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Re: [Paparazzi-devel] Question regarding servo motor

From: Christophe De Wagter
Subject: Re: [Paparazzi-devel] Question regarding servo motor
Date: Wed, 13 Jul 2011 08:47:56 +0200

Dear Dee,

You are not by any chance using a copy of my ./conf/airframes/CDW/chimu_tinyfw_spi.xml ? This one has ultra-fast servo updates (120Hz) with awesome performance on digital servo's but can burn and will jitter any old analog servo?

If you have the following define in your airframe file, remove it or change it to 8 or 10:

<define name="NB_CHANNELS" value="4" /> 

Other possibilities include: an older PPM-ENCODER (8MHz crystal) which has significant "digital noise" due to the interrupt routine that needs to measure 8 channels so whenever 2 pulses are of almost the same length one will be read with a (small) but noticable delay.

A last one we saw quite often: when too many (1 or 2) small and fast servo's are powered by the tiny/twog then it drains too much current from the 2Amp switching supply. This also makes servo's jitter and is very dangerous to fly with. Power the 5V of your servo's from the BEC/ESC instead.

If all of this is not the case, a scope would be useful to debug. How constant are the given pulses? What is the update rate?


On Wed, Jul 13, 2011 at 7:18 AM, Steffen Spies <address@hidden> wrote:
Hi Dee,

that is a BIG surprise to me.
Yesterday evening I made the same experience while I did some testing: one of my servos (Multiplex Tiny S) burned out!

And I also noticed big jitter even in manual mode sometimes and disappears when you move the sticks - but will return.

I use a Tiny V2.11


Am 13.07.2011 06:54, schrieb Long Di:
> Hello all,
>         I have started using the new paparazzi distribution for fixed-wing. Everything works fine for my implementation except the servo motors. Both of my servos jitter even under manual mode, and the right servo got burned out today after a long testing.
>         The strange thing is that when I moved the joystick handle, sometimes the jitter just disappeared, then it came back again. I tried to seal my servo with copper tape and added a glitch buster, didn't help. I also tried to play with the servo parameters (min, neutral, max), didn't get solved either.
>         I also noticed the old PPM_FILTERING code doesn't exist any more, wondering whether that should help.
>         I am using Hitec MG-82 servos. Anyone has had similar problems? Any inputs are appreciated.
> Dee
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