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Electrical Flashcards

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1
Q

Purpose of battery disconnect?

A

Will prevent slow discharge of the battery group when unit is parked.

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2
Q

Purpose of circuit protection devices?

A

Used to protect a machines electrical circuits from large current flows. Main circuits are around 60-80 watts

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3
Q

Type 1 circuit breaker?

A

Used when flow must be restored quickly. Opens and closes when a bi metal strip heats and cools opening the contacts

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4
Q

Type 2 circuit breaker?

A

Uses a heat producing resistor and holds the contacts open while the breaker rating is exceeded

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5
Q

Type 3 circuit breaker?

A

Non cycling and has a manual reset button. Used in non critical circuits

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6
Q

Sizing circuit protection

A

Lights —> amps x 1.2

Engine —> amps x 1.5

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7
Q

Higher beams produce what wattage?

A

80 watts

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8
Q

Low beams produce what wattage?

A

60 watts

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9
Q

Door switches are in what condition normally?

A

Normally closed

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10
Q

Limiting factors of a motor armature speed?

A

Counter-electromagnetic forces (CEMFs)

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11
Q

Windshield wiper motors are what kind of motor?

A

2 speed dc

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12
Q

2 types of anti theft systems?

A

Alarm system, theft deterrent

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13
Q

Temperature gauge circuits use what kind of thermistor?

A

Negative temperature coefficient

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14
Q

Equipment lighting circuits are used to provide illumination for?

A

Vision during night
Unit appearance
Unit/operator safety
Operator convenience

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15
Q

The intensity of a instrument panel can be controlled by?

A

Series connected rheostat

Pulse width modulated signal

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16
Q

Multiplexing reduces the amount of wires by how much?

A

40%

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17
Q

What is multiplexing?

A

The ability to send and receive digital electronic signals over a pair of wires

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18
Q

3 multiplexing network and protocols?

A

J1587/J1708

J1939/CAN

ISO11783/CAN

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19
Q

What is baud rate?

A

The speed of the data transfer over a network

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20
Q

What is backbone?

A

Networks method of connection, such as wires or fibre optic cable. Most common in heavy duty equipment is a twisted pair that is shielded with a copper wire to prevent emi

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21
Q

What is a stub?

A

Is a segment of data link that branches off the back bone and connects to each node. A stub can be a max of 1 metre. Also referred to as a branch.

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22
Q

What is a node?

A

Computer or other device that has a unique network address

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23
Q

What Is a terminating resistor?

Study These Flashcards
A

Is placed at each end of the data link to reduce electrical interference on the data link

24
Q

What is standing waves?

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A

Electrical reflections or waves that can cause major problems with module communication

25
Vehicle communication data bus
Communication network that connects to all of the multiplexed components of the mobile equipments system
26
What is protocol?
Common language for data communication between control modules. J1587 and can are common protocols
27
Controller area network CAN
Is a communication protocol used in on-highway trucks
28
Data links
Provide for the transmission of input and output signals between nodes and diagnostic scan tools
29
Non shielded twisted pair cable
Pair of cables twisted together protected by a plastic coating
30
Shielded twisted pair cable
Non insulated copper wire (drain wire) that wraps around the twisted pair. And wrapped with metallic foil for shielding
31
Why are conductors twisted?
Twist helps provide immunity to magnetic fields. And enables the conductors to maintain a constant capacitance
32
What is topology ?
Describes the logic structure of the control modules on the data bus
33
Loop or ring topology ?
All modules connected in series. If one module loses ground the whole network loses communication
34
Star topology?
Master module is connected to all slave modules in parallel
35
Modern data buses use what kind of topology?
Linear. Has a main backbone with stubs. All modules receive all broadcasts
36
What is a message identifier? MID
One bite long 8 bit and indicates the source address of the transmitting node
37
What is a parameter identifier? PID
Usually one byte long and indicates to what parameter the following data corresponds
38
Parameter data bytes
Must be followed by at least one data value. Can not exceed 18 bytes
39
J1587/J1708 standards?
Max 40 meters Max number of nodes is 20 Bus is an un shielded twisted pair and doesn’t require termination resistors
40
Why do J1587 interconnect pins must be gold plated?
Reduce the possibility of resistance
41
Why must you use a high impedance meter when testing multiplexed systems?
Will result in damage to electrical components
42
What is the arbitration field?
Identifies the priority of the message and which module sent it
43
What does the control and data field tell you?
PGN SPN FMI Fault codes
44
What does a circular reference check do?
Checks for errors
45
What does end of frame do?
Terminates the message frame so you can receive the next message
46
Colour of wires in can-high (+) | And can-low (+)?
Yellow is can high Green is can low
47
What happens if a terminating resistor isn’t working?
If one is missing communication will glitch. If both are missing communication will fail all together
48
J1939 terminating resistors have a value of?
120 ohms.
49
With two 120 ohm resistors hooked in parallel the total circuit resistance is?
60 ohms
50
When does signal corruption occur?
When electromagnetic force is induced into the data link
51
Is the data wire test performed with the key on or off?
Key on engine off
52
How do you test terminating resistors in j1930?
Can high to can low looking for 55-65 ohms
53
How do you test shield wire in j1939?
Shield bus (E) to good chassis ground looking for 0 ohms
54
ISO 11783 uses a how many wire backbone?
4
55
What terminates and validates the messages sent over j1587/j1708?
Checksum
56
Colour code for j1587/j1708 twisted pair wires?
Orange and white
57
When performing the can data wire test on j1939. What is the expected ohm reading?
1-4 M ohms

Electrical (1 decks)

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