I currently use an external 5 Amp BEC, because I need to power 2 servos for my camera gimbal.  My BEC is soldered to battery leads on PDB and plugged into the output side of the APM 2.5.  I purchased 3D Robotic APM 2.5 Power Module and I would like to use it to measure and log power.  Can I just plug it in or do I need to do something special?  My APM 2.5 is standard from the factory with no jumpers changed.  I really don't want to experience another brownout and crash.


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How do you power your gimbal servos? From A11/A12 (also known as CH10/11)?

If you remove JP1 the BEC you currently have will power anything connected to the PWM outputs 5V, the APM power module will power everything else, including the 5V rail on the A connectors.

You shouldn't power servos from the A side if using PM or power from PWM Outputs with JP1 in place as there is a fuse that limits e current in that path to 500mA
This has been a confusing topic. IVe been researching this since I bought a camera mount. The wiki page shows connection to A10 and A11. It also gives ou a warning to Not power the servos from those points with the jp1 out. They recommend getting power from a Pwm port or connect it to power elsewhere and only connect the signal line to A10 and A11. If you don't, you can cause a brownout and a reset. A lot of other people show different ways of setting it up.

So bottom line, what is the correct way to do this?

Please help.



see http://copter.ardupilot.com/wiki/arducopter/arducopter-setup/apm25b... and the third picture down. You will see from the PM there is a diode and a 500mA fuse. if you connect a servo to A11 and power it from there you will draw more than 500mA and the fuse will cut the power to the APM.

So you need to power from a separate BEC the servos or from a BEC that's in the ESCs and that can be via the Outputs section. You just need to make sure GND is common.

The other ways are older way, the APM2.0 did not have the protective diode and fuse, so it works in that case. The protection circuit was introduced with APM2.5 and that when the instructions differ.

Hi Bill,

Thanks for the link and help.


Great. Happy flying :-)

I tried robbing power from the outputs 7 & 8 but nothing happens. Not sure whats going on.

Looking at the the link you sent me, there is a tee at the jumper. To the right is a fuse and zener diode. There is a small drop in voltage due to the diode. To the right is the "A" port and input ports. They are fused for 500 ma. To the left of the tee is the output ports with no fuse or diode. It will source enough current to drive servos.

The truth table shows with the jumper installed I should get 5.37v onthe output rail and 5v on the "A" and input rail. All being powered by the PM.

With that said, why cant I install the JP1 and run my gimbal servos on the output rail voltage?

I am running a Tricopter with a roll and pitch gimble.

The APM 2.5 is powered via the power module.

The Jumper is removed.

I am providing power to the output side via a BEC on CH 4 out. The BEC is from one of my ESC's.

I have servos on the output side 7 (yaw), A9 and A10 (gimble servos)

I have about 30 flights in this setup with no problems. I do not get brown out problems with the APM, I do get a noticeable reduction of motor power if I push my flight time past my set limits.


I ended up connecting a bec to the output side on pin 7 and driving the servos on a10 & 11. Jumper is disconnected.
I haven't flown it yet in that configuration. Since the last attempted runaway, I pretty much shelved it.


I think I understand this and have a solution for us tricopter folks with Power Modules.

I have all three (black/red/white) cables going from my three ESCs into the output of the Ardupilot, so I'm supplying a vast amount of power to the output rail and should be able to plug a big honking servo into Output 7 to move my yaw mechanism?

JP1 is removed, that separates the in and out rails. So I just need to connect the Power Module to the Ardupilot "PM" connector where it will power the input rail which will get the juice it needs from the 5V output of the Power Module.

If I decide to run FPV transmitter and cameras I will need to get a UBEC to drive those from the main power that's not attached to the Power Module at all.

Can someone confirm this? I'll draw up a diagram if this is right and share with everyone.

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