Programmable Logic Controllers

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1 Programmable Logic Controllers PLC Addressing and Basic Instructions Dr. D. J. Jackson Lecture 3-1 Basic addressing For the Allen-Bradley PLCs and the simulator used, the input and output image areas (in addition to other data) are held in data files Each data file holds information such as Discrete input values Discrete output values Values associated with timers Values associated with counters Status information Etc. Dr. D. J. Jackson Lecture

C-counter Slot number (not used with the simulator) X1:x.

2 PLC data files Simulator data files AB PLC data files Dr. D. J. Jackson Lecture 3-3 I/O memory mapping Basic AB PLC addressing Data file type I input O output S status B binary T- timer C-counter Slot number (not used with the simulator) X1:x.0/0 Bit number Data file number (can be omitted for the basic data files) Word number: selects a specific word in a data file I/O located on the controller (embedded I/O) is slot 0. I/O added to the controller (expansion I/O) begins with slot 1. Dr. D. J. Jackson Lecture

3 Example Addressing CPU Module (slot 0) Digital Input Module (slot 1) 16 inputs Digital Output Module (slot 2) 8 outputs Would occupy addresses I1:1.0/0 through I1:1.0/15 Would occupy addresses O0:2.0/0 through O0:2.0/7 Dr. D. J. Jackson Lecture 3-5 Basic instructions Examine If Closed (XIC) Examine If Open (XIO) Output Energize (OTE) Output Latch (OTL) Output Unlatch (OTU) One-shot Rising (OSR) Dr. D. J. Jackson Lecture

4 Examine if closed (XIC) Alternate name: Normally open contact Use the XIC instruction in your ladder program to determine if a bit is on. When the instruction is executed, if the bit addressed is on (1), then the instruction is evaluated as TRUE. When the instruction is executed, if the bit addressed is off (0), then the instruction is evaluated as FALSE. Normally open switch is open Normally open switch is closed Dr. D. J. Jackson Lecture 3-7 Examine if open (XIO) Alternate name: Normally closed contact Use the XIO instruction in your ladder program to determine if a bit is off. When the instruction is executed, if the bit addressed is on (1), then the instruction is evaluated as FALSE. When the instruction is executed, if the bit addressed is off (0), then the instruction is evaluated as TRUE. Normally open switch is open An XIO instruction inverts the state of the bit it references. Normally open switch is closed Dr. D. J. Jackson Lecture

5 Output energize (OTE) Alternate name: coil This instruction is usually used in conjunction with XIC or XIO or any other input instruction. If the logic preceding the OTE instruction is true (1), the OTE instruction will be energized Not energized An OTE instruction can only be the last instruction on a rung. Energized Dr. D. J. Jackson Lecture 3-9 Output latch (OTL) The OTL instruction is used only to turn a bit on and latch it on Initially not energized L Energized Latched Dr. D. J. Jackson Lecture

6 Output unlatch (OTU) The OTU instruction is used only to turn a bit off and latch it off OTL and OTU are generally used in pairs U Dr. D. J. Jackson Lecture 3-11 One-shot rising (OSR) When the rung conditions preceding the OSR go from false-totrue, the OSR instruction goes true also but for only one scan The address on the OSR instruction is a bit that is used to reflect the state of the input to the OSR. OSR I:1/0 OSR output One PLC scan Dr. D. J. Jackson Lecture

7 Branches Branches can be inserted in ladder logic programs to create parallel combinations of various ladder logic elements Dr. D. J. Jackson Lecture 3-13 Multiple Series/Parallel Branches Multiple series/parallel branches can be utilized with multiple inputs and also affecting multiple outputs in parallel Dr. D. J. Jackson Lecture

PLC simulator usage Ladder logic elements (instructions) can be dragged and dropped onto the ladder window to create a ladder logic program The ladder logic program is executed by going online,

8 PLC simulator usage Ladder logic elements (instructions) can be dragged and dropped onto the ladder window to create a ladder logic program The ladder logic program is executed by going online, downloading the PLC program, and switching to run mode OFFLINE/ONLINE control Download PLC run mode Dr. D. J. Jackson Lecture 3-15 ProSim simulations The Logixpro simulator provides a set of built-in simulations The I/O simulation initially will be of most use since it provides access to simulated discrete inputs (switches) and outputs (lamps) Dr. D. J. Jackson Lecture

Other Prosim simulations Available simulators Door simulator Silo simulator Traffic simulator Batch simulator Dual Compressor simulator Bottle line simulator Four floor elevator simulator

9 Other Prosim simulations Available simulators Door simulator Silo simulator Traffic simulator Batch simulator Dual Compressor simulator Bottle line simulator Four floor elevator simulator Most projects will involve designing ladder logic programs to control these simulations Dr. D. J. Jackson Lecture 3-17 Batch simulator showing example I/O Dr. D. J. Jackson Lecture

Introduction to Programmable Logic Controllers (PLC's)

Introduction to Programmable Logic Controllers (PLC's) Industrial Control Systems Fall 2006 Lecture Introduction to PLC's MME 486 Fall 2006 1 of 47 The Need for PLCs Hardwired panels were very time consuming