Assembling a Wire harness for a CAN Bus with 3 or more devices.

General discussion about interfacing with the CAN bus
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Assembling a Wire harness for a CAN Bus with 3 or more devices.

Post by joewiki »

I'm working on a car project where I need to connect multiple devices ( more than 3) to the same CAN bus. One of these devices is supposed to go in the engine compartment and the rest of them inside the car (possibly as far as the trunk). Each device is an electronic board, like the CAN-BUS-Shield-V1.2 for Arduino, with screw terminals for the CAN-H and CAN-L signal wires.


(1) How should I make a 3 way connection to tap a device into the bus? Do I need any special connectors? I've search for Female-Male-Male DB9 Tee-connectors, but can't find anything online. What about M12 or 5 pin mini Circular connectors? Or doing soldered Tee splices (maybe Y splices).
Please include links to any online parts you would recommend.

(2) Any special wire/cable characteristics to look for such as..
- Gauge (considering that the signal has to go from trunk to engine compartment)?
-Shielded cable vs unshielded twisted pair?
- Characteristic impedance?
Again, links are greatly appreciated.

(3) All of the boards already have the CAN signals connected with 120 ohms resistors, but those resistors can be switched out. I understand that two and only two terminations should exist between the two CAN signals . Should I consider switching out the resistors in the boards, and instead use external 120 ohm terminators?

(4) Lastly. I never done any hands-on work. Anybody has an idea how to run wires through the firewall?. The car we are working on is a Kia Soul.

Please note that this CAN bus is separate from any CAN bus already in the vehicle and has nothing to do with the OBD connector that is found in the vehicle's cabin.

Thanks so much
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