1
\$\begingroup\$

I've got a circuit with a CAN bus connector like the following with two RJ11 connectors to be connected in a daisy-chain style:

this

But only one of them is working (I tested them by connecting to another terminal node with a single connector). The soldering is correct.

When I measured the resistance between CANH and CANL with a jumper on each end, the working connector resistance was 60 ohms as expected, but'll be 120 ohms when connected to the not-working connector or with both connected. What'll be the problem in this case?

\$\endgroup\$

1 Answer 1

3
\$\begingroup\$

It's not possible to find your bug remotely. The schematic is correct.

However you already found out that one of the connectors is not working. One or both CAN signal lines seem to be broken. Are you sure the soldering is really OK? And are the contacts clean and in a good shape?

You should also measure the resistance of one of the signal lines between certain points, e.g. between somewhere on the PCB and the contact inside the connector. Also, your cable to connect the next node may be broken.

\$\endgroup\$
5
  • 1
    \$\begingroup\$ Agreed. I vote for a cold-solder joint, or the heat of soldering allowed the contact housing to deform, resulting in no contact made. \$\endgroup\$ Apr 27, 2015 at 18:46
  • \$\begingroup\$ Will try to resolder and see if it works. \$\endgroup\$
    – rudwna
    Apr 28, 2015 at 1:18
  • \$\begingroup\$ Resoldering still didn't help. And what do you mean by measuring the resistance between contact and PCB for troubleshooting? If all else fails I'll try to get new PCB. \$\endgroup\$
    – rudwna
    Apr 28, 2015 at 12:47
  • 1
    \$\begingroup\$ The break can be everywhere. Measure resistance between pin 3 of J1 and J2 to check for a break in the CANL trace. Connect something to either J1 or 2 and measure the resistance between a CANL track on this and a CANL on the connected board to check cable/connector. Do that for CANH as well. Simply speaking: Measure the resistance between as many points as possible, until you found one which is not almost zero. \$\endgroup\$
    – sweber
    Apr 28, 2015 at 13:55
  • 2
    \$\begingroup\$ I've tested the connection between contact on PCB and the wire . They're somehow broken so I've replace the housing and now works perfectly. Thanks. \$\endgroup\$
    – rudwna
    Apr 28, 2015 at 20:03

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.