1. 8.0 Programmable Logic Controllers 1
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2. Programmable Logic Controllers
Introduction/background
Connections
Architecture
Programming
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3. Books PLC Programming for Industrial Automation by Kevin Collins
ISBN
Programmable Logic Controllers
Festo basic level TP 301
Order number:093311
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4. 8.1 Introduction/background
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5. Background
The first Programmable Logic controller was developed about 1968 by engineers in General Motors
The original task of a PLC involved the interconnection of input signals according to a program and to switch the corresponding output
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6. Background The task that the PLC can perform has rapidly multiplied
The plc now performs the logic functions of relays, timers, counters and sequencers.
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7. Why use a PLC ?
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8. Why use a PLC ?
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9. Why use a PLC ?
Timer relays
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10. Applications of a PLC
PLC used to control a CNC lathe
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11. Introduction
A plc is a digital computer with multiple inputs and outputs.
Inputs are switches and sensors
Outputs are actuators (solenoids, motors, lights, alarms etc.)
Toshiba plcs

12. Operation of a PLC
Input
Processing
Output
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13. Operation of a PLC
Input
Processing
Output
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14. Introduction
Advantages
Low cost
Reliability
Reprogrammed

15. PLC Architecture Inputs Input Module CPU Output Module Outputs
Programming Input

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17. Input Modules
Provide an interface between switches or sensors and the plc.
Input module circuits have opto-isolators to protect the plc.
Opto-Isolator
LED
Photo-Transistor

18. PLC Architecture Inputs Input Module CPU Output Module Outputs
Programming Input
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19. Output Modules Output Module
Relay (Volt-free): Signal from plc operates relay.
Transistor: Faster but only for d.c. and low current devices.
Triacs:Used for a.c. devices. Must be protected against over-current.

20. Output Modules Relay Output
The power supply is connected to the output common port.
The solenoid, light, etc is connected to the output main port.
The plc switches the output on by internally connecting the common port to the output port.
Internal relay contact
plc
Common port
Output port
Power Supply (+)
solenoid

21. 8.2 Architecture
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23. PLC Architecture

24. Programming Methods Ladder Logic Sequential Function Chart (Grafcet)
Others
Statement List (mnemonics)
Logic Blocks
Grafcet

25. Ladder Logic
Inputs
n/o contact
n/c contact
Outputs

26. Ladder Logic Series input connection Parallel input connection Input 1

27. Ladder Logic Outputs can be connected in parallel But not in series

28. Ladder Logic
Series input connection
Input 1
Input 2
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29. Input 1
Input 2
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30. 8.3 PLC simulator
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31. PLC simulator
During the lab sessions we will use the Matsushita NIAS FP1-C14 plc, this plc has been adapted to allow for quick connections of both inputs and outputs.
Also a TRiLOGI plc simulator is available for download
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34. Trilogi Simulator
Open the plc Program Editor

35. Click on red arrow to get toolbar

36. Select normally open (n/o) input symbol.

37. Click on the blue bar to get the
Define Label Name dialog box

38. Call the input Start_Button or Start Button and press return.

39. Select another n/o contact and call it Stop Button

40. It appears in series with the Start Button contact

41. Clicking on the right hand box of the tool bar allows you to change the selected contact to n/c.

42. Trilogi Simulator
Now select an output and call it light

43. Trilogi Simulator

44. Trilogi Simulator

45. Highlight Start_Button again and select the parallel contact button.
Call the contact light and it will act as a latch for the light.

46. Click on the Simulate menu and select Run (All I/O Reset)

47. The two inputs and one output can be seen on the simulator.
Click on the Start_Button input to switch it on.

48. The output Light comes on and stays latched on, until the Stop_Button is pressed.

49. Ladder Logic
An output can also appear as a contact to the left of the ladder diagram

50. Ladder Logic
Similarly, in the example below, when Output one is off, Output 2 is on.

51. 8.4 Example
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52. PLC Inputs and Outputs
Note S3 is a normally open switch which is closed in the rest position ie. cylinder back Y1 Y2 Y3 X1 X4 X2 X3 S1 S2 S3 S4
N.O.
N.C.
N.O.
N.O. S4 S3 Y1

53. PLC Inputs and Outputs
Note S3 is a normally open switch which is closed in the rest position ie. cylinder back S1 S2 S3 S4
N.O.
N.C.
N.O.
N.O. S4 S3 Y1 Y1 Y2 Y3 X1 X4 X2 X3
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54. PLC Inputs and Outputs

55. PLC Inputs and Outputs
Note S3 is a normally open switch which is closed in the rest position ie. cylinder back Y1 Y2 Y3 X1 X4 X2 X3 S1 S2 S3 S4
N.O.
N.C.
N.O.
N.O. S4 S3 Y1
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56. PLC Inputs and Outputs
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57. PLC Inputs and Outputs 19/11/2018 Y1 Y2 Y3 X1 X4 X2 X3 S1 S2 S3 S4 S4

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59. PLC Inputs and Outputs 19/11/2018 Y1 Y2 Y3 X1 X4 X2 X3 S1 S2 S3 S4 S4

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61. PLC Inputs and Outputs 19/11/2018 S1 S2 S3 S4 S4 S3 Y1 Y1 Y2 Y3 X1 X4

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73. 8.5 Summary
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74. Summery History of plc controllers and an Introduction/background
Connections (how they are made)
Architecture (structure of a plc)
Programming (outline of ladder logic)
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75. END
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