical Switch 3 legs – emitter, base, collector  PNP transistor The base is responsible for turning the transistor on. When a voltage is applied to the base, current will be allowed to flow through the collector to the emitter  NPN Transistor The difference between a PNP and a NPN is the voltage required to turn on the base. A PNP needs a negative voltage while a NPN needs a positive voltage  Pic of circuits like in lab that use transistors Which is this? What side of the circuit is it in?  Capacitors Work like a battery that can charge and discharge very rapidly (electron storage device) Can be used for electron storage, timer, reduce voltage spikes and filter out certain frequencies (noise) Does not consume any power Look different but do all the same work Lets build something  Speakers Attraction or repulsion of 2 magnets 1 magnet is an electromagnet, other is permanent magnet Voice coil is an electromagnet  Checking Speaker Polarity If battery positive is hooked up to speaker positive, speaker will move outward. If hooked up in reverse polarity, speaker will move inward  Electric Motors Changing electromagnet polarity will cause direction Most are bidirectional to change Uses permanent magnets and an electromagnet to create movement How electric motors works  Electric Actuators Use magnetism to create movement  Solenoid (Actuator) Electromagnet that creates movement and performs work Used in circuits such as power door lock and starter motor