Programmable Logic Controllers Flashcards
Name some of the industries PLC’s can be found in:
Chemical and Petrochemical
Automobile manufacturing
Metal smelting and mining
Lumber, pulp and paper
Food and beverage production
PLC’s are usually selected according to the number of ______ and _______ _______ they can service.
Input and Output points
A control system of a PLC consists of:
Input devices - switches, thermostats
Controller - hard wired or software program
Output devices - relays, solenoids that control operating devices (pumps, fans, valves)
State the four main advantages of PLCS
L.E.R.P.
Lower overall cost
Expandability
Reliability
Programmability
Name the four main hardware components of a PLC:
Backplane
Power Supply
Processor (CPU)
Input/Output (I/O)
Does a PLC have to be a chassis connected to the backplane?
No, the backplane can be disassembled and assembled with or without a chassis.
A means is required for the CPU to communicate with other components and and to distribute power for internal operation. This is done through the _____________
Backplane
A PLC that is a complete unit is often called a ____ ____
Shoe box PLC
The 3 primary functions of a PLC processor are to:
Read and store the status of the input devices
Execute the user program by solving the program’s logic
Update the status of the output devices
The processor of a PLC carries out its functions in a sequence called the ______________ _____
Processor Scan
Whats does RAM, ROM and EEPROM stand for?
RAM
Random Access Memory
ROM
Read Only Memory
EEPROM
Electrically Erasable PROgrammable Memory
Name an example of an EEPROM device
USB
Memory Cards
Special I/O modules are used for a variety of control functions. Name an example:
Position Control
High Speed Counters
Temperature Controls
Proportional Integral Derivative Control (PID)
Fuzzy Logic Control
Identification Sensors (ID)
Analog I/O
Describe a data highway.
A data highway is a local area network (LAN) cabling that connects a number of PLCS, or PLCs and PCs, allowing them to exchange programs and data.
A Remote I/O is used to:
Reduce the amount of cabling between the PLC & I/O devices
Discrete input and output circuits are electrically isolated from the actual circuitry that is internal to the processor module and backplane of the PLC. This is most often done by ____________ _______
Optoisolating devices - inputs/outputs from discrete device changed into lightbeam by the input/output modules.
For output circuits that require large currents than can be handled by the solid state electronic switch, a relay coil is operated by the solid state switch instead. This relay is called an __________ _______
Interposing Relay
You may be required to install analog cables for analog input and output devices. The most common type of cable is:
Shielded Twisted Pair (STP)
Conductor size may be as small as #22 AWG
Name the five PLC programming languages,
And what two categories there are:
Graphics based -Ladder Diagrams (LD) , Function Block Diagrams (FBD) and Sequential Function (or flow) Chart (SFC)
Text based - Structured Text (ST) , Instruction Lists (IL)
The most common PLC programming language is:
Ladder Diagram
Function Block Diagrams are commonly used where in the world?
Europe
Sequential Function/Flow Charts are used for large-process controls where complex functions take place. T or F?
True
Hand-held PLC programmers at one time were commonly using what programs?
Text based programs
What PLC language is similar to the computer programming language called Basic?
Structured Text (ST)
Instruction List programs are similar to assembler language programs. T or F?
True
Discrete means…
Electrically Isolated
(Inputs and Outputs)
