A potential application class is where there is a requirement for system-wide monitoring such as a call-for-parts system, for example, that delivers a tote of parts to a location. Wireless is often used on forklifts, so that the driver can have an indicator and real-time feedback, which identifies which areas are out of parts. Since the forklift is mobile, wireless offers a clear advantage.
Many manufacturing facilities are looking to create flexible layouts where production can be laid out for specific needs depending on their product mix. To collect information from a machine used in the process that might be moved on a periodic basis, wireless works well since you can move the machine without a need to rewire it.
One potential application concern is system reliability, but Gardner said that has been a focus of the design process. The signal used is extremely robust, powerful, and provides 10 to 100 times the range of a WiFi-based system, and also has built-in all of the characteristics of a PLC-based level network. This includes time-out mechanisms, CRC checks, and a pre-defined state for the output in case a link is lost.
The SureCross Q45 from Banner features a proprietary, self-contained battery, radio, and sensor in an all-in-one package.
For years, these techniques have been used in PLC level networks and have also been built into the wireless protocol. With its built-in site survey, which reports signal strength, if everything is set up properly and within range to guarantee good signal strength, the system is as reliable as a wired solution. It also provides immediate indication if communication is lost to a part of the system, and has been designed with the reliability and determinism issues firmly in mind.
The system can also implement a system heartbeat where wireless devices check on a regular basis, every five seconds, for example. If the devices don’t check in, those devices can be reset to a pre-defined state to fail in a predictable manner.
Banner Engineering has a lot of experience with the wireless system technology, but the breakthrough with the Q45 is a combination of low power operation, fast response, and the way it has been implemented as a tightly defined product. The unit provides the sensors, batteries, power management, and the wireless system all in a single housing. “All the user needs to do to establish communications is bind it to a gateway. Since there can be multiple gateways and devices in a single area, communications only occur with devices that they have been paired with,” Gardner told us.
He said engineers are sometimes concerned with noisy devices such as variable frequency drives (VFDs) operating in the same area. Noise can reduce the range of the signal, but not significantly. The wireless system has a very narrow band that it is operating within. Frequency-hopping, spread spectrum technology creates a very narrow, well-defined frequency, and these narrow frequencies are very noise immune because the system can filter out any frequencies above and below that level.
Engineers can also be concerned if it will affect their WiFi system since the sensor and laptops both operate at 2.4 GHz. But all ISM band products are certified to work well together, and Gardner said extensive testing has shown the two technologies don’t affect each other at all.
Customers have done extensive testing for WiFi interference but none of them have been able to sense the wireless sensor operating on the network. Because the system is sending just a few bits of information every 125 milliseconds, it is creating much less traffic than other WiFi devices. A PLC on the system using a WiFi radio access point to pick up the sensors, for example, would require 1,000 times more bandwidth than the Q45 system.