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I want to use my SmartSolar controller to control consumption, so I bought a VE.Direct data cable which I will connect to a relay that shall switch on when battery voltage reaches a certain level. But I can not find anywhere what signal is coming out (do not have the controller here). Is it TTL, open-drain / collector, 5V, 12V - and how many mA can it sink / source?
It is 5V TTL for the MPPT's. BMV is 3.3V TTL for what it's worth to you.
On my MPPT, the Tx pin is open drain (2N7002) via a 1K series resistor, so not very much current before the 1K resistor starts dropping significant Voltage over it.
Thanks a lot. Just to be sure: I've set Tx port to 'Virtual load output'. Then 'Load output' is set to 'User def. algoritm 1', with 'Load switch high voltage level' set to 13.8V. Am I right in assuming that when battery reaches this level, then the output transistor will switch ON, thus pulling the Tx pin DOWN? I'm asking because I cannot test it here...
Well, upon closer inspection, the MOSFET is configured as a level shifter. Of course, the μC is running at 3V3, and the VE.Direct is TTL 5V, so not exactly open drain, drain is pulled up to 5V with a 10KΩ.
So, the 5V signal is not inverted with respect to the μC output.
Therefore, with the Tx function set to Virtual load output, on = 5V.
