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

2. 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?
PLC
SLC AB
Autos GM
Ford
Bus
Sensor
Drive

3. Vocabulary Programmable Logic Controllers Drives Sensors
EE-100 Intro to EE
Friday, November 16, 2018
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
Dr. Glenn Wrate, P.E.

4. First Programmable Controller
EE-100 Intro to EE
Friday, November 16, 2018
First Programmable Controller
General Motors Corporation
Hydromatic Division
Replaced relay-controlled system
PDP-8 minicomputers?
MODICON 084
Modular Digital Controller
Dr. Glenn Wrate, P.E.

5. Programmable Controller
Information Flow
Process or Machine
Measure
Control
Programmable Controller

6. Genesis of Automation Operation sheets Listing of:
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

7. Industrial Revolution
EE-100 Intro to EE
Friday, November 16, 2018
Industrial Revolution
High-volume production
Interchangeable parts
Transportation system
Inexpensive energy (coal)
Frederick W. Taylor
Scientific management
Henry Ford
1895 paper to ASME
Dr. Glenn Wrate, P.E.

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

9. 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

10. The Case Against Automation
EE-100 Intro to EE
Friday, November 16, 2018
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.
He told of a new brewery built in Florida with a capacity of 1,300,000 barrels a year. The same-size brewery in Milwaukee turning out the same amount of barrels employed 586 men. The new plant hires 107 men. That's less than one-fifth, which means that 80 percent of brewery labor will go jobless as new plants go into operation.
Dr. Glenn Wrate, P.E.

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

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

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

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

15. 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

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

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

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

19. 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

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

21. Mechanically Operated Switches
Limit Switches
Temperature Switches
Pressure Switches
Level Switches

22. Electrically Operated Switches
Photoelectric Switches
Proximity Switches

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

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

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

26. Small Logic Controllers

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

28. Configurations Fixed I/O Rack SLC 500 is a fixed I/O device
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

29. Chassis Versus Rack One “Rack” is 128 inputs/outputs
EE-100 Intro to EE
Friday, November 16, 2018
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
Dr. Glenn Wrate, P.E.

30. 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

31. “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

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

33. Discrete I/O Modules Either “on” or “off” Bit oriented Various ratings
TTL
4 – 20 mA

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

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

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

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

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

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

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

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

42. 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

43. 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)

44. Counter Element Example
Name
Address
Example
Control Word
C5:0
C5:0/DN
Preset Word
C5:0.PRE
5000
Accumulated Word
C5:0.ACC
1240

45. RSLogix 500 Screen
Counter C5:0

46. Program Scan Program Scan I/O 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
I/O Scan

47. 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

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

49. 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

50. 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

51. 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

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

53. 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

54. 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

55. Control Bits CU = Count Up CD = Count Down DN = Done15 14 13 12 11 10 CU CD DN OV UN UA
CU = Count Up
CD = Count Down
DN = Done
OV = Overflow, UN = Underflow

56. 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

57. Cascading Example

58. 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

59. Down Counter Example EE-100 Intro to EE Friday, November 16, 2018
Dr. Glenn Wrate, P.E.

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

61. 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

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

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

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

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

66. Today’s Task Use what you have learned to “break the code”
EE-100 Intro to EE
Friday, November 16, 2018
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!
Dr. Glenn Wrate, P.E.