Contemporary Research TD960801-0MC - Manual (Page 26)

TD960801-0MC
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3.2.3 Topologies
CAN-based device networks usually operate over a multidrop
topology with provisions for short drops of typically six meters
each. The trunk length depends upon the data rate and at 500
kbps, the maximum length of the trunk is 100 meters.
Conceptually, the multidrop topology is easy to understand and
appears easy to implement and for many applications this is
true. However, for some machines or processes, the star or
distributed star topology would reduce wiring especially when
devices are clustered in all directions from the main control
panel. By incorporating bridges, the multidrop topology is
maintained since the ARCNET side of the bridges are bused;
however, since each CAN segment attached to a bridge can
comply with the maximum capabilities of the CAN segment, a
system is created with a long ARCNET trunk of 1000 feet and
eight long CAN “drop” segments of 330 feet each. If a true star
topology or longer distances are desired, each EXTEND-A-
BUS can be connected to a companion AI series active hub.
For distributed star topologies, multiple AI series active hubs
can be cascaded up to the ARCNET limit of four miles when
using coaxial cable. With increased distances comes increased
signal latency and potential real time performance degradation
of the network.
3.2.4 Power Requirements
Either low voltage AC or DC power will power the EXTEND-
A-BUS. A DC-DC converter accepts the input power and
converts it to +5 volts DC for use by the EXTEND-A-BUS.
The AC power must come from a floating secondary in the
range of 8 to 24 volts AC. The DC power source must be in the
range of 10 to 36 VDC. Power connections are derived from a
four position unsealed connector. The CAN port must still be
powered from the network itself since the EXTEND-A-BUS
does not serve as a network power supply; however, the
EXTEND-A-BUS can be powered from the 24 volt network
power supply.