Furuno M12-05BM+05BF-010 Design Manual page 14

Furuno CAN bus Network Design Guide
Practically, total LEN in the network is less than 20, so the overall cable length can be
extended up to 150 m with heavy cables and 15 Vdc power supply.
When both heavy and light cables are used in the network as shown in Fig.10, the length of
cable B is calculated by using the following formula.
B = (X – A )/4
Where, X is the maximum cable length obtained from the table.
A = 40 m
B
Heavy cable Light cable
Power supply
Fig.37
Assuming that the total LEN in the network is 50 and the heavy cable length, A is 40 m;
B = (80 m – 40 m) / 4 = 10 m
When power supply is connected to the middle of the network as shown in Fig.38, the cable
length of A and B is determined individually. For example, if the total LEN of devices attached
to the cable A is 75, the maximum length of cable A is 50 m from Table 7. Do the same for B.
The total length of cables A and B is less than 150 m.
A B
Power supply
Fig.38 Middle-powered CAN bus network
When the power cable is connected to both ends of the network, the cable length is double
the value obtained from the table. In any case, the cable length does not exceed 150 m. For
example, the maximum cable length is 150 m, even if the calculated value is 180 m.
Note that power supplies are isolated and the shield connection is made at only one power
supply (single-point ground) in multiple power supply configuration. Do NOT use a
combination of battery and power supply connections.
Device
Device
Device Device
Device
Power supply
Power supply
Fig.39 Multiple power supply configuration
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