PLC Homework

Mohammed Aljohani

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Ch 3 PLCs and Processing I/O 1

Chapter 3 PLCs and Processing I/O

Introduction

After an introduction of PLCs in chapter one, various characteristics of the PLC need to be

discussed. The purpose now is to discuss what parts constitute a modern PLC and how these

parts interface. The topology of a PLC system is also discussed as to how PLCs are distributed

in a manufacturing environment to best control a process efficiently.

Since each is electronic and operates using one or more microprocessors, a 5 volt power supply

and CPU (central processing unit) are the core of the PLC. Included in the CPU is a computer

with memory and communications hardware to communicate to a programming panel, the I/O,

and to a network which is either peer-to-peer or a multimode network.

Many PLC vendors divide the work of the PLC between multiple microprocessors with

coordination handled by a master microprocessor. One processor may be assigned to handle the

I/O. Another may handle the networking and communication to the programming panel. A

supervisory microprocessor handles the logic, scan, arithmetic, and other instructions solution of

the program.

Inputs and outputs complete the PLC with inputs reporting the status of the system and outputs

controlling the sequencing of the process. Inputs and outputs are of many types and forms. A

simple switch can be an input. Also, a high-speed pulse input can be an input providing speed

information from a motor. Inputs and outputs alike can be simple or complex in nature. Both

the simple I/O as well as the more complex will be discussed in the chapter and through the rest

of the book.

Overview of the PLC

Inputs form the portion of the PLC connecting switches, sensors, transducers and other devices

to the processor. Typically, the input is tied to a screw terminal. The PLC program reads the

status of the inputs and solves logic based on this status.

The CPU stores the program and controls communication with all peripherals including

programming devices as well as the I/O. The CPU executes the programs in an orderly manner

and guarantee that I/O responds per the program. The guarantee is not trivial if one is

experienced with most computer operating systems.

Outputs are connected to devices that control the process. Relays, motors, solenoids and other

outputs are some examples. A pulse wave PWM is one that controls stepper motors and

positional movement. The PLC program can control the status of this output and thus control the

motor speed and movement.

In the figures below, the simplified PLC is shown first followed by an expanded view of the

PLC. Each view shows the importance of the CPU (Central Processing Unit) as well as the

interconnection of the CPU to I/O (Inputs and Outputs). Other devices interact in such a way

that the program executes and solves logic in a timely manner.

Ch 3 PLCs and Processing I/O 2

Inputs Central

Processing

Unit

Outputs

Fig. 3-1a Simplified View of the PLC

Central Processing Unit

Arithmetic Logic Unit

Logic Operations

Math Operations

Operating Data

Input Image Table

Output Image Table

Timers/Counters

Datablocks

Program Memory

User Program

System OS

Interrupts

Task Scheduling

Peripheral

Devices

Real Time Clock

Run/Stop Switch

etc

Bus for Data, Control, Power Supply

Input Modules

Output Modules

Communication

Modules

Specialty

Modules

Programming

Terminal (PC)

HMI (Human

Machine Interface)

Process

Operator

You

Fig. 3-1b Expanded View of the PLC

The second view gives a greater detail of data flow into and out of the PLC. As the devices and

programs become more involved, the flow of data must both increase while being as secure as

with simple systems. All systems may not use communication modules or specialty modules.

Some may use a great number. All will use some kind of programming terminal and “you” will

be responsible for providing the program to run it.

Most PLCs also have a table reserved for health status of the cpu, the I/O, and the software. This

table can be monitored to find if processor errors have occurred. Status tables may be ignored

for the most part until something goes wrong. When an error occurs, their use is extremely

important to the programmer and to the recovery of the processor. The programmer must

monitor the status table in order to determine what went wrong and to restore the processor to

running condition again.

Also along-side the PLC's cpu is a watch dog timer (WDT). The WDT monitors health

throughout the PLC and shuts down the I/O and program if there is a danger that the program or

hardware has caused a major breakdown of the PLC's integrity to process the program and

control the process. The WDT is helpless to shut down the machine being controlled if the

program in the PLC is not functioning correctly due to poor programming. Care must be taken

to consider all possible conditions of a program. The proper control of the machine or process

under all conditions and circumstances is critical.

Ch 3 PLCs and Processing I/O 3

The following Figure shows the Lab Trainer used at the Engineering Technology lab at the

University of Toledo. It is an old Modicon trainer with the pushbutton and pilot lights mounted

together with switches and two modern PLCs at the left. Also, a thumbwheel switch assembly

can be found. The hole is for an LED readout that was never implemented.

The two PLCs are the Allen Bradley 1769-L23E-QBFC1B processor and the Siemens S7-1200 (CPU 1200 DCDCDC.

Allen Bradley 1769-L23E-QBFC1B

Siemens S7-1200 (CPU 1200 DCDCDC Pushbutton-Pilot Light Assembly Selector Switches

Thumbwheel Switch Assembly

Fig. 3-2 The Trainer at U of Toledo

An Ethernet switch is located in the Siemens rack. The Allen-Bradley Ethernet switch could

have been used as well but only one was needed. The network is to be established with both

PLCs having full access to the programming panels in the lab, the 16 workstations that are

available for use.

Ch 3 PLCs and Processing I/O 4

How is the Program Processed in the Siemens PLC?

The program is processed in the PLC cyclically, in the following sequence:

1. First, the status is transferred from the process image of the outputs (PIQ) to the outputs, and switched on or off.

2. Then the processor -which is practically the PLC’s brain- inquires whether the individual inputs are carrying voltage. This status of the inputs is stored in the

process image of the inputs (PII). For the inputs that carry voltage, the information

1 or "High“ is stored, for those that don’t the information 0 or "Low“.

3. This processor then processes the program stored in the program memory. The program consists of a list of logic operations and instructions that are processed

one after the other. For the required input information, the processor accesses the

PII that was entered previously, and the result of the logic operation (RLO) is

written into a process image of the outputs (PIQ). If necessary, the processor also

accesses other memory areas during program processing; for example, for local

data of sub-programs, data blocks and flags.

4. Then, internal operating system tasks such as self-tests and communication are performed Then we continue with Item 1.

Note: The time the processor needs for this sequence is called cycle time. In turn, the cycle

time depends on the number and type of instructions and the processor capacity.

PLC’s program in the program memory 1st instruction 2nd instruction 3rd instruction 4th instruction ... Last instruction

1. Transfer the status from the PIQ to the outputs.

2. Store the status of the inputs in the PII.

3. Processing the program instruction by instruction with access to PII and PIQ

4. Perform internal operating system tasks (communication, self-test, etc…)

PII

Local data

Flags

Data blocks

PIQ

Ch 3 PLCs and Processing I/O 5

What Happens Electrically

Figure 3-3 demonstrates the flow of current in a simple circuit. The battery provides power to

the lamp but is blocked in Fig. 3-3b because the switch is open. With an open switch, no current

flows and the circuit is incomplete. When the switch closes, however, current flows and the

lamp is illuminated (Fig. 3-3c). As simple as this circuit is, it contains the fundamental principle

of input and output flow in a control circuit and the PLC.

- +

battery

switch

lamp

Fig. 3-3a Simple Electrical Components

- +

battery

switch

lamp

no flow

Fig. 3-3b Simple Electrical Circuit (Open, No Flow)

- +

battery

switch

lamp

flow

Fig. 3-3c Simple Electrical Circuit (Closed, Flow)

Ch 3 PLCs and Processing I/O 6

The schematic for these circuits resembles the circuit below (Fig. 3-3d). Symbols have replaced

their physical devices but the functionality remains the same.

Fig. 3-3d Simple Electrical Schematic

Fig. 3-4 shows the PLC solving logic in a similar manner to the simple circuit above. The

complication of additional circuits solving logic adds to the sophistication of the circuit. This

allows much more sophistication in the defining of how a circuit will perform under all

conditions.

P L

C I n

p u

PLC CPU

Logic solved:

If Input = 1 then...

P L

C O

u tp

u ts

Electric Motor

Conveyor

Centrifugal pump

Lamp

Fig. 3-4 Simple PLC Circuit with Real-World Devices

Ch 3 PLCs and Processing I/O 7

In addition to simple PLC networks such as that above, the PLC may contain network I/O

allowing inputs and outputs to be communicated with at remote locations. Fig. 3-5 demonstrates

this type of system.

L o

c a

l In

p u

PLC CPU

Logic solved:

If Input = 1 then...

L o

c a

l O

u tp

u ts

Electric Motor

Conveyor

Centrifugal pump

Lamp

PLC Network (for Inputs, Outputs, Operator Information)

Human

Machine

Interface

Human

Machine

Interface

R e

m o

te I n

p u

R e

m o

te I n

p u

Conveyor

Fan

Fig. 3-5 PLC Circuit with Remote I/O

Inputs and outputs may even be communicated over wireless networks and this type of network

is becoming increasingly more popular as wiring costs continue to rise and the equipment is

designed for safe operation in all environments. Safe wireless networks are the latest advances

in PLC equipment and offer expansion of logic into areas formerly off-limits to the PLC.

The PLC program is generated on a PC using the manufacturer’s software, and temporarily

stored there.

After the PC is connected with the TCP/IP interface of the PLC, the program can be transferred

with a load function to the PLC’s memory.

The PC is no longer needed for further program processing in the PLC.

Ch 3 PLCs and Processing I/O 8

The Generic PLC

How does the PLC replace relay logic from a ladder logic diagram? Consider the following

example. Pictured below is a simple generic PLC with four inputs and four outputs. One input

is wired to a push button and one output is wired to an indicator light. While not exactly the

same as our PLC processor, the steps of installing a program and wiring the PLC are the same.

Run

+ -

Fault

Input

+24 VDC

Inputs Outputs Indicator

Light

0 VDC

Fig. 3-6 Generic PLC Layout

Notice when wiring an input and energizing the button that the green indicator light for the input

comes on:

Input Not Pushed

Input Pushed

Fig. 3-7 PLC Inputs

In the program, contacts referring to the input conduct as shown below:

Fig. 3-8a Internal Logic

Ch 3 PLCs and Processing I/O 9

If a program exists in the PLC similar to the following:

I0 Q0

Fig. 3-8b Internal Logic

and the Run light is on: Run

then the output will turn on and the light will turn on.

When the program shows the output on, the output LED turns on and the output terminal

energizes the light as shown:

Indicator

Light

Fig. 3-9a Output Power On

When the program is turned from Run to Program, the output LED turns off and the output turns

off. The outputs also turn off and the Run light goes off if a fault occurs.

Indicator

Light

Fig. 3-9b Output Power Off

From Liptak’s Process Control: “Input Systems

Inputs are defined as real-world signals giving the controller real-time status of process variables.

These signals can be analog or digital, low or high frequency, maintained or momentary.

Typically they are presented to the programmable controller as a varying voltage, current, or

resistance value.”

Analog signals include thermocouple and resistance temperature devices. Digital signals include

on-off signals from relay contacts or push buttons. Signals such as flowmeters provide

frequency input with the frequency varying with the flow.

Signals to the programmable controller are input from single wire devices or from parallel

signals. A thumb-wheel switch or scale system can input a four-digit number from four BCD

parallel digits. Many signals such as the scale system also require a synchronization signal before

Ch 3 PLCs and Processing I/O 10

data can be read.

Inputs include the following types or attributes:

DC voltage

AC voltage, ranges of 50 Hz or 60 Hz available

True High or True Low DC voltages

Analog inputs, ranges 0-10V or 4-20 ma most popular

BCD, Binary Coded Decimal

Thermocouple

Scale/load cells/LVDT, weight and force sensors

RTD, Resistance Temperature Detector

Latching

Isolated or Common Neutral

Intelligent (Smart with own CPU on board I/O card)

Resolver

Encoder

Serial Communications Port

An example is the limit switch shown below:

Fig. 3-10 Picture of Limit Switch (Input)

From Liptak’s Process Control:

“Outputs

There are three common categories of outputs: discrete, register, and analog. Discrete outputs

can be pilot lights, solenoid valves, or annunciator windows (lamp box). Register outputs can

drive panel meters or displays; analog outputs can drive signals to variable speed drives or to I/P

(current to air) converters and thus to control valves.”

Output signals are similar to input signals in that signals can be either analog or digital. Digital

signals can be either single data or a parallel arrangement of bits. Most modules are ordered in

arrangements of 4, 8, 16, or 32 devices per card.

Both input and output signals are optically isolated in designs for the US market. This protects

signals from entering the interior of the PLC and allows the designer to wire circuits less

carefully than in circuits without optical isolation. One main design difference between US and

Ch 3 PLCs and Processing I/O 11

European PLC design is the lack of optical isolation in the European design.

Outputs include the following types or attributes:

DC voltage

AC voltage, ranges of 50 Hz or 60 Hz available

Isolated or Common Source

True High or True Low DC voltages

Analog Output

Serial Communications Port

Intelligent (Smart with own CPU on board I/O card)

Servo Controller

While I/O modules vary in type and number, recent developments have caused even these

general rules to change. Distributed I/O is an example of a small number of inputs and outputs

isolated at a machine that control a portion of a machine remotely from the PLC. Typical remote

I/O requires a rack, power supply and a large number of cards while distributed I/O is

pre-configured for only a small number of inputs and outputs. A number of advantages occur

with the use of distributed I/O in that the machine can be wired and tested in one facility, broken

down and shipped to a second facility, and re-connected with very little change in the wiring.

This leads to quicker start-ups and cheaper overall wiring costs. Typical distributed I/O is

controlled over a communications network that is daisy-chained from device to device.

Some examples of PLC outputs include:

Fig. 3-11a Picture of Solenoid Valve (Output)

Ch 3 PLCs and Processing I/O 12

Fig. 3-11b Picture of Relay (Output)

The relay pictured may provide input contacts but is primarily used to turn on or off various

other signals from the PLC and is connected to a PLC output to accomplish this task.

Linking to the SIMATIC S7-1200

Fig. 3-12 Siemens S7-1200

Ch 3 PLCs and Processing I/O 13

Pictured below is a S7-1200 PLC from Siemens. It is a powerful new controller with many

capabilities only available in more expensive models until recently.

Power

Connector

User Wiring

Connectors

Status LEDs PROFINET

connector

Fig. 3-13 New S7-1200 PLC from Siemens

The S7-1200 is referred to as a micro PLC and is programmed in STEP 7 Basic, the newest

software offering from Siemens. The processor has capabilities of adding additional I/O to the

basic unit shown above. The processor communicates to a programming panel through an

Ethernet port referred to as the PROFINET interface found on the bottom of the unit. This port

offers access to other controllers, a programmer’s console and various HMI (Human Machine

Interface) units.

Capabilities of this model – the CPU 1214C - include:

User Memory - Work memory 50 Kbytes

Load memory 2 Mbytes Retentive memory 2 Kbytes

On-board digital I/O 14 inputs 10 outputs

On-board analog I/O 2 inputs Process image size Inputs 1024 bytes

Outputs 1024 bytes Bit memory (M) 8192 bytes SM modules expansion 8 SMs max SB expansion 1 SB max CM expansion 3 CMs max High-speed counters 6 total

Single phase 3 at 100 kHz and 3 at 30 kHz Quadrature phase 3 at 80 kHz and 3 at 20 kHz

Pulse outputs 2 Pulse catch inputs 14 Timedelay/cyclic interrupts 4 total with 1 ms resolution Edge interrupts 12 rising and 12 falling Real time clock accuracy +/- 60 sec/mon

Ch 3 PLCs and Processing I/O 14

Execution speed boolean 0.1 microsec/instruction Move Word 12 µsec/instruction Real Math 18 µsec/instruction

Communication 1 Ethernet port Data rate 10/100Mb/s Isolation xfmr isolated Cable type CAT5e shielded

Connections HMI 3 PG 1 User program 8 CPU to CPU 3

Sample wiring for the S7-1200 CPU is provided below (refer to the S7-1200 Systems Manual for

additional details):

L+ M G L+ M 1M .0 .1 .2 .3 .4 .5 .6 .7 .0 .1 .2 .3 .4 .5 24VDC 24 VDC DI a DI b

Input Output

VDC

VDC -

2M 0 1

Analog

Inputs

VDC

DQ a DQ b

L+ M .0 .1 .2 .3 .4 .5 .6 .7 .0 .1

AQ 1x12 bit +/- 10 VDC/0-20 mA

QM 0 G - - -

Specifications of the PLC include:

Digital Inputs Number of inputs 14 Type Sink/Source Rated voltage 24 VDC at 4 mA, nominal Continuous permissible 30 VDC, max Surge voltage 35 VDC for 0.5 sec Logic 1 min. 15 VDC Logic 0 max. 5 VDC Isolation 500 VAC for 1 min. High Speed Clock Single phase rate 100 kHz and 30 kHz Analog Inputs Number 2 Voltage (single-ended) Range 0 to 10 V Full-scale range 0 to 27648 Overshoot range 27649 to 32511 Overflow 32512 to 32767 Resolution 10 bits Max withstand voltage 35 VDC Smoothing None, weak, medium or strong Noise rejection 10, 50, or 60 Hz Impedance >= 100 KΩ Isolation None Accuracy 3.0% - 3.5%

Fig. 3-14 Wiring Layout

of S7-1200 (CPU 1214C)

Ch 3 PLCs and Processing I/O 15

Common mode rejection 40 dB, DC to 60 Hz Operational signal range Signal plus common mode voltage less than 12V and

greater than -12 V Cable length 100 m, twisted and shielded

Descriptions of S7-1200 Modules:

- Central modules CPU with different capacity, integrated inputs/outputs and

PROFINET interface (for example, CPU1214C)

- Power supply PM with input AC 120/230V, 50Hz/60Hz, 1.2A/0.7A, and output

DC 24V/2.5A

- Signal boards SB for adding analog or digital inputs/outputs; whereby the size of

the CPU does not change

(signal boards can be used with the CPUs 1211C/1212C and 1214C)

- Signal modules SM for digital and analog inputs and outputs

(for CPUs 1212C a maximum of 2 SMs can be used, for 1214C a maximum of 8)

Fig. 3-15a S7-1200 (CPU 1214C)

Fig. 3-15b Power Supply

of S7-1200 (CPU 1214C)

Fig. 3-15c Signal Board

of S7-1200 (Analog I/O)

Ch 3 PLCs and Processing I/O 16

- Communication modules CM for serial communication RS 232/RS 485

(for CPUs 1211C/1212C and 1214C, up to 3 CMs can be used)

- Compact Switch Module CSM with 4x RJ45 socket connectors 10/100 MBit/s

- SIMATIC memory cards 2MB or 24MB for storing program data and simple CPU

replacement for maintenance

Note: For this module M01, any CPU with integrated digital inputs and digital outputs

Fig. 3-15d Signal Module

of S7-1200 (Analog I/O)

Fig. 3-15e Communication

Module of S7-1200

Fig. 3-15f Switch Module

of S7-1200

Fig. 3-15g Memory Card

of S7-1200

Ch 3 PLCs and Processing I/O 17

is sufficient.

The SIMATIC Memory Card (MC) stores the program, data, system data, files and projects. It

can be used for the following:

- Transferring a program to several CPUs

- Firmware update of CPUs, signal modules SM and communication modules CM

The part number for this memory card is PN# 6ES57954-8LF00-0AA0. You may want to have

this card on hand when you upgrade your software since the version of firmware onboard the

PLC must be upgraded at the same time or you may be unable to properly link the PLC to the

software in the programming terminal. At present, the version of firmware is 2.2 and the Portal

software is V11, SP 2.

Operating Modes of the CPU

The CPU has the following operating modes:

● In the operating mode STOP, the CPU does not execute the program, and you can

load a project

● In the operating mode STARTUP, the CPU performs a startup.

● In the operating mode RUN, the program is executed cyclically. Projects can not be

loaded in the CPU’s RUN mode.

The CPU does not have a physical switch for changing the operating mode. The

operating mode (STOP or RUN) is changed by using the button on the operator panel of

the software STEP7 Basic. In addition, the operator panel is provided with the button

MRES to perform a general memory reset and displays the status LEDs of the CPU.

Fig. 3-15h Memory Card

being installed

Fig. 3-16a Controlling

Run/Stop Mode of CPU

Ch 3 PLCs and Processing I/O 18

The color of the status LED RUN/STOP on the front of the CPU indicates its current

operating mode.

In addition, there are the LEDs ERROR to indicate errors and MAINT to indicate that maintenance

is required.

Network

Connecting to the CPU by means of TCP/IP, and Resetting to Factory Setting or other IP

address:

To program the SIMATIC S7-1200 from the PC, the PG or a laptop, you need a TCP/IP

connection.

For the PC and the SIMATIC S7-1200 to communicate with each other, it is important also that

the IP addresses of both devices match.

First, we show you how to set the computer’s IP address.

1. From the System control, call the Network connections. Then, select the Properties of the

LAN connection ( Start  Settings  System control  Network connections Local Area

Connection  Properties)

2. Select the Properties from the Internet Protocol (TCP/IP) ( Internet Protocol (TCP/IP)  Properties)

3. You can now set the IP address and the Subnet screen form, and accept with OK ( Use the

following IP address  IP address: 192.168.0.99  Subnet screen form 255.255.255.0  OK

 Close)

MAC address:

The MAC address consists of a permanent and a variable part. The permanent part ("Basic MAC

Address") identifies the manufacturer (Siemens, 3COM, ...). The variable part of the MAC

address differentiates the various Ethernet stations and should be assigned uniquely world-wide.

On each module, a MAC address is imprinted specified by the factory.

● Yellow light indicates the STOP mode. ● Green light indicates the RUN mode.

● Blinking light indicates the STARTUP mode.

Fig. 3-16b Location of

Run/Stop LEDs

Ch 3 PLCs and Processing I/O 19

Value range for the IP-address:

The IP address consists of 4 decimal numbers from the value range 0 to 255, separated by a

period. For example, 141.80.0.16

Value range for the subnet screen form:

This screen form is used to recognize whether a station or its IP address belongs to the local

subnetwork, or can be accessed only by means of a router.

The subnet screen form consists of four decimal numbers from the value range 0 to 255,

separated by a period. For example, 255.255.0.0

In their binary representation, the 4 decimal numbers of the subnet screen form have to contain -

from the left- a series of gapless values "1" and from the right a series of gapless values "0".

The values "1" specify the area of the IP address for the network number. The values "0" specify

the area of the IP address for the station address.

Example:

Correct values: 255.255.0.0 Decimal = 1111 1111.1111 1111.0000 0000.0000 0000 binary 255.255.128.0 Decimal = 1111 1111.1111 1111.1000 0000.0000 0000 binary 255.254.0.0 Decimal = 1111 1111.1111 1110.0000 0000.0000.0000 binary

Wrong value: 255.255.1.0 Decimal = 1111 1111.1111 1111.0000 0001.0000 0000 binary

Value range for the address of the gateway (Router):

The address consists of 4 decimal numbers from the value range 0 to 255, separated by a period.

For example, 141.80.0.1.

Relationship of IP addresses, router address, and subnet screen form:

The IP address and the gateway address are to differ only at positions where a "0" is located in

the subnet screen form.

Example:

You entered the following: for the subnet screen form 255.255.255.0, for the IP address 141.30.0.5

and for the router address 141.30.128.1.

The IP address and the gateway address must have a different value only in the 4th decimal

number. However, in the example, the 3rd position already differs.

That means, in the example you have to change alternatively:

- the subnet screen form to: 255.255.0.0 or

- the IP address to: 141.30.128.5 or

- the gateway address to: 141.30.0.1

Ch 3 PLCs and Processing I/O 20

Starting a Project and Logging onto the S7-1200

First, find the TIA V11 Button and click:

View the following:

Fig. 3-17a The Siemens Portal

Select a name of your project. Be aware that you will need to address the project from the H

drive or from a stick drive.

Fig. 3-17b Continuation of the Portal Screen

Choose Configure a device and then Add new device. This will allow the establishment of

communication over the Ethernet with the PLC in your rack.

Ch 3 PLCs and Processing I/O 21

Fig. 3-18 The Siemens Project

Then choose Configure a device (see above). If versions of firmware are the same, you may attach

using the following: Unspecified CPU 1200

Fig. 3-19 Add a Device (Unspecified CPU 1200)

Ch 3 PLCs and Processing I/O 22

Double Click on the unspecified CPU 1200 as shown below:

Fig. 3-20 Use Unspecified CPU 1200

Click Detect:

Fig. 3-21 Using “detect” to Find the CPU

Ch 3 PLCs and Processing I/O 23

Find your processor and click on this processor and again click Detect:

Fig. 3-22 Fine Our PLC from the List

You should then be able to see the following screen:

Fig. 3-23 Resultant Screen for Specific CPU

Ch 3 PLCs and Processing I/O 24

Expand the PLC to see the device under the Project Tree.

Click Go Online:

Fig. 3-24

Project Tree for PLC_1

Fig. 3-25

Online Choice Tree

Ch 3 PLCs and Processing I/O 25

The following should be seen:

Fig. 3-26 Shows Online Status

Under Online Tools, find the box and check Run. Notice that the PLC’s Run light turns green.

Then select Stop and notice the Run light turn yellow. Notice also that the light may blink for a

time period when the processor is first starting up.

If the above method does not succeed in attaching to the PLC, the following procedure may also

be used. From the Project View, click Add new device.

Fig. 3-27 Add New Device

Ch 3 PLCs and Processing I/O 26

In the Add new device screen, make sure the version is compatible with your machine. Today, the version of firmware in the machine is V2.2 and the software on the computers is 11 SP2. These

are compatible.

Fig. 3-28 Add new device – Checking Version

Fig. 3-29 Also Add a Signal Board

There is also an analog signal board installed on these PLCs. This board must be added to the

configuration prior to attaching. This board identification may be seen above.

Ch 3 PLCs and Processing I/O 27

Next, double click on the green Profinet port on the PLC.

Fig. 3-30 Setting the Profinet Port Correctly

Double clicking on the Ethernet port on the picture of the PLC below will bring the Ethernet

address page shown at the bottom of the screen.

Change the address to the static IP address and Subnet mask shown on the sticker on the PLC.

Then right click on the PLC again and choose Compile.

Fig. 3-31 Changing IP and Subnet

Ch 3 PLCs and Processing I/O 28

Fig. 3-32 Compiling and Downloading

Right click on the gray area of the PLC. Then compile the PLC’s program and configuration.

Then choose Download to device and then all. From the Download screen, choose PN/IE and the

interface card in your computer as shown below. If your device does not show on the screen at

bottom, click the Show all accessible devices and try again. If you still are not able to connect, look

at each device in the list and check for MAC address to determine if you can connect using the

MAC address. If still there is no connection, disconnect from the network and show only the

device attached to the PLC from the computer. This is the device. Then click Load.

Ch 3 PLCs and Processing I/O 29

Fig. 3-33 Downloading to Device

Choose the type of PG/PC interface as well as the card in the interface as shown above first:

The above has been used to connect to a number of PLCs in the lab and change the IP addresses

to their proper static addresses. This method seems to work well across the board when coming

at the problem of connecting to the PLC without having each device properly set prior to starting

the project.

It is important that the student practice the programming steps outlined above to be able to start a

new project, download a project to the Siemens 1200 PLC and start and stop the processor. The

ability to do this will pay dividends in later labs.

Make sure the PLC is properly named. The name is not PLC_1 but rather the name on the label

along with the IP address. Change the name to this name before downloading.

Also, learn to PING a device. Under the Command prompt from your computer, type:

Ping 131.183.20.175

(changes depending on IP address) and see if the device responds. A correct response would

show a number of tries and responses from the device being pinged.

Example of Wiring to Siemens PLC:

Given the wiring diagram of Figure 3-14, draw the wiring necessary to attach a normally open

pushbutton to the input I0.2, an output to a lite at Q0.5.

Ch 3 PLCs and Processing I/O 30

L+ M G L+ M 1M .0 .1 .2 .3 .4 .5 .6 .7 .0 .1 .2 .3 .4 .5 24VDC 24 VDC DI a DI b

Input Output

VDC

2M 0 1

Analog

Inputs

DQ a DQ b

L+ M .0 .1 .2 .3 .4 .5 .6 .7 .0 .1

AQ 1x12 bit +/- 10 VDC/0-20 mA

QM 0 G - - -

L+ M G L+ M 1M .0 .1 .2 .3 .4 .5 .6 .7 .0 .1 .2 .3 .4 .5 24VDC 24 VDC DI a DI b

Input Output

VDC

2M 0 1

Analog

Inputs

Wire PB input to I0.2

DQ a DQ b

L+ M .0 .1 .2 .3 .4 .5 .6 .7 .0 .1

VDC

Wire Lite to output Q0.5

Fig. 3-34 Wiring Layout of Siemens PLC

Ch 3 PLCs and Processing I/O 31

Allen-Bradley’s CompactLogix L23E Programmable Automation Controllers

Integrated Architecture for Smaller Applications

1769-L23E-QBFC1B:

Fig. 3-36 Front View of CompactLogix L23E

Fig. 3-37 View of CompactLogix L23E with

Wiring Exposed

Ch 3 PLCs and Processing I/O 32

Benefits

• Extends benefits of the Logix Control Platform into smaller applications

• Three packaged controller forms lower costs and simplify configuration

• Integrated EtherNet/IP ports offer cost-effective connectivity

• Pre-configured, embedded I/O simplifies use, reducing development and start-up costs

• High functionality supports advanced Integrated Architecture features including Alarms

and Events, drive integration and PhaseManager™

• Use of a common database between FactoryTalk View and PanelView Plus offers easy

HMI integration to reduce development and start-up costs

CompactLogix programmable automation controllers (PACs) offer you the benefits of the Logix

Control Platform—common programming environment, common networks, and common control

engine—in a smaller footprint for machine-level control applications. The new CompactLogix

L23 extends these benefits into even smaller applications. The CompactLogix L23 controllers

include the Logix control engine, power supply and two of the most common I/O configurations,

lowering costs and simplifying configuration. Each CompactLogix L23 PAC offers 512Kb of

memory, up to three tasks, four programs and embedded EtherNet/IP capabilities for ease of use.

Up to two local Compact I/O or communication cards can also be added for additional flexibility.

1769-L23E-QBFC1B

Embedded Communication Ports Isolated Serial (DF1 or ASCII) Ethernet/IP with (MSG + I/O)

EtherNet/IP Connections 8 TCP/IP – 32 CIP

Memory 512 KB

Embedded I/O 16 DC in, 16 DC out, 4 Analog in, 2 Analog out, 4 High-Speed Counters (250 kHz)

Expansion 2 Additional 1769 I/O Modules or 1 1769 Communication Module

Tasks 3-Continuous, Periodic or Event

Programs 4

Routines Unlimited

Languages LD, FBD, ST, and SFC

Alarms & Events Supported

PhaseManager Supported

Add-on Instructions Supported

Dimension 130x293x90mm

Power Requirements 19.2 – 31.2 VDC – 50VA

Table 3-1 CompactLogix L23E Capabilities

Ch 3 PLCs and Processing I/O 33

In 0

In 1

In 2

In 3

In 4

In 5

In 6

In 7 DC

Com 1 In 9

In 8

In 11

In 10

In 13

In 12

In 15

In 14 DC

Com 2

24 V DC

+24 VDC

0 VDC+24 VDC

0 VDC

Fig. 3-38 A-B Sample Input Wiring

+VDC

OUT 1

+24 VDC

OUT 3

OUT 5

OUT 7

OUT 9

OUT 11

OUT 13

OUT 15

Out 0

OUT 2

OUT 4

OUT 6

OUT 8

OUT 10

OUT 12

OUT 14

DC COM

0 VDC

24 V DC (source)

Fig. 3-39 A-B Sample Output Wiring

Ch 3 PLCs and Processing I/O 34

V in 0+

V in 0-

I in 0+

V in 2+

V/I in 2-

I in 2+

AoutCOM

V out 0+

I out 0+

V in 1+

V/I in 1-

I in 1+

V in 3+

V/I in 3-

I in 3+

Ain COM

V out 1+

I out 1+

Analog IN/OUT

Out 1

Out 3

A 0+

B 0+

Z 0+

A 1+

B 1+

Z 1+

Out 0

Out 2

Out

DC Com

A 0-

B 0-

Z 0-

A 1-

B 1-

Z 1-

Counter

Out DC

+5/24DC

Fig. 3-40 A-B Analog In/Out and Counter Interface

Two programs are used to set up and program the A-B CompactLogix processor. First is

RSLinx. On the next page is an explanation of setting up RSLinx to establish the network

connection between the computer and the PLC. Once this connection is in place, programming

can begin. RSLogix 5000 is used for this function. On the pages following are examples of

starting RSLogix 5000 and samples of beginning a program for the PLC and downloading to the

PLC. Explanations of programming both the Siemens and the A-B processors continue in the

next chapter.

Ch 3 PLCs and Processing I/O 35

Use RSLinx to configure the EtherNet/IP Driver:

Choose ‘Communications’, then

‘Configure Drivers’.

From the list of Available Driver Types,

choose ‘Ethernet/IP’

Click ‘Add New…’ and then ‘OK’

Check ‘Browse Local Subnet’ and then

click ‘OK’

Verify that the driver is ‘Running’.

Close the ‘Configure Drivers’ window.

Verify that Ethernet/IIP is ‘seeing’ the

PLC by clicking ‘RSWho’

and expanding the Ethernet link to see

the specific CompactLogix processor

Ch 3 PLCs and Processing I/O 36

When launching RSLogix 5000 , have the icon on your desktop or launch using

Rockwell Software, RSLogix 5000 Enterprise Series , RSLogix 5000 .

When launched , the following will appear :

When starting with no program , choose New from the File menu . The New Controller

dialog appears . Choose our controller ,

the 1769 -L23E-QBFC1 controller , add the revision level , 19 at present , add a name

(text) in this example and click ‘OK’

Fig. 3-41 First Screen for RSLogix 5000

Fig. 3-42 Configuring a Program Name

Ch 3 PLCs and Processing I/O 37

Congratulations ! You have a PLC that can do absolutely nothing . There is no tag database and no program

stored yet .

There is , however, an I/O Configuration prepared . It includes the L23E, an Ethernet Port and some

Embedded I /O. Note that there is also room for expansion I /O to the right of the processor .

Fig. 3-43 Basic Programming Page of RSLogix 5000

Fig. 3-44 I/O Configuration for L23E

On the left is a tree of folders. These show the controller, its tasks, any trends, data tables and

the I/O configuration.

Ch 3 PLCs and Processing I/O 38

Click MainProgram and then MainRoutine to show the figure below. You are ready to program a

rung of logic. Above the MainRoutine logic is the Ladder Instruction toolbar. From this toolbar,

you can choose the type of contact to place in the rung of logic.

Fig. 3-45 Programming Area for RSLogix 5000

Ch 3 PLCs and Processing I/O 39

The embedded I /O may need to be configured . For instance, the 16 point input section has the following

configuration screens :

Fig. 3-46 Imbedded I/O Configuration Screen

Fig. 3-47 Filter Times for Imbedded Input Group

It is important that the student practice the programming steps outlined above to be able to start a

new project, download a project to the Siemens 1200 PLC and start and stop the processor. The

ability to do this will pay dividends in later labs.

Ch 3 PLCs and Processing I/O 40

The embedded I/O is addressed automatically in the ‘Controller Tags’ entry. This resembles the following:

The 16 inputs from the input card section are addressed as follows: Local:1:I.Data.0 (bit 0) ...

Fig. 3-48 Embedded I/O Addressing

Fig. 3-49 Embedded I/O Addressing

Expanded

Ch 3 PLCs and Processing I/O 41

In 0

In 1

In 2

In 3

In 4

In 5

In 6

In 7 DC

Com 1 In 9

In 8

In 11

In 10

In 13

In 12

In 15

In 14 DC

Com 2

+VDC

OUT 1

OUT 3

OUT 5

OUT 7

OUT 9

OUT 11

OUT 13

OUT 15

Out 0

OUT 2

OUT 4

OUT 6

OUT 8

OUT 10

OUT 12

OUT 14

DC COM

Local:1:I.Data.0

Local:1:I.Data.1

Local:1:I.Data.15 Local:1:I.Data.14

Addresses of

Inputs

Addresses of

Outputs

Local:2:O.Data.0

Local:2:O.Data.1

Local:2:O.Data.14

Local:2:O.Data.15

Fig. 3-50 Tying I/O Addresses to Wiring Points

It is important that the student practice the programming steps outlined above to be able to start a

new project, download a project to the Allen-Bradley L23 PLC and start and stop the processor.

The ability to do this will pay dividends in later labs.

Ch 3 PLCs and Processing I/O 42

Exercises

1 For the Siemens 1200 processor below, draw the wires to connect a NO limit switch to input

I1.4. Draw the wires to connect a solenoid to output Q1.0.

L+ M G L+ M 1M .0 .1 .2 .3 .4 .5 .6 .7 .0 .1 .2 .3 .4 .5 24VDC 24 VDC DI a DI b

Input Output

VDC

2M 0 1

Analog

Inputs

DQ a DQ b

L+ M .0 .1 .2 .3 .4 .5 .6 .7 .0 .1

AQ 1x12 bit +/- 10 VDC/0-20 mA

QM 0 G - - -

Fig. 3-51 Siemens Wiring Diagram

2 For the Allen-Bradley L23E processor below, draw the wires to connect a NO limit switch to

input Local:1:I.Data.3. Draw the wires to connect a solenoid to output Local:2:O.Data.2.

In 0

In 1

In 2

In 3

In 4

In 5

In 6

In 7 DC

Com 1 In 9

In 8

In 11

In 10

In 13

In 12

In 15

In 14 DC

Com 2

+VDC

OUT 1

OUT 3

OUT 5

OUT 7

OUT 9

OUT 11

OUT 13

OUT 15

Out 0

OUT 2

OUT 4

OUT 6

OUT 8

OUT 10

OUT 12

OUT 14

DC COM

Fig. 3-52 A-B Wiring Diagram

Ch 3 PLCs and Processing I/O 43

3. Watch a portion of the following three videos:

http://www.youtube.com/watch?v=-Au6m45GIvA&feature=related

Siemens SIMATIC S7-1200 Part 1 - Getting Started

Getting started with your first SIMATIC S7-1200 Compact Controller and Step 7 Basic Software. See how easy it

is to configure, program, and test your first S7-1200 in less than 8 minutes. This is part one of a four part series

showcasing the time and cost saving benefits of the new S7-1200.

http://www.youtube.com/watch?v=zvS_BuQlSXo&feature=related

Introduction to PLC ladder logic programming training video. This educational video is an

introduction to what ladder logic is and how it works. (Part 1 of 2)

More videos are available on http://www.PLCMentor.com by http://www.AutomationNC.com

http://www.youtube.com/watch?v=-Au6m45GIvA&feature=related

http://www.youtube.com/watch?v=zvS_BuQlSXo&feature=related

http://www.plcmentor.com/

http://www.automationnc.com/