Proximity Sensing Via Wireless Network
A manufacturer of railcar moving equipment needed to integrate wireless technology that could “withstand extreme temperatures, dirty environments, high vibration, and three shifts of operation,” says Brad Goldbeck, a Calbrandt Inc. engineer. Calbrandt is an international original equipment manufacturer of railcar indexers, movers, and gate openers based in Delano, MN.
|ONLINE extra , below, includes links to more than 30 wireless resources.|
Requirements: rugged, no power
In this application, Calbrandt’s axle mover, capable of pulling up to 75,000 lb, uses four 15-ft cylinders that extend underneath the train car carriage. Train car distribution centers are extremely harsh and are subject to high traffic volumes, which make running cables impossible. Another hurdle is that there is no power available on Calbrandt’s axle pushing system. Prior solutions required a long-range photoelectric sensor to be installed wherever power was available, often at least 50 ft from the rail car sensing location. This distance caused the sensor to be affected by weather and other environmental factors. Operators responsible for these processes are constantly seeking ways to be more efficient and decrease the time between unloading and loading each railcar, making wireless solutions with more reliable sensing capabilities a popular new choice. Calbrandt chose the Banner Engineering SureCross Wireless Network DX80 Gateway and FlexPower Node.
Moving rail cars
A railcar wheel triggers the trip arm, which actuates the limit switch connected to a SureCross FlexPower Wireless Node, which, in turn, signals the “high dog” or pusher arm to rise. This action moves the railcar forward to the next loading/unloading station. The gateway—or wireless network controller—is located outside of the axle sensing area.
Range from the gateway to the node is often less than 100 ft, making signal interference a possible hindrance. To decrease radio frequency traffic and thereby increase the system’s dependability, one gateway was used with multiple nodes—each employing frequency hopping spread spectrum (FHSS) technology with bidirectional transceivers in each device for acknowledged data transmission. The network also uses time division multiple access (TDMA) slots to guarantee bandwidth to each node, improving communication reliability.
The Banner Engineering FlexPower battery module powers the wireless node for approximately five years based on actuation frequency. This allows for the sensing device to be installed on the track at the sensing location. For Calbrandt, the SureCross system resulted in more dependable tripping of the high dog arm than its previous use of a long-distance photoelectric sensor.
“We no longer have to depend on cable carrier systems or high-maintenance sensors to locate railcar trucks,” Goldbeck said. “Engineers at Banner worked with us to customize their product to meet our specific power requirements. As a result, we have had great success and fewer maintenance issues.”
SureCross Wireless Network has a proprietary Radio Frequency (RF) design and bidirectional Rx/Tx communications to facilitate monitoring and control; devices also can be powered by 10-30 V dc power or solar power.
This type of system also is used often at ports and grain handling facilities.
Wireless Communications for Industry
Industrial Wireless Implementation Guide (Contains links to more than 30 resources)
And… in this issue: Demystifying ZigBee and its Application