Thomas Baier, qmd4: "Open source at Conmeleon also means that everyone has access to the design documents - right down to a usable housing for 3D printing."

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Mr. Baier, the first Raspberry Pi saw the light of day ten years ago. Why has it still not managed to establish itself as a control platform in industry?

Baier: The Raspberry Pi was deliberately designed as a learning and tinkering solution and, in addition to its openness, scored highly in terms of price. On the one hand, this gave it the reputation of being 'cheap', but on the other hand, a low-cost solution was often not as much in demand as it is now. In addition, nobody has taken on the task of turning the Raspberry Pi into an industrial-grade controller - until now!

The Conmeleon project has set itself the task of changing this. What and who exactly is behind this open source initiative?

Baier: First of all, I would like to make it clear that although we at qmd4 are associated with the project, it is being driven independently of us. There are some very experienced and resourceful people behind Conmeleon, all of whom are professionally involved in industrial control technology and therefore do not want to be named publicly at the moment - unfortunately.

Ultimately, the initiative is based on the desire to have a system that can be used professionally and is open to everyone. The open source concept here refers to the hardware design, the firmware and drivers for the Raspberry Pi and the use of Raspbian, which is based on Debian GNU Linux.

A first result of the project is the 'Conmeleon C1 PLC' - what exactly is behind it?

Baier: The Conmeleon C1 PLC is a complete system consisting of a Raspberry Pi 3, a carrier board for the Raspberry Pi - the Conmeleon C1 - a suitable housing for top-hat rail mounting and the associated software to turn the hardware into a complete automation system. The C1 carrier board virtually adapts the Raspberry Pi to the standards of the automation world: 24 V power supply, four digital inputs, four digital outputs. As a special feature, the latter are equipped with relays so that 230 volts can be switched directly. Four analog inputs round off the overall picture. The C1-PLC can be programmed according to IEC 61499 with 4DIAC or according to IEC 61131 with our fully graphical IEC 61131 development environment, which runs in a web browser just like the associated q4Viz visualization.

What about the industrial suitability of the hardware?

Baier: One of the major weaknesses of solutions based on the Raspberry Pi is that they are usually not tested for CE conformity. With the Raspberry Pi 3, however, this is much easier. Admittedly, the C1 board still lacks CE conformity, but with the successor system, based on the Conmeleon C2 carrier board, this will also be a given. The upcoming C2 board will also increase the number of digital inputs to eight and make industrial use more charming with other extensions.

Last but not least, communication is essential for integrating controllers into the automation environment. Which standards are supported in this respect?

Baier: As part of the Conmeleon project, industrial I/Os are offered directly on the carrier board. If these are not sufficient, there is a microBUS port within the C1-PLC for extensions. Alternatively, we offer Ethercat master software for the Conmeleon PLC in conjunction with q4Logix, which uses the integrated network interface of the Raspberry Pi.

What does a complete Conmeleon system ultimately cost and where can it be obtained?

Baier: Conmeleon is an open source project, which means that anyone is free to produce the devices themselves. If you don't want to do this, you can purchase a Conmeleon C1-PLC from one of our partners - in Germany from the engineering firm Lachnit, for example, or from us in Austria. Whether and how the Conmeleon project team will distribute the devices themselves in the future is something I cannot and do not want to speculate on at the moment. In terms of price, a Conmeleon C2 PLC will certainly be in the same application segment as a Logo from Siemens, for example, although the CPU offers much more.

Raspberry Pi versus Arduino

At SPS IPC Drives 2015, various industrial control solutions based on the Arduino were the focus of several exhibitors - this year it is the Raspberry Pi. What is the fundamental difference between the two approaches? An assessment by Thomas Baier, qmd4:

"Arduino and Raspberry Pi are two very dissimilar brothers. The Arduino with its microcontroller is ideal for many tasks, but the Raspberry Pi is based on a CPU that is perfect for running operating systems such as Linux or Windows IoT. In a closed system - such as a finished PLC - the two approaches differ primarily in terms of performance and memory. When using third-party software, the Arduino is already in a much thinner position. Due to its 'standard conformity' - i.e. Raspbian as a Linux system - it is much easier to integrate new software such as an Ethercat stack. Or a web server that can host programming and visualization editors. To make a comparison here: The same binary image of our PLC runtime environment runs on the Conmeleon C1-PLC with Raspbian as on a Wago PFC-200 controller, for example. On the software side, the systems only differ in the I/O connection.

It will also be very difficult to use the additional benefit of data processing with an Arduino. Especially if you want to use ready-made software such as 'R'. With an Arduino, big data starts two powers of ten below the Raspberry Pi. And this doesn't just apply to big data, but starts with the use of secure communication via SSL. An SSL library simply costs memory - flash and RAM.

However, this is not to say that an Arduino-based system is not suitable for automation - but the use cases are certainly more narrowly defined."