The direction of ALUM1250 about diybms HOT 9 CLOSED

Now you've got me started :D ...
https://github.com/tvixen/diy-BMS-with-Arduino-Nano

from diybms.

Hi Tim, in the situation of this circuit where both sides of the i2c bus are communicated with processors which are i2c compatible (not compliant) it doesn't really matter which way around the comms is.

The spec sheet mentions that "Side 2 of the ADuM1250/ADuM1251 is I2C compliant, whereas Side 1 is only I2C compatible" which would be important if side 2 needed to be i2c compliant - but in this scenario it doesn't.

from diybms.

Hmm, well I still think this could be a issue, as you can pull 10 times more power from side2 (with all the slaves) + the 2K2 on side1 is is way to high. As I read the specs, they should be 1K when using 100n as C4 ;o)
Any way, you have done a great job, but I think I will give it a try, turning it the right way, in my next print layout.

Br Tim

from diybms.

That's the beauty of GitHub, happy to accept a pull request with the fixes/changes. Thanks

from diybms.

Hi Stuard
I would be glad to, but im using Eagle and your using Kidcad.... I think this will be a miss match of different files, and confusion for the users.

Br Tim

from diybms.

Agreed, so you are starting a new project then?

from diybms.

Well the project are already 99% done. and I'm doing the final work tonight. Then order a new set of PCB's, and then test them. So I don't know if I'm gonna write it on github.... seems as a good idea, but I have never done it before so I don't really know how to start :o/

Br Tim

from diybms.

Just a comment on the 2k2 resistor on the i2c bus - the spec does mention the lowest resistor should be 1k, however as there is only 1 item on this side of the i2c bus (the ATTINY chip) then the capacitance of the bus will be fine. The resistor on the other side of the bus should be 1k to the NodeMCU.

No reason not to make it 1k, but it does work as it is.

from diybms.

I don't think the capacitance of the bus on the ATTiny chip side, will be the biggest problem, and if we keep the wires short, probably not at problem on the slave side, but because you have turned the IC 180 degrees, I think the power can turn out to be a issue in combination with the pullup's to I2C compliant level.
I have made the new ones with side2 to the common I2C bus. Let's see if it makes the bus more stabile.

from diybms.