PLC

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Sequence

A series of actions required to be taken to achieve a specific outcome, arranged in an orderly fashion.

Producer Tag

A tag that a controller makes available for use by other controllers.

Consumer Tag

A tag that receives the data of a producing tag.

Six Logic Elements

AND, OR,NOT,NAND,NOR, and Memory

ACC

Accumulative Value

Power Distribution Failures Show One of Two Symptoms:

All PLC Indicators are off and No Output devices will energize.

Active High Input Module

An input module that's terminals are true when a voltage is applied to them.

Active Low Input Module

An input module that's terminals are true when a voltage is not applied to them.

From BCD Instruction

An internal output instruction that converts a BCD value, such as an input tag, into a decimal equivalent of the BCD value and stores it at another word or element (memory location).

Reset Instruction

An output instruction that resets timer instructions having the same tag name.

Output Latch Instruction (OTL)

An output instruction, similar to OTE instruction in that it writes a 1 to the output tag when the rung is true. The output tag remains a 1 when the rung is false.

PLC Timer Instructions

Are internal output instructions used to provide time-based control logic.

PLC Applications

Assembly machines, automatic transfer lines, packing lines, robots

Five Atomic Data Types

BOOL, SINT, INT,DINT, REAL

FRD

From BCD Instruction

GSV

Get System Value Instruction

Five Types of Numbering Systems

Hexadecimal, Decimal, Binary, Octal, Binary Coded Decimal (BCD)

OTL

Output Latch

OV

Over Value

Test Mode

PLC programming mode that allows the user to test program operation without energizing outputs.

Three methods of entering a PLC project

Personal Computer SD Card Handheld Terminal

PRE

Preset Value

Seven Types of PLC Faults

Process Hardware, Processor Programs, Power Supply, I/O Chassis, I/O Modules, I/O Devices, Controller Networks

Four Diagnostic Indicators

Processor module indicators, Discrete input module indicators, Discrete output module indicators, chassis power supply indicators.

Energy Storage Module (ESM)

Provides backup power to transfer the program and status data from working memory to the nonvolatile memory on power loss.

Initializing

Puts all outputs into startup state and checks inputs to verify that the process can safely be restarted.

Three Types of Surge Suppressors

RC Network, Metal-oxide Varistor (MOV), Diode (DC outputs only)

PLC Timer Instruction Applications

Reduced voltage starting, plastics injection molding

Logic Nesting

Refers to program logic that places one branch circuit inside another.

Preset Value

Represents the length of time the timer instruction must be enabled for the instruction to set.

RES

Reset Instruction

RTO

Retentive Timer On

Two classifications of PLC Timers:

Retentive and Non-Retentive

Basic Operation of a PLC

Scan instructions, monitor the status of inputs, produce outputs based on the status of inputs.

Input Modules

Sense the condition of real-world devices and transmit this information to the PLC's processor module.

Interlocks are used in two applications:

Sequencing and Safety

Three Applications Given Output Address

Sequencing operation, simultaneous operation of more than one output, motor control programs

PLC Programming Languages

Sequential Function Chart, Structured Text, Functional Block Diagram, Ladder Logic

Done Bit

Sets when the instruction tag's accumulated value is equal to the preset value.

Under Value Bit

This bit is set when a count down instruction tag's accumulated value rolls over from its smallest negative value of -2 billion to +2 billion.

Count Down Bit

This bit is set when the rung controlling a count down instruction is true and reset when the rung is false or overridden by a RES instruction.

Count Up Bit

This bit is set when the rung controlling an up counter is true and reset when the rung is false or overridden by the RES instruction.

First Scan Flag

This flag is set during the first normal scan of the routines in the current program.

Control Zone

This zone lies between the MCR Rung and END MCR Rung. This zone determines which rungs are to be controlled by the MCR instruction.

TOF

Tiimer Off-Delay

TON

Timer On-Delay Instruction

TT

Timer Timing Bit

Non-Retentive Timers

Timer instructions that accumulate the total amount of time the instruction has been energized and does not retain this value when the instruction is off

Retentive Timers

Timer instructions that accumulate the total amount of time the instruction has been energized and retains this value even when it's off.

S:FS

First Scan Flag

JMP

Jump Instruction

JSR

Jump to Subroutine Instruction

MCR (instruction)

Master Control Reset Instruction

Nonvolatile Memory

Memory that won't reset when power is lost.

S:Minor

Minor Fault Flag

MOV

Move instruction

PLC Loading Conditions

On Power Up (Automatic), On uninitialized memory (automatic), User Initiated

Direct Control

When the motor is directly connected to the output module.

Output Unlatch Instruction (OTU)

Writes a 0 to the OTL instruction when the rung is true.

Action (sequence)

a step in a sequence

RSLinx

A collection of drivers to connect programming software in the PC to Allen-Bradley controllers such as ControlLogix.

Routine

A collection of logic instructions in one programming language that provides the operating instructions for the controller.

Array

A collection of numerically indexed tags containing related data and arranged in consecutive locations in the controller.

Move Instruction

A data transfer instruction that is used to copy data contained in one tag to another tag.

Interlocking

A method of using logic in a PLC program to cause an output to turn on or off if certain inputs or outputs are in a particular state.

Attributes

A name, property, parameter, or value for the device to which the object data applies

Who Active

A network search utility that shows the layout of every network that has a driver configured for RSLinx.

Jump to Subroutine Instruction

A program control instruction that causes the processor to run subroutine files.

Jump Instruction

A program control instruction that, when energized, causes the processor to jump over rungs of ladder logic The outputs of jumped rungs are frozen in their last state.

Subroutine

A program that can be executed by another routine.

Event Driven Sequence

A sequence that uses an input device of some type to sense that one step has been completed and signal the next step to begin. Logic is then used in the PLC to cause each step to occur by turning output devices on and off.

Pre-Defined Data Tags

Commonly used data types that Studio 5000 provides in the software as a convenience to users.

MCR Rung

Component of an MCR instruction that determines when the MCR zone is enabled and marks the beginning of the MCR instruction's control zone.

END MCR Rung

Component of an MCR instruction that marks the end of the MCR instruction's control zone.

Signaling

Connecting the PLC inputs to a machines outputs and the machines inputs to the PLC outputs

Input Par

Contains a program constant or tag of a parameter to be sent to the subroutine. Allows the user to pass values for the Main Routine to subroutines.

Routine

Contains the actual operating instruction (or executed code) that determines the operation of the controller.

Master Control Relay

Control Relay circuit that is used to provide control power to the system's output devices.

CD

Count Down Bit

CTD

Count Down Instruction

CU

Count Up Bit

CTU

Count Up Instruction

Three Common Stop Functions

Cycle-stop, halt, fail-safe emergency stop

Single Cycle Program

Cycles once each time the operator presses the start pushbutton.

Objects

Data structures used to store status and identifying data about the controller and its operation, hardware, and program.

User-Defined Data Tag

Data types created by a user.

Return Par

Defines a tag which data calculated in a subroutine is returned to the Main Routine.

PLC Output Can Control a Motor Two Ways:

Direct and Indirect Control

Accumulated Value

Displays the actual time that the timer instruction has been enabled.

DN

Done Bit

EN

Enable Bit

Timer Timing Bit

Indicates that a timing operation is in progress. Sets when the timer instruction is enabled.

Enable Bit

Indicates that the timer instruction is enables. This bit is set when the timer instruction rung is true and reset when either the instruction goes false or a Reset Instruction resets the timer.

Programmable Logic Controller

Industrial computers that control machines and other industrial applications.

Discrete Input Device

Input devices that have two discrete conditions, on or off.

Basic components of PLC's

Input modules, output modules, processor modules, PLC Power Supply, Programming Device, I/O Chassis

Label Instruction

Instruction that are used with the Jump instruction and defines the destination of the processor jump.

Master Control Reset Instruction

Instruction that controls a zone of a PLC program rungs. When true the zone is active. When false the zone is inactive.

Get System Value Instruction

Instruction that gathers an object's attribute data and puts it in a user-created tag of the same data type.

Count Up Instruction

Instruction that increases the instruction tag's accumulated value by one each time the rung containing the instruction goes from false to true.

Retentive Timer On (RTO)

Instruction that increases the value stored in the tag's accumulated value by the amount of time the instruction is true.

Set System Value Instruction

Instruction that is used to change the controller system data in an object.

Count Down Instruction

Instruction the decreases the instruction tag's accumulated value by one each time the rung containing the instruction goes from false to true.

Timer Off-Delay

Instruction used to turn outputs on or off after the timer has been disabled.

Timer On-Delay Instruction

Instruction used to turn outputs on or off after the timer has been enabled, or on, for a preset time.

Program Controller Instructions

Instructions that are used to alter the program scan of a PLC from its normal sequence.

Data Transfer Instructions

Instructions which are used to change the preset (PRE) value of a timer without having to edit the program.

Minor Fault Flag

Is set when program execution generates a minor fault in the process.

Surge Suppressors are sometimes called:

Snubbers

Communication Driver

Software programs that connect software to hardware.

Cycle Stop Function

Stop function that causes the machine to stop after the machine finishes its last step in its cycle.

Halt Function

Stop function that causes the machine to stop immediately after finishing its current step. Resume operation beginning with the next step when a start signal is received.

Controller Status Flags

Store status information about the operating condition of the controller, similar to controller objects. The can be directly accessed by the user as a tag instead of an instruction.

Module-Defined Data Tag

Tags that are automatically assigned when a module is added to a ControlLogix project

Tag

Text-based names given to PLC memory locations.

Radix

The number system base.

RC Network

The simplest form of surge suppressor is a capacitor and resistor in series across the coil .

Continuous Cycle Program

The start/stop pushbuttons control an internal coil instruction, which in turn, starts and stops the sequence.

The Timer Timing Bit resets when:

The timer is de-energized, the Done Bit is set, a Reset instruction resets the Timer.

Time-Driven Sequencing

The use of timers and limit switches to sequence events.

Considerations When Selecting Input Modules

Types of current, level of voltage, number of inputs, active high or active low.

Serial Communication

Used to communicate and exchange data electronically.

Indirect Control

Uses a set of relay contacts that separate he PLC's control electricity from the electricity that drives the motor.


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