2. Basics of PLC Programming EE 100 – Intro to EE Fall 2004 Dr. Stephen Williams, P.E.

3. Overview  How did we get where we are today?  How does a project at GM in 1968 relate to the work of Henry Leland in the late 1800s? Ford Drive Sensor GM Autos Bus AB SLC PLC

4. Vocabulary  Programmable Logic Controllers  Definite-purpose computers design to control industrial processes and machines  Drives  Solid-state devices designed to control motors  Sensors  Transducers used to obtain information

5. First Programmable Controller  General Motors Corporation  Hydromatic Division  Replaced relay-controlled system  PDP-8 minicomputers?  MODICON 084  Modular Digital Controller

6. Information Flow

7. Genesis of Automation  Operation sheets  May date back to the 1830s  Listing of:  All machining operations  The machine tools employed  Tools, jigs, fixtures, and gauges  Organization and flow of work

8. Industrial Revolution  High-volume production  Interchangeable parts  Transportation system  Inexpensive energy (coal)  Frederick W. Taylor  Scientific management Scientific management  Henry Ford

9. Purpose of Automation  Increase productivity  Standardize components or processes  Free workers from repetitive, and sometime dangerous, tasks

10. Early Automation Applications  1869 – Refineries in Pennsylvania automatically covert crude oil to kerosene  1937 – Pictured is the loading and unloading of stators via an overhead conveyor for dipping in continuous process oven

11. The Case Against Automation  Las Vegas Sun, August 2, 1961  Jimmy Hoffa saw a new industrial revolution forming with automation being a threat to his giant union more menacing than the Justice Department, Attorney General Bobby Kennedy and the president himself.  He felt he could cope with the Senate committees, the FBI, and all the new legislation being written, which he thinks is aimed at unionism. It is with automation that all his talents, energy and ability must be directed.

12. Forces Driving Automation  Lower costs  Faster production  Better quality control  How have they remained relevant today?

13. Engineering Resources  Why do you need all of these engineers running around to make all of this stuff work?

14. Breakthroughs and Plateaus  Where have we seen breakthroughs, and then plateaus of technology?  Microprocessors  Graphical User Interfaces  Power Electronics  Software Systems

15. Brief Review of Technology  Traditional (ancient?) devices  Still used in many plants  If it ain’t broke …  Where are we going?

16. Traditional Relay Logic  Used since …  Control via a series of relay contacts  On and off inputs  Race conditions on the outputs  Very expensive  Hard to design and construct  Difficult to maintain

17. Traditional Devices  Relays  Contactors  Motor Starters  Manually operated switches  Mechanically operated switches  Electrically operated switches

18. Relays  Original control elements  Now used as auxiliary devices  The PLC is not designed to switch high currents or voltages

19. Contactors  Used for heavy-duty switching  Provides isolation from high voltages and large currents  Usefully for large inductive currents, such as motor starting

20. Motor Starters  Contactors + Overload Relay  Overload relays were usually heaters and bimetal strips  The bimetal strip separates when heated  Next steps:  PLCs and motor starters  Electronic overloads  Intelligent starters

21. Manually Operated Switches  Pushbuttons  Normally open  Normally closed  Break-then-make  Make-then-break  Selector switches  Maintained or spring return

22. Mechanically Operated Switches  Limit Switches  Temperature Switches  Pressure Switches  Level Switches

23. Electrically Operated Switches  Photoelectric Switches  Proximity Switches

24. What's ahead?  Solid state devices to replace motor starters  Distributed smart sensors  Micro- and nanomachines  Adaptive control  Smart maintenance

25. Summary  A very brief history of industrial automation  Overview of some of the older technologies  Some thoughts on the future

26. PLC Systems  CPU  Processor  Memory  One Module  Power Supply  Part of the chassis or a separate module  Programming/ Monitoring Device  I/0 Modules

27. Small Logic Controllers

28. Input and Output  Input Modules  Convert “real world” signal to PLC input  24 V, 120 V, Analog, etc.  Output Modules  Convert PLC signal to “real world” output  24 V, 120 V, Analog, etc.  Limiting values  PLC power supply

29. Configurations  Fixed I/O  Limited expandability  Rack  Many modules, with the possibility of chaining many racks together  SLC 500 is a fixed I/O device  SLC 5/02 uses a rack configuration

30. Chassis Versus Rack  One “Rack” is 128 inputs/outputs  A chassis is the outer shell of the PLC  Chassis ≠ Rack  SLC 5/02’s in S-340 have a ten-slot chassis  Slots are numbered from 0 to 9

31. SLC Image Tables  Hex numbering  Addressing  I1:2.0/01  I is for the file type  1 is the file number  2 is the element number .0 is the sub-element number (>16)  /01 is the bit number

32. “Real World” Address  I1:3.0/01  I is the module type  1 is redundant  3 is the slot number .0 is for terminals above 15  /01 is the terminal number

33. Remote Racks  I/O racks located close to the equipment being monitored  Simplifies wiring  Communication modules  Similar to LAN  Fiber Optic  Coaxial cable

34. Discrete I/O Modules  Either “on” or “off”  Bit oriented  Various ratings  24 V  120 V  TTL  4 – 20 mA

35. Special I/O Modules  Analog  High speed counter  Thumb-wheel  TTL  Encoder  PID  Servo

36. Memory Organization  Not the same on all manufactures  Allen Bradley uses two main types  Memory Maps  Data table  User program  Internal registers  Memory allocation could be fixed or variable

37. SLC Program File Structure Program File Number Use 0System Functions 1Reserved 2Main Program 3-255Subroutines

38. RSLogix 500 Screen  Define controller attributes  Model  Memory  Communication  Program files  Main program  Subprograms

39. SLC Data File Structure Data File Number Use 0Output Image Table 1Input Image Table 2Status Table 3Bit Table

40. SLC Data File Structure Data File Number Use 4Timer Table 5Counter Table 6Control Table 7Integer Table

41. SLC Data File Structure Data File Number Use 8Reserved (Floating Point Value Table) 9Network Table 10-255Any combination of Bit, Timer, Counter, Control, or Integer Tables

42. RSLogix 500 Screen  Access to input and output tables  Access to timer and control control files

43. Address Format  What type of device or module  Where is it located physically or in memory  For example, T4:0/DN is the done bit for timer 0 in file 4  I:2.0 is an input module in slot 2  Word versus bit addresses  I:3.0 is a word, I:3.0/04 is a bit

44. Multiword Elements  Timers, counters, and control elements  Three words used  Control word to store status  Preset word to store desired value  Accumulated word to store present value  Control file store a length and position value (on functions other than counters and timers)

45. Counter Element Example NameAddressExample Control WordC5:0C5:0/DN Preset WordC5:0.PRE5000 Accumulated Word C5:0.ACC1240

46. RSLogix 500 Screen  Counter C5:0

47. Program Scan  Each cycle through the program and I/O process is called a scan  Scan times vary with the length of the program and the speed of the processor

48. Programming Environments  Languages available  Ladder logic  Boolean  Function chart  Ladder logic is the most common  Function chart is the future  C, BASIC, etc., are also possible

49. Transducers  Converts energy from one form to another  Input transducers  Real world into the PLC  Output transducers  PLC to real world

50. Sensors  Sensors are transducers used to measure or detect  Convert mechanical, magnetic, thermal, or optical variations into electrical quantities  Sensor input is the basis for most of the decisions made in a large system

51. Proximity Sensors  Detect the presence of a object (target) without physically touching the object  Solid-state devices  Completely encapsulated  Used when:  Detecting small objects  Rapid response is required

52. Inductive Proximity Sensors  Senses a metallic object  A change in the magnetic field occurs when a metallic object enters into range  This type of sensor can “see” through cardboard boxes and other enclosures  Current-sourcing or current-sinking output

53. Manually Operated Switches  Pushbuttons  Normally open  Normally closed  Break-then-make  Make-then-break  Selector switches  Maintained or spring return

54. Counter Instructions  Count Up or Down  Similar to timers, but without an internal source  Two methods used: block and coil  SLC 5/02s use the coil format  PREset and ACCumlated values  RESet similar to RTO

55. How Counters Work  Increment or decrement on a false to true input transition  They are retentive  The accumulated value remains when the rung goes false  PREset can be changed by the program  Move a new value into C5:0.PRE

56. Control Bits 151413121110 CUCDDNOVUNUA  CU = Count Up  CD = Count Down  DN = Done  OV = Overflow, UN = Underflow

57. Integer Limits  PREset and ACCumulator values must be integers  Integers on the SLC 5/02 range from 32,767 to -32,768  Cascade counters to go beyond these limits

58. Cascading Example

59. Down Counters  The SLC 5/02 does not have a true down counter  The counter does not start at a value and become true when the ACCumulator is zero  The SLC 5/02 CTD works with another counter with the same address

60. Down Counter Example

61. Types of Data Instructions  Math Functions  Add, subtract, multiply, etc.  Data Conversion and Comparison  Integer to BCD, Less than, Equal, etc.  Logical Operations

62. Bits, Words, and Files  A bit is the smallest unit of information  T4:0/DN is a bit  A “word” is another name for a register  T4:0.PRE is a word  A “file” is a block of words, also known as a table  T4 is a file

63. Data Transfer – Move  The move instruction takes a value from a register, or a constant value, and places it in another register

64. BCD Move Into a Register  Moves an integer value into a BCD device.  In lab, the LED Display

65. BCD Move From a Register  Moves an BCD value into an integer register.  In lab, the thumb-wheel inputs

66. Comparisons  Greater than, less than, equals, etc.  When true, output is true

67. Today’s Task  Use what you have learned to “break the code”  Each bench has a PLC program  The first bench to turn on all five lamps wins!