Right now, there is no JP1 on my 3dr quad, and as I see it, the outputs are powered by the PDB.
There is also a power module from the PDB which goes to PM on the APM board.
My question is : Why the requirement to keep the output power rails separate from the inputs and S pins?
Since both are coming from the batteries, no? Could someone explain this to me?
Thank you!
Replies
Have you seen THIS post?
THIS page completely addresses alternate powering the APM 2.5+
From what I have read, the decision to separate the output rails is based on history and to provide the user some flexibility of changing the Output voltage needed. The oldest versions of APM had 5 VDC regulation on the shield board. Not so with APM 2+.
With the 3DR PM, JP1 is not used. The Output rail is powered by the PDB ESC/BEC or what ever you wish to power it with. This allows you to use 6V (or higher) servos without JP1 installed. High current servos could cause a drop in the rail that lead to brown/black outs of the 3.3V regulation. This was discussed almost ad nauseum in circa 2011/12.
The 3DR PM was a response to multiple cases of users incorrectly powering their APM and the voltage regulation discussion.
In addition to an 'any voltage' (with common return/ground) approach, some ESCs - DJI for example - are opto isolated and contain no BEC
The skill sets of hobbyists are very broad. The applications of APM needed to be just as broad.]
-=Doug