Technology

Key data of the CANopen field bus system

• Bus topology: Line with short stubs 
• Twisted pair line, shielded
• Typical line impedance: 120 Ω (equivalent to line termination). Note: Reflections on the line ends can be avoided by bus line termination on both ends with the bus line's characteristic impedance (120 Ω). 
• Max. 32 nodes without repeater, with repeater up to 128 nodes
• Max. stub length: 30 cm
• Relation between baud rate and bus length: 5000 m at 50 kBaud; 10 m at 1000 kBaud
  

Line structure

The CANopen bus system is implemented as a line structure with bus terminations on both line ends. The use of shielded lines improves its electromagnetic immunity.  Electromagnetic interferences can also be avoided by the use of optical fiber cables. However this variant is more expensive compared with shielded cables. Connection of optical fiber cables is via integrated or external opto-couplers.
The figure below shows an example of how to use the DOLD CANopen PLC IL 5504 MINIMASTER for distributon boards as well as further bus nodes for the CANopen field bus system.

Bus connection

Bus nodes can be looped in the bus line or connected to the bus line via a short stub (max. 30 cm). To identify bus nodes an address (node ID) is assigned to each of them. The figure below shows the basic structure of a typical CANopen node connection to a bus with DOLD-PLC IL 5504 MINIMASTER and output module IP 5503: