Micro computer based process control Programmable logic controller
Micro computer based process control Programmable logic controller
CONTROL EQUIPMENT-Principles • Relay based system to electrical noise » DIGITAL LOGIC based • Computer based • PLC based complex functions speed or resistance
DIFFERENCE BETWEEN VARIOUS CONTROL EQUIPMENT • • Operating speed Physical size Capacity for complicated operations Ease of changing configuration Electrical noise immunity Installation Ease of maintenance Price for function
PLC-history`` • • 1970 -Electro mechanical relays 1968 -PLC-General motors company 1977 -Microprocessor based plc ALLEN BARDLEY –USA 8080 Micro processor 256 Bytes to Mega bytes PID Feed forward etc
Advantages
PLC selection
PLC architecture Selectorswitch proximity, Pilot light, horn, timer contact
Architecture details • • • Power supply I/O systems Real time CPU Memory unit Programmer unit Peripheral devices-
• Power supply • I/O Devices • Bcd, thumbl. RTD, TC, Flowmeters, strain gauges, pushbuttons, limit switch, electromechanical relay, registers, bcd, thumbwheel etc • Output-pilot lights, solenoidvalves, annunciatorwindows, displays,
• Programmer units: handheldunits, standalone crt units, pcs, • Peripheral devices: pc compatible software • Colur graphics, crt,
Basic structure
Plc programming • Ladder diagrams:
Ladder translation of plc programming
6 rung Ldder diagram
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