Gateways Make Systems Multilingual

Industrial settings, where multiple types of equipment must communicate with each other, can benefit substantially from an Ethernet gateway.

Industrial Ethernet gateways streamline equipment communication by handling protocol conversion. They’ll also monitor energy use and add functionality to older equipment. 

If you don’t know about the industrial Ethernet gateway, you may be missing an opportunity to improve communication among your automated equipment, make older equipment more functional, and simplify activities such as network troubleshooting and energy monitoring. The Ethernet gateway—also referred to as a protocol converter or simply a gateway—is a standalone device that converts a signal from one protocol to another. It can convert a Modbus RTU (remote terminal unit) to Modbus TCP (transmission control protocol), for example, or make other conversions, such as Modbus RTU to PROFIBUS or Profinet. It achieves this with a built-in CPU and memory-storage capability that allows connected equipment to communicate directly with the gateway instead of with each other using the PLC. This eliminates the need for separate—and more complicated—protocol-conversion processes, and is handled entirely by the gateway.

This is a typical gateway connection linking a variable-frequency drive, using Modbus RTU, with an Ethernet-enabled PLC.

New capabilities

Gateways have existed for at least a decade, but have recently acquired new capabilities. “They’re smaller and more compact and there’s support for more protocols,” said Paul Wacker, product manager, Americas, for Moxa, a Brea-CA-based maker of gateways and other automation solutions for industry. “And for maintenance, there are more maintenance and monitoring features that make it easy for troubleshooting and access to data, such as for plant-energy use.”

The added protocol capabilities also help extend the life of equipment that uses older protocols. “One of the gateway’s real values is making something old work with something new,” said Wacker, who uses variable-frequency drives (VFD) as an example. “Most drives installed within the last five years have a built-in Modbus port,” he stated. “But Modbus is one of the oldest protocols for communication in industrial automation, and suppose you need to get an older drive to talk to a newer PLC that doesn’t do Modbus. Instead, it does, say, Ethernet IP, which is the predominant standard for some PLC makers in the U.S. There aren’t many options that allow you to do this.”

The available options might include buying a conversion card for the PLC or installing a more-complex third-party device that would need a program written for it. The simpler, less-costly gateway option, said Wacker, requires, “dropping in a small DIN-rail mount box and, through simple configuration of fill-in-the-blanks, telling the gateway what you want to read, and to make it available to your PLC on Ethernet IP.”

Installation and set-up does require planning, of course, but the fill-in-the-blanks approach was devised to eliminate the need for a programmer, IT technician, or engineer. “We spent a lot of time making sure it’s easy to set up and use,” said Wacker. “So you don’t have to be an engineer who must know all the intricacies of all the protocols, which can be detailed. We’ve made it high-level enough so someone with basic skills can put it together.”

The gateway device is also designed to be versatile. It allows monitoring of various aspects of a VFD, for example, after the system is up and running, and makes it easy to add VFDs simply by reserving I/O space in the PLC and the gateway configuration for future expansion. When new drives are added, only the gateway needs reconfiguration, not the PLC.

Gateways are also used in the field for oil and gas well-head monitoring, and are acquiring a growing role in power monitoring. The Modbus serial ports found on most power meters installed within the last 10 years make this easy, said Wacker. “Using this, the gateway can tie into the meter and pull all of them back to a central-monitoring application.” This leverages the gateway’s ability to give users a window into the data that travels through it, a benefit that’s also helpful when troubleshooting hard-to-find network problems.

“A common troubleshooting problem is when a worker moves a few connections or disconnects something and doesn’t put it back correctly,” said Wacker. “It could also be as simple as a tripped circuit breaker that’s not allowing communications with the attached devices, or it could be a broken cable, but these are typically hard to locate.

“Because the gateway allows you to see the communications going in and out of it, this information is there whenever you need it. This makes troubleshooting far easier than other methods, which usually involve bringing in a laptop with third-party software to locate the problem. And you can do it remotely.”

Industrial Ethernet gateways, though they have existed for years, are now smaller and have more protocol capability than their predecessors.

Challenges

Plant personnel face two challenges regarding the gateway, said Wacker. “The biggest may be simply not knowing the available solutions,” he stated. “People might put this off thinking you need to know a lot about programming because they’re seeing it from a PLC-centric standpoint. The other challenge is that, even though Modbus has been out there forever, younger controls engineers might not be as familiar with Modbus or may not be as experienced with communications issues. In these cases, the challenge is knowing what to ask on these projects and knowing how to put together a solution [using Modbus]. For someone new at this, knowing what to ask can be hard, so it’s important to know what help is available.”

Naturally, this help can come from any gateway maker, such as Moxa, Schneider Electric, Siemens,  and Comtrol, or a plant’s systems integrator. But this task is likely to only become easier. “Right now, choosing a gateway depends partly on what you’re connecting,” said Wacker. “There’s still no such thing as a universal gateway that connects everything. But we’re working on that. We want to have just one gateway that handles many different protocols, perhaps just by turning on special features.”

Wacker also expects future gateway designs will offer more detailed views of the data that travel through them and be able to collect the data. “Users want to offload information to the gateway so it can collect it, store it, and make it available for retrieval by something else,” he said. “We want to make this process more efficient,” added Wacker, “so the gateway will become a consolidation point that might take different types of data pipes and allow the PLC or factory-monitoring application to bring a big chunk of that data over all at once.”