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How do I integrate an optocoupler into a CAN-bus to isolate one node from the bus?

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E-Floyd

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Hello everyone,

I should install an optocoupler into CAN-bus that I can galvanically isolate one of my nodes from the bus. I´ve actually found a right optocoupler already. Still I don´t know how do I connect this between the CAN-bus and the node that I want to isolate. This optocoupler is meant for CAN-bus but there is nothing told in the datasheet how the electrical connection are supposed to do with CAN-bus application.:roll:

The datasheet of the optocoupler is attached to this message.

Thank you for all kind of help!

E-Floyd
 

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  • optocoupler_CAN_bus.pdf
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There are many useful CAN bus example circuits, especially in the user install manuals from vendors of CAN bus interface cards.
Here is a link to one --> LINK
At ni.com, there is a range of (expensive!) CAN bus cards. The user manuals explain connections.

It is not too hard to see the places you would connect the Opto-Isolator to Tx and Rx drivers to make a node which drives the bus, and receives signals from the bus, but does not make any current-sinking connection at all.
 

Hello Darktrax,

thank you for your kind help. What I realised now is that everyone is doing the galvanic isolation between the CAN tranceiver and CAN controller. However I can´t access the node´s electronics so I have to do the isolation between the CAN tranceiver and the CAN-bus. This means that the isolation would be in the middle of the CAN-bus. I think that I have to design some kind of gateway which includes the isolation in itself. The CAN-bus comes from the node into the gateway and comes out from the gateway and continues to the rest of the CAN-bus system. How does is sound for you? Do you have better ideas? This means that inputs and outputs to the isolation barrier are CAN-signals (not tx rx - signals).

- - - Updated - - -

Is it a good solution to buy two of these bidirectional TTL-CAN converters and put them in the order of CAN-TTL-TTL-CAN ? Then I have two galvanic isolations in the string and I just connect these converters in series with the CAN-bus. Sounds working idea?

Here are the converters: http://www.deditec.de/en/entwicklungstools/prod/ttl-can-adapter.html
 

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