Chapter 2 ladder


Published on

Published in: Education
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Chapter 2 ladder

  1. 1. Chapter 2 FUNDAMENTALS OF PLC PROGRAMMING Industrial Electronics DEK 3113
  2. 2. Ladder Diagram <ul><li>Ladder diagrams are specialized schematics commonly used to document industrial control logic systems. </li></ul><ul><li>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. </li></ul><ul><li>Basic concept of this diagram is similar to the electrical wiring. However in ladder logic, the symbol has changed and been standardized. </li></ul>
  3. 3. Ladder Diagram cont.. <ul><li>Type of graphic language automatic control systems. </li></ul><ul><li>A drawing program of a switching circuit. </li></ul><ul><li>Called &quot;ladder&quot; 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 . </li></ul>
  4. 4. Ladder Diagram Operational Principle <ul><li>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. </li></ul><ul><li>On the left , we put all kinds of input . While on the right , we place all types of the outputs . </li></ul><ul><li>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. </li></ul>Input Interface Output +24V -0V
  5. 5. Ladder Diagram Symbols <ul><li>Ladder diagram uses standard symbols to represent the circuit components and functions found in a control system. </li></ul>
  6. 6. Example 1: Lamp circuit <ul><li>simple ladder diagram showing a lamp that is controlled by a hand switch </li></ul>
  7. 7. Normally Open Schematics (NO)-Input Schematics
  8. 8. Normally Closed Schematics (NC)-Input Schematics
  9. 9. Output Schematics
  10. 10. Logic Function <ul><li>There are 5 logic functions can be developed by combination of switches </li></ul><ul><ul><li>AND </li></ul></ul><ul><ul><li>OR </li></ul></ul><ul><ul><li>NOR </li></ul></ul><ul><ul><li>NAND </li></ul></ul><ul><ul><li>EX-OR (XOR) </li></ul></ul>
  11. 11. Logic Function…cont <ul><li>AND logic </li></ul><ul><li>coils is not energized unless both switch A and B closed. Fig. (b) represent for PLC input. </li></ul>
  12. 12. Logic Function…cont - AND
  13. 13. Logic Function…cont <ul><li>OR logic </li></ul><ul><li>Coils is not energized until either A or B closed </li></ul>
  14. 14. Logic Function…cont - OR <ul><li>DeMorgan's Theorem would predict: </li></ul>
  15. 15. Logic Function…cont <ul><li>NOR logic </li></ul><ul><li>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. </li></ul>
  16. 16. Logic Function…cont - NOR
  17. 17. Logic Function…cont <ul><li>NAND logic </li></ul><ul><li>There is no output when both A and B have an input </li></ul>
  18. 18. Logic Function…cont - NAND
  19. 19. Logic Function…cont - NOT
  20. 20. Logic Function…cont <ul><li>XOR logic </li></ul><ul><li>There is no output when both input 1 and 2 given. </li></ul>
  21. 21. Combination of AND , OR , and inverter (NOT) gates
  22. 22. Control Circuit <ul><li>Start stop circuit </li></ul>-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. 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. 24. Overload protection device <ul><li>There are several overload protection </li></ul><ul><li>device: </li></ul><ul><li>1) TOR: Thermal Overload Relay </li></ul><ul><li>-excess heat </li></ul><ul><li>2) CB: Circuit Breaker </li></ul><ul><li>-excess current </li></ul><ul><li>3) Fuse </li></ul><ul><li>-excess current </li></ul>
  25. 25. Control circuit has Overload Protection Device
  26. 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. 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. 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. 29. Two-Wire Control Circuit <ul><li>Used in application of automatic system. </li></ul><ul><li>Two wire used to provide voltage to load. </li></ul><ul><li>Applications: pump, heater or compressor. </li></ul><ul><li>Typically closed a disconnect switch or circuit breaker to energize the circuit. </li></ul><ul><li>An overload coils is located to protect the circuit against over current. </li></ul>
  30. 30. Thank You & Have A Nice Day