Civil Engineering Reference
In-Depth Information
Fig. 5.22
Basic principle—throttle control compared to pump control
From the many established bus systems, a preselection was made and a bench-
mark was carried out on this selection.
The selection was to be made among the following bus systems: EIB, LON,
BACnet and CAN.
The following reasons finally led to the decision in favour of CAN as the me-
dium for the Geniax system.
• Comparatively low costs per communication node of about 1 €,
• EIB and LON are partially subject to license costs, leading to node costs of more
than 10 €,
• Long-term availability of standardized transceivers from the automotive industry,
• The energy-saving functions of the CAN transceiver to be used for further en-
ergy saving at every individual node and
• The possibility to develop an exact proprietary protocol to meet the needs of the
Geniax system.
Besides the relatively high costs for the hardware design of each communication
participant, EIB, BACnet and LON already have a fixed protocol format which
cannot be used directly with the Geniax system.
Not the least for this reason, a bus system was selected for the Geniax system
which is adaptable when it comes to speed and protocol format and is also becom-
ing better established in other areas of house and building automation.
After the decision was made to use the CAN bus, the transfer speed had to be
determined. This would implicitly determine the maximum network expansion. By
using low baud rates, a huge expansion of the topology of more than 2,000 m is
possible, theoretically. This expansion exceeds the expected network expansion in
