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RS485 PI Last PV Inverter isn’t answering

663 Views - Created 07/09/2018

07/09/2018

Posted by:
Grisu

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I’m using the RS485 PI. I’ve connected 3 Kaco Inverters to it, the last one is not answering. A termination resistor is added at the end.

I’ve also got an USB RS485, this one is working with all three inverters.

Does someone has an advice?

Sebastian

07/09/2018

Posted by:
andrew

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Location:
United Kingdom

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Hello Sebastian

Are you using a shielded twisted pair cable to join the inverters together?  It is possible that the RS485 Pi is more sensitive to noise than your USB device so a twisted cable will give you better noise performance.  Maxim has a good article on wiring an RS485 network at https://www.maximintegrated.com/en/app-notes/index.mvp/id/763

You could also try adding a 10K resistor between the Raspberry Pi’s 5V pin and the A output on the RS485 Pi and a second 10K between the ground and B output.  This should make the RS485 Pi less susceptible to noise and hopefully solve the problems you are having.

AB Electronics UK Tech Support

16/09/2018

Posted by:
Grisu

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Thank you very much, it works great!

Sebastian

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