Intro to PLC's Flashcards
1
Q
T/F: Programmers can force an output action to operate after a worker has pushed in the E-stop button.
A
True
2
Q
What are the 4 sizes of PLC’s?
A
- ) Nano (Up to 32 I/O)
- ) Micro (32 to 128 I/O)
- ) Medium (128 to 960 I/O)
- ) Large (960 to thousands of I/O)
3
Q
How many Inputs/Outputs can a nano-sized PLC have?
A
Up to 32
4
Q
How many Inputs/Outputs can a micro-sized PLC have?
A
32 to 128
5
Q
How many Inputs/Outputs can a medium-sized PLC have?
A
128 to 960
6
Q
How many Inputs/Outputs can a large-sized PLC have?
A
960+
7
Q
T/F: PLC’s were first used in large industrial processes and machines.
A
True
8
Q
T/F: PLC’s are not used in commercial or residential applications.
A
False
9
Q
A ____ occurs when any body part becomes part of an electrical circuit.
A
Electric Shock
10
Q
T/F: All facilities have the same color code for different types of conductors/cables.
A
False, facilities will have their own code, which is important to know.
11
Q
T/F: PLC’s can control DC, AC, or both.
A
True
12
Q
____ grounding is the connection of an electrical system to the earth, and provides protection for the structure from lightning strikes.
A
Building Grounding
13
Q
____ grounding is the grounding of all machinery electrical systems and all non-current carrying exposed metal to earth.
A
Equipment Grounding
14
Q
____ grounding is establishing a quality ground to protect sensitive electronic equipment from electrical noise and fault currents.
A
Electronic Grounding
15
Q
The NEC states that the GEC (Grounding Electrode Conductor) should have less than __ Ohms to ground.
A
25
16
Q
T/F: The NEC states that the Electronic Grounding Conductor should have less than 5 Ohms to ground.
A
False, there is no code for grounding electronics, but it will usually be specified by the owner/engineer/manufacturer.
17
Q
T/F: Electronic Shield drains are always grounded on both sides.
A
False
18
Q
____ is an electrical charge at rest.
A
Static Electricity
19
Q
Usually, it takes no more than __ Volts to destroy a circuit board, which makes PLC’s so vulnerable to ESD.
A
5V
20
Q
The electronic ground (Shield Drain) is usually grounded at which end?
A
The end in the panel
21
Q
A snubber circuit utilizes a ____ to suppress voltage spikes by absorbing excess voltage, and dying.
A
MOV (Metal Oxide Varistor)
22
Q
All input devices can be put into two basic categories, ____ and ____.
A
Manual and Automatic
23
Q
What is the most common voltage for PLC Input terminals?
A
24V
24
Q
The ____ terminals of a PLC deliver voltage to any device or actuator controlled by the PLC.
A
Output
25
T/F: Input devices can be wired in any configuration.
True
26
T/F: Output devices can be wired in any configuration.
False, they cannot be wired in series.
27
How many Output devices can be displayed on each rung of a ladder diagram?
1
28
Can combination circuits be used for Input devices?
Yes, such as a 250 Ohm resistor between a 4-20mA system and a 1-5Vdc device.
29
Why is polarity important for both inputs and outputs?
Because reversed polarity can give you a negative reading, which creates issues for the PLC's logic and for actuation of outputs.
30
PNP, switched on the positive or negative side?
| Sinking or Sourcing?
Positive, Sourcing
31
NPN, switched on the positive or negative side?
| Sinking or Sourcing?
Negative, Sinking
32
T/F: PLC control voltages are based on what devices are to be connected to the PLC.
True
33
It is important that the ____ is installed in dual-voltage rated PLC's. (Or that the selection switch is in the correct position)
Jumper Link
34
A(n) ____ relay is a smaller relay (with a smaller control current) switching a larger load, such as power to a motor starter.
Interposing Relay
35
Why are common input voltage ratings on 12 or 24 volts?
Because they're safer to work on, and require less power.
36
T/F: Most larger PLC's have a variety of different cards.
True
37
What are some common Output voltage ratings?
- 12v
- 24v
- 50v
- 120
38
A ____ is the negative power supply terminal of a DC-powered PLC.
Sink
39
A ____ is the positive power supply teminal of a DC-powered PLC.
Source
40
____(s) are graphic representations of a device on a diagram.
Symbols or Glyph
41
____ symbols are drawn as very generic symbols, but with text describing the component.
PLC
42
"____" = Shelf State
Normally
43
A ____ drawing is literally a rendered picture of what the cabinet/device looks like.
Pictoral
44
A ____ shows the connection of all devices and components of a PLC.
Wiring Diagram
45
A ____ diagram has a series of single lines (rungs) that indicate the simplest representation of the control circuit logic.
Ladder
46
What is AND logic?
Two NO contacts in series, both must be closed to energize the load.
47
What is OR logic?
Two NO contacts in parallel, one must be closed to energize the load.
48
What is NOT logic?
One NC contact in series, powering the load, if the contact is opened, the load loses power.
49
What is NOR logic?
Two NC contacts in series, if either is opened, the load loses power.
50
What is NAND logic?
Two NC contacts in parallel, unless both are opened, the load will remain energized.
51
____ is when a device is wired point to point, with no use of terminals.
Direct Wiring
52
____ is when wires are brought to a terminal block, and from that block to its destination.
Terminal Wiring, this method makes it easier to trouble shoot or modify.
53
What are the 5 sections of a PLC?
1. ) Inputs (Terminal Screws receiving inputs)
2. ) Outputs (From CPU out to the devices instructed)
3. ) CPU (Makes decisions)
4. ) Power Supply
5. ) Programming Device
54
The CPU of a PLC makes decisions based on what two things?
Input from sensors/devices, and Programmed logic/parameters.
55
What is the common voltage of a PLC CPU?
5V
56
How long can a PLC power supply last on its own when power is shut off? (Hold Up Time)
10ms to 3 seconds
57
What are the 4 ways to program a PLC?
1. ) Integrated Buttons
2. ) HMI
3. ) Handheld Unit
4. ) PC (best)
58
What is the difference between volatile memory and nonvolatile memory?
Volatile is erased when power is lost.
59
What does RAM stand for?
Random Access Memory (Volatile)
60
T/F: The program being ran on a PLC is on its RAM.
True
61
What does EEPROM stand for?
Electrically Erasable Programmable Read-Only Memory
62
What is a bit?
The smallest unit of memory.
63
What is a Nibble?
4 Bits
64
What is a Byte?
8 Bits
65
What is a Word?
16 Bit
66
What is the 5 step operating-cycle of a PLC?
1. ) Input Scan
2. ) Program Scan
3. ) Output Scan
4. ) Service Communications
5. ) Housekeeping and Overhead
67
What are the two general types of files in PLC programming?
1. ) Program Files
| 2. ) Data Table Files
68
What are the 3 Program files we are concerned with?
File 0 - System File
File 1 - Reserved by the Processor
File 2 - Main Program File
(Files 3-255 are subroutines)
69
T/F: The first 9 Data Table files (0-8) are default files.
True
70
Which Data Table file cannot be added to, deleted, or changed in any way?
Status files (File 2) or "S" type files.
71
T/F: Nested branches cannot overlap.
True
72
What does XIC stand for?
Examine if Closed
73
What does XIO stand for?
Examine if Open
74
What does OTE stand for?
Output Energize
75
What do OTL and OTU stand for?
```
OTL = Output Latch
OTU = Output Unlatch
```
76
How do CPU's scan the program within a PLC?
From Top to Bottom, Left to Right
77
T/F: If you have parallel inputs, putting the path that is true most frequently on the bottom is fastest.
False, putting it on the top is fastest because the CPU reads from the top down.
78
What two ways are addresses labeled in the book?
1. ) Slot/Bit
| 2. ) Slot/Word/Bit
79
Can outputs be placed in series?
| Can they be placed in parallel?
Series - No (Only one per rung)
| Parallel - Yes
80
T/F: When timers are moved in the realm of programming, they are logic functions happening in the CPU, not actual devices.
True
81
What are the 3 types of timer functions?
1. ) TON (Timer On-Delay)
2. ) TOF (Timer Off-Delay)
3. ) RTO (Retentive)
82
```
Timer Instruction Words: What do they stand for?
EN
TT
DN
RES
CTU
CTD
```
1. ) Enable
2. ) Timer Timing
3. ) Done
4. ) Reset
5. ) Count Up
6. ) Count Down
83
The Count Up (CTU) and Count Down (CTD) Instructions are located in data table __.
5
84
What Timer instruction is missing?
- Timer Address
- Time Base
- Timer Preset
- _____
Time Accumulated
85
Timers are located in Data Table __.
4
86
T/F: If a timer is non-retentive, it will maintain its accumulated time if it loses power.
False
87
____ system of a building Transmits and Controls the movement of SOME form of energy.
Primary
88
What are the 4 building system types in the book?
| Besides Informational
1. ) Electrical
2. ) Electronic
3. ) Fluid Power
4. ) Mechanical
89
A ____ device is required any time a device is not directly compatible with a PLC.
Interface
90
A ____ system allows primary systems to work with and communicate with other building systems.
Interface
91
____'s are different from electromechanical relays in that they don't have coils or moving parts, and they use much less power.
SSR's
92
Electromechanical Relays have Coils and Contacts,
| SSR's have ____ and ____.
Inputs and Outputs
93
A ____ is a heavy-duty relay for switching high-power loads.
Contactor
94
A ____ is basically a contactor with overload protection.
Motor Starter
95
T/F: According to the book, Interface devices can change one voltage level to another.
True
96
When you receive your components for a PLC system from the supply house, and you are cross referencing to make sure you receive every part (and correct parts), what piece of documentation should you use?
The Purchase Order
97
T/F: It is not important to pay attention to spacing and temperature limitations when installing a PLC.
False
98
What are the 3 ways to terminate a PLC?
1. ) Direct Hardwire
2. ) Terminal Block
3. ) Interface Devices
99
T/F: Solid wire is used for wiring PLC's , in most installations.
False
100
____ and ____ connections should always be used with stranded wire.
Pin and Fork
101
What is the very first thing to do when performing a Visual inspection on a PLC?
Lock out the disconnect. For Safety
102
Maintaining a PLC is at its most basic level keeping the ____ and ____ issue free.
Hardware and Software
103
How often should PLC software be backed up?
| And generally inspected?
Annually
104
T/F: Anyone can work on any given PLC, because they are so simple.
False, certified and competent technicians only.
105
What are the two types of PLC maintenance inspections?
1. ) Visual Inspection (De-energized)
| 2. ) Energized Maintenance
106
What is the purpose of Energized Maintenance?
To verify that the Master Control Relay (MCR) is functioning correctly
107
T/F: The PLC will give a notification light when the battery voltage level falls below the threshold.
True
108
If the battery is located in the ____ card, you have to shut the PLC off to remove and replace it.
Processor
109
If the battery is located ____, you can change it while the PLC is running.
Behind the hinged door or cover of the PLC
110
When vacuuming any debris off of PLC components or anywhere near the PLC enclosure, it is important to use a(n) ____ safe vacuum.
ESD
111
What are the three TYPES of PLC status lights?
1. ) Input
2. ) Output
3. ) Operational
112
What are the 5 different Operational Status lights, located on the power supply/processor of a PLC?
1. ) Power
2. ) Run Mode
3. ) Forces
4. ) CPU Faults
5. ) Battery
113
What are the four IEC 1010 standard classifications of Electrical Test Instruments?
CAT I
CAT II
CAT IIII
CAT IV
114
When the CPU hits the ____ it will go back to the beginning of the program and keep only scanning to the ____ until it is removed.
TND
115
A voltage drop of more than _____ on the PLC output supply terminals indicates that they are overloaded.
5%
116
PLC power supply voltage should be within ____ of the rated voltage.
10%
117
A very short unwanted voltage.
Transient
118
A sustained increase in voltage by at least 10% for a more than 1 minute.
Overvoltage
119
A sustained decrease in voltage by at least 10% for a more than 1 minute.
Undervoltage
120
A sustained decrease in voltage by at least 10% for a less than 1 minute.
Sag
121
A sustained increase in voltage by at least 10% for a less than 1 minute.
Swell
122
Any Vacuum used on a PLC component must be ___
ESD safe vacuum
123
What steps must be taken to safely remove a battery mounted to the processor card of a PLC?
LOTO
Remove card
Change battery
124
When can a battery be changed on a running plc?
Only if the battery is located on the back of the door.
125
How do you know to change the PLC battery?
PLC will notify you if the battery charge drops below its threshold.
126
What are the 8 steps of energized maintenance?
1. ) Remove LOTO
2. ) Turn disconnect on
3. ) Open door
4. ) Verify that the machine or process won’t be started.
5. ) Test the MCR
6. ) Test and record incoming 3-phase voltage, and DC power supply voltage.
7. ) Verify cooling fans/units are working correctly
8. ) Check the PLC power supply and CPU indicator lights.
127
Energized maintenance is done for what reason?
To verify correct operation of MCR or safeties
128
What is the first step of visual inspection?
Look for damage. Just Damage. Damage.
129
What are the 8 steps of visual inspections?
- 1.) LOTO
0. ) Verify that power is off
1. ) Look for damage, physical or from heat
2. ) Air intakes and outlets for dirt, dust, and obstructions.
3. ) Cooling fans
4. ) PLC and its components for dirt and contaminants
5. ) Verify that the environment surrounding the enclosure hasn't changed
6. ) Inspect Input and Output devices.
7. ) Inspect the enclosure for damage or uncapped holes.
8. ) Tighten all connections
130
Who can perform inspections or maintenance on PLCs?
Certified Technicians Only
131
How often is maintenance performed on PLCs?
Annually. (remember this one)
132
Why is preventative maintenance necessary for PLCs?
To keep Hardware and Software issue free.
133
What are the two types of components you will have to maintain in a PLC?
Hardware and Software
134
Backups of _____ is necessary to keep for PLCs.
Program
