APM2 No servo movement

I finally got time to assemble my flybarless 450 trad heli, I swear sometimes Hobbyking is slower then monkey spit rolling uphill.  And I bought the Assembled APM2 with out GPS back in June, it arrived July 10th.  

  I hooked up everything per the wiki and the discussion here.  Installed the correct firmware for Trad Heli. and calibrated my radio.  I pulled the main rotor, tail blades and started testing and all I got was throttle with no servo movement.  I checked my Throttle Pitch curve 50 50 50,  So I adjusted to 0 25 50 75 100 on both throttle and pitch.  Still nothing from the servos.  I pulled the APM and added JP1 hooked it all back up and still nothing.  I charged up the little 1 cell battery that I use for radio setup,  applied 4.2v to the servo rail on the APM with jumper 1 removed and there i got servo movement.  I don't have a working multimeter at home so I was unable to check voltages.  

I am using a 80 amp Turnigy Super Brain for my ESC, Overkill I know but it has so many options that even the options have options.  It is governed with data logging and a hefty BEC BEC: 5V/4A (Switching BEC, supports above 4 digital servos).  That provided exactly 5.0 volts.  I performed the mechanical setup with out the APM installed and all 4 servos are good and move properly without the APM installed.

I have the blades set  for 0* pitch at 50% swash throw and perfectly level.  


I am using 3 x Digital Solar Servo D220 for my swash, and 1 Digital Solar Servo D221 for the tail rotor.


Is there a separate step for digital servos?   Is my APM defective? 

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  • Thanks guys,  I am going to build this tonight and it should solve my power problem.   Since it is just a 450 I am going to use the ESC BEC with a Y wire to split power between the RX and APM and the servo's.  But on a larger heli it could have its own BEC.   


  • And just in the interest of completeness since this thread is relevant:

    On anything other than a 450, I really recommend using a servo power breakout board of some kind.  The circuit traces on the APM are NOT designed with big digital servo loads in mind!  You will quite possible burn out a trace and your servos will be dead in-flight.  Not cool.

  • Developer


         So I think what's happening is that the servos aren't moving because you're not providing power to the output servo rail.  Is that correct?  It's best to keep the power going to the servos (i.e. the rear servo rail) and the power used by the APM's CPU and radio separate.  I fear the servos will add a lot of noise if you join the jumper to make the servo rail and internal power on the same circuit.

  • Just reread through the Wiki, and Digital servos are not only supported but recommended. 

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