Many embedded and PC-based HMIs can provide remote access via PCs, smartphones, and tablets. The low cost and small footprint of an embedded HMI is a good example of common remote access connectivity via the HMI’s web server to remote devices (figure 1). Because the HMI has web server functionality, web pages can be configured to reside in it, and these web pages can be accessed by any device capable of running a web browser.

Some HMIs can log and store data on a periodic basis or when triggered by events. As part of a remote monitoring daily routine or when a message or alarm is received, the user can access the HMI via a web browser to view additional information. This same information can be sent to interested users by email using file transfer protocol (FTP). This type of remote monitoring provides usable information related to both real-time and historical trends to help reduce cost and downtime, while increasing productivity.

HMI mobile apps enable remote users to connect using Wi-Fi, cellular, and Ethernet connections. These remote users can operate and monitor the local HMI system with limited access to functions and controls of the HMI application.

PLC remote control

As with the HMIs discussed above, remote access to local PLCs is possible via PCs, smartphones, and tablets. This remote access can provide control functions as well as access to logged data, or direct access to a PLC’s tag data.

PLCs often have some data handling capabilities built in, including data logging, a key requirement considering today’s quest for more data storage. Some controllers include built-in and removable storage for many gigabytes of data, and remote access to same.

Web server functionality is also available on some controllers for remote monitoring purposes. With an Internet connection and a device capable of hosting a web browser, remote users can view system tags, error logs, and event history. They can also view any data logged to the controller’s internal memory, thumb drive, or MicroSD card.

This web server functionality can often be accessed by a remote monitoring app running on a smartphone or a tablet. Apps simplify remote Wi-Fi or cellular connections to smartphones and tablets from PLCs. Users can monitor the local PLC system via tags configured for remote access inside the tag database of the controller. Security log-on requirements are provided to protect the data, but that is not enough in some critical applications, where a VPN connection is needed for a higher level of cybersecurity.

Remote monitoring in action

When it comes to PLC remote access apps, especially if no VPN is used, many users choose to implement only data monitoring to minimize the security risk, with no remote control allowed. Some call this concept a data diode, because it only permits access via one-way communication from the PLC to app, just as a diode only permits the flow of electricity in one direction.

Remote monitoring enabled quick notification and response to pump system problems, as well as to related process and equipment faults. The embedded HMI’s remote access functionality provided low-cost and simple monitoring via smartphones and tablets.

For remote locations without Ethernet or Wi-Fi access, a cellular-hosted VPN router was installed. Adding a simple, secure client and mobile app, personnel could service, monitor, and troubleshoot the pump station remotely.

PLCs and HMIs can save data locally and format it as required, while providing some degree of security when this data is accessed by remote devices such as PCs, smartphones, and tablets. These types of IIoT-based solutions are common and work well in many instances, especially in applications where access is one way only, from the PLC or the HMI to the remote devices. For added security, often needed when control from remote devices to PLCs and HMIs is required, the use of firewalls and VPN access are a best practice.

The Transcend Teknologies, as one of the fastest-growing Industrial IoT companies to offer a growing suite of solutions that include asset tracking, and industrial process controls – all in an integrated, open, real-time platform, that gives you the flexibility to connect your assets to the cloud via Industrial Gateway or open API. Collect data from sensors, controllers, historians, and servers to gain real-time visibility into your operations.