Presentation on theme: "Automotive Electrical Notes PHS Auto 2"— Presentation transcript:
1Automotive Electrical Notes PHS Auto 2 Basic notes for auto shop classstudy and refer back to your text book
2Electron theorythe electrical phenomenon is produced by a flow of electrons from one area to another.
3Flow of electronsThe flow of electrons is caused by having an excess number in one area, shortage in another surplus negative short supply positive
4MatterAnything that takes up space and has mass: solid, liquid or gas
5MoleculeSmallest portion of matter and retain all original properties of the original matter, it is made up of atoms
6Atoms 100 + different types One molecule of water, is made up of one atom of oxygen, two atoms of hydrogen H20
7Atom make up PROTON - positive charge + ELECTRON - negative charge - NEUTRON - no charge (neutral) If there are more protons in the atom then electrons, it is a positive charged atom. proton and neutron in center; electrons orbit
9Bound electronsAre in the inner orbits, Bound electrons are very difficult to remove from their orbit.
10Free electronsOuter orbits only, one, two or three electrons, are easily knocked out of their orbit
11ConductorsHave 1-3 electrons in outer orbit, (Free electrons)easily knocked out of orbit. Materials such as silver, copper, aluminum, gold make good conductors.
12Semi-Conductors 4 electrons in outer orbit Not a good conductor Not a good insulator
13Non conductorsInsulators, 5 or more electrons in outer orbit, glass, ceramics, plastics, rubber, fiber, porcelain, paper and wood are common Insulators. Hard to knock the electrons out of orbit if they have a strong magnetic pull to the protons in the nucleus of the atom.
14CurrentMovement of free electrons through a conductor current flow is measured in amperes(Amps). Must have shortage of electrons at one end, surplus at other one electron does not go the whole distance moves and bumps others.
15Voltage (electromotive force, EMF) Pressure differential causes current to flow, this pressure is known as voltageVoltage is a measure in volts with voltmeter.
16ResistanceCaused by electrons bumping into other atoms, a poor conductor has greater resistance than a good conductor. Poor conductors will heat up (like a heater).
17Larger conductors (wire size) offers less resistance then a smaller one, Resistance is measured in ohmsCurrent will flow in the one path with least resistance.Current will flow from negative to positive, negative has surplus of electrons, positive has short supply.Which way does it flow ? Ask the experts
18Circuits Must have a power source. A load (something to operate such as a light bulb or motor)Wiring for path of electron flow (Conductor)SwitchCircuit protectionThanks Kevin
19Series circuit, only one path for current to flow
20Parallel circuit, more than one path for current to flow, current flows through all units at once.
22Circuit Problems Open circuit, Wire is broken Short to ground, Wire is touching groundShort to voltage, wire is touching a hot wire. Load device is on even though switch is off.High resistance, current is being slowed by corrosion or a poor connection
23Car frameActs as a ground wire, some cars like a corvette have to run ground wires because of fiberglass bodyGround symbol:
24Ohms law Amperes = I - Intensity Volts = E - Electromotive force Ohms = R - Resistanceto find E = I x R I = E / R R = E / IEI X R
25Ohms laws For Auto Techs Some Auto Techs will use the followingAmperes = A - AmpsVolts = V - VoltsOhms = R - Resistanceto find V = A x R A = V / R R = V / AVA X R
26M, m, K, μ Prefix Symbol Factor Numerically Name giga G 109 billionMegaM106millionkilok1031 000thousandcentic10-20.01hundredthmillim10-30.001thousandthmicroμ10-6millionthnanon10-9billionth
27Magnetism Materials that have this are called Magnets Some are Natural Some are made
28Magnetic DomainsThese small sections of a magnet must all line up to be a strong magnet. If not, they will cancel each other out and the piece of metal will be unmagnetized
29Lines of Force Leave north pole, enter south Unlike poles attract Like poles repelLeft hand rule, know which way current flows, fingers point in direction magnetic field is movingMagnetic fields surround any conductor carrying an electrical current
31magnetic effects of parallel conductors, magnetic effects of conductors with current flowing in opposite direction, spark plug wiresmagnetic field in coils compared to single wire left hand rule for coils thumb points northsoft iron core in coils, lines of force increase several hundred times
32Solenoidcan be used to push or pull iron core if off set will be drawn into the middle
33Battery Electro Chemical Device 4 functions1. provides electrical energy to start car.2. provides electrical energy to ignition system3. provides electrical energy to accessories when demands exceed alternators output4. voltage stabilizer absorbs abnormal voltages created by electrical components
35side and top postA side and top post is becoming very common today because it will fit so many cars.
36Batteries a little history Up to 1955 most batteries were 6 voltGeneral Motors started the move to 12 volts, Volkswagen was the last in 1966 to switch over.By 2010 some cars may have a 42V/14V System. Several problems lie in wait such as cost of the components. Life of batteries & arcing between components.
37Battery Construction Elements consist of two groups of plates one more negative than positive plates with insulated separators in betweenusually 9, 11, or 13 plates. 54, 66, or 78 total.case is made of hard rubber (rough service) or plastic (light service)
41Electrolyte 64% water 36% Sulfuric acid H20-water 64% specific gravity 1.00H2S04-sulfuric acid 36% specific gravity cautionelectrolyte 100% specific gravity 1.270
42Chargedpositive plate negative plate electrolyte H2S pb pb lead peroxide lead
43Dischargeoxygen and hydrogen form water, lead and sulfate form lead sulfatepbso4 H20 pbSo4
44Charging send electrons through opposite way reversing the cycle Sulfated plates refer to plates harden with lead sulfateSlow long charge to correct sulfated plates sometimes can't
45Little brown particles floating around can short out battery (flakes off of the sulfated plates ) Batteries can freeze if discharged H2O is waterCharging battery emits oxygen and hydrogen gas - can explodeTo replace add distilled water
46Battery typesWET CHARGE shipped with electrolyte must charged during storageDRY CHARGE shipped empty manufacture gives forming charge dries the cell elements and seals it. If you keep moisture out it will remain fully charged for long time. When needed just add electrolyte
47Group sizeBatteries come in many different group sizes. A battery's group size simply determines it's length, width, height, and terminal configurationWill have a number like group 75,78 or 24 or 24F, 26, 34
48Battery capacity1) Plate size, the case same size, plates are different size Larger plates more amps2) Number of plates3) Amount of acid in electrolyte and battery additives increase the sulfuric acid content of battery
49Battery capacity rating Cold Cranking Amperes CCA most common “Number of amperes load of battery will maintain at 0 degrees Fahrenheit for 30 seconds without battery voltage falling below 7.2 volts” (1.2 volts per cell)Size of engine should be smaller than cold cranking ampere
50Do not be misled by CA that’s just cranking amps Do not be misled by CA that’s just cranking amps. It will give you a higher reading but it misleads you because it is tested at a higher temperature.Cranking amps are the numbers of amperes a lead-acid battery at 32 degrees F (0 degrees C) can deliver for 30 seconds and maintain at least volts per cell (7.2 volts for a 12 volt battery).
53Battery checking visual Inspection Cracked or leaking case liquid level, add water use distilled water preferred (No minerals) or ice melted out of a freezerVoltage can discharge across top from post to postClean battery top and post and cables, battery hold downs
55Cleaning The Battery Mix baking soda and water to clean batteries Clean post and cable with a terminal brush or post cutterCoat all connections with grease or use a spray like NOCO NCP-2 Battery corrosion spray
56Battery leakage test Voltmeter – lead at negative post Voltmeter + lead drag across batteryNo voltage should be present anywhere if it is clean the battery.
57Battery Open Circuit Voltage Test Measure what the voltage is with the key off Find out it’s state of charge. It is a good starting point, should be at least volts12.66 = fully charged12.4 = 3/4 charged12.2 = 1/2 charged12.0 = 1/4 charged
58Battery Terminals & Bolts Post or top terminalSide terminalL terminal used on importMarine
59Terminal Test This is the first step. Take a voltmeter DVOM (Digital volt ohm meter)Turn to DC VoltsHook up like picture on next page.
60Terminal TestThis is just a voltage drop test done on the battery terminals. You must disable the ignition and crank over the engine. Should be under .2 volts Make sure you do both terminals Positive &Negative
61Battery Drain test Battery Drain Key off Hook up a ammeter in series reading should not exceed the following77 older cars .01 amps, 10 ma (milliamps)amps-.025 amps, ma1986 & newer .05 amps, 50 ma
62Testing specific gravity Hydrometer check before adding water fully charged battery should read should not vary more than 50 points between cells if it does recharge and check againMaintenance free batteries are sealed, cannot get into some. No way to add water or check specific gravity.
63Charging batteries Clean up first Unhook cables - check liquid level Don't charge over 16 volts if plates are sulfated or if battery has been discharged for some timeSlow charge for a long period 24 hours don't allow temperature to exceed 100Never fast charge batteries
64Most batteries in cars are 12 volt with negative ground. 6 volt older cars and 18 wheelers may have positive ground
65SAFETY: do not allow battery acid to contact eyes skin or fabrics if you do flush with lots of water, and get teacher or medical help flush eyes for 15 minutes
66Jump starting cars positive to positive negative to negative Hook up negative cable last on car with dead battery on a good ground. Not on the battery. If sparks occur no Hydrogen to blow up
68Did You Know Batteries Lose Power While Sitting on the Shelf? A battery can permanently lose some of its capacity when it's stored in a partly or fully discharged state. Periodic charging during storage can minimize the deterioration, but not all battery distributors and dealers do the necessary charging. That's why you may want to know how to read the date codes, which show when the product was manufactured, on a new product, to help you make sure you're really buying a fresh battery.So, how do you read a date code?
69Most Brands of Batteries JOHNSON CONTROLS, INC. - INTERSTATE BATTERIES,Motorcraft, East penn - Deka, GNB -Champion, Stowaway:The letters and numbers are on a sticker affixed to the battery or hot-stamped into the case cover along the top edges of the battery. The ship date codes begin with a letter: A stands for January, B for February and so on (some shipping codes skip the letter I, so it cannot be confused with the number 1. In those cases, J would represent September, K - October, L - November and M - December). The next digit is a number which represents the year the battery was shipped. Therefore, an A6 would mean the battery was shipped in January of 1996.
81Alternators More efficient at lower speeds Lighter - aluminum constructionRequires only 2 or 3 amps passing through slip rings compared to high amperage in D.C. generatorGoverns its own maximum current output
82AlternatorGenerators - moving conductor through stationary field to induce voltageAlternator - a permanent magnet is rotated inside a stationary conductormaximum voltage occurs when conductor cuts heaviest lines of force