Plc Flashcards by Benjamin Dunlop

Where and what kind of field were plcs first used and what were they called

GM
Automotive
Modicon

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Plcs are programmed using ____________ ladder __________.

Relay ladder logic

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Plcs can typically run _____________ programs at a time

One

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T/F relay ladder logic is the same as motor control ladder schematics.

False

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Plcs also include communications for _____________/_________/________________.

Internet/wifi/programming devices

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What are the basic parts of a Plc.

-input module
-isolations
-cpu
-power supply (battery backup?)
-programming device
-output module

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What could a programming device be?

-remote
-pc
-laptop
-phone?
-programming pack

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What kind of isolators are typically used in plcs

Opto-isolators

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T/F there is electrical connection between input module-cpu-output module

False

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Advantages of a Plc

-robust power
-reliable in high electric noise areas
-lots of various I/I voltage combinations
-low power pilot devices like pb’s and limit sw
-led indicators on input and output modules
-work in wide range of temperatures
-reduced use of electromechanical relays.

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Memory structure of a Plc

Executive
Scratch pad
Data tables
User program

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Which parts of the memory structure are part of the system memory (firmware like bios)

Executive
Scratch pad

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Which parts of the memory structure is part of the application memory

Data tables
User program

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One word equals ___ bits

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___ bits make a byte

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___ bits make a nibble

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Data tables includes what?

Bits
Timers
Counters
Input image
Output image

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Scanning includes

Reading inputs
Executing program
Updating outputs

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Scan time depends on what

Number of inputs and outputs
Program length
Types of instructions

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In a block from how does the scanning process look

Read input image table

Solve program logic

Update output image table

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Scan time in the 1990’s was around
______msec

100

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Scan time in the 2000’s was ______msec

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Scan time in the 2010’s ______msec

5-20

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Scan time in the 2020’s was improved to about _______msec

1-20

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Inputs can be ___________ which means on/off

Descreet

What is another word for a discreet input

Digital

Inputs can be ______ or _____

Ac or DC

Common input voltages are

24vac, 24vdc, 10-60vdc, 5vdc 120vac etc

Inputs can also be ___________ which is variable

Analog

Common variable input values are

4-20mA, 1-5vdc, 0-10vdc etc

Analog input modules have a __________ to ____________ converter and give a __________ value out.

Analog to digital Binary

Outputs are usually ______________

Discreet or digital

Outputs can be _____ or ______ or ___________ outputs

Ac DC Relay outputs

Relay outputs are also known as ____________ or ___________

Potential free or dry contacts

Ac outputs typically use a ___________ for switching

Triac

Triac (AC) have about a ____A max

Triac outputs have a small ________________ when off, which may activate small high impedance output devices. Why is this bad?

Leakage current It's dangerous(could be voltage when not expected )

_______________ relays or ____________ resistor can be used to prevent the leakage current in a triac output

Interposing Burden

Analog output modules use a ____________ to ____________ converter to convert a _____________ value into a 4-20mA, 1-5vdc etc signal

Digital to analog (DAC) Binary

1 word is 2^15 which would have ______________ distinct levels

32,768

If current is flowing from a switch to the output device: The switch is ______________ The output is ______________

Sourcing Sinking

If current is flowing from the output device to a switch then: The switch is. _______________ And the output is _______________

Sinking Sourcing

--------] [----------- this is a?

Examine if on instruction

-----]/[----- this is a?

Examine if off instruction

An examine if on instruction is looking for a ___ if it has one the instruction will be ______

1 True

An examine if off instruction is looking for a ___ if it has one the instruction is ______

0 True

Plc logic scans from ________ to ________ And _________ to ___________.

Left to right Top to bottom

-----( )----- this is a?

Out put instruction

What are these called I:0.0/00 ^^ ^ ^ 12 3 4

#1 input #2 slot # #3 word# #4 bit#

An internal bit is essentially a ___________ coil

Virtual

Internal bits are _____________

Registers ( little memory places)

Internal bits are used for ____________

One shots

Internal bits are updated ___________ the logic and not _______________

During At the end of scan

Internal bits will be on ________________ scan.

Every other

What instruction will set an output on even if the logic in the rung becomes false

Latch

What instruction remains true even in the even of a power outage

Latch

A latched output will only become false when the ____________ is true

The unlatch output

A _______ is an input instruction that will be true for one scan only.

Osr

Osr stand for

One shot rising

When the prior input instructions are true the osr will be true for __________________.

One scan only

An osr is placed in a ring after other _________________________.

Trigger input instructions

The output instruction of an osr will only be true for the ______________________.

Duration of the scan

Applications of an osr

Incrementing speed of a motor equally with one press of a button Capturing a fast computer which otherwise would be unreadable

Fusing for a plcs output must be _____________

External

If you needed to switch a load with a voltage higher than the output voltage of the Plc what would you use

Interposing relay

What are the different kind of power supply that can be applied to a Plc from okay to best (5)

Raw power Isolating transformer Voltage regulating transformer Conditioned power Uninterruptible power supply

______________ voltages have less effect on current type inputs

Transient

______________ input wiring for sensors reduces I'll effects of EMI and RFI

Shielded

For shielded input wiring the bonding must be only __________________

Connected on one end of the shield

________________ is critical for sensitive signals

Good bonding

_______________ uses very large conductors

Brute force

A _____________ retains the accumulated value when the timer is done

RTO

A RTO must have a __________ instruction addressed to it

Reset

Applications for an RTO

Track the running time of a motor for maintenance Runtime counter for a back up generator

A counter or timer reset is not used for which kind

TOF

OV is when

But=1 When accumulated is greater than preset

In is when

Bit=1 When accumulated is less than ∅

Input devices for fail safe operation should not be wired ________ they should be ______ or in some cases ___________

No Nc Nohc

A twisted conductor will have _____ the voltage on each conductor

1/2

A locap conductor with a line and a return is considered

Unbalanced