Wireless switches solve the remote sensor connection conundrum: 802.15.4 networks provide reliable, robust operation.
For many facilities, the answer is a wireless network that connects the various remote switches and sensors with a centralized control infrastructure.
Industrial wireless networks, based on the IEEE 802.15.4 wireless standard, are very robust and reliable. Snow, rain, and dust storms have minimal impact on its transmission range and reliability.
With a range of over 1000 feet (304 meters), 802.15.4 wireless networks provide excellent results in large open buildings and outdoor installations with a relatively open line-of-sight between switch and monitor. A 35 dB link margin ensures that minor obstacles or even intense precipitation will not compromise communications. Depending on composition, the signal can even penetrate intervening walls.
To ensure reliable operation and provide for almost limitless options for installation, 802.15.4 draws so little power, the switches can be operated by industry standard batteries rather than depending on unreliable and expensive energy scavenging. With the proper design, a wireless switch should operate for several years without a battery replacement or re-charging.
802.15.4 supports a simple star network configuration with each switch in the network communicating to a monitor/receiver. Communications links are point-to-point between switch and monitor; there is no signaling between switches. This network architecture keeps the switches isolated from one another so there is no opportunity for the behavior of one switch to affect the behavior of any other.
The Honeywell Limitless wireless solution consists of a variety of wireless limit switches and receivers. The wireless switch sends a status signal to the receiver that in turn relays that signal to the network infrastructure. The WDDR receiver can connect up to 14 wireless switches at a time.
One interesting application is the security systems for diesel and gasoline pumps at large multi-acre truck stops. One common problem associated with fuel costs is truck operators stealing fuel by breaking open the door of the pump to get access to the controls. These pumps are often located a distance away from the truck stop operations office and can be hidden from sight by the bulk of the trucks themselves. By mounting Honeywell wireless switches on the pumps, cashiers are notified instantly when a pump is being tampered with.
Why wireless? Running data cables is also an option, but using wireless instead is the best option. Cabling requires tearing up the pavement between the pumps and the office, which is expensive and requires that the truck stop restrict operations, reducing revenues. Installing a wireless network is much simpler. As these pumps already have power, the system integrator just needs to install the switches on the pumps and a receiver in the register area.
To view the expanded online version of this article, visit http://www.ecnmag.com/articles/2012/08/wireless-switches-solve-remote-sensor-connection-conundrum
By Todd Hanson, Honeywell Sensing and Control, http://sensing.honeywell.com
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|Title Annotation:||Remote Sensors Focus|
|Publication:||ECN-Electronic Component News|
|Date:||Sep 1, 2012|
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