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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With JP1 OFF, using a separate battery/BEC for the input side, which rail are the camera pitch/roll servo ports (A10, A11) powered from?

In the picture show dont show but you can get the power come from RC or USB in the case of JP1 OFF.

When JP1 ON power come from ESC.

The need of JP1 was to let ESC/Servo to be powered from other value than 5V let say some have servo and esc who can work at 12v not at 5V that will fry your board if JP1 is ON.

But some want to separate the AMP power from any other source of noise like ESC/Servo this JP1 allow you to do that w/o any problem to get you safe combo.

Think you can put a mux on power too when 1 of the source (saying this assume you use 2 powers) you AMP battery get lower than ESC power just put a relay on of the free sensors rail and when see on telemetry that happend just switch that relay to on and use ESC lipo for powering amp too (is true you will need some capacitors to prevent lose power on the switching process but that is good to have in any case when you intend to work with ESC power).

Hope will help

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

I've got the APM1 board and IMU (oilpan).  I can see the solder pad which can be de-soldered to separate the ESC/servo common +V rail from the +5V supplied to the APM board.  The separate connector to power the the APM is near that solder pad and it apparently needs between 7-10v.  Can I use a UBEC on those pins even though it will only feed 5V or is there some other point on the APM or IMU board I should feed the +5V to the APM/IMU?

I'd rather not have a separate two cell LiPo for the APM power.  I just need a 6V BEC on the ESC/Servo common rail and a 5V BEC to drive the APM with one source three cell battery.  That way I can run my camera stabilisation servo's at 6V (faster response).

Hang on, the Vin on the base of the APM1 board says 6V-12V.  If I de-solder the pad and put a jumper across from the 6V common rail to that Vin it should work.  The APM's own voltage reg will drop it to 5V.  Not sure how that will go with noise on Vin?

I've yet to fry anything with dual power and a USB, has something changed?

A10 and A11 is from Amtel2560 so will be powered from wher you let your board to get power and is the same as A0 - A9. Sorry im not home and i dont have board with me but im 90% positive about this.

Think about why was this board made to be you guid in air and this line was to use for sensors or other things you need to get info.

Hello everybody,

While the APM2.5 is already available, would be great if somebody could refresh this topic. What are the major changes regarding the powering on this board? Everything which was described here is valid for the new board too or we have now more flexibility to choose the combination?

If the board is powered through the output rail (as usual), due the built-in Schottky diode which must prevent to burn something when also the USB cable simultaneously is connected, it is an voltage drop on the Input rail which is relative low for the connected Weatronic receiver. Have anybody ideas how could be this issue solved?

I think the remaining solution is to power separately the receiver through a second ESC (by multirotor) or using a BEC but only the ground will be remaining common for the entire system. Other tips are welcome.

Thanks in advance,


Zolton: I'm not quite sure why people thought you couldn't power the original APM 2.0 with both USB and the output rail at the same time (you could), but at any rate APM 2.5 is the same. You can power it from USB and ESC at the same time. 

As for the voltage, with an input voltage of 5v, the drop due to the the diode should be less than .2v. That should still be well within the tolerance for any Rx. I've certainly never seen a problem. Are you saying that you've got a Rx that won't work at 4.8v?

The new power protection circuitry protects you if you plug in a connector wrong on the output rail (offset by one pin was the old killer) and also protects the USB/Serial mux from being fried from weird current glitches when plugging in radio modules and USB. Overall, it's just a more robust design that deals with EMF noise better.  

Thanks Chris for your quick reply! I have already powered my APM 2.5 on the output rail and the USB port at the same time, no issues. The alarm level for the RX supply is set to 4.6V as default and with my quick test gear (awaiting the frame and accessories for the quadro) I get some alarms from the telemetry as the RX has reached the supply low level limit. For sure, that was tested in airplane mode with two servos and a small ESC which can support up to 1 Amps . Anyway, if calculating the voltage drop of 0.2 Volts on the protection diode, I will get 4,8V on the receiver which will be low to be in the green area. I will supply the complete gear with ~5.2..5.4V and will be fine or using two separate BEC output from the available ESC's I will power the board and the receiver separately. We will see.

I will take a look if somebody else has started a dedicated topic for the APM 2.5 board but just for information, I have already tested the composite signal on CH5 and seems to work fine

There is a blocking diode between the USB connection and the output rail so you cannot power the servos from the USB power.


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 .

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