Case SKS – Wireless LoRa based sensor
SKS Automation needed a sensor suitable for industrial use that works wirelessly. The sensor developed transmits measurement data wirelessly outdoors up to tens of kilometers, and it connects easily to Industrial Internet applications. No cables required. ARM mbed technology significantly reduced the time needed to pull off the project.
Reliable measurements are essential for controlling and monitoring industrial devices – it doesn’t matter whether we’re talking about a paper factory or a waterworks. The long cables required by traditional sensors for transmitting the measurement data and getting power are an important cost item of automation systems.
“SKS Automaatio is Finland’s leading importer of automation and electrical components for the machine building industry. Many of our customers need wireless measurements. This is part of our monitoring system for industrial machines and processes that makes use of the Internet of Things (IOT). A suitable product wasn’t available on the market, so we decided to give the job of developing one to Etteplan”, says Rami Hakala, SKS Automaatio’s managing director.
“Industrial sensors have to be extremely reliable, and they have to be able to work in harsh conditions with as little maintenance as possible. Such demands are fortunately familiar to us from many other projects. But a wireless, smart, and maintenance-free sensor is quite a challenge even for experienced designers”, says the project’s main architect, Mikko Elomaa.
The challenge was accepted. The key to the solution is LoRa technology.
Low Power LoRa technology
Traditional wireless transmitters use lots of electric power, and a smart sensor’s processor, analog-to-digital converters, and other electronics also need electricity. But big batteries don’t fit into a sensibly sized sensor housing.
LoRaWAN (Long-Range Low-Power Wide Area Network) is using the free 868 or 915 MHz frequency. Due to the patented modulation, the LoRa signal is hindered much less by obstacles than traditional frequency modulated signal. LoRa also works well in buildings with thick reinforced concrete walls.
The range of LoRa signals is up to dozens of kilometers under optimal conditions.
“LoRa is a very interesting technology for IoT. Gateways and other networking solutions needed are already available. Most important of all, LoRa is optimized to use very little electricity”, Mikko Elomaa stresses.
ARM mbed – a huge improvement in the productivity of programming
ARM is the most common processor architecture of embedded systems and therefore the most natural choice. “We chose the power efficient STM32L series microcontroller from ST Microelectronics, which contains all the features the product needs”, Mikko Elomaa recounts.
“The ARM mbed environment made the programming project significantly faster and easier. For example, the LoRa wireless driver and communication stack were available as a package compatible with ARM mbed. We were able to get the wireless programs to work with the help of the ARM mbed development tools even before the first prototype was ready. ARM mbed saved us weeks, even more than a month of work”, he explains with enthusiasm.
“The program code becomes more portable due to the ARM mbed library, which supports many different processors. Things get more efficient when you don’t have to reinvent the wheel all the time. There’s also less risk of programming errors. ARM mbed is developing all the time, and the newest mbed OS is even more versatile”, he adds.
The sensor is connected to SKS’s IoTKey cloud service and portal either through its own router or a public LoRa network. The cloud service’s user interface monitors the process’s various measurements, and external information can be connected with the measurement data. The user interface works well on PCs and mobile devices so the data is always available.
“The wireless sensor created by our team worked reliably in field tests. It’s easy to start using without installing a single wire. All you need to do is change the lithium batteries every few years”, Elomaa sums up.
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