Plc Siemens Training Notes

SiemensS7-200 PLC training courses

PLC history

• Classical control - More complicated

- Longer time for maintenance

- Time consuming troubleshooting

- Occupies larger area in switchboards

- Requires more wiring

- Standard reliability

History

• Large projects requirements

-More inputs and outputs points

- Large program memory

- Several programming instructions

- Communication with other equipments

- Deal with analogue signals

-Deal with large number of counters, timers

and markers

History

• Historical view

Course contents

• Introduction to PLC

• Bit logic

• compare

• Timers

• Counters

• Memory instructions

• Analog I/O

• Move , shift

• Practical examples

Introduction

• What is a PLC

Introduction

• Basic PLC operation

introduction

• S7 200 family

introduction

• S7-200 configuration

introduction

• S7-200 configuration

mode switch and analog adjustment

introduction

• S7-200 configuration

optional cartidge

Introduction

• S7-200 configuration

expansion modules

Introduction• S7-200 configuration

status indicator

Introduction• S7-200 configuration

I/O numbering

Introduction• S7-200 configuration

inputs

Introduction• S7-200 configuration

outputs

Introduction• S7-200 configuration

programming software

Analogue I/O =Typical analogue signals from 0-10 VDC or 4-20 mA

=They are used to represent changing values such as speed, temperature, weight and level

Introduction

Analogue outputs may be used to produce variable reference signals for devices such as:

# Control valves

# Chart recorders

# Electric motor drives

# Pressure transducers

# Analogue meters

Introduction

Introduction

Introduction

PLC Programming

Programming languages

Statement list Function block

Ladder diagram

The instructions are represented by graphic symbols:

Contacts, Coils & Boxes

The ladder diagram is the most popular programming language

Instructions Standard instructions:

They are used in most programs.

Examples: timer, counter, math, logical, incr., decr. and move

High speed instructions:

They allow for events and interrupts to occur independently of the PLC scan time.

Examples: High speed counters and interrupts

Special instructions:

They are used to manipulate data

Shift, table, conversion, real time instruction.

Bit Logic instruction

Normally Open contact

Normally Open Immediate contact

Normally Closed contact

Not contact

Normally Closed Immediate contact

Positive Transition contact

Negative Transition contact

Input Instructions

Input contacts example

Output instructions

Output Instruction

No Operation instruction

Output Immediate instruction

Set (N bits) instruction

Reset (N bits) instruction

Set Immediate (N bits) instruction

Reset Immediate (N bits) instruction

Output, Set & Reset example

Starting a motor

Hard-wired DOL starting

Induction Motor

Circuit Breaker

Contactor

Thermal Overload

Induction Motor

Aux. contact

Contact coil

Stop

O.L. contact

Start

Using PLC

Before start

Starting

After start

Stopping

Input & Output connections

Timer instructions

On-Delay Timer

Retentive On-Delay Timer

Off-Delay Timer

On-Delay & Retentive On-Delay timers

They count time when the enabling input (IN) is ON.When the current value (Txxx) is > the preset time (PT), the timer bit is ON.

The On-Delay timer current value is cleared when (IN) is OFF, while the current value of the Retentive On-Delay Timer is maintained.

You can use the Retentive On-Delay Timer to accumulate time for multiple periods of the input ON .

Off-Delay timer

The Off-Delay Timer is used to delay turning an output OFF for a fixed period of time after the input turns OFF.

When (IN) turns ON, the timer bit turns ON immediately, and the current value is set to 0 .

When (IN) turns OFF, the timer counts till PT and the timer bit turns OFF and the current value stops counting.

If the input is OFF for a time shorter than PT, the timer bit remains ON.

Timers numbers & resolutions

Note

You cannot share the same timer numbers for TOF and TON .For example, you cannot have both a TON T32 and a TOF T32.

Timer examples

On-Delay

Off-Delay

RetentiveOn-Delay

Hard-wired on-delay timer

Timer example

TONR example

Timer example

Counter instructions

Up counter

Up/down counter

Down counter

A bottling machine, for example, may use a counter to countbottles into groups of six for packaging.

Up-counter

It counts up on the rising edges of the Count Up (CU) input.

When the current value (Cxxx) > (PV), the counter bit (Cxxx) turns on.

The counter is reset when the Reset (R) input turns on.

Up/Down counter

It counts up on rising edges of the Count Up (CU) input .It counts down on the rising edges of the Count Down (CD) input.

When the current value (Cxxx) > (PV), the counter bit (Cxxx) turns on.

The counter is reset when the Reset (R) input turns on.

Down counter

It counts down from the PV on the rising edges of the (CD) input.

When the current value is equal to zero, the counter bit (Cxxx) turns on.

The counter resets the counter bit (Cxxx) and loads the current value with the (PV) when the load input (LD) turns on .

Down-counter example

Up/down-counter example

Counter example

A counter might be used to keep track of the number of vehicles in a parking lot. As vehicles enter the lot through an entrance gate, the counter counts up. As vehicles exit the lot through an exit gate, the counter counts down. When the lot is full a sign at the entrance gate turns on indicating the lot is full.

The ladder logic

Memory types• You can access data in many CPU memory areas - process image input register (I) - process image output register (Q) - variable memory area (V) - Bit memory area (M) - sequence control relay memory area (S) - special memory bits (SM) - local memory area (L) - Timer memory area (T) - counter memory area (C) - Analog inputs (AI)

Accessing a Bit of Data in the CPU Memory (Byte.bit Addressing)

Memory addressing

Memory addressingYou can access data in many CPU memory areas (V, I, Q, M, S, L, and SM) as:bytes, words, or double words by using the byte-address format.

Memory types• Process-image input register (I)

Format:Bit I[byte address].[bit address] I0.1Byte, Word, Double Word I[size][starting byte address] IB4

• Process-image output register (Q)Format:Bit Q[byte address].[bit address] Q1.1Byte, Word, Double Word Q[size][starting byte address] QB5

• Variable memory area (V)You can use V memory to:

•store intermediate results of the control logic operations .•store other data pertaining to your process or task .

Format:Bit V[byte address].[bit address] V10.2Byte, Word, Double Word V[size][starting byte address] VW100

Memory types• Sequence control relay area (S)

They are used to organize machine operations or steps into equivalent program segments. SCRs allow logical segmentation of the controlFormat:

Bit S[byte address].[bit address] S3.1Byte, Word, Double Word S[size][starting byte address] SB4

• Special memory bits (SM)The SM bits provide a means for communicating information between the CPU and your program. You can use these bits to select and control some of the special functions of the S7-200 CPU, such as:

•A bit that turns on for the first scan cycle •Bits that toggle at fixed rates

•Bits that show the status of math or operational instructionsFormat:

Bit SM[byte address].[bit address] SM0.1Byte, Word, Double Word SM[size][starting byte address] SMB86

Memory types• Local memory area (L)

The S7-200 PLCs provide 64 bytes of local (L) memory of which 60 can be used as scratchpad memory or for passing formal parameters to subroutines. Format:Bit L [byte address].[bit address] L0.0Byte, Word, Double Word L [size] [starting byte address] LB33

Memory types

• Analog inputs (AI)The S7-200 converts a real-world, analog value (such as temperature or voltage) into a word-length (16-bit) digital value. You access these values by the area identifier (AI), size of the data (W), and the starting byte address. Since analog inputs are words and always start on even-number bytes (such as 0, 2, or 4), you access them with even-number byte addresses (such as AIW0, AIW2, or AIW4),as shown in Figure Analog input values are read-only values.

Format: AIW [starting byte address] AIW4

Memory types

The S7-200 converts a word-length (16-bit) digital value into a current or voltage, proportional to the digital value (such as for a current or voltage). You write these values by the area identifier (AQ), size of the data (W), and the starting by address. Since analog outputs are words and always start on even-number bytes (such as 0, 2, or 4), you write them with even-number byte addresses (AQW0, AQW2, AQW4) ,

Format: AQW [starting byte address] AQW4

•Analog outputs (AQ)

Move instructionsThe Move Byte instruction moves the input byte (IN) to the output byte (OUT). The input byte is not altered by the move.

The Move Word instruction moves the input word (IN) to the output word (OUT). The input word is not altered by the move.

The Move Double Word instruction moves the input double word (IN) to the output double word (OUT). The input double word is not altered by the move.

The Move Real instruction moves a 32-bit, real input double word (IN) to the output double word (OUT). The input double word is not altered by the move.

The block move instructions

The Block Move Byte instruction moves the number ofbytes (N) from the input address IN to the output addressOUT. N has a range of 1 to 255. Example

Move byte immediate instructions

The Move Byte Immediate Write instruction reads fromlocation IN and writes to physical output OUT.

The Move Byte Immediate Read instruction readsphysical input IN and writes the result in OUT.

=Typical analogue signals from 0-10 VDC or 4-20 mA

=They are used to represent changing values such as speed, temperature, weight and level

Analogue I/O

=The expansion module converts the standard voltage and current values to 12-bit digital representation. These digital values are transferred to the PLC for use in its program

Analogue outputs may be used to produce variable reference signals for devices such as:

# Control valves

# Chart recorders

# Electric motor drives

# Pressure transducers

# Analogue meters

Analog o/p example

Analog i/p example

Analog i/p example