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24V Power Rail on CAN bus or RS-485

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Ishaan Karnik

Member level 3
Jun 16, 2012
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We are building an automation system where by sensor will be separated form indicators/totalizator by few meters. We have decided to use CAN bus for communication between sensor and indicators.
We are suppling 24V to the sensor module. I would like to know if it is possible to supply power over the same cable (multi-core cable) as CAN Bus (using different core) without causing problems to CAN network.
One totalizator will be connected to one sensor only. We are open to protocol change also provided cost benefits and decrease in complexity.
Can someone point out practical implications for the same and pitfalls that can/need to be avoided.
We are planning to use DB-9 Connector but this (connector) can be changed as the project is still in development state.
Kindly inform me can such routing of power rail (24VDC) along with RS-485 can cause problems.


on first sight i don´t expect problems.

But in detail it depends on 24V DC current and 24V current noise and voltage noise and it´s frequency spectrum.
Filtering on the 24V lines both sides may avoid problems.

if you do a web search for power over can bus you will get a number of relavent links, e.g.
Sir, I thank you for our suggestion.
I had looked at this particular IC but was passed over as our vendor (Digikey) does not provide it. We have selected TLE6250GV33 provided by Infineon AG. The power was provided by dual output LDO as specified in application circuit for the IC.
My only question was providing power on the same bus as CAN line will cause any problems to CAN and the question was answered by KlausST.
As for the filtering issue we are using LDO on our slave/sensor hence switching noise will be avoided. We have also introduced a ferrite 742792133 from Wurth Electronics Inc. providing impedance of 600 Ohm @ 100MHz.
Will this be enough or more filtering be required.

CAN over power line is a different topic than wiring power supply along with the bus.

The latter is quite simple and in fact implemented in many systems, e.g. using RJ45 connectors. I believe that the usual CAN bus common mode chokes will already avoid power supply interferences, additional filtering isn't a bad idea of course.

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