Programming Logic Controllers
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Transcript of Programming Logic Controllers
Programming Logic Controllers
Overview - Chapter 1
PLC Use
• Machine control• Process control• Motion control• Batch control• Diagnostic• Other• Usually Multiple applications
History and Development
• 1960’s• “Five hours to find it, five minutes to fix it”
History
• Richard Morley – Modicon• First PLC• ladder logic programming
• Odo Josef Struger• Allen-Bradley
History and Development
• http://en.wikipedia.org/wiki/Programmable_logic_controller
• http://en.wikibooks.org/wiki/Introductory_PLC_Programming
• http://www.isa.org/Content/ContentGroups/News/2006/February24/History_of_the_PLC.htm
• http://www.barn.org/FILES/historyofplc.html
• http://www.control.lth.se/media/Education/DoctorateProgram/2012/HistoryOfControl/Vanessa_Alfred_report.pdf
• http://www.plcs.net/chapters/history2.htm
Block Diagram
Block Diagram
Block Diagram
Central Processing Unit
• http://en.wikipedia.org/wiki/Central_processing_unit
• A central processing unit (CPU) is the hardware that carries out the instructions of a computer program by performing the basic arithmetical, logical, and input/output operations of the system.
Memory Devices
• RAM• ROM
• ROM• Programmable ROM (PROM)• Erasable programmable ROM (EPROM or
UVEPROM)• Electrically Erasable ROM (EEPROM)
• Static RAM• Dynamic RAM
Address Decoder Unit
• Address to circuit• Binary number to path
Binary• http://www.jodyculkin.com/category/comics-2/countingbinary
Decimal pattern
Binary numbers
0 0
1 1
2 10
3 11
4 100
5 101
6 110
7 111
8 1000
9 1001
Transisters and Gates• http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html
• http://www.cs.bu.edu/~best/courses/modules/Transistors2Gates/
• http://www.cs.bu.edu/~best/courses/cs101/F95/lectures/FromGatesToAdder.html
• http://www.electronics-tutorials.ws/logic/logic_10.html
Peripheral Chips
• Buffers
• Data conversion
• Networking
• Voice
• Voice Recognition
• more
Discrete Input Modules• Discrete means enumerable, countable, not continuous
but distinct• Digital not analog• Real numbers are not discreet
• Between 1.0 and 2.0 we have 1.50. • Always a number between x and y
• Integers are discrete. No number falls between 1 and 2
• Generally • On or Off • 1 or 0• True or False• Closed or Open
Discrete Output Modules
• Set to on/off
• Set to true/false
• Set to 1/0
Analog Input/Output Devices
• Analog is a continuous signal (wave)
• Set to varying voltage levels
• Inputs converted to digital via analog to digital converter logic
• Digital to analog conversion occurs for outputs
PLC Power Supply
• Battery backup• Capacacitor allows battery exchange
Allen-Bradley Programmable Logic Controllers
• PICO• MicroLogix• Small Logix• SLC 500 Series
• LAN and WAN capabilities
• PLC-5• May have thousands of I/0 ports