Download Basic Electrical Systems Theory and Repair

Basic Electrical Systems
Theory and Repair
Chapter 29
Page 387
So, Where is Electronics in a Car
Everywhere
Antilock brakes, engines, emissions,
dash, fuels system, transmissions, tires,
suspension, windows, safety systems,
lighting.
 ----Well, I could go on and on and on.
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The Basics
Atoms
Positive
Negative
Conductors and Insulators
Conductors
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.
Insulators
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 Flow
Electron 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 plastic to
insulate the copper wiring.
Color Chart
Circuit Requirements
= A full circle is provided
Switch
+
Source
12 v
(Battery)
Complete path
Load
_
(light)
Source – Battery or voltage supply
Load – Electrical components, lights, radio, etc.
Complete path for electron flow – Wires and
connections
Protection Devices
Circuit Devices
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Controls Devices
Switches for on and off
Fuses and Circuit Breakers
Protect form Overloads
Fuses and Circuit Breakers
Other Symbols
Electrical Terms

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Voltage- 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 Terms
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AC – 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 Types
Series
Parallel
Combination
Series Circuit
Series Circuits
• Series circuits provide only one path for electron
flow through a circuit.
• When one component fails, the remaining
components quit working.
Light
Light
12 v
Light
Parallel Circuit
Parallel 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 in the first
part of the circuit (series) and the rest of the
circuit is wired in parallel.
12 v
Lights
Ohm’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 Law
E
I
E = Voltage (Electromotive Force)
R
I = Current (Intensity)
R = Resistance (Ohms)
E = IR
I = E/R
R = E\I
E
Ohm’s Law
E = IR
I=E/R
I
R
R=E\I
E = IR
12 = 3 X 4
4 ohms
12 volts
I=E/R
3 = 12 / 4
3 amps
R=E/I
4 = 12 / 3
Magnetism
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
N
S N
S
S
S
N
Magnetic Fields
Magnetism
Magnetic FieldOccurs when a current is flowing through a
conductor.
ElectromagnetsArtificially creating a magnetic field. A coil
of wire with a voltage applied.
Electromagnets
Switch
M
Battery
Starter
Solenoid or Relay
Electromagnets
Resistors
A Few More Terms

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Semiconductors- Can act as both insulator and
conductor.
Diode- an electronic one way check valve, it
allows flow one way but doesn’t allow it to
reverse the other way.
Transistor- electronic relay. Its very fast, and no
moving parts.
Basic Tests

Meters

Analog and Digital
Digital Volt-ohm Meter (DVOM)
or Digital Multimeter (DMM)
Measurements
Voltage Testing
Voltage Check
Testing Voltage After Switch
Open = wire broke or fried wire
Circuit Test
3
1 = 12 v
2 = 12v
3 = 12v
1
2
2
Continuity Testing
Ohmmeter Test
Diode Check
Diode 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 Ohmmeter
with Power Removed
Continuity
Should be
.000 if
Good
Infinity
Should
be 1. if
Bad
Testing Amps
Need to change
red probe lead to
Amp on meter
Test Light
Test Light
Using a Jumper Wire
Bypassing Ground
Bypass a Switch with Jumper Wires
Circuit 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 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 Defects
Open Circuits
Circuit Defects
Short Circuits
Circuit Defects
Ground Circuits
Your Job.
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Complete chapter Questions 1-15 (review) and
1-10 (ASE-style). Page 401-402
Write 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.