Industrial programmable logic controllers (PLCs) and their associated operations technology (OT) software and communication protocols have traditionally been best suited for localized installations. They lacked the computing performance, connectivity options, and security needed to easily integrate them with higher-level information technology (IT) resources.

Figure 1. Accessing valuable plant data from field PLCs has traditionally required significant amounts of hardware, software, networking, and expertise. (Courtesy of AutomationDirect)

Users are looking for better ways of connecting with the data available from smart sensors and intelligent systems in the field as they create Internet of Things (IoT) solutions. Fortunately, some newer PLCs are leveraging software advances so users can easily extract manufacturing system data and transmit it to business systems.

Due to the nature of field signals and conditions, it makes a lot of sense to install robust and reliable PLCs near the data sources. Traditional PLC limitations in years past made it necessary to create and manage a relatively complex architecture of PCs and gateways above these PLCs, to concentrate and route the data (Figure 1). Custom code was often required and users spent a lot of effort adding contextual information such as engineering units and tag descriptions. Cybersecurity provisions were lacking at best and non-existent at worst.

Figure 2. Modern PLCs combine robust OT form factors with IT-capable software and protocols, so users can seamlessly transmit valuable data from edge-located sources up to enterprise and cloud systems. (Courtesy of AutomationDirect)

Most PLCs today include OT protocols like ASCII, Modbus RTU, K-Seq, Modbus TCP, and EtherNet/IP. However, only the most modern models incorporate IT-capable software and protocols such as SNTP DNS, MQTT, SMTP, SSL, and web services (Figure 2). With the right IT software running on an OT PLC platform, users can choose one or more ways to connect their data directly to the cloud, all without needing intermediate computing (Figure 3).

Figure 3. AutomationDirect BRX Series PLCs can use multiple protocols to efficiently and securely transmit field data to enterprise computing resources. (Courtesy of AutomationDirect)

For bulk data transactions that do not need to be near-real-time, the PLC can aggregate data and periodically transmit it as a file using FTP.

  • Web Server: If users only need to visualize data using a web browser, a PLC capable of hosting HTML5 displays with a built-in web server are an effective approach that requires no licensing.

  • MQTT over TLS: The MQTT protocol, using standard transport layer security (TLS), has emerged as a standard way to establish two-way communications securely from PLCs to the cloud over low-bandwidth connections. Users can access the data with software clients, or they can integrate it with cloud computing solutions and software like Microsoft Azure and IBM Watson IoT.

  • REST API: The preceding three approaches need users to manage and configure source data at the PLC. However, the newest PLCs offer a representation state transfer (REST) application programming interface (API), by which external software clients can initiate communications and dynamically request whatever data is needed after satisfying all cybersecurity provisions.

Today’s OT-based PLC technology now includes IT-capable software features, enabling users to easily access field data without complex layers of intermediate hardware and software. IT-type security is built in such as firewalled connections, username/password credentials, IP whitelisting, and secure communication protocols. These platforms are ushering in a new era of connectivity, providing convenient options for end users to create IoT solutions.

This article was written by Damon Purvis, PLC Product Manager at For more information, visit here .