I am completely new to the world of hobby UAVs so apologies if this question sounds a bit trivial, but any help on the matter would be greatly appreciated.

I recently purchased a new ardupilot mega and oilpan. After soldering and downloading the software I am keen to connect my RC gear and get going, but am terrified of doing it wrong!

Firstly should I connect my receiver to the input channels on the Mega Board, and then connect my servos to the output channels.

However, if I then put attatch my battery and motor to the ESC, and connect that to the output channel of the Mega Board, will that operate correctly?

Again, apologise for the probably trivial question, if you need any additional information please comment.


Charles Winter.

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Hi Charles,

your APM2 comes with a jumper (JP1) as shown here:


if its "On" your whole equipment would be powered by the output rail, normally from the ESC in chanell 3. Thats meens, all the power pins in output rail, all the power pins in input rail and APM will be in parallel, so the servos conected to output pins, your radio receiver conected to input pins and your APM will be powered by de motor ESC. This is the case you described so Yes, it would operate correctly.

If Jumper is off (open) your servos will operate powered by the ESC as allways, but your radio receiver and your APM2 will need another battery. It could be usefull for example if your motor and servos battery get empty and your aircraft couldn't return home you would be still having telemetry and position of it. Im sure there are many more cases but i dont imagine them.

Hope it will be usefull for you.

Have a nice fly.


HEy Marcos, that was a really helpful post.
I'd like to hang a question on to that.
If i am using APM2 on Arducopter, i have all the ESCs getting their power from the main battery.
I want to power all the Electronics + 2 Servos in the camera gimbal with an BEC.
Do i now hook the BEC into the servorail of the APM (input or output?) or do i attach the BEC to my Reciever?
And Jumper on or off?

I'd love to hear your opinion.


Hi Daniel,

Setting the jumper off, you will separate the output rail from the rest.

You could hook the BEC either to the receiver or to the input rail. I'd prefer to conect it to the APM input rail, because i think APM is the main control unit, not de receiver, so if in a misterious way all of your receiver's wires get unpluged, you still got power on your autopilot to control it by a CGS or to execute a failsafe.

I'm asumming you are conecting the servo wires as shown here:


it works so nice.

In any case, it dosen't matter if you connect it to the input rail or to the receiver, allways you connect at least one 3-wires servo cable between them.

Have you got a video TX?, in my short experience, its much more important to separate the video feed power from the main batteries than other thing. When my batteries goes down and i push throtle up, video disapears. So i use one batteri for video feed and one for the rest.

Enjoy it.


Thanks, i will do it like that, put the power to the APM.
Yeah, my videofeed gets an extra battery.


Does the APM 2.0 have a built in LM317 regulator like that APM1.0 for external power supply?

No its doesn`t, as refered at the end of this document:


In the section: "Difference between APM 1 and APM 2"

I'm also a beginner. For the initial phase, I want to  use the board only as a datalogger which will get the sensors and GPS readings of several manually flown air vehicles. Please correct me if anything is wrong with what I think:  Board must have its separate battery. Also I don't need servo power so I will leave the jumper off. In order to power up sensors processor and sdcard  which pin should I connect the 5V supply? Thanks. 

Hi Onur,

If you leave your jumper off, the only way you could power your board would be by the input rail.

The + pin in all RC 3-wires wires used to be the center one, to avoid polarity change when hooking it in the wrong way (+ allways stay in center of the 3 pins). Here you can see the polarity of your input rail:


You can use any of the inputs and anything but the output rail will be powered.

Good day UAgroV. I have a problem which seems to be common for a number of people on the forum. I have a APM 2 V 2.4.1 and wish to power up the board by only using the 5V supply from the ESC on channel 3. I have left the jumper J1 on (default) which the manual states is supposed to supply power to the output servo rails and the board, but my board does not power up. Similarly with JP1 off. I always need to provide power to the board via the USB connector or via the input rails or the RC receiver. What may be the problem and how is this resolved?

Thanks in advance of someones response.


Reply to my own query. Actually another query!!!!

In the case that the two rails need to be separately powered (regardless of the jumper) may I use a two wire bridge between the output + and - and the input + and - to power the board using the power on the output rails supplied by the ESC or will there be a regulator on the board that would cause problems with the regulator on the ESC/BEC?

I'm having a bit of a different issue and could use some clarification on how to power everything.

In my case I am use a large servo that requires 6v or 7v and my Castle Creations Phoenix Ice 50 BEC is programmed to output 6v accordingly.

So I need 6v to my servo.  I don't really want second battery right now. Can somebody diagram for me how I might set this all up for use with the APM 2.0 + telemetry.



I would think a second BEC, set to 5V, just to feed the APM and telemetry, RX, radios etc. That way you keep servos separate (on the existing 6-7V BEC)

I have 2 BECs and a switch on each, so that I can turn things on in stages. 

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