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Ghost
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Posted: 07 June 2019 at 7:56pm | IP Logged Copy link to clipboard   Quote Ghost

Am more concerned about the firmware , when will it be ready ?


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Solar Mike
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Posted: 07 June 2019 at 8:24pm | IP Logged Copy link to clipboard   Quote Solar Mike

Ghost wrote:
Am more concerned about the firmware , when will it be ready ?


Good question, now that very few CPU IO pins are required, will see what small cpu's I have lying about and make a small board to do an initial test; looking in the cpu tin on the bench are several ATtiny85, 14, 18, 28 pin PIC's, some 32bit cpu modules arrived few days ago also.

For those less patient, then grab your Arduino or similar and have a go, gerbers etc for the other boards have been posted.

Currently renovating a house, new bathrooms, wallpaper, paint, so a little busy at the moment...


Cheers
Mike
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Solar Mike
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Posted: 12 June 2019 at 9:57pm | IP Logged Copy link to clipboard   Quote Solar Mike

Work continues; the main Lead Carbon bank (50v, 900 AH) will have 4 mppt chargers, one being a master, the others slaves and a spare, ie they will switch to bulk, float etc when directed by the master controller.

Have decided to use a form of 1-Wire bus system to network the PV controllers together, the master is also a form of slave in that it will be linked in to the BMS and the site control management system that monitors the 50 or so non-contact capacitance soil sensors for irrigation control. The 1-wire cable will be up to 500m in length with sensors clipped across its 3 wires (0v, +12v, Data).

I maybe asking too much of the cpu in the mppt controller to also talk to the external network, will have to try it out, the network wont be that fast, but may have to use a second cpu (ATTiny85) perhaps for this.

Anyway here is the proposed circuit of the 1-wire interface, it will be on its own tiny pcb that can plug into any of the slave devices, I have bread boarded some of it for initial tests, have used a data isolator chip for slave isolation as they are more immune to external interference than opto's.



Cheers
Mike
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Ghost
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Posted: 13 June 2019 at 3:51pm | IP Logged Copy link to clipboard   Quote Ghost

Impressive, but as you said slow network, will it be fast enough to control slaves very fast , in order to maintain battery levels during charging ?..
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Ghost
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Posted: 13 June 2019 at 3:55pm | IP Logged Copy link to clipboard   Quote Ghost

Almost done with my 50a PCB.
I may adopt some part of your code.
Currently adopting libresolar mppt project.



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Solar Mike
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Posted: 13 June 2019 at 9:30pm | IP Logged Copy link to clipboard   Quote Solar Mike

Ghost wrote:
Impressive, but as you said slow network, will it be fast enough to control slaves very fast , in order to maintain battery levels during charging ?..


The communications between mppt chargers is limited, switch to Bulk, Constant voltage or Float, so that wont be a problem. What Im not sure about is the comms between the Master charger and the rest of the network, will have to build and test. Depend on final cpu spec.

Cheers
Mike

Edited by Solar Mike on 13 June 2019 at 9:32pm
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Solar Mike
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Posted: 14 June 2019 at 9:47pm | IP Logged Copy link to clipboard   Quote Solar Mike

1-Wire PCB: I need quite a few of these, can fit 4 of them inside a 100x100 pcb, JLCPCB allows this if not panellised, cut them up with a guillotine no problem.




Cheers
Mike
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Solar Mike
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Posted: 16 June 2019 at 5:15pm | IP Logged Copy link to clipboard   Quote Solar Mike

CPU board: Other than the cpu, there isn't much required for this board; the power mppt board connects via a terminal connector, the IO relays and temperature sensors connect via an I2C interface, the network interface is a modified 1-Wire connection and the LCD can be serial or I2C.

Because of the high charge currents, I think it is essential to have a remote sense of battery voltage, so have added a simple instrumentation circuit with gain of 1 to read the battery voltage at the battery bank terminals. (may put this on a tiny plugin pcb)

Also added a 2.5v reference that the CPU can use for accurate readings.

No CPU showing as I intend to try different types, need 15 free IO pins, have some PICs with 20 pins, try them first, then various Arduino's


After this prototype is running and debugged, the CPU board will be re-visited..

Cheers
Mike


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