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Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
Chapter 2 ladder
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Chapter 2 ladder


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  • 1. Chapter 2 FUNDAMENTALS OF PLC PROGRAMMING Industrial Electronics DEK 3113
  • 2. Ladder Diagram
    • Ladder diagrams are specialized schematics commonly used to document industrial control logic systems.
    • It is a language or a method to create a program. The first PLCs were programmed with a technique that was based on relay logic wiring schematics.
    • Basic concept of this diagram is similar to the electrical wiring. However in ladder logic, the symbol has changed and been standardized.
  • 3. Ladder Diagram cont..
    • Type of graphic language automatic control systems.
    • A drawing program of a switching circuit.
    • Called "ladder" diagrams because they resemble a ladder, with two vertical lines representing the power trails (supply power) and circuits are connected in horizontal lines called rungs. Connection between the element in the rung called link .
  • 4. Ladder Diagram Operational Principle
    • Referring to figure below, between these two rails, a horizontal straight line was drawn with two symbols . These two symbols refer to the input and output devices , which are used in the actual process/system.
    • On the left , we put all kinds of input . While on the right , we place all types of the outputs .
    • Once we complete one line of the program it seems like a ladder. This horizontal line which places the input and output make one rung.
    Input Interface Output +24V -0V
  • 5. Ladder Diagram Symbols
    • Ladder diagram uses standard symbols to represent the circuit components and functions found in a control system.
  • 6. Example 1: Lamp circuit
    • simple ladder diagram showing a lamp that is controlled by a hand switch
  • 7. Normally Open Schematics (NO)-Input Schematics
  • 8. Normally Closed Schematics (NC)-Input Schematics
  • 9. Output Schematics
  • 10. Logic Function
    • There are 5 logic functions can be developed by combination of switches
      • AND
      • OR
      • NOR
      • NAND
      • EX-OR (XOR)
  • 11. Logic Function…cont
    • AND logic
    • coils is not energized unless both switch A and B closed. Fig. (b) represent for PLC input.
  • 12. Logic Function…cont - AND
  • 13. Logic Function…cont
    • OR logic
    • Coils is not energized until either A or B closed
  • 14. Logic Function…cont - OR
    • DeMorgan's Theorem would predict:
  • 15. Logic Function…cont
    • NOR logic
    • Since there has to be an output when neither A nor B have an input, and when there is an input either A or B.
  • 16. Logic Function…cont - NOR
  • 17. Logic Function…cont
    • NAND logic
    • There is no output when both A and B have an input
  • 18. Logic Function…cont - NAND
  • 19. Logic Function…cont - NOT
  • 20. Logic Function…cont
    • XOR logic
    • There is no output when both input 1 and 2 given.
  • 21. Combination of AND , OR , and inverter (NOT) gates
  • 22. Control Circuit
    • Start stop circuit
    -PB is pressed, output IR is activated -IR contact will closed -When PB is depressed, the output IR is still activated since current can go through contact IR unless is disturbed by stop button.
  • 23. Vibrating/Jog circuit -When, PB is pressed, output IR is activated. -But after several microsecond, the normally closed IR is open then will stop the output IR. -This applicable to move an object which need to locate at precise location.
  • 24. Overload protection device
    • There are several overload protection
    • device:
    • 1) TOR: Thermal Overload Relay
    • -excess heat
    • 2) CB: Circuit Breaker
    • -excess current
    • 3) Fuse
    • -excess current
  • 25. Control circuit has Overload Protection Device
  • 26. Control circuit in ladder diagram. -When PB is pushed(forward/reverse),motor will move according to the command. -But, when there is an overcurrent,CB will stop the current flow by blow the fuse. -Means, NC of CB will open and stop the current flow to the circuit. -The circuit can be recovered by change the fuse. -If there is thermal overload, TOR will cut the current flow. -Lamp,L3 will turn on and TOR need to be reset.
  • 27. Two wire control -only has one contact for switching device either ON or OFF state. -When ON state, M will energize and activate three phase motor. -Heater will heat if there is over current and open the circuit.
  • 28. Three wire control -the connection almost the same as two wire circuit except has an extra set of contact connected in parallel as the pilot switch. -this extra contact provide extra third wire. -this auxiliary contact keep coil M energize even after start push button release.
  • 29. Two-Wire Control Circuit
    • Used in application of automatic system.
    • Two wire used to provide voltage to load.
    • Applications: pump, heater or compressor.
    • Typically closed a disconnect switch or circuit breaker to energize the circuit.
    • An overload coils is located to protect the circuit against over current.
  • 30. Thank You & Have A Nice Day