Programmable logic controller(plc)


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Programmable logic controller(plc)

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  • The above slide illustrates the different compartments of a PLC. Explain the different types of input devices, output devices and how the information is stored in the PLC.
  • Input scan examines the external devices. The status of the inputs is temporarily stored in an input image memory file
  • Programmable logic controller(plc)

    2. 2. CONTENTS • • • • • • • • • RLC Ladder logic Disadvantages of RLC PLC Its components Operation cycle Information Flow Types Manufacturers
    3. 3. RELAY 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.
    4. 4. LADDER LOGIC USING LINE DIAGRAM-1 AND Logic X Y Z ( ) OR Logic X Z ( Y )
    5. 5. 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.
    6. 6. Architecture of PLC Programming Device Input Table User Program Output Table Data Storage Input Devices Input/Output System Output Devices
    7. 7. What are PLC’s component? Programming / Communication Devices I n p u t Optical Isolation Barrier C i r c u i t s Central Processor MEMORY program data Low Voltage POWER SUPPLY O u t p u t C i r c u i t s CR??????? Optical Isolation Barrier
    8. 8. What' happens in an operating START cycle? 1.Input 3. Output Scan Based on the data in the output image file the PLC energises or de-energises it’s output circuits,controlling external devices. - -PLC OPERATING CYCLE TYPICALLY 1 to 25 ms. 2. Program Scan Scan 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 will be energised.The resulting status of the outputs is written to the output image memory file.
    9. 9. Information Information Flow… Internet Internet Webcast Server Web Server & Firewall Email from PLC-1 Failure Report Ethernet TCP/IP ! Switch/Router ! Control Ethernet TCP/IP Modbus ! ASi BusX BusX
    10. 10. MANUFACTURERS• • • • • • Modicon Schneider Electric General Electric Mitsubishi Allen Bredley Seimens
    11. 11. Thank you ALI BYMUSTAHID
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