Don't stop us if you've heard this one. "One of our co-op students this summer was looking for the Raspberry Pi he was using to set up an HVAC damping system, and asked the 25 people at our daily huddle," says Sandra Buffett, P.Eng., founder and CEO at Jordan Engineering Inc., a CSIA-member system integrator in Niagara, Ontario. "After the huddle, one guy asked, 'What's this pie everyone's talking about?' "         

(Cue drum-and-cymbal.) Ba-dum, chhh!

While unfamiliar terms are quickly cleared up, learning new concepts and technologies usually takes longer. Even those in-the-know at Jordan aren't all Raspberry Pi experts yet. "We began learning about it when one of our chemical compounding clients put one on the back of a wall-mounted TV monitor with an Ethernet jack and WiFi to display alarms and notifications on their plant floor," says Buffett. "This let them go from a typical LED display scrolling text, and upgrade to more graphics, colors and maybe dashboards, and gain those capabilities with less expense."

Buffett reports some of Jordan's engineers bought a couple of Raspberry Pi kits and adapters two years ago, started playing with one, and gave the other away at one of its annual automation workshops. "We're very relationship-based, and we partner with our clients for a long time," explains Buffett. "We've been holding our workshops for the past 14 years. They usually include staff presentations and project demos, and give everyone a chance to sit down and swap useful information. This past May, we did workshops in three cities for the first time, and gave away Raspberry Pis to 150 clients with help from Schneider Electric Canada, which has been a close partner for 18 years."

During the workshops, Schneider Electric conducted a lab for attendees to explore Raspberry Pi. "To open their minds to its possibilities, groups at each table came up with different ideas about how to use Raspberry Pi, such as monitoring the weather, energy prices, interest rates and inventory costs, which could empower their operators by helping them make better decisions on the best times to make their products," adds Buffet. "Our co-op student completed the design of his demo project to dampen the HVAC system in a two-story house, and deliver more heat to the lower floors in winter and more cooling to upper floors in summer.

"We're not using Raspberry Pi on plant floors or for critical or safety controls. It's best for monitoring and non-critical functions right now, and making small improvements you couldn't do otherwise. Many users like us have little applications that used to be prohibitively expensive to monitor and control. Well, now we can do them. We don't think of Raspberry Pi as taking away from PLCs and DCSs because it can also do monitoring and provide alerts to them."

Alain Zagar, technical sales manager in Schneider Electric's Process Automation division in Canada, reports his team has been running its seminars, "2017 Innovation Talks: From Sensors to Business Sense," across the country, and that Raspberry Pi has been part of its efforts to show users how they can begin to take advantage of the Industrial Internet of Things (IIoT). "Clients are asking how they can implement the IIoT, so we felt is was a good time to show how Raspberry Pi and other technologies can tie things together and do it securely," says Zagar. "The public thinks of Raspberry Pi is an accessible engineering tool, and partnering with Sandra and Jordan Engineering let our users get some hands-on experience, better understand Schneider Electric's EcoStruxure IoT-enabled system architecture, learn to leverage the IIoT with the assets they already have, and achieve business benefits."

Long time to overnight success

New names and learning curves aside, pretty much everyone had to know this was coming. The moment analog signals and data began to be sliced and diced into strings of digital snapshots 40 years ago, the eventual emergence of computing with open-source software on generic silicon boards for monitoring and control was inevitable. Just as manual, pneumatic and relays gave way to programmable logic controllers, those PLCs—like all computers—began to shrink in size and price, gain power and capabilities, and widen and accelerate their networking with emerging Ethernet cabling and Internet protocol (IP) communications to the web, cloud-based services, IIoT and whatever comes next.

Likewise, just as other wiring and devices become more commoditized and as software becomes more open-source, some process engineers, system integrators and developers are also asking why they have to pay several thousand dollars for controllers with only $40-50 worth of hardware inside. Just as they're asking why their plant-floor devices and process systems can't offer the same features and functions as the apps on their tablet PCs and smart phones. This is coaxing embedded computing boards out of the shadows, and enabling developers to begin freeing them from proprietary configurations and formats—often at the request of their end users, as was the case at Jordan Engineering. So, while it can seem like Raspberry Pi, Arduino and similar devices came out of nowhere, these embedded and generic boards actually have a long history in the computing field.     

"The typical PLC today can cost $5,000-$7,000 and can help run a whole plant on one server with its I/O connections to field devices via its dedicated backplane, but the computing power inside that PLC is typically only worth about $100," says Abhijit Jog, vice president of projects at Panacea Technologies Inc., a CSIA-member system integrator in Montgomeryville, Pa. "Now, Raspberry Pi and similar computers are popular, but these technologies have existed since microcontrollers first become available in the early 1980s when PLCs and many types of proprietary machine controls emerged. In fact, I did my B.S.E.E. project at KLS Gogte Institute of Technology in India by designing a basic board and developing a two-axis control program for positioning a drilling device.

"For a long time, it was just easier to use standard controls from large, individual suppliers, but lately all I/O is distributed and connected to PLCs via Ethernet, so there's more flexibility and no reason to keep brains in one box because they can be in a server on a rack or in the cloud. What's been lacking is a server-based machine that runs PLC-style software in a deterministic way, but Dell and other manufacturers have standardized servers that just need the right software to run like a PLC, and Codesys has come out with scalable control software that's very flexible, so we'll get there sooner or later."

Codesys is a development environment for programming PLCs using the IEC 61131-3 standard. It recently launched an adapted control runtime system, Raspberry Pi SL, which contains a Codesys control application for all Raspberry Pi devices, including its compute module and extension modules Raspberry PiFace Digital, Raspberry Pi Camera and several devices/breakouts with SPI, I²C or one-wire communication interface.

Benson Hougland, vice president, marketing and product strategy at Opto 22, adds, "The notion of massive I/O systems home-runned to a central PLC or DCS is dated thinking. Today, I/O termination and conditioning is occurring remotely, or at the network edge. Now, users can run a Raspberry Pi on edge devices for remote I/O at very low cost. Plus, moving process and plant data through a $35 Raspberry Pi or other single-board computer proves that IIoT can work without having to use a $5,000 PLC. In fact, our engineering vice president, Ken Johnson, challenged his team to prototype a vision system to test and confirm LED illumination for our newly developed control system, which could have required thousands of dollars worth of software. However, our intern, Terry Orchard, used a Raspberry Pi 3 running Linux software programmed with Python language to manage I/O, a camera, the video feed, software library and RESTful application program interface (API), and completed the prototype proof-of-concept in four days for less than $100."      

Jaroslav Sobota, head of customer success and control system engineer at Czech Republic-based Rex Controls, adds, "We've been considering using Raspberry Pi for monitoring and control ever since it was introduced to the market, but we got serious about it when model B+ was released in 2014. Our answer is a clear 'yes' that Raspberry Pi is a perfect platform for programmable data loggers, data bridges or communication gateways. Especially in this era of the IIoT and Industrie 4.0, the Raspberry Pi definitely has a place in the world of PLCs, PACs and IPCs. However, one must understand that using Raspberry Pi in industrial environment might be a bit tricky, mainly because of its uncommon 5 VDC power supply and microUSB power supply connector. It also does not have any standard industrial interface like RS-485 or 24 V-tolerant inputs."

Board basics for process

While it might initially seem foolish to attempt monitoring, let alone process control, using a generic computer board, Doug Reneker, just-retired senior manager at broadband access supplier ARRIS Technology Inc., and technical writer Peter Welander recently collaborated on a demonstration project that employed a cigarette pack-sized Arduino Uno board, an Adafruit shield stacked on top to help with the display, one sensor and one actuator to start a pump, and a flowmeter to measure water flow.

"There are a lot of maker boards available like Raspberry Pi, Arduino and Beagle Bones, but we decided Arduino would be easiest because of the simple environment that its code runs in," says Reneker. "We programmed a start-up routine written in C called 'setup()' that gets executed once at the beginning, and a second routine called 'loop()' that's called repeatedly once ‘setup()’ has completed. Nothing else goes on. Next, we used an algorithm to read the sensor in 'loop,' calculate the difference with a setpoint, apply proportional and integral terms, adjust both in about 100 milliseconds, and create a control report."