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Electrical Systems and Components
Commercial Products

Electrical
Systems
and
Components

Part No. 96885SL, Rev. A
Introduction
Electricity plays an important role in modern turf
equipment. Modern 12 volt electrical systems are
used almost exclusively in turf equipment.
The demands on the electrical system include:
starting, lighting and ignition systems. Electrical
circuits control the operation of the machines and
monitor certain machine functions. They enhance
the overall operation and also improve the opera-
tors safety, through various safety circuits. New
methods to control the operation and the function of
the machine are made possible because of electri-
cal devices.
With the use of microprocessor based controls, the
potential of electrical and electronic circuits and
controls will greatly change the ease of operation
and the reliability of current and future equipment.
These new advances in electrical systems will re-
quire a better understanding of electricity and com-
plete electrical systems, to enable technicians to
diagnose and repair these systems.
Safety
While the risk of electrical shock is relatively low
when working on a 12 volt electrical system, care
must be taking when working on equipment elec-
trical systems.
Fumes from battery electrolyte are flammable.
Keep all sparks and fires away from the battery.
When charging the battery, explosive fumes are
produced more rapidly. Be sure the room or area
where batteries are being recharged is well venti-
lated.
Battery acid is harmful on contact with the skin
or most materials. If acid contacts the skin, rinse
the affected area with running water for 10 to 15
minutes. If acid contacts the eyes, force the eyelids
open and flush the eyes with running water for 10 to
15 minutes. Then see a doctor at once.
To avoid injury from sparks or short circuit,
Dis-
connect the negative battery ground cable when
working on any part of the electrical system.
Remove all Jewelry and watches when working
on live circuits.
Injury can result from high temperature caused
when jewelry, rings or watches come in contact with
powered circuits and ground circuits.
When removing batteries always disconnect the
negative battery cable first. When reconnecting the
battery wait until last to connect the negative ca-
ble.
Do not lay tools or parts across the battery, the
metal parts or tools can short across the battery
posts and a fire or explosion can result. 1
INDEX
1: ELECTRICAL PRINCIPLES, PAGE 2.
OBJECTIVE: To familiarize the technician with the basic fundamentals of electrical systems and their
operation.
2: TEST EQUIPMENT, PAGE 5.
OBJECTIVE: Inform technicians of proper use of electrical test equipment.
3: BASIC CIRCUIT TEST, PAGE 9.
OBJECTIVE: Provide technicians with helpful information on the procedures for testing basic electrical
circuits.
4: ELECTRICAL COMPONENTS AND TESTING, PAGE 11.
OBJECTIVE: Explain the operation and function of basic electrical components. Instruct technicians on
the proper methods to test various common electrical components.
6: BASIC CIRCUITS, PAGE 21.
OBJECTIVE: Examine various electrical circuits.
7: REVIEW QUESTIONS, PAGE 24.
Review Answers
1 - B.
6 - B.
11 - B.
16 - C.
2 - B.
7 - D.
12 - B.
17 - C.
3 - B.
8 - C.
13 - D.
18 - A.
4 - C.
9 - C.
14 - A.
19 - A.
5 - B.
10 - B.
15 - C.
20 - A. 2
Electrical Principles
Electricity
Electricity is a form of energy created by the
movement of electrons. Directing these electrons
through a circuit, we can perform work. Electricity
can produce light, heat, magnetism or mechanical
work.
Basic System Requirements
Every electrical system requires 3 basic compo-
nents and usually 2 accessory components.
1: Power Source
2: Load Device
3: Conductors
Accessory Components.
4: Switch
5: Fuse
Basic Circuit Types
Series Circuit
A series circuit is a circuit that may include more
than one load.
Characteristics of a series circuit:
1: The current is constant through out the circuit.
2: The current must pass through each component
in the circuit.
3: The total resistance of the circuit controls the
current in the circuit.
4: The total resistance of the circuit is the sum of
all the resistances in the circuit.
5: The sum of the voltage drops across the resis-
tors will equal the applied voltage.
Resistance in a series circuit equals the sum of all
resistances (that is, R = R1+R2+R3+ etc...)
Electricity
Basic System Requirements
Figure 2
Series Circuit
Figure 1
Figure 3 3
Parallel Circuits
A parallel circuit is a circuit that has two or more
loads connected so that current can divide and flow
through the load. Most electrical circuits are paral-
lel.
Characteristics of a parallel circuit:
1: The current has many paths.
2: The resistance in each load will determine the
current flow for that resistance.
3: The total resistance will always be less than the
smallest resistance in the circuit.
4: The voltage drop across all loads will be battery
voltage.
The formula for calculating resistance in a parallel
circuit is:
R = R1 x R2



R1 + R2
Basic Electrical Elements
Current is the directed flow of electrons through
the circuit.
Voltage is the electrical pressure that causes the
electrons to flow.
Resistance is a restriction to current flow.
Parallel Circuits
CIRCUIT
ELEMENT
DEFINITION
UNIT OF
MEASUREMENT
UNIT
SYMBOL
MEASURED
WITH
FUNCTION
SWITCH
POSITION
OHMS
LAW
CURRENT
The flow of
electrons
around a circuit
Amperes
(amps)
A
Ammeter
AC amps
or
DC amps
C=V÷R
VOLTAGE
The force
(pressure)
which causes
current to flow
Volts
V
Voltmeter
ACV
or
DCV
V=CxR
RESISTANCE
The opposition
(restriction) to
current flow
Ohms Ohmmeter
Ohms
R=V÷C
Table 1
Figure 4 4
Ohms Law
The three electrical elements have a direct effect
on each other. The formula to calculate this effect
is Ohms Law.
The illustration at the right is Ohms law. The letters
represent the properties in the system.
V = Voltage,
C = Current,
R = Resistance.
(Hint: remember VCR.)
If you know any two of the values you can apply the
proper mathematical formula and find the third.
Lets apply Ohms Law to a circuit
Example 1: A starter motor for a WORKMAN 3200
Gas draws 90 amps when the system is operating
correctly.
Since we know the voltage and the current, we find
the resistance by taking the voltage and dividing it
by the current. (fig.6) 12.5 volts ÷ 90 amps =
0.135 .
Example 2: If we increase our system resistance to
0.2 , what will happen to our current flow? 12.5
volts ÷ 0.2 = 62.5 amps. An increase in our sys-
tem resistance will decrease the current flow in our
circuit. This will result in what symptom? (Answer
= slow crank or no start.)
What happens if we decrease our starting system
resistance to 0.04 ? 12.5 volts
÷
0.04 = 312.5
amps. This will result in what symptom? (Answer =
slow crank or no start.)
How can higher resistance cause the same symp-
toms as lower resistance? With higher resistance,
the amount of current flowing to the starter is lim-
ited by the additional resistance in the circuit. In the
case of lower resistance, the only way to lower re-
sistance in a circuit is to provide a shorter path to
ground or another path to ground. (That means that
a portion of the amperage flow is taking a different
path to ground than originally intended. So the re-
sult is actually a lower power output from the
starter).
Ohms Law
Example 1
Example 2
Figure 5
Figure 6
Figure 7 5
Example 3: A circuit contains a light bulb that
measures 4 ohms. The current flow is 3 amps.
What is the voltage of the power source? 3 amps X
4 = 12 volts.
Example 3
Figure 8
Figure 9 shows some common electrical symbols.
Figure 9 6
Electrical Testing
Equipment
Lets look a some common test equipment
Test lights
Features
1. Used for checking for power in a circuit.
2. Cant give actual voltage readings.
3. Should not be used on electronic circuits
Analog meter
Features
1. Voltage (Pressure) testing.
2. Amperage(Flow) testing.
3. Resistance(Restriction) testing.
Digital-Volt-Ohm meter (DVOM)
Features
1. Voltage (Pressure) testing.
2. Amperage(Flow) testing.
3. Resistance(Restriction) testing.
4. Diode (Check valve) testing.
Test lights
Analog meter
Digital-Volt-Ohm meter (DVOM)
Figure 10
Figure 11
Figure 12 7
Advantages of a Digital meter vs.
Analog meter
DVOM Advantages:
1: