revpi connect - rs485 header specs / power output?

jobijobi · Post by **jobijobi** » 08 Jul 2020, 01:28

Hi,

What is the specs for the power-pin in the rs485 header?
i.e. voltage and max current?

jobijobi · Post by **jobijobi** » 11 Jul 2020, 18:37

anyone?

Post by **dirk** » 21 Jul 2020, 10:34

jobijobi, the RS485 connector itself can be 6A / 200V.
Voltages or currents of this magnitude on the RS485 interface will in any case lead to
that the smoke necessary for the proper functioning of the device escapes.

The RS485 connector is not intended to supply or take power.

Please only use the RS485-N and RS485-P pins for the actual data transmission.
If necessary, connect the shield of the RS485 line to the functional earth pin.
Only use GND if you really know what you are doing.

jobijobi · Post by **jobijobi** » 21 Jul 2020, 17:19

Hi Dirk,

I just found the schematic, I thought pin-1 was 5V supply.

For RS485 devices that require to be bus-powered (similar to profibus).
What would you recommend?

Does kunbus provide a module with RS485 and/or profibus with power-supply and signaling + galvanic isolation?

Thanks

jobijobi · Post by **jobijobi** » 07 Aug 2020, 11:39

ping!
Does kunbus provide a RS485 with galvanic isolation?

jobijobi · Post by **jobijobi** » 07 Aug 2020, 11:41

please also help specify the voltage spec for the rs485 phy

it's not clear from the schematic that has both 3V3 + "VCCIO", see below:

jobijobi · Post by **jobijobi** » 30 Aug 2020, 15:40

Dirk,

What did you mean by "Only use GND if you really know what you are doing." ?

Post by **dirk** » 05 Oct 2020, 17:17

Hi jobijobi, RS485 is actually a differential transmission.
For this purpose one A/B pair is sufficient.

Potential differences of the individual bus participants, if they have no galvanic separation, then flow off over this RS485 line.
Since the RS485 input is not completely low-impedance, a voltage is generated there.

The RS485 driver module installed in the (old) Connect can handle a maximum of -7 V to 12 V permanently.
If there is a danger of higher (common mode) voltage, a potential equalization should be created.
For this purpose, the shield can be connected to GND, for example.
However, the shield as well as the entire GND of the Connect cannot cope with large currents.

A potential equalization, e.g. between switching cabinets, should be available in any case with an appropriate cross section.

Translated with www.DeepL.com/Translator (free version)

AnthonyR4 · Post by **AnthonyR4** » 14 Oct 2020, 12:09

Hello,

Why did you mark P/N instead of the standard A/B denomination? It makes things not obvious.

revpi connect - rs485 header specs / power output?

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