Frequently asked questions are about powering an APM2.5 or why the same does not work or why it has failed.

Here is a simplified schematic showing the major components of the 5V/Vcc circuit on the APM2.5

Target Audience: Readers who do not have Eagle or are confused about using it.

You Need: Basic electronic schematic reading ability

Note that I have separated the PWM Output section into the upper left corner with a heavy purple line that is bridged by the jumper JP1 on the APM2.5. This is to emphasize that diode D1 passes current through JP1 (and drops voltage). The remaining energy is then called 'Vcc'.  Everything outside the purple corner is Vcc.

This is why the USB will power the APM2.5 when connected to a computer/USB hub. Note the fuse on the APM2.5 side of the USB connector AND another fuse on the output of D1. Another change from APM2.0 is the D4 6.0V Zener diode. If an over voltage is applied to the board, D4 will crowbar what it can to protect devices.

As with APM2.0, any 5V source connected to any of the indicated Vcc/5V points outside the purple corner (with GND of course) will power the APM2.5.

Also of note is the 'Mystery Port'. This port takes 5VDC before D1 and the fuse and is called 'JP_VCC'. Other clues to the mystery are the lines to 'ADC 12' and 'ADC 13'. A mystery indeed!

Any errors in this drawing from editing are mine.

I hope this can be used as reference for solving problems.



27-FEB-2014 Eagle files are now located HERE


Tags: (UAV)-autopilot-hardware, APM2.5

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Thanks for that post.

So, I never quite understood why I cannot power an APM 2.6 from both the servo side and the power module side.

The diode is there to make sure power module power doesn't flow to servos, so I don't understand why you'd ever want to remove JP1 and get into a non redundant power situation.

Do you happen to know?


I never quite understood why I cannot power an APM 2.6 from both the servo side and the power module side

The power module is directly connected to the 5V Servo rail with JP1 installed.

The diode D1 stops servos from being powered from the USB port.

The diode D4 shorts to ground with a voltage over 6V, the main load being dissipated with the 500mA (now 1.1A) solid state fuse F2 (as current goes up, its resistance increases, having a larger voltage drop across it)


Aaah, the power module isn't protected from powering the servo rail with the diode when JP1 is installed?

Ok, not sure why it would be designed that way, but now that makes sense, why you'd have to remove JP1 if you use the power module.



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