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


Views: 75160


Reply to This

Replies to This Discussion

Thinking a little more about your question, there are two GPS ports. The red boxed above is the new style, the one just below it is the old style. This is clearly shown for a 2.5.2 release in THIS graphic.

HERE is a link to Digi Key showing the old style connector. The mating products are shown in the colum further down the page.


...and thinking more about your question, THIS graphic labels the PM port as the Expansion port... a nod to early secrecy of the PM development.


Guys, about protection of the APM. This is what happened to me today:

Hi (again),


I’m not having much luck.

Today I experienced a serious problem which destroyed a just purchased APM 2.5, the received MinimOSD as well as the uBlox GPS.


The situation was as follows: I had the APM 2.5 plugged in to my laptop via USB. All was working well.

I’m using 4s batteries and as soon as I plugged it in to the APM’s 3dr power supply, disaster happened: it fried (I could smell it) the APM. Upon trying a different power supply, second APM 2.5, I discovered that the uBlox was destroyed (I tried an older Mediatek, which worked fine) and that the connected MinimOsd was destroyed. I suspect a power spike by the power supply.


The MinimOSD is ONLY powered by the 5V coming from the telem port, which I believe comes from the APM's power supply and not from the ESC's?

I had also one APM2.5  blown   I also think spikes are to blame   

I find that the Dean plugs are very difficult to connect as a clean contact connection  one has to try,re try twist and eventually the two prongs engage... this causes various transients to be sent through to the ESC's and the electronic boards.

I am sure that changing type of connector could solve some blow ups.

I think two battery supply would be better one for ESC one for electronics

Another suggestion is to insert a proper toggle switch  or to have the board to have some kind of load shedding timer

to allow the ESCs to be power once the electronic is powered   this would prevent spikes and transient

I was during my working like an instrumentation trouble shooter in industrial digital distribution systems and yes  today's low voltage electronic does not like surges spikes and transients.

I was using an XT-60 plug. The APM was powered by the provided power plug supply. I'm going to change my setup by using a spike protected power switch. I.e. Pololu has a very good write up on spikes and specifically designed this switch.It will sit between the power supply and APM,  


eh that is perfect  I am sure one will blow less 2.5 !!  I have one sitting as a paper weight  sad

it took many email to convince the makers that there is a problem  at powering on  I mean its pretty obvious on an Hex  sparks from the Dean connectors  just as bad has switch bouncing.. GREAT THANKX WILL ORDER    IT IS A MUST HAVE  (vvdd)

We have shown that power-up transients induced by the interaction of high wire lead inductance and low capacitor equivalent series resistance (ESR) can be destructively large. The phenomenon can be especially frustrating for those getting started in electronics because the mere application of power, even with the correct polarity and with a seemingly safe voltage, can destroy a circuit before it ever begins functioning. Repeated voltage spikes outside of maximum ratings can also gradually weaken components, leading to early failure that is difficult to explain: a circuit might function normally for some time before unexpectedly failing after a power cycle.

I hope it will help and I hope 3DR is willing to replace my $275 worth of damage. I ordered a Low Voltage and Standard switch for both APM and FPV. I'm sure this is the cause of my continues issues with the MinimOSD that I have bricked (and 3DR has replaced under warranty)


I was reading about this and I am concerned that it will add another failure point to my setup.. I understand your experience and it sounds like it might help.

1. concern is the switch gets "bumped" physically .. unlikely , maybe I can prevent that..

2. Switch fails electronically?

seems like there should be a better answer such as a filter of some sort that can be put inline... but I don't know anything about that..


I share your concern as it adds another level of complexity. However, it is still better than bricking $275 worth of equipment by simply powering it on.

Additionally, I tend to use to solder everything and not use less reliable connectors. It adds complexity and makes maintenance more difficult, but it certainly eliminates failure points.


I've been out of town with work and out of contact with this thread but - OUCH!

Was JP1 installed on your (now dead) APM2.5?

When using the 3DR Power Module (rated to 4S), JP1 should NOT be installed.

I use a Dean's based 'arming plug' (see my blog post) on my APM2.0 and have had no issues, so far, with an arc. Most of the arc is the front end caps of the ESCs charging up, usually.

With the 3DR PM, I still think an arming plug could be inserted between the +5VDC line coming from the 3DRPM to the APM2.5.

On-Off switches are good things.

Sorry to hear about the failures.


Reply to Discussion


© 2020   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service