total CAN node numbers in a fixed range

[DavidLee]

hello,

Assuming the communication range is 5000m of a CAN bus network, I'd like to know how many CAN nodes can be loaded and keep the communicating rate at 250k/s .due to some one told that the more the CAN node in a network , the lower the communicating rates. Thanks.


David

[biker2000]

Hi David,

You are right, there are certain limitations regarding the number of nodes in the network and the length of the bus (or the baud rate accordingly). However, the number of nodes is usually limited by characteristics of the individual transceivers used by the CAN nodes as each transceiver influences the overall impedance of the network.

In this particular case however, I have doubts. The ISO 11898 specification calls out a maximum cable length of 40 m at a baud rate of 1Mbit/s. Thus, in order to achieve a more than 100 times longer range you would need to decrease the bit rate to a much lower value than 250 kbit/s.
Also, the DeviceNet specification lists 200 m as the maximum length when using a 'thick' cable at a baud rate of 250 kbit/s.

For more information on this topic, please take a look at the "Connectors and Cables" chapter of the NI-CAN Hardware and Software Manual.

-B2k

[DavidLee]

hi biker2000,

If want to fix the communication lenth at 5km, at the same time, also hope can transfer data over the CAN bus at 128k/s ,could you advise me that how many nodes can be loaded ? Thanks.


David