OMRON Electronics has released the WD30 wireless DeviceNet interface unit. DeviceNet is a high-functionality, remote I/O network that is open to any vendor, and has been widely used in many industrial applications.
The WD30 series provides an indoor wireless link of up to 60 metres and can be used to extend the overall cabling distance of a network.
The use of WD30 units adds considerable flexibility to the DeviceNet systems which have, until now, always been wired.
Wireless connections have proven invaluable for applications where cabling is difficult or very expensive to install. For example, many industrial applications require connections to moving cranes or rotating turntable platters.
While expensive slip-rings have traditionally been used for these applications, they have proved to be inflexible and less than reliable.
Other installations do not allow penetrations to be made in walls, such as enclosed testing laboratories or even heritage-listed buildings. All these types installations lend themselves very well to wireless systems.
Like many wireless computer connections (conforming to the 802.11b standard), the WD30 series utilises the 2.4-2.4835GHz ISM (industrial, scientific, medical) band, which can be used without a license.
Using Spread Spectrum transmissions at just 10mW with Direct Sequence modulation, the WD30 uses the same technology as most wireless computer LANs (WLAN) and is therefore able to ensure reliable transmissions.
Multi-path fading and reflections are reduced by each unit have dual antennas, which can be either pencil or mobile units with a magnetic base that can be mounted on the outside of a control cabinet.
However, unlike the 802.11b standard, the WD30 series divides its spectrum into 34 channels.
A WD30-ME master unit occupies one of these channels and can communicate with to up to 64 WD30-SE slave units (provided its I/O capacity of 1600 input + 1600 output points is not exceeded).
Channel frequencies can be selected to allow a maximum of ten master units to be used within the same transmission area.
The WD30 units can also be configured to work as a relay unit, where a single WD30 unit acts as a relay node between the master in the main network and the slave unit in the remote network. Up to three networks can be joined such using relay connections.
Radio transmission systems tend to be slower than wired equivalents, as is the case with the WD30 which transmits data at 100kHz. (DeviceNet allows baud rate selections of 100K, 250K or 500K).
These delays must be considered in high-performance real-time systems. Also safety applications proclude the use of communications system, let alone wireless links.
Nevertheless, the wireless links provided by the WD30 series will prove invaluable for certain applications and will add enormously the to functionality and flexibility of DeviceNet systems.