Programmable Logic Controller and ladder logic programming

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Learn about Programmable Logic Controller and Ladder Logic Programming from the very basic level

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Programmable Logic Controller and ladder logic programming

  1. 1. Introduction to Programmable Logic Controllers and Ladder Logic
  2. 2. Welcome The purpose of this Presentation is to give you a very simple look Programmable Logic Controllers and its programming using Ladder Logic. There is no need for you to be familiar in any way with this field. The only requirement is that you enter with an open mind.
  3. 3. To begin with.. What is automation?
  4. 4. You may have come across the word “automated” very usually!
  5. 5. Automation is the use of machines, control systems and information technologies to monitor and control the production. In other words, an automated system is any system that require minimum or no human intervention.
  6. 6. Automation has made our life extremely simple.
  7. 7. Earlier, processes were carried out by operator, hence were much prone to human errors.
  8. 8. So we can imply that with Industrial control, factory automation, and PLC (if are done well), we can save a lot of time, materials, energy, and money.
  9. 9. Where do we begin?
  10. 10. Let’s recall the story of an explorer in Africa who asked the native tribesman,
  11. 11. How does one eat a huge animal like an elephant?" The tribesman looked at the explorer in astonishment and replied, "We eat it just like everything else, one bite at a time."
  12. 12. Simple as it is, industrial control is comprised of many smaller circuits. By exploring and learning simple smaller circuits, you can learn to build a complete automated system.
  13. 13. Programmable logic controllers Lets Start With… What is
  14. 14. a small computer with a built-in operating system which monitor inputs and other variable values, make decisions based on a stored program, and control outputs to automate a process or machine. Programmable logic controllers What is
  15. 15. Well, that was simple isn’t it ? Lets put it in another way..
  16. 16. A PLC is similar to a computer which is designed to be programmed once, and run repeatedly as needed.
  17. 17. Elements of PLC Let’s have al look at..
  18. 18. Input Modules Senses the input signal, isolates it and converts it to DC level.
  19. 19. Central Processor Unit (CPU) microprocessor system that contains the system memory and its decision making unit very similar to that of a computer’s CPU. Input Modules Senses the input signal, isolates it and converts it to DC level.
  20. 20. Output Module receives the convert control signals from the CPU and them converts them into digital or analog values that can be used to control various output devices. Central Processor Unit (CPU) microprocessor system that contains the system memory and its decision making unit very similar to that of a computer’s CPU. Input Modules Senses the input signal, isolates it and converts it to DC level.
  21. 21. Programming Device Personal computer or a Laptop And Communication Cable Output Module receives the convert control signals from the CPU and them converts them into digital or analog values that can be used to control various output devices. Central Processor Unit (CPU) microprocessor system that contains the system memory and its decision making unit very similar to that of a computer’s CPU. Input Modules Senses the input signal, isolates it and converts it to DC level.
  22. 22. PLC scan What is a
  23. 23. Reads Inputs Execute Programs Diagnostics & Communication Updates Outputs PLC scan
  24. 24. PLC scan
  25. 25. Programming PLC
  26. 26. The first and still most popular programming language used with PLC is Ladder Logic Programming (LAD).
  27. 27. They are called "ladder" diagrams because they resemble a ladder, with two vertical rails (supply power) and as many "rungs" (horizontal lines). The first and still most popular programming language used with PLC is Ladder Logic Programming (LAD).
  28. 28. Basic Ladder Logic Symbols Normally Open (NO) contact Passes power (on) when coil driving the contact is on. Contacts
  29. 29. Normally Closed (NC) contact Passes power (on) when coil driving the contact is off. Basic Ladder Logic Symbols Normally Open (NO) contact Passes power (on) when coil driving the contact is on. Contacts
  30. 30. Output or Coil When power flows through the Coils via contacts they are energized. Basic Ladder Logic Symbols
  31. 31. Schematic of ladder diagram
  32. 32. Selecting a PLC Criteria • Number of logical inputs and outputs. • Memory • Number of special I/O modules • Scan Time • Communications • Software
  33. 33. Functional Operation AND Operation OR Operation NOT Operation
  34. 34. Lets have a look at their truth table and Ladder Logic diagram
  35. 35. 35 AND Operation Both inputs S4 and S5 must be true (1) in order for the output L3 to be true (1). Ladder diagram
  36. 36. OR Operation Ladder diagram Either input S1 or S2 is true (1), or both are true, then the output L2 is true (1).
  37. 37. 37 NOT Operation If input S1 is be true (1), then the output L1 is true (0) or when A is (0), output C is 1. Ladder diagram
  38. 38. Programming Functions Timers Counters
  39. 39. Timers  On-Delay Timer (TON)  Off-Delay Timer (TOF)  Retentive On-Delay Timer (TONR)
  40. 40. Counters  Count UP Counter (CTU)  Count DOWN Counter (CDU)  Count UP/DOWN Counter (CTUD)
  41. 41. ProgrammingExamples Lets start with simple examples…
  42. 42. Programming Examples  D = (A AND B) OR C
  43. 43. Programming Examples Triggering the Relay Coil
  44. 44. Ladder Diagram for Triggering the Relay Coil
  45. 45. Learn the Basics of Programming Logic Controller & Ladder Logic by Downloading this E-book
  46. 46. This E-book contains Programmable logic controllers PLC Scan Basic Ladder Logic Symbols Functional Operation Programming Functions Programming To PLC (Practical Examples) Illustration of PLC Scan
  47. 47. For Further Reading Introduction to Programmable Logic Controller and Ladder Logic

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