I'm setting up a nitro heli.

Is it a good idea, to give the APM and receiver and servos one power supply from the APM output side.

I know i must power up the servo side, because of the high current of the servos.

Can I place the JP1 to supply the APM from the output side.

Or is it better, to power up the APM separate, the battery is the same anyway.


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NEVER share the APMs power source with servos. JP1 should be removed.

Ya,  Run the APM off the power module with the J1 jumper removed.  Power your servo rail with a BEC.  I have used a BEC set to 5.7 volts without any problems.  I think the max voltage to the servo rail that is recommended is 6 volts.


David R. Boulanger

If JP1 is removed then the servo rail will not be connected to the APM. In this case, there is no voltage limit other than what your servos can handle.

iskess,  I think your wrong.  Look at the Wiki on this subject.


David R .Boulanger

Which part am I wrong about?
That the servo rail is totally isolated with JP1 open?, or that there is no voltage limit with it open?
How could there be an APM voltage limit if the APM isn't connected to the voltage?
I didn't see the wiki info, but it is often wrong and if so, let's report it and get it fixed.

The servo rail is isolated but there is a limit on voltage according to the Wiki which I believe to be right.


David R. Boulanger

Do you mean the the actual rail traces themselves? That would be current limited, not voltage. Where is the wiki reference, I can't find it.

No its voltage.  I think it is in the Traditional Heli part of the Wiki


David R. Boulanger

Its in the Wiki in the full table of contents under hardware overview for the APM 2.5 and 2.6


David R. Boulanger

I see the info you are referring to. That has to be some sort of error in the Wiki.

In looking at the actual schematic for the APM, with JP1 left unconnected that center +5 Volt rail on the output does not connect to any of the circuitry of the APM. Its ONLY connection is via JP1. With no JP1, no connection.

Of course there has to be some sort of current capacity limitation on the actual +5 Volt rail board trace, but there doesn't appear to be any reason it can't be run at (reasonable) higher voltages.

I have a 3 A ubec adjustable. I set it to round 5.5 V to supply the servos, hope the current is enough.

For the APM i use this module from ebay: http://www.ebay.de/itm/APM-2-5-2-APM-2-6-Pixhawk-Power-Module-V1-0-...

It was in the set with the APM.

@David, I changed my receiver and servo connections, some reverse of channels and my heli is correct working.

i can arm the APM and test it in all 3 axis. The APM controls the correct servo in the opposite direction when I move the heli by my hands. Now is the time to power up the nitro machine.

I tried today, but my starter battery was down. So I order a new one. Maybe tomorrow i have little time and use the car battery. We will see if it works or if i need a new heli.


@david did you read my last reply in the other discussion?

It's confusing with the words throttle and pitch and elevator.

This is totally different between copter and heli. Copter throttle is pitch. Heli throttle is only speed up the blades.

In Mission Planner Throttle moves for Elevator in calibration screen.

And the heli throttle you can only see channel 8 moving.

But finally i got it.

This should be corrected in the traditional heli wiki. But this is not the first wrong explanation I found in the wiki.


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