Electronics > Projects, Designs, and Technical Stuff
Canbus without ground.
Sived:
Dear all,
I need to connect 2 devices with canbus interface.
I have no ground reference. There are available only the CanH, CanL and Power+ pins.
How can I connect them in order to exchange can messages?
The positive pin of the first device is at 42 Vdc from its internal ground.
The positive pin of the second device is at 30 Vdc from its internal ground.
Can I connect the positive line and choose a canbus driver +/-15V common mode tollerant?
See the enclosed sketch.
Any your help is very appreciated. Thanks a lot. Best regards.
Sived
rounin:
Electrically isolated can drivers like ADM3053 can be happy with no ground, sometimes. The moderate input impedance floats it to a somewhere safe common mode voltage.
In a super noisy environment this would still be bad, and there are some EMI considerations that are beyond me.
https://e2e.ti.com/support/interface/f/138/t/128310?Is-CAN-communication-working-between-two-different-ground-suppling-cards-
https://ez.analog.com/interface-isolation/f/q-a/84965/isolated-can-with-adm3053-and-ground-wire
T3sl4co1l:
How has it come to this point and no one thought to ask: why don't we have a signal ground here?
Use an isolated transceiver.
Tim
Dave:
You could use an isolated interface on one side.
There are three common ways to implement this:
1. Power isolator, signal isolator and regular CAN transciever.
2. Power isolator and isolated CAN transciever.
3. Isolated CAN transciever with integrated power isolator.
The former tends to be cheaper, the latter tends to have a smaller footprint/BOM length.
dietert1:
Maybe Sived wants to find a way to use the CANL and CANH lines as a power return. Sometimes there is an existing bus with a shielded twisted pair and it would be nice to use the shield for powering a remote node. This is not possible. You need something like a USB cable with four wires to do this, so you need to upgrade the bus.
Regards, Dieter
Navigation
[0] Message Index
[#] Next page
Go to full version