I have an APM2.5 board and I am building my first hexacopter, so the first build seems harder.
Now I am trying to understand the basics of powering of the APM board. At first, do I understood correct, that if JP1 jumper is not set, I should power both inputs and outputs? And if it is set, I should power either inputs or outputs, isn't it?
The second problem I have with my BEC (built-in the ESC). Its output voltage is 5,67 V which is greater than recommended 5.00 +-0.5V. Could the difference in 0.1V cause troubles?
I would not overdo it. You didn't get the PM with your 2.5? (I don't have one with mine.)
If not, you can leave JP1 in and power the APM from the output side only with your BEC. Then the voltage would be in spec. You remove JP1 when you want to power the input and output sides separately.
Alternatively, you could put a regular silicon diode (1N400x etc. or better) in series with your + BEC output (mount the diode right on the PDB) and that would drop it enough to power the input side of your APM (JP1 in or out) and still be in spec. (Don't power via the output side this way, voltage would be a tad low but would still work...unnecessary.)
The point here is that the output side is specced for ~0.37V more than the input side (there's a diode V drop in there).
Have you considered using the new Power Module? That way you would have the correct voltage and have main battery voltage, current, and MAH transmitter over the TM link and recorded. http://store.diydrones.com/SearchResults.asp?Search=power+module
When you do that remove the jumper on the board.
There is another potential problem using ESC’s with built in BEC. If you connect them all then the BEC’s will be fighting each other and can sometimes cause a problem. A couple of years ago I was having random ESC problems and finally traced it to BEC interaction. The ESC’s use the internal BEC to power its electronics so it has to have clean power or it can crash the CPU internal to the ESC. The solution is to cut the red wire on all the ESC’s. Actually you can leave one connected but I just remove all so I can swap ESC’s without worrying about it.
No, I didn't get Power Module, probably, that was an early version of APM2.5.
Thank you for your answer and for solution with diode. I'll try it. I am going to use one with the maximum current of 300 mA. That should be enough, considering typical consumption is about 200 mA.
Have you considered using the new Power Module?
Thank you, I will take that potential problem with ESCs into consideration. Should I cut two of three wires or power only? Wiki is a bit unclear at that point.
I have one question left unanswered: how much wires should connect ESC to APM? I am not sure, docs says that one, but usually there should be at least two for a closed circuit.
Is this question too dumb to answer or nobody knows it?