Paul Mold at PKM Solutions, a system integrator, explains: “The first option considered, due to the customer already having a grip on the technology, was a Smart Relay based solution, which would utilise standard wireless Ethernet as a communication bridge, but due to temperature sensitivity, the Ethernet equipment would have to be placed in heated cabinets to avoid freezing during the winter months. When this option was costed it was deemed to be overly expensive and an alternative was sought.”
The solution that Paul eventually devised, sounds simple, but Rockwell Automation believed it had never been attempted before. It comprised three Allen-Bradley® Micro830® PLCs, one at the reservoir and one on each tank, with each PLC working side by side with a ProSoft Technology ILX800-SMSG Micro800 SMS Plug-in Module and a magnetic mount antenna.
The PLC and SMS module working in tandem was not a new idea; but the way that PKM Solutions and Routeco configured them potentially was. In all the instances both companies could find, the SMS modules had only ever been used to communicate from a PLC to a cellular phone and back again. In this installation they were going to get the PLCs speaking to each other using SMS messages. “We think that this PLC-to-PLC communication via text messaging is a new thing,” Paul explains.
In operation, it is remarkably simple. When a water tank issues a low level warning, its PLC sends an SMS to the central reservoir PLC, which initiates the pumps. When the level is correct, a second SMS is sent to cease pumping. It really is no more complicated than that.
As well as being an extremely elegant solution, this Micro830-based solution offered a significantly lower capital outlay.
Paul concludes: “The customer now has a much more flexible and expandable system than they could have ever imagined. We have seen first-hand the simplicity and power of the Micro800 range and the end customer is already thinking of other potential ideas for using this combination of technologies moving forwards.”