programmable logic controller(plc)
DESCRIPTION
Programmable logic controller(plc)TRANSCRIPT
PROGRAMMABLE LOGIC PROGRAMMABLE LOGIC CONTROLLER(PLC)CONTROLLER(PLC)
CONTENTSCONTENTS
• RLCRLC• Ladder logicLadder logic• Disadvantages of RLCDisadvantages of RLC• PLC PLC • Its components Its components • Operation cycle Operation cycle • Information Flow Information Flow • Types Types • ManufacturersManufacturers
RELAY LOGIC CONTROLRELAY LOGIC CONTROL
• Before the invention of the Programmable Logic Controller (PLC), most industrial control was done using relay control panels.
• Relay logic is a method of controlling industrial electronic circuits by using relays and contacts..
• Switches and relays can be arranged in circuits to make logical decisions.
• It uses ladder logic.
LADDER LOGIC USING LINE LADDER LOGIC USING LINE DIAGRAM-1DIAGRAM-1
AND Logic
( )
X Y Z
( )
X
Y
Z
OR Logic
Problems with relay control panels
• Mechanical Relays and switches failed regularly (coil failure, contact wear and contamination, etc.)
• Difficult to diagnose problems and replace relays and switches
• Difficult to change hardwired logic (example: changing an “OR” circuit to “XOR”)
• Consumed a lot of power.
Architecture of PLCArchitecture of PLCProgramming
Device
Input/OutputSystem
OutputDevices
InputDevices
UserProgram
Data Storage
OutputTable
InputTable
What are What are PLC’s componentPLC’s component??
CR???????
Optical IsolationBarrier
Optical IsolationBarrier
CentralProcessor
MEMORYprogram data
Low Voltage
POWER SUPPLY
Output
Circuits
Input
Circuits
Programming / Communication Devices
Based on the data inthe output image filethe PLC energises or de-energises it’s outputcircuits,controllingexternal devices.
What' happens in an operating What' happens in an operating cycle?cycle?
1.Input Scan
2. ProgramScan
3. OutputScan
START
-- -
-
PLCOPERATING CYCLETYPICALLY 1 to 25 ms.
During the input scan PLC examines the external input devices -On or Off. The status of the inputs is temporarily stored in an input image memory file.
The PLC scans the instructions in the ladder logic program,uses the input status from the input image file & determines if an output willbe energised.The resulting status of the outputsis written to the output image memory file.
Information Flow…Information Flow…In
form
atio
nC
on
tro
l
InternetInternet
Modbus ASi
Ethernet TCP/IP
Ethernet TCP/IP
ServerWeb Server
&
Firewall
Switch/Router
BusX BusX
!!
!
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PLC-1FailureReport
Webcast
MANUFACTURERS-MANUFACTURERS-
• ModiconModicon
• Schneider ElectricSchneider Electric
• General ElectricGeneral Electric
• MitsubishiMitsubishi
• Allen BredleyAllen Bredley
• SeimensSeimens
Thank youThank you
BY-BY-
MUSTAHID MUSTAHID ALIALI