Download PLC Fundamentals: Introduction, Architecture, and Applications and more Exams Advanced Education in PDF only on Docsity!
PLC Programmable Logic Controller New Study
Set 100% Verified!!
PC advantages
- lower initial cost - less proprietary hardware and software required - straightforward data exchange with other systems
- high-speed information processing
- easy modification
PLC specialized computer to control machine and process.
Relay Control Logic combinational logic in electrical control circuits by using several electrical relays wired in a particular configuration
PLC stores instructions and execute specific functions
- On/Off control
- timing
- counting
- sequencing
- arithmetic
- data handling.
Advantages of a PLC Control System (1) Eliminates much of the hard wiring that was associated with conventional relay control circuits.
Advantages of a PLC Control System 2 Increased Reliability: Once a program has been written and tested it can be downloaded to other PLCs. Advantages of a PLC Control System 4 lower costs compared to relay control logic Advantages of a PLC Control System 3 Programmable: It is more convenient to write and alter a program in a PLC compared to wiring and rewiring a circuit. End-users can alter the program at the site.
Advantages of a PLC Control System 5 Communications Capability: A PLC is able to communicate with other controllers or computer equipment.
Advantages of a PLC Control System 6 Faster Response Time: PLCs operate in real-time which means that an event taking place in the field will result in an operation or output taking place.
Advantages of a PLC Control System (7) Easier To Troubleshoot: PLCs have resident diagnostic and override functions that allows users to easily trace and correct software and hardware problems.
PLC Architecture Refers to the PLC hardware or software.
An open architecture connect easily to devices & programs made by other manufacturers. A closed architecture/proprietary system difficult to connect devices & programs made by other manufacturers. I/O Configurations
I/O Section Input/ Output Modules Comprise input modules and output modules. Forms the interface by which input/output field devices are connected to the controller The terms "field" and "real world"are used to distinguish actual external devices that exist and must be physically wired into the system. PLCs employ an optical isolator which uses light to electrically isolate the internal components from the input and output terminals.
A programmable logic controller (PLC) is a special ___________ designed to control machines and process. computer
A PLC system eliminates much of the hard wiring that was associated with conventional relay control circuits.
PLC control systems are more reliable and easier to troubleshoot than relay based control systems.
A PLC operates in real-time. True
A proprietary PLC system allows the system to be connected easily to devices made by other manufacturers.
The fixed I/O module configuration a. is the normal small PLCs units b. has no separate removable units c. is limited as to the availability of modules
At what point, in a PLC, is any decision making effected? processor module
The input interface module conditions the signal received from a field device.
The output interface module connects to Load devices such as lamps or solenoids
The programming device connected to the the controller
- while entering a program whii it is not monitoring a program.
Mixer motor to automatically stir the liquid in the vat when the temperature and pressure reach preset values.
The temperature and pressure sensor switches close their respective contacts when conditions reach their preset values
Motor starter coil is energized when both the pressure and temperature switches are closed or when the manual pushbutton is pressed
These devices are wired to the input module according to the manufacturer's labeling scheme
one cycle of this process completed
scan time
- duration required for a single complete cycle
- indicates the responsiveness of the PLC
O/1 is energized when contacts I/1 and. I/2 are closed or when contact I/3 is closed.
Either of these conditions provides a continuous path. from left to right across the rung that includes the coil.
The can be considered to represent a coil that, when energized, will close a set of contacts.
The change requires that the manual pushbutton control should be permitted to operate at any pressure but not unless the specified temperature setting has been reached.
If a PLC is used, no rewiring is required! The inputs and outputs are the same All that needs to be done is to modify the PLC program PLC vs PC same basic architecture PLC (PLC vs. PC)
- operates in the industrial environment
- is programmed in relay ladder logic
- has no keyboard, CD drive, monitor, or disk drive
- has communications ports, and terminals for input and output devices PC (PLC vs. PC) capable of executing many programs simultaneously in any order several vendors have software and interface cards which will enable a PC to act as a PLC
PLC Size Classification Criteria I/O count cost size
The control plan that resides inside the PLC is known as: program
This is how this symbol is used in a ladder logic diagram: can be interpreted as a normally open contact.
This symbol in a ladder logic diagram represents an imaginary coil that, when energized can close an output interface contact
Any change to a PLC program normally involves some change in wiring as well. True
"high" or "low", "on" or "off", "yes" or "no", and "1" or "0".
two-state binary concept applied to gates, can be the basis for making decisions
The gate is a device that has
one or more inputs with which
it will perform a logical decision
and produce a result at its
one output.
Logical AND
Used to only execute the following statement or block of statements if both conditions are true
Logical AND example
(eg.) The automotive high beam light can only be activated if light switch OR high beam switch is switched on.
OR Function Result or output Y and the input signals are A, B, C etc. Binary 1 represents positive signal or happening of an event while Binary 0 depicts the absence of the signal or non happening of the event. Logical OR
Used to execute the following statement or block of statements if one of the conditions are true
Logical OR example
The automotive high beam light can only be turned on when the light switch AND high beam switch are on.
AND Gate: The device has two or more inputs and one output
AND Gate: If any input is 0,
the output will be 0
