I've a 3DR hexacopter, new. 

It has the PM (Power Module), the PDB (Power Distribution Board) and an APM2.5 with no jumper on jp1.

Online, I've found some instructions telling me that when using the PM, one is to leave jp1 unjumpered, and to plug in the +5v coming from the PDB.


Is this correct?


Yesterday, I USB'd into the APM2.5, and downloaded 2.81 firmware.  So I know it's alive - so far.  Don't want to plug things in incorrectly.

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What do you mean b y PDB?  (The bottom plate of the DJI F550 for power distribution - PDB)

- for ESC's and battery connection.

Are you using DJI ESC's ?  I haven't purchased the ESC's yet.  I was planning on purchasing the DJI ESC OPTO's, but to my understanding, they are without BEC's

I am confused per the Ardupilot instructions if the BEC is necessary due to the APM Power Module and cable connected to the ArduPilot Mega V2.5+ PM..




>>>Then I understand according to this copied parapgraph that I would need a second battery to power the R/C ? (while the first one only power the motors through the power module connected to the PDB) Is this correct understanding or not ?

No, you only need one battery.  Power module will provide power to the APM and no further connections are required.

See if this helps:

The green is ground.  The "-" of all batteries is connected to ground.

The RED bus is the APM Vcc (+5V).  (It's also the +5V from the USB port).

The ORANGE bus is the +5V from the ESC's through the PDB.

JP1 basically connects the orange and red busses.

If you are using a separate +5V supply for the APM, receivers and servos, you pull JP1 and connect the power supply to any pair of red/green pins on the the analog I/O.  The separate APM supply can be from a second battery and BEC, or from the main battery and a BEC.  From the Glossary: 

BEC: Battery Elimination Circuit. A voltage regulator found in ESCs (see below) and as a stand-alone product. A BEC is designed to provide constant 5v voltage for RC equipment, autopilots and other onboard electronics.

As Bill indicated above, if you are using a separate supply for the APM, then a second battery is recommended.

A brownout occurs when the only battery momentarily drops in voltage enough that the +5V from the ESC or BEC fails to keep the APM powered up.  A crash is certain because of the time it takes for the APM to reboot and for your radio to re-establish a connection.

Good points about the confusing text -- thanks to everyone who pointed this out. We'll clean that up over the next few days. 

In general, most Copter users should leave APM 2.5+ just the way they got it, with the jumper off. 

Thx a lot Bill and Stephen for an excellent schematics, this should be put on the wiki as base documentation to understand the power circuits in Arducopter, this is now perfectly clear.

A doubt: there's only one +/- wire that feeds APM2.5 via the cable supplied with the Power Module?
In this case I'm a little hesitant, because in all my setup i use a redundancy on power as a matter of safety, in 25 years I never crashed a model "double powered" for power problem.

I haven't check the schematic, there's six wire, i hope 2 wire for + and 2 for -, the other two for current and voltage data.
In all my drones i use two 6V voltage regulator for power the flight board, with two 5A diode connected with the positive (5.3V to the board), or two BEC with protected input.

There's way to connect the PM without power APM with the internal 5.3V regulator and still detect voltage and current?
I am sure the reliability of the module, but I prefer to use my power system, as it's redundant.

Just look at the schematic & you can see the pinout.

I'm sorry Craig, where? :-)
PS: thanks for the "black box", is here...

There is a link to the full schematic on the page where the APM is in the store but there is a simpler one here too


Nice, if is the port called "Mystery" all is ok, double wire for + and -, 3DR rulez, cool thanks! :P

Yes.  We should update the schematic and give it a more appropriate name.


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