September 2011 | Programmable logic controller

PLC Remote Input / Output Units

PLC remote I/O units are used for the inputs and outputs that are not in the electrical room, including all of the controls and lamps in the operator's cabin. This significantly reduces the number of control cables and intermediate terminations. Each remote I/O unit is connected to the Master PLC by a high speed serial link. A monitoring function in each unit de-energizes all of the control outputs in the event of a fault. This includes the loss of the data highway from the master PLC.

what is hmi ? (Human Machine Interface)

A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through which the human operator controls the process.

An HMI is usually linked to the SCADA system's databases and software programs, to provide trending, diagnostic data, and management information such as scheduled maintenance procedures, logistic information, detailed schematics for a particular sensor or machine, and expert-system troubleshooting guides.

The HMI system usually presents the information to the operating personnel graphically, in the form of a mimic diagram. This means that the operator can see a schematic representation of the plant being controlled. For example, a picture of a pump connected to a pipe can show the operator that the pump is running and how much fluid it is pumping through the pipe at the moment. The operator can then switch the pump off. The HMI software will show the flow rate of the fluid in the pipe decrease in real time. Mimic diagrams may consist of line graphics and schematic symbols to represent process elements, or may consist of digital photographs of the process equipment overlain with animated symbols.

The HMI package for the SCADA system typically includes a drawing program that the operators or system maintenance personnel use to change the way these points are represented in the interface. These representations can be as simple as an on-screen traffic light, which represents the state of an actual traffic light in the field, or as complex as a multi-projector display representing the position of all of the elevators in a skyscraper or all of the trains on a railway.

An important part of most SCADA implementations is alarm handling. The system monitors whether certain alarm conditions are satisfied, to determine when an alarm event has occurred. Once an alarm event has been detected, one or more actions are taken (such as the activation of one or more alarm indicators, and perhaps the generation of email or text messages so that management or remote SCADA operators are informed). In many cases, a SCADA operator may have to acknowledge the alarm event; this may deactivate some alarm indicators, whereas other indicators remain active until the alarm conditions are cleared. Alarm conditions can be explicit – for example, an alarm point is a digital status point that has either the value NORMAL or ALARM that is calculated by a formula based on the values in other analogue and digital points – or implicit: the SCADA system might automatically monitor whether the value in an analogue point lies outside high and low limit values associated with that point. Examples of alarm indicators include a siren, a pop-up box on a screen, or a coloured or flashing area on a screen (that might act in a similar way to the "fuel tank empty" light in a car); in each case, the role of the alarm indicator is to draw the operator's attention to the part of the system 'in alarm' so that appropriate action can be taken. In designing SCADA systems, care is needed in coping with a cascade of alarm events occurring in a short time, otherwise the underlying cause (which might not be the earliest event detected) may get lost in the noise. Unfortunately, when used as a noun, the word 'alarm' is used rather loosely in the industry; thus, depending on context it might mean an alarm point, an alarm indicator, or an alarm event.
Contents from wikipedia

SCADA (supervisory control and data acquisition)

SCADA (supervisory control and data acquisition) generally refers to industrial control systems (ICS): computer systems that monitor and control industrial, infrastructure, or facility-based processes, as described below:
•   Industrial processes include those of manufacturing, production, power generation, fabrication, and refining, and may run in continuous, batch, repetitive, or discrete modes.
•   Infrastructure processes may be public or private, and include water treatment and distribution, wastewater collection and treatment, oil and gas pipelines, electrical power transmission and distribution, Wind farms, civil defense siren systems, and large communication systems.
•   Facility processes occur both in public facilities and private ones, including buildings, airports, ships, and space stations. They monitor and control HVAC, access, and energy consumption.
A SCADA system usually consists of the following subsystems:
•   A Human–machine interface or HMI is the apparatus which presents process data to a human operator, and through this, the human operator monitors and controls the process.
•   A supervisory (computer) system, gathering (acquiring) data on the process and sending commands (control) to the process.
•   Remote terminal units (RTUs) connecting to sensors in the process, converting sensor signals to digital data and sending digital data to the supervisory system.
•   Programmable logic controller (PLCs) used as field devices because they are more economical, versatile, flexible, and configurable than special-purpose RTUs.
•   Communication infrastructure connecting the supervisory system to the remote terminal units
                                                                                     Contents from wikipedia

What is PLC [ Programmable logic Controller ]

What is PLC ? [ Programmable logic Controller ]
A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a hard real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result.

Contents from wikipedia

Parameter Assignment of PID Control

Calling the Parameter Assignment User Interface

You call the parameter assignment user interface of PID Control under
Windows 95 using the following menu options:
Start SIMATIC STEP 7 V3 PID Control Parameter
Assignment
In the first dialog, you can either open an existing instance data block (DB)
for an FB41 “CONT_C” or FB42 “CONT_S” or create a new data block as
the instance data block. If you create a new instance data block, you will be
prompted to assign the instance DB to an FB.
FB43 “PULSEGEN” does not have a parameter assignment user interface.
You must set its parameters with STEP 7 tools.

PID Control,Standard Software for S7-300 and S7-400

The Concept of PID Control

The function blocks (FBs) of the PID Control package consist of controller
blocks for continuous control (CONT_C), for step control (CONT_S), and
the FB for pulse duration modulation (PULSEGEN).
The controller blocks implement a purely software controller with the block
providing the entire functionality of the controller. The data required for
cyclic calculation is stored in data blocks assigned to the FB. This allows the
FBs to be called as often as necessary.
FB PULSEGEN is used in conjunction with FB CONT_C to implement a
controller with a pulse output for proportional actuators.

Basic Functions

A controller created with the FBs consists of a series of subfunctions that you
can activate or deactivate. In addition to the actual controller with its PID
algorithm, integrated functions are also available for processing the setpoint
and process variable and for adapting the calculated manipulated variable.

Applications

A controller implemented with the two controller blocks is not restricted to
any particular application. The performance of the controller and its
processing speed is only dependent on the performance of the CPU being
used.
With any given CPU, a compromise must be made between the number of
controllers and the frequency at which the individual controllers are
processed. The speed at which the control loops must be processed, in other
words, the more often the manipulated variables must be calculated per unit
of time, determines the number of controllers that can be installed (faster
loops mean less controllers).
There are no restrictions in terms of the type of process that can be
controlled. Both slow processes (temperatures, tank levels etc.) and very fast
processes (flow rate, motor speed etc.) can be controlled.

Actuator Sensor-interface AS-i

What is AS-i?

A simple network for actuators and sensors

Connects input / output devices to a PLC or PC

Connects I/O devices to a two-wire flat cable

Eliminates multiple terminations

Easily replaces point-to-point wiring systems

A complete networking solution

Point-to-Point Wiring vs. AS-i Networking

Point-to-Point Wiring

Large wire bundles take up valuable space

Installation time is considerable

Troubleshooting is complex

Actuator Sensor-interface Networking

Completely eliminates wire bundles

Plug-and-play wiring supports all topologies

Eliminates junction boxes and reduces the size of the control cabinet

Why Choose AS-i…

A simple 2-wire flat cable

Extremely fast system

Insulation displacement

Flexible topology

Cost effective

Best fit

Modular system

An Overview of AS-i System Components

Two methods to connect AS-i to your existing control platform:

Method 1: Backplane Master Connection

Fits in a standard card slot in a plc rack

Plugs into backplane

Replaces traditional I/O cards

I/Os are mapped directly to I/O tables

Programmed via the standard plc software

Method 2: Fieldbus Gateway Connection

Connects to higher-level fieldbus systems

Gateway becomes a single node on the fieldbus network

Reduces the price per point for connecting sensors and actuators

After selecting connection method, choose an AS-i Power Supply

An integral and necessary part of an AS-i system

Provides power to all input devices and modules

Couples the master data and 24 VDC power for transmission over the yellow flat cable

Field Input and Output Modules

Connects the AS-i master and periphery equipment Compact Modules

Designed for harsh environments

Rated IP67 for washdown environments

M12 connectors for simple plug-and-play wiring Classic modules

DIN rail mountable

For areas with limited mounting space

Rated IP67

Equipment such as pushbuttons and motor starters can be connected to cabinet modules Cabinet Modules

Rated IP20

I/O modules may be daisy-chained together inside the enclosure

DIN rail mounting

Intelligent System Solutions

Pneumatic Modules

The airbox is a single AS-i node with up to four inputs and two integrated pneumatic outputs

Stainless steel options for heavy washdown environments

Ideal solution for distributed valve applications

Quarter-Turn Valve Feedback

One cable can connect 31 quarter-turn valve feedback devices and 31 solenoid valves

IND sensor and integrated output for a solenoid valve are networked with AS-i

The AS-i Networking System Complements Existing Bus Systems

Dramatic cost savings for actuators and sensors

Reduced engineering design time

Eliminates trunk and drop line calculations

Communication is transparent

No terminating resistors

No technical descriptive data files

• On Devicenet: EDS files

• On Profibus: GDS files

Benefits to Equipment Builders

Reduces engineering design time

Reduces BOM costs

Easy commissioning for new machines

Easy troubleshooting

No additional software

Benefits for End-Users

Reduced maintenance costs
Easy troubleshooting
Easy expansion of existing systems in-house
Free training seminars by ifm efector

ifm efector introduces Controller-e

High-speed, integrated AS-i master and PLC
Can be used as a gateway to higher-level bus
systems and as a stand-alone PLC
Supports all 2.1 AS-i specifications
Integrated backlit LCD display with status LEDs
1 MB of total memory with 128 Kwords
program memory
Connects 124 AS-i nodes for a total 868 I/O points
Standard IEC 61131-3 programming

CPU's	CPU312IFM	CPU313	CPU314IFM	CPU314
Mem Statement/Bytes	2K/6KB	4K/12KB	8K/24KB	16K/48KB
Memory Cards	-	512KB FEPROM	-	512KB FEPROM
Processing Time 1024 Statements	0.6 ms	0.6 ms	0.3 ms	0.3 ms
DI & DO Max	256	256	1024	1024
AI & AO Max	64	64	256	256
Rack Configuration	1-Tier	1-Tier	4-Tier	4-Tier
Expansion Modules Max	8	8	31	31
Bit Memories	1024	2048	2048	2048
Counters	32	32	64	64
Timers	64	64	72	128
MPI Interface 187.5 Kbit/s Max 32 Nodes	Yes	Yes	Yes	Yes
Integrated functions+Interfaces	10DI/6DQ onboard. int. functions:Counters/Freq. Measuremensts	-	20DI/16DQ ,4AI,1AO onboard. int. functions:Counters/Freq. Measuremensts/Positioning PID Control	-

CPU's	CPU315	CPU315-2DP	CPU316-2DP	CPU318-2
Mem Statement/Bytes	16K/48KB	16K/48KB	42K/128KB	256KB
Memory Cards	512KB FEPROM	512KB FEPROM	4MB FEPROM	4MB FEPROM
Processing Time 1024 Statements	0.3 ms	0.3 ms	0.3 ms	0.1 ms
DI & DO Max	1024	2048	4096	16384
AI & AO Max	256	256	256	1024
Rack Configuration	4-Tier	4-Tier	4-Tier	4-Tier
Expansion Modules Max	32	32	32	32
Bit Memories	2048	2048	2048	8192
Counters	64	64	64	512
Timers	128	128	128	512
MPI Interface 187.5 Kbit/s Max 32 Nodes	Yes	Yes	Yes	Upto 12Mbaud
Integrated functions+Interfaces	-	PROFIBUS-DP Master/Slave (64 DP stations,12Mbaud)	PROFIBUS-DP Master/Slave (64 DP stations,12Mbaud)	PROFIBUS-DP Master/Slave (125 DP stations,12Mbaud)

* 1 K statements correspond to approx. 3Kbytes of user memory.

THE DIFFERENT TYPES OF MODULES AVAILABLE ARE

1. SIGNAL MODULES - FOR DIGITAL AND ANALOG SIGNALS

DIGITAL INPUTS	DIGITAL OUTPUTS
· 16 X 24 VDC · 8 X 120 / 230 VAC · 16 X 120 V AC · 32 X 24 V DC	· 16 x 24 VDC ,0.5A · 8 X 24 VDC ,2A · 8 X 120 / 230 VAC, 2A · 16 X 120 VAC, 1A · 32 X 24 V DC, 0.5A
RELAY OUTPUTS	DI/DO MODULES
· 8 X Relay 30 VDC ,0.5A · 8 X Relay 250 VAC ,3A · 16 X Relay 30VDC,0.5A · 16 X Relay 120VAC, 2.5A	· 8DI/8DO X 24VDC 0.5A

ANALOG INPUTS PARAMETERIZABLE	ANALOG OUTPUTS PARAMETERIZABLE
· 8 Analog Inputs/ 2 Analog Inputs · +/- 10V , +/- 50 mV, +/-1 V, +/-20 Ma, 4 to 20mA, Pt100, Thermocouple	· 4 Analog Outputs/ 2 Analog Outputs · +/-10V, +/-50mV, +/-1 V, +/-20 mV, 4 to 20 mA

2. FUNCTION MODULES

· High Speed Counter Modules - Upto 100 KHz range

· Positioning Modules - For position control, Stepper Motor Control, Cam Controllers

All function modules are enclosed and can be installed in any slot.

3. COMMUNICATION PROCESSORS - FOR DATA EXCHANGE WITH PRINTERS,COMPUTERS, SIMATIC SYSTEMS

· CP340 - Point to Point Communication for the serial link with RS232, 3964R and any ASCII protocol

4. INTERFACE MODULES - FOR MULTI TIER CONFIGURATION

· For Central Controller Expansion

· For Expansion Unit Connection

5. POWER SUPPLY MODULES - FOR 24 VDC LOAD CIRCUITS WITH DIFFERENT RATINGS.

MPI - MULTI POINT INTERFACE FOR COMMUNICATION

· MPI INTEGRATED IN CPU

· DATA EXCHANGE RATE : 187.5 Kbits / s

· SIMULTANEOUS COMMUNICATION WITH PG/PC/OP(OPERATOR PANEL) AND FURTHER PLCS REQUIRING NO ADDITIONAL HARDWARE

· UPTO 32 NODES CAN BE CONNECTED

Programmable logic controller | PLC

Pages

PLC Remote Input / Output Units

what is hmi ? (Human Machine Interface)

SCADA (supervisory control and data acquisition)

What is PLC [ Programmable logic Controller ]

Parameter Assignment of PID Control

PID Control,Standard Software for S7-300 and S7-400

Actuator Sensor-interface AS-i

Siemens STEP 7 WinLC

Siemens STEP 7 WinLC RTX

Siemens S7-400 CPU 412-2 PCI

Siemens S7-400 CPU 416-2 PCI

Siemens S7-300 CP 343-2 P

Siemens S7-300 SM 338 POS-INPUT

Siemens S7-300 AO4x16Bit

Siemens S7-300 AI8x14Bit

Siemens S7-300 DO16xDC24V/0.5A

Siemens S7-300 DI16xDC24V

Siemens S7-300 DI16xDC24V, Alarm

Siemens S7-300 DI16xDC24V, Alarm

Siemens S7-400 CP 443-5 Ext

Siemens S7-400 DI16xDC 24V Interrupt

COMPARISON OF CPU'S in Siemens PLC

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