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### Transcript

• 1. Chapter 2 FUNDAMENTALS OF PLC PROGRAMMING Industrial Electronics DEK 3113
• 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.
• Type of graphic language automatic control systems.
• A drawing program of a switching circuit.
• 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 .
• 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
• 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.
• 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