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.


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?

It's a bit tricky because you can do many kind of power connection.

1. Power from USB

2. Power From ESC

3. Power from BEC + ESC 

4. Power from USB + BEC/ESC

5. Power from BEC + BEC

Some of them will fry something. What will be you will see. Can be AMP or can be USB, or BEC .

Powering isnt explained well in wiki docs and many new user of AMP can get lost in pages looking for a valid information.

1. Power from USB 

JP1 OFF and dont put any power from ESC/BEC on IN V+ will fry the USB 

Can use radio modem AND can power the telemetry / OSD but ony power last 2 because cant comunicate with them as long usb is linked. (Didn't try to just give power from usb because is clean 5v and dont link D+ and D- from usb but im sure will switch SERIAL 0 to USB and cant use as data line the Serial0 RX and TX.

If you need to test your motors and/or servo you will need to go in case 3,4 and 5 when you connect the second power on the OUT V+ line (just ONE if you have many ESC or BEC)

2. Power from ESC/BEC


Cant connect USB will fry it or some power line will get burn in case you usb dont die first.

This case is used usual with only 1 LiPo for all you got connected to AMP 2 and when you are away from PC.

Dont care wher you put the power on IN V+ or OUT V+ is up to you where is more easy.

3. Power from BEC + ESC 


Powering from BEC connected to the same battery or separate battery is used to get a proper 5V to your AMP2 and your radio.

OUT V+ will get power from ESC (if is need another power for the servo who require other than ESC power will supply that power to the OUT V+  case 5). It can be use a second BEC with other than 5V or even with 5V but with more power to drive all your servos. In this way servo wont affect the 5V from AMP + Radio and/or Telemetry + OSD.

4. Power from USB + BEC/ESC


This is used to test/set AMP2 and is connected to PC via USB and can test radio and motors / servo who will get power from OUT V+ who will be supply from BEC/ESC.

5. Power from BEC + BEC


This is use for separate the power of AMP (fragil electronics) from Servo. Is good when you have 2 battery also the separation is more complete in this case but can be used with 1 LiPo too.

I guess on other case to powering the AMP can be.

PS. You can see the JP1 is need only 1 time when all get power from 1 ESC/BEC and dont CONNECT USB EVER

1. Power from USB  = JP1 OFF

2. Power From ESC/BEC = JP1 ON

3. Power from BEC + ESC = JP1 OFF

4. Power from USB + BEC/ESC = JP1 OFF

5. Power from BEC + BEC = JP1 OFF

I hope some one will find this value

APM 2.0 sounds horrible to power up. Did the APM 1.0 have similar issues?

DahaS: #1 is incorrect. You can power from ESC and USB at the same time with no problem. 


I am on the process of testing all electronics , before running the motors.

I would like to power  transmitters and video TX, from an external power source ( I have not received my lipo battery yet), 

So how could i power , the TX  boards that do not get power from USB, and needs additional supply .

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"


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