PLC
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.