APM2.5 5V/Vcc Schematic

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


APM2_5 Simplified Power.PNG

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –


          • Developer
            Sorry, saw that, Unmannedtech.
            So you need to ask for the 2.5 drawings, but need to specify, Not the 2.5.2 or 2.6.
            • Ok Philip,

              So it is just called 2.6 because it has no mag chip?

              The board is really a 2.5 not 2.5.2 (for which I have the Eagle files)

              Confusing eh?

              Big chages in the board from 2.5 to 2.5.2.

              Thanks for this really critical clarification.

              All the best,


              • Developer

                >>>So it is just called 2.6 because it has no mag chip?

                Correct.  The whole assembly is called a 2.6, but the board is just a 2.5 w/o the mag stuffed.

                • Ok, next question.  Where can find the Eagle files for 2.5 (not 2.5.2).


                  • John, I've got zip of 2.5 from 2012.

                    Let's be friends so we can exchange pleasantries and email address. I can then attach the zip and email it to you.


    • Hi,

      Took a look at the Eagle file and they are the wrong ones.  Not close to the 2.6?

      These files are APM2.5.2. The chip layout of the APM2.6 is different.  And so is the chip numbering.

      Got the ratsnest sorted (I am used to CAD systems).


      Any idea where the 2.6 Eagle files are?



  • There is a significant thread discussing  the 3.3V (usually induced failure).

    You should have seen the number of posts about issues before I put this partial schematic (and the sister post for APM2.0) up.

    Things are much better with the 3DR PM and the new packaging but...situations still occur like this.

    NAZA is a packaged, RTF, system...mostly. It is not bullet proof, I have seen many posts where users have not succeeded with it.

    APM is targeted toward DIYers. I think more care and knowledge are required to employ it successfully.

    HERE is the 3.3V discussion. It is quite active.


    • Well I am used to using the other Arduino boards,  I use the 2560 mega R3 which is nearly the same size as the APM to control my observatory power and humidity etc.

      That board runs from a 12volt supply and I also have a USB plugged into it.  It does not destroy itself.

      Why wouldn't the APM board do the same?

      Seems like a lack of consistancy of board design.  I would have thought a couple of diodes would do the trick.

      The other aspect of this board is that it seems that the input pins 5V are somehow connected to the USB 5V?

      However, the output pins have the jumper JP1.

      Maybe the missing bit is diodes between the USB and the input 5V so that you can power the board from either.


      I think what you may be saying is that the PM takes all this into account and you dont need rx power.

      I think it was the track melting next to the USB that took out the 3.3V.


      I have visited the 3.3 discussion and it does not really address the 5V problems.

      It does not tell me an easy way to get 3.3 to my MP6000 - How about the PM does that supply 3.3?

      I think there is a 3.3 pin on the connector..


      Anyone know if there are any board layouts and diagrams?  See if I can supply the 3.3 to the MP6000.






      • The 3DR PM only supplies 5 VDC to the APM connector marked 'Mystery Port' in the schematic at the top of this page.

        3.3 VDC is regulated on the APM proper. There was another 3.3V discussion that, depending on your board build, addressed changing the 3.3 regulator.

        Regarding other, 'genuine' Arduino boards, 3DR significantly drifted away from them starting with APM2. APM 1 is closer to 'stock' in that it uses the shield board. If you are familiar with Eagle, the entire layout and schematics were on the store site. If you cannot find them, I have the zip files for a couple builds. (I just looked and didn't see them under the first APM link.) APM has reflashed code for a couple chips that makes it less plain vanilla Arduino.

        JP1 - Often a point of misunderstanding in the past.

        On the schematic above, notice that '5VDC' from the upper left becomes 'Vcc' if JP1 is installed, passing through D1 zener and F2 fuse. JP1 is used only if no 3DR PM is in place.

        Using the 3DR PM requires removing JP1 so that no extra load is placed beyond design spec (servos, etc). When JP1 is out, you can supply the PWM Output 5V rail with anything your application requires. It is isolated from the the rest of the APM except for the ground/return. We have seen several incidents where the ground/return traces were blown due to various reasons but, never due to correct use (usually due to an ESC plugged in wrong).

        Note the USB power is passed through F1, 500 mA and connects to Vcc.


        • Doug,

          Thanks for that info.  Where did you get the APM2.6 Eagle files from?

          I am trying to find a way to repair the APM by providing a bypass of the blown track.

          I also notice that the first two sensor ports labelled SPI are in fact two ports?

          The pins are not the same as labelled on the cover??

          Pin labled - is in fact 5v  pin labelled + is also 5v pin lebelled S is actually 5V on the second SPI connector??

          A0 to A11 seem to be as the normal servo wiring?  0V, 5V, Signal

          In fact the only ground pin on the two SPI connectors is the S pin on the last three pins???


          I guess I need the Eagle files to work out the connections.

          Seems to be no instructions on the sites about APM2.6 or the SPI connections?




This reply was deleted.


DIY Robocars via Twitter
DIY Robocars via Twitter
May 14
DIY Robocars via Twitter
May 13
DIY Robocars via Twitter
RT @f1tenth: Say hi to our newest #F1TENTH creation for @ieee_ras_icra next week in Philly. It’s going to be huge! 😎 🔥 @AutowareFdn @PennEn…
May 13
DIY Robocars via Twitter
May 11
DIY Robocars via Twitter
May 8
DIY Robocars via Twitter
RT @SmallpixelCar: Noticed my car zigzagged in last run. It turned out to be the grass stuck in the wheel and made the odometry less accura…
May 8
DIY Robocars via Twitter
RT @SmallpixelCar: Test my car. RTK GPS worked great. Thanks @emlid for their support. https://t.co/EkQ6qmjmWR
May 8
DIY Drones via Twitter
RT @chr1sa: @kane That's @diydrones circa 2009. Still have a box of those Canon cameras that we used to strap into planes, just like this.…
May 3
DIY Robocars via Twitter
RT @chr1sa: Our next @diyrobocars race is going to be outside at a real RC racetrack in Fremont on May 28. Fully autonomous racing, head-to…
Apr 30
DIY Robocars via Twitter
RT @f1tenth: Our Spring 2022 F1TENTH course @PennEngineers is coming to an end with a head-to-head race as a big finale. So proud of our st…
Apr 26
DIY Robocars via Twitter
RT @DanielChiaJH: I wrote a thing! Throughout the development of my @diyrobocars car I've been using @foxglovedev Studio to visualize and d…
Apr 23
DIY Robocars via Twitter
RT @SmallpixelCar: My new car for high speed. Low body, everything ( @NVIDIAEmbedded Jetson Xavier NX, @emlid RTK GPS, IMC) under the deck…
Apr 23
DIY Robocars via Twitter
Apr 21
DIY Robocars via Twitter
RT @f1tenth: F1TENTH Race training setup @PennEngineers for our upcoming ICRA2022 @ieee_ras_icra competition. @OpenRoboticsOrg @IndyAChalle…
Apr 21
DIY Robocars via Twitter
RT @fatcatFABLAB: Proud to be hosting a restarted DIY Robocars NYC Meetup April 26. Come by if you want to talk about and race self-driving…
Apr 17