Plc (analog and special io)

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Plc (analog and special io)

  1. 1. 1
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  5. 5. Conversion of an analog signal by a transmitter and transducer 5
  6. 6. Single-ended input 6
  7. 7. Differential inputs 7
  8. 8. ANALOG OUTPUT SIGNALS 8
  9. 9. 9
  10. 10. 10
  11. 11. Single-ended outputs 11
  12. 12. Differential outputs 12
  13. 13. Block diagram of bypass/control backup unit 13
  14. 14. The signal chain within a PLCy y(i) y(i) time time time analog filtering analog- 011011001111 digital- analog variable & sampling digital analog amplifier variable (e.g. 4..20mA) scaling converter converter e.g. -10V..10V 1 processing binary transistor binary variable filtering sampling or variable (e.g. 0..24V) 0001111 relay non-volatile counter memoryy time 14
  15. 15. 15
  16. 16. Special function I/O interfacesThey provide the link between programmablecontrollers and devices that require special types ofsignals.These special signals are not very common (only 5–10% of PLC applications).They are divided into two categories: • direct action interfaces • intelligent interfaces 16
  17. 17. Direct action I/O interface application 17
  18. 18. Intelligent I/O interface application 18
  19. 19. FAST-INPUT/PULSE STRETCHER MODULES•They detect input pulses of very short duration.•They operate as pulse stretchers, enabling the input signal toremain valid for one scan. 19
  20. 20. Wire input fault module diagramThey are special input interfaces designed to detect short-circuitor open-circuit connections between the module and inputdevices. 20
  21. 21. Fast-response interfaces•They are extensions of fast-input modules.•These interfaces detect fast inputs and respond with an output.•The speed at which this occurs can be as short as 1 msec fromthe sensing of the input to the output response.•The output response time is independent of the PLC processorand the scan time. 21
  22. 22. Weight input modulesThey are special types of analog interfaces designed to readdata from load cells. 22
  23. 23. THERMOCOUPLE INPUT MODULES 23
  24. 24. RTD INPUT MODULE 24
  25. 25. PID MODULESProportional-integral-derivative (PID) interfaces are used inprocess applications that require continuous closed-loopcontrol employing the PID algorithm. 25
  26. 26. Block diagram of the PID algorithm 26
  27. 27. Connection Diagram for AB 1771-PID module 27
  28. 28. POSITIONING INTERFACESThey are intelligent modules that provide position-relatedfeedback and control output in machine axis control applications. 28
  29. 29. Encoder/counter modules interfaceThey interface encoders and high-speed counter devices withprogrammable controllers.There are two types of encoder/counter interfaces:•Absolute encoders provide an angular measurement of the shaft.•Incremental encoders measure shaft rotation over distance byoutputting a fixed number of pulses per shaft rotation.The communication between the interface and the processor isbidirectional. The module accepts the preset value and othercontrol data from the processor and transmits values and statusdata to the PLC memory.The interface also lets the PLC know when the marker and limitswitch are both energized, indicating a home position. 29
  30. 30. 30
  31. 31. STEPPER MOTOR INTERFACES 31
  32. 32. Stepper motor with a position/velocity feedback scheme 32
  33. 33. SERVO MOTOR INTERFACES 33
  34. 34. Servo motor interface connection diagram 34
  35. 35. ASCII input/output interfaces•They send and receivealphanumeric data betweenperipheral equipment and thecontroller.•Typical peripheral devices includeprinters, video monitors, anddisplays.•The information exchange in eithertype of interface generally takesplace via an RS-232C, RS-422, RS-485, or a 20 mA current loopstandard communications link. 35
  36. 36. COMPUTER MODULES—BASIC modules•They also referred to as data-processing modules, areintelligent I/O interfaces capable of performingcomputational tasks without burdening the PLCprocessor’s computing time.•In contrast to other intelligent I/O interfaces, such asservo controls, a BASIC module does not actuallycommand or control specific field devices.•It complements the performance of the PLC system. 36
  37. 37. Network interface modulesThey allow a number of PLCs and other intelligent devices tocommunicate and pass PLC data over a high speed local areacommunication network. 37
  38. 38. 38
  39. 39. FUZZY LOGIC INTERFACES 39
  40. 40. 40
  41. 41. Data transfer between I/O modules and fuzzy module 41
  42. 42. SERIAL COMMUNICATION(a) Unidirectional,(b) half-duplex,(c) full-duplex. 42

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