Busheavy with terminated bus

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bilal44
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Joined: Wed 29. Sep 2021, 14:43

Busheavy with terminated bus

Post by bilal44 » Wed 29. Sep 2021, 14:53

Hello,

I'm attempting to communicate with a fuel cell while using a CAN-bus system, as shown on the pictures in attached.

I use shielded cables to transmit CAN-High and CAN-Low informations. Both bus ends have 120 Ohms resistors, and the resistance of the bus is 60.5 Ohms.

The CAN-Low and CAN-High wires have been enveloped in aluminum tape in a desperate attempt to shield them as they are mounted near to a 12V supply cable (in red).

However when I try to send a message to the fuel cell, a busheavy message appears (sometimes switching with bus light), and I get no received messages.

I also confirm the pin connections (2 low, 7 high) are correct.

I'm struggling to find any hardware issue. Hence do you have any idea of what might be wrong in our setup please?

Thank you in advance.

Regards,
Attachments
Fuel cell with shielded CAN wires
Fuel cell with shielded CAN wires
IMG_3181.jpg (690.33 KiB) Viewed 811 times
The grey cable containes two wires connected to CAN high and low. They are plugged on the PEAK converter
The grey cable containes two wires connected to CAN high and low. They are plugged on the PEAK converter
IMG_3182.jpg (786.17 KiB) Viewed 811 times
The PEAK converter is detected and you can notice the 120 Ohm resistor
The PEAK converter is detected and you can notice the 120 Ohm resistor
IMG_3183.jpg (736.58 KiB) Viewed 811 times
Busheavy error after sending a message to the  fuel cell.
Busheavy error after sending a message to the fuel cell.
IMG_3184.jpg (683.62 KiB) Viewed 811 times

M.Maidhof
Support
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Joined: Wed 22. Sep 2010, 14:00

Re: Busheavy with terminated bus

Post by M.Maidhof » Wed 29. Sep 2021, 17:32

Hi,

sure your connected CAN system is active and uses a bitrate of 250kBit/s? Please check your physical cables again, for me they look terrible....

regards

Michael

bilal44
Posts: 3
Joined: Wed 29. Sep 2021, 14:43

Re: Busheavy with terminated bus

Post by bilal44 » Wed 29. Sep 2021, 19:03

Hello Mr. Maidhof,

Thank you for the quick reply.

Yes, the CAN system is active (which is indicated by a green LED light), and the configuration recommended for the use of the fuel cell by the manufacturer is with a bit rate of 250 kB/s.

What is exactly wrong with the cable? It's a shielded cable with two wires of 0.75 mm² (this one https://benl.rs-online.com/web/p/twiste ... le/8124684). Would you recommend something else?
Attachments
IMG_3142.jpg
IMG_3142.jpg (44.7 KiB) Viewed 788 times

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U.Wilhelm
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Joined: Fri 10. Sep 2010, 19:34

Re: Busheavy with terminated bus

Post by U.Wilhelm » Thu 30. Sep 2021, 12:18

Please use a correct CAN cable. (for example LAP CAN Network Cable)
A luster terminal has no place in a CAN network. The cable should comply with the standards, and the termination should be properly installed.
Also the exact bit timings in the network must be correct. 250K are not just not 250K. There are other timing parameters that must fit.

Measure the internal resistance of the CAN network when the system is switched off. This should be around 60 Ohm.
If the unit running normally without your "cable" there is no need to add a extra Termination. (But it is your system - you should know...)
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bilal44
Posts: 3
Joined: Wed 29. Sep 2021, 14:43

Re: Busheavy with terminated bus

Post by bilal44 » Thu 30. Sep 2021, 22:37

Understood. I will pay proper attention to the CAN bus standards, use the right material and will come back to you.

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U.Wilhelm
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Joined: Fri 10. Sep 2010, 19:34

Re: Busheavy with terminated bus

Post by U.Wilhelm » Mon 18. Oct 2021, 09:25

Thread closed - no feedback - looks like it´s solved by using real CAN cable and industrial connectors...
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