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Digital Servos and APM2

Posted by Brian McGrath on July 13, 2012 at 12:56pm

I have a Y6 running AC2.6 and am using a separate battery (2S/460mAh/25C) to power the APM2.

I've heard that digital servos can draw a lot more current than similarly sized analog servos, but that they provide much tighter control. Is there an issue using digital servos on ports AN10 and AN11 or any recommended limit to the size and power?

Thanks!

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Replies

  • Brian McGrath July 14, 2012 at 6:20am
    Thanks, guys! I appreciate the feedback. I've also received suggestions that I should be using a 3300uF electrolytic capacitor in the power supply to the servos to prevent sag when there is high demend. Have you tried this? Do you suggest using two BECs?
  • Rick Stewart July 13, 2012 at 1:48pm

    I have used digital servos connected to the apm2 via the camera gimbal tilt, and roll connections.  They work quite well, you hear them fidget allot but that is the constant updating from the APM2.  Unfortunately I cannot comment on anything else other then they work.  One is a micro servo, and the other is a standard size.  I use a separate battery for my APM so I don't know the effects of flight time.  One thing you might consider is using a larger battery with a lower C raiting.  I say this because its my understanding that the APM uses 200mah when in operation.  Add some sensors, some telemetry and some hungry digital servos and you could be around 300 - 350.  That doesn't leave allot of wiggle room for having a battery that is not fully charged / old / etc.  Just a thought.   My previous APM2 battery was a 780 4S but I decided to save 20 grams and use a larger capacity (1200 mAh) battery with a lower voltage ( 14.8v vs 7.4v).  I hope this helps, if you have any more questions just ask.  Cheers,

    Rick

  • Rob_Lefebvre July 13, 2012 at 1:42pm

    I have run 4 digital servos on Outputs 1-4 with my heli, but it's becoming not recommended.

    I would recommend building a little servo breakout board.  Bring the PWM to the signal pin, and then power and ground for the servos that doesn't go through APM.  The ground must be tied to the APM ground, however, in star formation.

    Here's a picture of one that I made, which includes a 2803 chip for the LED's, you don't need to worry about that:

    DSC00242.jpg

    DSC00244.jpg

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