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Forum Index : Electronics : Comms between multiple PV Controllers

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Solar Mike
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Joined: 08/02/2015
Location: New Zealand
Posts: 1164

Posted: 12:03pm 23 Sep 2020

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I want to setup some sort of communications between PV chargers (slaves) and a master aggregator device or a controller acting as a master.

Purpose being to send common data to the PV chargers such as Charge settings, max charge current etc. Then allow interrogation of the slave devices for average charge current, voltages etc.

Thought up this simple circuit using inexpensive schmitt opto couplers to form essentially a 1-wire data bus. The master powers the bus and has a common pullup to 5v rail, its circuit is essentially same as the slaves. Up to 5 slave devices will be connected across the 3 wires, only 1 device talks at a time. Wire distance approx. 1 to 10 meters.

Seeking more ideas here, many bright sparks out there, the last time I built something like this used balanced lines and NRZ data 30 years ago.
Perhaps there is a chip that does this...

Cheers
Mike
Edited 2020-09-23 22:05 by Solar Mike

Solar Mike
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Joined: 08/02/2015
Location: New Zealand
Posts: 1164

Posted: 11:47am 24 Sep 2020

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The schematic below, developed a year ago, is more complicated but has much greater hysteresis between low-high logic on the wire, so will probably continue with it.

Will write a custom bit-bang protocol for the data transmission, I don't want to use standard serial data as not all controllers have the 20X2\28X2 chips, so have limited internal receive buffers.

Thought using a pulse width modulation system where the width of the "On" period determines the data values.

Cheers
Mike

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