Basic Electrical Systems Theory and Repair

Basic Electrical Basic Electrical Systems Theory Systems Theory

and Repairand RepairChapter 29Chapter 29

Page 387Page 387

So, Where is Electronics So, Where is Electronics in a Carin a Car

EverywhereEverywhere Antilock brakes, engines, Antilock brakes, engines,

emissions, dash, fuels system, emissions, dash, fuels system, transmissions, tires, suspension, transmissions, tires, suspension, windows, safety systems, lighting.windows, safety systems, lighting.

----Well, I could go on and on and ----Well, I could go on and on and on. on.

The BasicsThe Basics

AtomsAtoms

Negative

Positive

Conductors and Conductors and InsulatorsInsulators

ConductorsConductors

Conductors

A 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.

InsulatorsInsulators

Insulators

A 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 FlowElectrical Flow

Electron MovementElectron Movement

This is what we are taught!Positive to Negative

This is the way it really is!Negative to Positive

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

Color ChartColor Chart

Circuit RequirementsCircuit Requirements== A full circle is providedA full circle is provided

Source

(Battery)

12 v

Complete path

Load

(light)

+

_

Switch

Source – Battery or voltage supplyLoad – Electrical components, lights, radio, etc.Complete path for electron flow – Wires and connections

Circuit DevicesCircuit Devices Controls DevicesControls Devices

Protection DevicesProtection Devices

Fuses and Circuit Breakers Protect form Overloads

Switches for on and off

Fuses and Circuit Fuses and Circuit BreakersBreakers

Other Symbols

Electrical TermsElectrical Terms

VoltageVoltage- Also called Electromotive - Also called Electromotive Force, Pressure of electricity or the Force, Pressure of electricity or the amount of force it takes to move amount of force it takes to move electrons. Measured in electrons. Measured in voltsvolts..

Current-Current- The movement or flow of The movement or flow of electrons, measured in amperes or electrons, measured in amperes or ampsamps for short.for short.

ResistanceResistance--Anything that impedes or slows the flow of electrons. Measured in ohms.

More Electrical TermsMore Electrical Terms

AC – Alternating Current (shop AC – Alternating Current (shop lights and equipment)lights and equipment)

DC – Direct Current (Auto battery DC – Direct Current (Auto battery and most systems)and most systems)

Auto voltage used is normally Auto voltage used is normally between 12 and 15 voltsbetween 12 and 15 volts

Circuit TypesCircuit Types

Series

Parallel

Combination

Series CircuitSeries Circuit

Series CircuitsSeries Circuits

• Series circuits provide only one path for electron flow through a circuit.

• When one component fails, the remaining components quit working.

Light

12 v

Light

Light

Parallel CircuitParallel Circuit

Parallel CircuitsParallel Circuits

• Parallel circuits provide two or more paths for electron flow through a circuit.

• When one component fails, the remaining components are not affected.

12 v Lights

Combination

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

12 v Lights

Ohm’s LawOhm’s Law

Greg Simon Ohm (1787 – 1854)

Ohm’s Law: It takes one volt to push one ampere of current through one ohm of resistance.

*Look at page 394 for more.

Ohm’s LawOhm’s Law

E

I R

E = Voltage (Electromotive Force)

I = Current (Intensity)

R = Resistance (Ohms)

E = IR

I = E/R

R = E\I

Ohm’s LawOhm’s LawE

I R

E = IR

I = E / R

R = E \ I

4 ohms

3 amps

12 volts

E = IR

12 = 3 X 4

I = E / R

3 = 12 / 4

R = E / I

4 = 12 / 3

MagnetismMagnetism

Laws 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.

N SN S

N S S N

Magnetic FieldsMagnetic Fields

MagnetismMagnetism

Magnetic Field-

Occurs when a current is flowing through a conductor.

Electromagnets-

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

ElectromagnetsElectromagnets

M

Solenoid or Relay

Starter

Switch

Battery

ElectromagnetsElectromagnets

ResistorsResistors

A Few More TermsA Few More Terms

SemiconductorsSemiconductors- Can act as both - Can act as both insulator and conductor.insulator and conductor.

DiodeDiode- an electronic one way check - an electronic one way check valve, it allows flow one way but valve, it allows flow one way but doesn’t allow it to reverse the other doesn’t allow it to reverse the other way.way.

TransistorTransistor- electronic relay. Its very - electronic relay. Its very fast, and no moving parts.fast, and no moving parts.

Basic TestsBasic Tests

MetersMeters Analog and DigitalAnalog and Digital

Digital Volt-ohm Meter (DVOM) or Digital Multimeter (DMM)

MeasurementsMeasurements

Voltage TestingVoltage Testing

Voltage CheckVoltage Check

Testing Voltage After Testing Voltage After SwitchSwitch

Open = wire broke or fried wire

Circuit TestCircuit Test

1

2

2

1 = 12 v

2 = 12v

3 = 12v

3

Continuity TestingContinuity Testing

Ohmmeter TestOhmmeter Test

Diode CheckDiode 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 doesn’t do this toss the diode.

.000 one way and 1. the other.

Testing Device with Testing Device with Ohmmeter Ohmmeter

with Power Removedwith Power Removed

Continuity Should be .000 if Good

Infinity Should be 1. if Bad

Testing AmpsTesting AmpsNeed to change red probe lead to Amp on meter

Test Light Test Light

Test LightTest Light

Using a Jumper WireUsing a Jumper Wire

Bypassing Ground

Bypass a Switch with Bypass a Switch with Jumper WiresJumper Wires

Circuit DefectsCircuit Defects

Open

Incomplete or broken circuit. The circuits quits working.

Short

Two wires unintentionally connecting with each other. Could cause more than one component to operate.

Circuit DefectsCircuit Defects

Ground

When 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 DefectsCircuit Defects

Open Circuits

Circuit DefectsCircuit Defects

Short Circuits

Circuit DefectsCircuit Defects

Ground Circuits

Your Job.Your Job. Complete chapter Questions 1-15 Complete chapter Questions 1-15

(review) and 1-10 (ASE-style). Page (review) and 1-10 (ASE-style). Page 401-402401-402

Write on a separate paper and write out Write on a separate paper and write out the complete question and your answer. the complete question and your answer. ( do not write the other answer options). ( do not write the other answer options).

Complete the chapter worksheet (I will Complete the chapter worksheet (I will give it out). You may write on it. give it out). You may write on it.

File all items in your note book.File all items in your note book. Notebooks will be graded in the future.Notebooks will be graded in the future.