I am currently in the process of designing a wiring loom for a race car control system which must also connect a number of devices via a CAN bus.
This is my first encounter with CAN bus (J1939-15) systems which call for a 120 Ω UTP bus cable terminated by 120 Ω resistors on each end, and my question relates to the correct method for connecting stubs (device cables) to the bus.
Asking around within my industry, the solutions proposed by colleagues are the following:
- Strip insulation only and solder stub connections onto the bus without cutting the cable.
- Cutting the cable and using Y or T splitter connectors. (Amphenol and Deutsch seem to make J1939 specific Y-splitter connectors. No mention on either product datasheets about impedance matching however.)
- Cutting and using 2-1 environmental splices instead of Y-splitter connectors (e.g MIL-S-81824/1 or Raychem MiniSeal splices).
Is there a better or correct way to attach stubs to the main bus?
If not, of the three above options, would the use of the splices linked in the third option adversely affect the network?
Note: In this instance the job specification does not allow me to use solder unless the joint is also encapsulated in a specified potting compound, and I would also prefer avoid the Deutsch Y-splitter connectors due to bulk.
The baud rate is 1 Mbit/s, and bus length is 20 ft (6 m). Stubs in most cases will be less than 1 ft (0.3 m) length.**