Basic Electrical Systems Theory and Repair (2)

Basic Electrical Systems Theory and RepairChapter 29

Page 387

So, Where is Electronics in a CarEverywhereAntilock brakes, engines, emissions, dash, fuels system, transmissions, tires, suspension, windows, safety systems, lighting.----Well, I could go on and on and on.

The Basics

AtomsNegativePositive

Conductors and Insulators

ConductorsConductorsA good conductor must not have more than four electrons in the outer valence ring of an atom. Copper is one of the best conductors; along with aluminum and gold, conductors have one electron in the outer valence ring.

InsulatorsInsulatorsA good insulator must have more than four electrons in the outer valence ring of an atom. Rubber, glass, and porcelain are the best insulators with many electrons in the outer valence ring.

Electrical Flow

Electron MovementThis is what we are taught!Positive to NegativeThis is the way it really is!Negative to Positive

Wiring is coated with PVC, a flexible plastic to insulate the copper wiring. Color Chart

Circuit Requirements= A full circle is providedSource(Battery)+_SwitchSource Battery or voltage supplyLoad Electrical components, lights, radio, etc.Complete path for electron flow Wires and connections

Circuit DevicesControls DevicesProtection DevicesFuses and Circuit Breakers Protect form OverloadsSwitches for on and off

Fuses and Circuit Breakers

Other Symbols

Electrical TermsVoltage- Also called Electromotive Force, Pressure of electricity or the amount of force it takes to move electrons. Measured in volts.Current- The movement or flow of electrons, measured in amperes or amps for short.Resistance-Anything that impedes or slows the flow of electrons. Measured in ohms.

More Electrical TermsAC Alternating Current (shop lights and equipment)DC Direct Current (Auto battery and most systems)

Auto voltage used is normally between 12 and 15 volts

Circuit TypesSeries

Parallel

Combination

Series Circuit

Series CircuitsSeries circuits provide only one path for electron flow through a circuit.When one component fails, the remaining components quit working.

LightLight

Parallel Circuit

Parallel CircuitsParallel circuits provide two or more paths for electron flow through a circuit.When one component fails, the remaining components are not affected.

12 vLights

Combination

The simplest type is to use a switch in the first part of the circuit (series) and the rest of the circuit is wired in parallel.12 vLights

Ohms LawGreg Simon Ohm (1787 1854) Ohms Law: It takes one volt to push one ampere of current through one ohm of resistance.

*Look at page 394 for more.

Ohms LawE = Voltage (Electromotive Force)I = Current (Intensity)R = Resistance (Ohms)

E = IRI = E/RR = E\I

Ohms LawE = IRI = E / RR = E \ IE = IR12 = 3 X 4I = E / R3 = 12 / 4R = E / I4 = 12 / 3

MagnetismLaws of magnetism:1. Like poles repel each other.2. Unlike poles attract each other.3. The attractive force increases as the distance between the magnets decreases.

Magnetic Fields

MagnetismMagnetic Field-Occurs when a current is flowing through a conductor.

Electromagnets-Artificially creating a magnetic field. A coil of wire with a voltage applied.

ElectromagnetsSolenoid or RelayStarterSwitchBattery

Electromagnets

Resistors

A Few More TermsSemiconductors- Can act as both insulator and conductor.Diode- an electronic one way check valve, it allows flow one way but doesnt allow it to reverse the other way.Transistor- electronic relay. Its very fast, and no moving parts.

Basic TestsMetersAnalog and DigitalDigital Volt-ohm Meter (DVOM) or Digital Multimeter (DMM)

Measurements

Voltage Testing

Voltage Check

Testing Voltage After SwitchOpen = wire broke or fried wire

Circuit Test1221 = 12 v2 = 12v3 = 12v3

Continuity Testing

Ohmmeter Test

Diode CheckDiode is a one way street only. Reversing the multimeter leads will tell us if the voltage is allows one way and is stopped the opposite way. If it doesnt do this toss the diode..000 one way and 1. the other.

Testing Device with Ohmmeter with Power RemovedContinuity Should be .000 if GoodInfinity Should be 1. if Bad

Testing AmpsNeed to change red probe lead to Amp on meter

Test Light

Test Light

Using a Jumper WireBypassing Ground

Bypass a Switch with Jumper Wires

Circuit DefectsOpenIncomplete or broken circuit. The circuits quits working.ShortTwo wires unintentionally connecting with each other. Could cause more than one component to operate.

Circuit DefectsGroundWhen a positive and negative wire contact each other. Could cause sparking and extreme heat due to high current flow. Very low resistance blows fuses, circuit breakers, or fusible links.

Circuit DefectsOpen Circuits

Circuit DefectsShort Circuits

Circuit DefectsGround Circuits

Your Job.Complete chapter Questions 1-15 (review) and 1-10 (ASE-style). Page 401-402Write on a separate paper and write out the complete question and your answer. ( do not write the other answer options). Complete the chapter worksheet (I will give it out). You may write on it. File all items in your note book.Notebooks will be graded in the future.