Month: March 2018

In terms of computing and networking, the Ethernet or the Local Area Network (LAN), MAN and WAN of computer systems that we use for commercial purposes or otherwise has a rich set of protocols and formatting regulations that enable a smooth network connection. It is responsible for the clear and smooth transmission of data across network devices as well as over the network connection.

In order for the Ethernet to control, monitor and regulate data being transmitted across networks, it makes use of specific technology and features including an Ethernet gateway. Let’s learn more about how the Ethernet facilitates communication across networks.

What is an Ethernet gateway?

An Ethernet gateway, sometimes called a router is basically a node or one of the communication endpoints in a computer network that uses the Internet Protocol Suite that is responsible for forwarding data packets to other networks in cases where the network protocols are similar.

In other words, a default gateway serves as a router or a forwarding host to redirect data packets, while also being a common access point to other networks. This may involve not just address changes but also completely different networking technologies with different network prefixes as well. Such gateways are called internet gateways.

Now both the internet gateway and the router or the Ethernet gateway, are nodes that connect and regulate traffic between two or more networks. But the type of networks being handled is what is different.

A Windows 2000 network that uses the TCP/IP internet protocol as its primary protocol can use a router or an Ethernet gateway to connect to the internet as it is the same primary protocol that the internet uses.

An internet gateway on the other hand would be used to connect a Windows NT network for example with a NetWare network.

How does the Ethernet gateway work?

The Ethernet gateway is always connected to two or more different data lines from different networks. It reads the destination IP addresses on data packets coming in from the data lines and determines the ultimate destination. Then it makes use of the information on its routing table or the Routing Information Base (RIB) and directs the data packet to the next network on its route or journey. RIB is basically a data table that has a list of routes to particular destination addresses and sometime even the distance information associated with these routes.

The Ethernet also makes use of Ethernet converters and serial to Ethernet converters for converting media and data signals.

What is an Ethernet converter?

An Ethernet converter also called an Ethernet media converter is basically a device that is designed to enable the communication and smooth connection between different networking media such as fibre and co-axial cables used by different networks. It usually comes in the form of a small box and typically it is used to connect fibre media coming from an optical fibre based network and a copper-based network which is more conventional.

What is a serial to Ethernet converter?

Just like the media used by different networks, the data signals across networks may also come in serial form, which need to be converted to Ethernet packets in order to be routed and processed. This job is done by serial to Ethernet converters which are also called terminal servers or device servers as they are devices that have their own IP address.

It basically is a device that converts serial RS232, RS485 or RS422 data to Ethernet packets and also Ethernet TCP/IP packets back to these serial data signals. It comes in different models that facilitate different conversions.

How does a serial to Ethernet converter work?

A serial to Ethernet converter device usually comes with driver software that you need to install on your PC. The program creates virtual COM ports within the system when the converter is connected to the system. You can see all the virtual ports created by the software on your device manager list.

When you connect a serial device to one of the hardware ports on your converter device, the peripheral gets redirected to the visual serial port of your system and is identified by your PC as a local device. The circuitry within the converter then goes about converting each of the signals to Ethernet data packets for effective communication.

One of the biggest boons that the industrial sector of the world at large received came in the last century. We are talking about the invention of the Programmable Logic Controller (PLC) by Dick Morely back in 1969.

Ever since then, there have been many innovations in terms of functionality and hardware features for the control system and needless to say, each new one has been tough to beat. There are predominantly two giants who have had the duopoly in the manufacture of efficient PLCs for a long time now and they are Siemens and Allen Bradley.  

While each of these are established and top notch companies who have already proved the worth of their super-efficient TLCs individually, there has forever been a debate over which of these is better.

So here is a detailed comparison between the Allen Bradley and Siemens PLCs.

Before we begin, a quick word about what a PLC is.

What is a PLC?

In the simplest of terms, a Programmable Logic Controller or PLC is an industrial computer control system that allows you to get the most out of industrial processes. It helps enhance the processes while at the same time allowing you to switch up, replicate or change the processes as well quite easily.

Allen Bradley Vs. Siemens PLC

First things first, the quality and functionality of the hardware are significantly distinct. Both the AB and the Siemens PLCs work pretty much the same way and are equally reliable. The difference lies in their installation processes.

While the Allen Bradley requires you to connect the PLC to both the Allen Bradley power supply as well as the Allen Bradley rack, the Siemens one works with pretty much any 24 V DC supply of power. Also, you might need to install additional safety communication ports for Rockwell while Siemens already comes with built-in communication ports.

Another major difference is in the protocols they use. AB uses mostly native American IPs such as DeviceNet, ControlNet and EthernetIP, and also the DH+ or DH485.

At the same time, Siemens uses European native IPs such as Profibus and ASI and also serial MODBUS or MODBUS TCP/IP.

Coming to the interface and ease of use, AB has a more intuitive and easier user interface and it allows users to manage and control their processes even without a lot of programming knowledge. It also has excellent features like communicative abilities with third party hardware, mass production of code and even export and import of tags from Excel to scada databases.

Siemens might be a little complex for the maintenance staff that may not have a programming background.

On the flip side, Siemens offers a lot of options to program and customise the process to suit your business model.

As for the pricing aspects, Allen Bradley definitely is more expensive when compared to the Siemens PLC. However, Siemens offers standard technical support at all times at no additional costs while AB does charge you for technical support according to the amount of hardware you have installed.

That said, it would be ideal to choose one of these according to your priorities in terms of business processes.

Now if you have both Allen Bradley and Siemens devices and you want them to communicate, then you can use Equustek DL3500-MODBUS/DH+ or DL3500-MODBUS/DH485 for All Siemens that can handle uses serial MODBUS and Allen Bradley that support DH+ or DH485, or use the DL6000-MEDH+ or DL6000-MEDH485 that allow Siemens with MODBUS TCP/IP to communicate with Allen Bradley DH+ or DH485 devices.

FactoryTalk services platform is a suite of services developed by Rockwell Software. It includes Alarm and Events, Activation, Security, Audit, Directory, and Live Data. FactoryTalk is not a product that can be purchased as a standalone software package. FactoryTalk is embedded in most of the products from Rockwell Software; that is, it is the prefix to the majority of the Rockwell Software’s products.

To better understand each component of FactoryTalk services, here is a brief description to give more of an understanding of the proficiencies of each module.  

• Alarm and Events

Provides both device-based and server-based process control alarm server

• Activation

Provides a safe software-based system for activating the products of Rockwell Software along with managing software activations

• Security

Provides the users with a range of security services that are pre-installed in the FactoryTalk directory. The user groups and users are identical when it comes to managing them in the active directory. Moreover, they can be linked to the active directory as well. This functionality enables the users with centralized authentication and access control resulting in ‘single-user sign in’ when using FactoryTalk enabled products and services.

• Audit

It collects messages documented by the user regarding the management, design, and operation of production. It works as a configuration management tool and a process control system asset for smooth operations.

• Directory

The directory allows the products to share a standard address book that locates and provides access to factory-floor resources that includes graphic displays, tags, roles, and users. Using the FactoryTalk Administrative Console application, the directory can be managed.

• Live Data

It provides with real-time data between the servers and clients. That is, it will show the connection between the PLC and the HMI server, or between a PLC and FactoryTalk Historian SE. The live data server of FactoryTalk is for Rockwell Automaton devices that allow to manage the link between OPC-DA servers and clients for non-Rockwell Automation devices.

What is FactoryTalk Viewpoint?

FactoryTalk Viewpoint is an extension to the PanelView Plus and the View Site Edition, which adds web server features to the FactoryTalk View project.

When Viewpoint was first implemented by Rockwell, they did so as a Silverlight browser plugin. That means FactoryTalk Viewpoint is limited to Windows devices including tablets.

Its updated version was released in 2017 that went from being a Microsoft application to an HTML 5 application. The update improved FactoryTalk Viewpoint’s compatibility with devices, operating systems, and browsers that do not support Microsoft Silverlight.

However, people using FactoryTalk Viewpoint has complained about the software being slow.  

What is FactoryTalk security?

FactoryTalk security is a primary source of authentication and authorization controls. Instead of enforcing the same controls on each system with the RSLogix application, the users are entered and managed in one location.

Moreover, the authorization is a bit coarse, meaning it can be based on multiple actions individually aligned for each system. What makes things easier is that the application supports groups for role-based access control; thus, not everybody can access the system without mentioning the role.

FactoryTalk security allows users to access the application locally or using proxy authentication. In case, if the users have arranged a separate domain, they can leverage that existing infrastructure.

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In the world of industrial internet communication and networking, there are a lot of minute details that contribute towards giving us the convenience of information at our fingertips. From the type of computer network at the client end to the internet protocol to the databases being used, there are a lot of things that must come together in order to make a simple search request or process automation successful.

One such detail that plays a very important role in making exchange of information smooth and successful is the Modbus protocol along with the RS485.

These are two different but related concepts that people are often confused with. So let’s see what they are in detail.

What is Modbus and Modbus RS485?

Simply put, Modbus is basically a protocol that facilitates communication between the “master” or the host and the “slaves” or the connected devices. It enables the host to read the measures and aids in the configuration of devices.

On a basic level, the Modbus protocol facilitates communication with the help of messages that equate to simple operations necessary to read and write regular 16 bit words and binary details or registers called “coils”. The host or the master usually initiates the exchange and the slave or the device usually replies.

Hence, as is evident, the Modbus protocol literally defines the messaging structure used in the exchange of data between the host and the slaves or the devices.

It must not be confused with a medium of communication though. It forms the messaging structure alone and is not the physical medium of data exchange.

Now, in a normal stream of industrial data exchange or communication during process automation, there usually is a master which most often is a Building Automation System or a BAS, a communications gateway device, and a PLC or a software program that is running on a computer.

In order for the data exchange to happen, the host requires a medium that not only facilitates the exchange but also determines the pace.

Enter RS485.

It is basically an electrical or serial transmission standard that defines the physical level of electrical signals between the host and the slaves and also the wiring that enables the transfer of data. It is a popular standard used in data exchange as it allows the usage of several devices using the same standard on the same bus, which eliminates the need to multiply interfaces on the host while querying multiple devices.

Hence, when we say Modbus RS485, it denotes the protocol being used in process automation along with its ability to communicate effectively by the name of serial transmission standard.

On a normal case, a single multi-drop RS485 serial bus can facilitate up to 127 slave devices, which again is a good reason for its popularity.

Is Modbus the same as RS485?

The answer is no, because both of these are relative concepts that need each other in order to fulfil their purposes. Modbus defines the protocol type and RS485 defines the signal level on the protocol.