Tag Archives: Networking & Communication

What is a DCS?

DCS stands for “Distributed Control System” which is an automated control system that streamlines the functionalities of the different devices used throughout a work space. DCS utilizes a wide range of controllers to permit all the parts to converse with one another just as PCs do. These controllers are distributed geographically across a plant to allow for high-speed communication to the control process. When utilizing various kinds of modules, the framework may require diverse correspondence norms, for example, Modbus and Profibus.

Learn the difference between a Distributed Control System (DCS) and a Programmable  Logic Controller (PLC) here: PLC vs. DCS: What’s the difference? – MRO Blog

Components of a DCS

A distributed control system or DCS is a control system in which the controller components are not local but are dispersed throughout the system with every component sub-system controlled by one or more controllers. The entire arrangement of controllers is associated by systems for correspondence and observing. DCS is an extremely wide term utilized in an assortment of enterprises, to monitor and control hardware. Below is a list of places that use Distributed Control Systems.

  • Radio signals
  • Dry cargo and bulk oil carrier ships
  • Electrical power grids and electrical generation plants
  • Traffic signals
  • Water management systems
  • Oil refining plants
  • Chemical plants
  • Sensor networks
  • Environmental control systems

History of the DCS

The first Distributed Control System was made by Honeywell in 1969. This new design depended on a vast distributed control to the computer modules. Every one of these modules controlled a few different processors, for the most part, one to four. They were associated with a high-speed data communications link, known as a data highway which made communications between each of the computer modules and the central operator console possible. This plan permitted the administrator to monitor the activity of every local process. 

Moving forward, microprocessor-based modules replaced hardwired computer modules in the 1970’s. However, Today’s distributed control systems are much more powerful and faster than the early systems because of advancements in microprocessors and other electronic circuits. The next section of this blog illustrates how a present DCS operates and is shown in the diagram below.

DCS Operation “ The Three Qualities”

A DCS has three main qualities. The first quality is the conveyance of different control capacities into little arrangements of subsystems, which are of semiautonomous, and are interconnected through a rapid correspondence transport. A portion of these capacities incorporate securing information, information introduction, process control, process supervision, revealing data, and the saving and recovery of data.

The second trait of DCS is the computerization of assembling processes by coordinating propelled control techniques. Furthermore, the third quality of the DCS is organizing the entire process as a system. A DCS sorts out the whole control structure as a solitary computerization system where different subsystems are brought together through an appropriate order and data stream.

These qualities of the DCS are shown in the figure below. The essential architecture in a DCS include engineering workstation, operating station or HMI, process control unit or local control unit, smart devices, and a communication system.

Important Features of a DCS

  1. HMI: A DCS can monitor and control through HMI’s, otherwise known as a Human Machine Interface, which gives adequate information to the administrator to charge over different procedures which acts as the center of the system. However, this type of industrial control system covers large areas whereas a DCS covers one region. A DCS uses the whole process plant to control the process as a PC window. Trending, logging and graphical representation of the HMI’s give effective user interface. A Powerful alarming system of a DCS helps operators to respond more quickly to the plant’s shape when needed. 
  2. Security: Access to control the various processes leads to plant safety. The DCS design offers a perfect and secure system to handle framework functions for top notch factory automation control. Security is also provided at different levels such as an operator level, engineer level, and an entrepreneur level.
  3. The handling of complex procedures: APLC or Programmable Logic Controller is utilized to control and monitor the procedure parameters at a rapid speed. Click here for more information about PLCs. However, a DCS is preferred for more complex control applications because with a higher number of I/O’s with dedicated controllers, it is able to handle such processes. These are used in assembling processes where the structuring of various products is in multiple procedures such as a batch process control.

Considerations When Choosing a DCS

The bulk of control system decisions include the use of a programmable logic controller (PLC) or a distributed control system (DCS). In some cases one alternative is clearly better for a plant while the choice is not as simple in others. Selecting the control system entails several considerations that will help the customer meet their short-and long-term goals.

Difference between PLC and DCS systems: A PLC is an industrial computer that is built to control manufacturing processes such as robots, high-speed packaging, bottling, and motion control. In the last 20 years, PLCs have gained functionality and provide benefits for small plant applications. PLCs are usually solitary islands of automation that can be unified so they can communicate with one another. PLCs are great for smaller applications that are unlikely to expand in the future. 

A DCS distributes controllers throughout the automation system and offers a standard guidance, automated monitoring, a systemwide database, and easy-to-share information. DCSs are commonly used in process applications and larger plants, and are easier to maintain throughout the plant’s life cycle for large device applications.

The Application type determines the platform: PLCs and DCSs are typically suited to one of two forms of production: discrete manufacturing and process manufacturing. Discrete manufacturing facilities, which typically use PLCs, consist of separate manufacturing units which generally assemble components, such as labeling or fill-and-finish applications. Facilities for process manufacturing typically use DCSs, automate continuous and batch processes and enforce formulations consisting of components rather than parts. Process manufacturing facilities calculate their production in bulk. DCS automation is used by large continuous process installations, such as refineries and chemical plants.

Several aspects must be considered when finding the right DCS such as:

  • Process size
  • Integration needs
  • Functionality
  • High availability
  • Expansion or modification plans
  • ROI on the facilities lifespan

What is a PLC?

A Programmable Logic Controller, abbreviated as “PLC” is a computer used to address the issues of a particular assembling process. These devices come in a wide range of shapes and sizes, with numerous alternatives for computerized and simple I/O, as well as protection from high temperatures, vibration, and electrical noise. The invention of the PLC allows for computers to be streamlined into the industrial automation process.

A PLC can be a solitary device figuring and executing operations, or a rack of various modules utilized to meet whatever your automation system requires. A portion of the extra parts include processors, power supplies, additional IO, interfaces, and more. Each part cooperates to have the option to run open or shut circle activities that are appraised at fast and high accuracy. Take a CNC machine for instance; a PLC would be utilized to control positioning, motion, and torque control. These devices are popular since they are inexpensive in relation to the amount of power and lifespan they possess. PLCs can run for hours on end. 

The diagram below displays the process of a Programmable Logic Controller system.

History of PLCs

Programmable Logic Controllers (PLCs) first hit the scene in the late 1960s. The essential purpose behind planning such a device was eliminating the high cost required to replace the complicated relay based control systems for major U.S. vehicle makers. There was a primary issue and that was that they were mechanical. This implies that they wear out and must be replaced from time to time. Additionally, relays take up too much room. These, alongside different contemplations, prompted the advancement of PLCs. More enhancements to PLCs happened during the ’70s. In 1973 the ability to communicate between PLCs was introduced. This made it possible to have the controlling circuit perform at a distance from the machine it was controlling. In several cases, the absence of institutionalization in PLCs caused a few different issues. This was improved in the 1980s. The size of PLCs was additionally decreased, which meant plants were utilizing space much more effectively. The ’90s expanded the assortment of manners by which a PLC could be modified such as block programs and a guidance list. They also observed PLCs being replaced by PC’s in a few cases. Be that as it may, PLCs are still being used in a wide range of businesses, and it’s going to remain that way in the foreseeable future.

How It Works “The Three Tasks”

The way a PLC works is very straightforward: The PLC receives data from associated sensors or information devices, processes the information, and triggers outputs dependent on pre-customized parameters. 

Depending on the inputs and outputs, a PLC can monitor and record run-time data such as machine productivity or operating temperature, automatically start and stop processes, generate alarms if a machine malfunctions, and that’s just the beginning. Programmable Logic Controllers are a versatile and powerful control arrangement, adaptable to practically any application.

A PLC essentially performs three tasks: a PLC checks the information inputs, goes through the program, and changes the outputs. Then, it circles back to the top and starts once more. This appears incredibly straightforward, however, it tends to be made very complex with various sources of I/O. The scan time is the time it takes for the PLC to experience the three fundamental tasks. This time is significant, as it influences how rapidly the inputs of info can be read. The sources of info should be on or off long enough for the PLC to read them. On the off chance that they are not on that long, issues begin to occur. Luckily, there are approaches to fix this issue. Perhaps the most ideal way is to utilize an interrupt at whatever point an input goes to high. This will guarantee that the PLC doesn’t miss the change.

Inputs and Outputs (I/Os)

As we’ve seen up until this point, inputs and outputs are very important to the activity of a PLC. Two key components to consider in picking the privilege PLC are the quantity of I/Os and their location. Since PLC controls undergo a large process, you will need to ensure it can deal with various I/Os. The quantity of both analog and discrete devices that your system has will affect this choice too. Remember that the quantity of I/Os will likewise decide the size of your PLC’s body. The location of I/Os will also have an effect on your choice. Will your framework require a local I/O, or will you need both local and remote I/Os? Subsystems are needed to answer these questions sufficiently. Keep in mind that the speeds and distance at which your PLC operates is important for this.

PLC Acronyms Worth Knowing

These acronyms will help you better understand what exactly you are looking for.

ASCIIAmerican Standard Code for Information Interchange
BCDBinary Coded Decimal
CSACanadian Standards Association
DIODistributed I/O
EIAElectronic Industries Association
EMIElectroMagnetic Interference
HMIHuman Machine Interface
IECInternational Electrotechnical Commission
IEEEInstitute of Electrical and Electronic Engineers
I/OInput(s) and/or Output(s)
ISOInternational Standards Organization
LLLadder Logic
LSBLeast Significant Bit
MMIMan Machine Interface
MODICONModular Digital Controller
MSBMost Significant Bit
PIDProportional Integral Derivative (feedback control)
RFRadio Frequency
RIORemote I/O
RTURemote Terminal Unit
SCADASupervisory Control And Data Acquisition
TCP/IPTransmission Control Protocol / Internet Protocol

What to Consider When Buying a PLC

  • Will the framework be powered
  •  by AC or DC voltage? 
  • Will the system be situated in one spot or spread out over a huge region?
  • Does the system run quick enough to meet my application’s necessities? 
  • What kind of programming is utilized to program the PLC? 
  • Whenever required by your application, can the PLC handle simple data inputs and outputs, or perhaps a mix of both? How am I going to speak with my PLC? 
  • Do I need to arrange availability and would it be able to be added to my PLC? 
  • Will the PLC have the option to deal with the quantity of information inputs and outputs that my application requires? 
  • Does the PLC have enough memory to run my user program? 
  • Inputs and Outputs (I/Os)

Looking To Buy?

Check out our collection of PLCs at the link “Showing PLC”  below. We provide you with the thousands of Program Logic Controllers by the brands Schneider Electric, SIEMENS, and Yaskawa at the best prices. Below are just a few PLC devices we have for sale on our website. Please visit and contact us if you have any questions.  Showing PLC.

UD75 Configuration and Setup

You can check out our previous blog post  on the UD75 here for more information. Check out the UD75 product page on our website along with all of our other Unidrive options.

UD75 Configuration
  1. Isolate the drive from the mains supply and allow 5 minutes for the DC Bus capacitors to discharge.
  2. Insert Large Option Module as shown below. Ensure that it is correctly inserted. The module will click firmly into place.
  3. To remove the module, pull on the black tab, and the module will disengage from the connector and pull out of the drive.
UD75 Configuration: Cable Screen
The screen of the cable at every node on the network MUST be connected to the screen terminal (pin 3) on the CTNet terminal block. When the screen is stripped back to connect the twisted pair to the CTNet terminals, keep the exposed section of the cable as short as possible. On the CTNet PC Interface Adapter Card, there is no screen terminal. The screen should be cut and taped back to prevent it coming into contact with any other surfaces. The on-board terminal resistor should not be connected.
UD75 Configuration: Network Termination
The network MUST be fitted with terminating resistors AT BOTH ENDS!!! If resistors are not fitted, the network appear to work OK, but the noise immunity of the network will be drastically reduced. The terminating resistor value should match the nominal characteristic impedance value for the cable; in the case of the customized CTNet cable, the terminating resistors used should be nominally 78Ω. PC ISA and PCMCIA cards for interfacing a PC to CTNet are available from CT SSPD.

For price and ordering info you can email sales@mroelectric.com or call 1-800-691-8511. We have these and all the other Control Techniques Unidrive Classic option modules in stock, along with the drives themselves.

UD75 Configuration
UD75 Configuration

UD73 Configuration and Setup

You can check out our previous blog post on the UD73 here for additional setup and configuration info.

For UD73 configuration, most common parameters are arranged in one concise menu. Hundreds of user-configurable functions separated into 20 logical menus provide quick setup for advanced application. For positioning, ratio control, camming and multi-axis systems, plug-in option modules easily extend the Unidrive’s capabilities. High horsepower Unidrives cover the range from 200 to 1600 HP. The 300 amp power module and control pod (the “brain”) are available as components. They are also available as a packaged drive solution that includes fusing and a disconnect. (See our Packaged Drive Section, pages 120-123 and 128-133.) With the UD73’s extensive selection of communication, application, feedback and I/O modules, you can easily upgrade the performance of your drive. Yet, it is simple to configure by using the drive keypad, a remote keypad (CTKP), or UniSoft, the UD73 Windows based drive set-up tool. You can tailor each Unidrive to be the drive you want when you want it.
    • Digital AC Drive
    • 1 to 30 HP, 3 Phase, 208-230 VAC
    • 1 to 1600 HP, 3 Phase, 380-460 VAC
    • Five operating modes
        • V/Hz
        • Open loop vector
        • Closed loop vector
        • Brushless AC servo
      • Regenerative
    • UniSoft Windows based configuration tool
    • Configurable analog and digital I/O
  • Complete Motor Solutions
The UD73 configuration is suited for use with AC brushless servo motors. Servo control is ideal for applications requiring load transfer to and from any position, at any speed. The UD73 is designed for both stand-alone and multi-axis system applications.
In regen mode, two standard UD73’s operate together to provide full four-quadrant control of an AC motor. The system consists of two basic sub-systems, one being a Unidrive operating in any of its standard operating modes (open loop, vector or servo), and the other is a Unidrive operating in its regenerative mode. The link between the two sub-systems is simply the DC bus connections. In this mode, the UD73 is capable
of either supplying power to the DC bus of the Unidrive controlling the motor or removing power from the DC bus of the Unidrive controlling the motor and returning it back to the power line.
If you would like to order a module or get more info you can email sales@mroelectric.com or call 1-800-691-8511.

UD75: Beyond the User Manual

The UD75 CTnet Interface card for the Unidrive Classic series is supplied in a large option module. It is an add-on card for the UD70 applications card. The UD70 processor and operating system handles all network activity, and uses a dual-port RAM interface to transfer data between itself and the drive.

The UD70 CTnet retains full functionality, allowing the user to download normal DPL application programs. No program modifications are required to allow existing DPL programs to run. A different UD70 operating system file (“UD70NET.SYS”) is used, and the UD70 has this system file pre-loaded.

The Unidrive must be disconnected from the mains supply before installing or removing any option module, including the UD75.

Isolate the drive from the mains supply and allow 5 minute for the DC bus capacitors to discharge. Insert the large option module. Ensure that it is correctly inserted. The module will click firmly into place. To remove the module, pull on the black tab and the module will disengage from the connector and pull out of the drive.

For more info you can visit the UD75 product page here. For price and ordering info you can email sales@mroelectric.com or call 1-800-691-8511. We have these and all the other Unidrive Classic option modules in stock, along with the drives themselves.

UD75 CTnet

UD73 Module: Beyond the Manual

The Control Techniques UD73 large option module is a high speed microprocessor that provide a low cost facility for a system designer to write app specific programs without needing a PLC or other stand-alone controllers. The module is programmed via the RS232 port using the Control Techniques system programming toolkit.

The UD73 module uses a dual port RAM to interface to the drive’s main processor which provides intimate high-speed bi-directional access. It can ready and modify any of the parameters within the drive. This enables customized real-time calculations under a multi-tasking run-time environment.

The optically isolated RS485 port serves as a communication for for the CTIU operator interface units. It is fully configurable, supporting many communication modes. In addition, the module has the Profibus-DP port for additional communication options.

For additional info you can visit the UD73 product page on our website here. We will continue to post info about the Control Technique option modules in the future. If you would like to order a module or get more info you can email sales@mroelectric.com or call 1-800-691-8511.

The table below shows a quick reference for all of the different option modules that can be used with the Unidrive Classic series. We have all of the different modules available and in stock.

UD73 Table
UD73 Table

Assigning a 140 NOE Module Ethernet Address Parameter


If you have just received the Schneider 140 NOE 771 xx module but have not yet programmed it with an Ethernet configurable extension, you will need to assign an IP address to your module. In this guide you’ll receive information about assigning a 140 NOE Module Ethernet Address Parameter.
Using the BOOTP Lite software utility you can assign IP address parameters. One thing to note, however, is that with the modules 140 NOE 771 01, -11, and NWM 100 00 you can assign the IP address using web pages.

Continue reading Assigning a 140 NOE Module Ethernet Address Parameter

Modbus, Traditional Networks still Dominant over Industrial Ethernet

Modbus, Traditional Networks still Dominant over Industrial Ethernet

We’re always keeping an eye on innovation, and a big trend in the PLC world is the move toward industrial ethernet communications rather than traditional networks. However, Bill Lydon (Editor for Automation.com) recently posted an article asserting that it’s going to be 15-20 years before industrial ethernet becomes the dominant market technology. In the meantime, customers are relying on networks like Modbus, Fieldbus, DeviceNet and others.

Modbus, designed by Modicon in 1979, is a request/reply protocol and offers services specified by function codes. Our Modicon Quantum Communications Modules utilize Modbus protocol to communicate with the drives and input/output modules on the same network, and has become so popular since its inception that many other industrial electronics also support the protocol.

MRO Electric and Supply has new and refurbished FANUC CNC, FANUC Robotics, Control Techniques,  Siemens, Modicon, Yaskawa, MagneTek, Saftronics, and Omron products available. We also offer repair pricing. For more information, please call 800-691-8511 or email sales@mroelectric.com

Real-Time Data Collection using PLC Networking

This article from Control Engineering offers a great preview of the future of manufacturing with PLCs. Ethernet connections allow for real-time data collection, which introduces great networking potential between workers and the machines. Because PLCs can be programmed to make decisions based on input variables, we can automate more tasks but still be confident that process variables are under control. The development and innovation of Modicon Quantum I/O Modules create the backbone of the PLC networking configuration.

Another exciting revelation in the article:

To meet the growing operation needs of industrial automation, networks continue to expand, offering monitoring and control capabilities in areas not previously possible. Device networks are now using fieldbus-to-Ethernet integration to develop enterprise-wide control networks. Merging networking functionality with PLCs enables users to off-load main processor tasks for distributed control in the field, placing control-level devices closer to the action. Additionally, by combining control with distributed I/O, manufacturers can lower their total cost of operation by streamlining data acquisition, communication, and factory-wide connectivity.

We can’t wait to see how users pair the networking capabilities of PLCs with infrastructure already in place on the factory floor.

MRO Electric and Supply has new and refurbished Modicon products available including the Modicon Quantum series. We also offer repair pricing. For more information, please call 800-691-8511 or email sales@mroelectric.com.