Re: [Paparazzi-devel] Question regarding servo motor

[Aka]

Hi Steffen,

you probably gave the explanation now...

Having BEC´s working in parallel often leads to problems. Divide your power 
sources!
I would guess that solves the problems. When moving the sticks you increase 
current and the resistance of the cables equalizes the BEC´s. But with the low 
current with no movement you get spikes or something...

Hope this was it :-)

Marc

-------- Original-Nachricht --------
> Datum: Wed, 13 Jul 2011 22:25:09 +0200
> Von: Steffen Spies <address@hidden>
> An: address@hidden
> Betreff: Re: [Paparazzi-devel] Question regarding servo motor

> Christophe,
> 
> thanks for your hints.
> The thing is: I have two BECs giving enough juice to power the servos.
> 
> I try to explain again what my Tiny is doing.
> There are 4 servos connected and two BECs are delivering 5V parallel to 
> the  Tiny source.
> When I turn on the power, the servos start to jitter even in manual mode.
> Moving the sticks stops the jitter, but it can come back later with out 
> any changes.
> 
> The one Multiplex Tiny S is clearly burned out and I think I have to 
> replace all 4 now to prevent damages during flight.
> 
> So the scope shows clear signals, so I think the next step is to use the 
> latest software and retry.
> Unfortunatly I won't fly before the jitter is gone. :-(
> 
> Thanks for help,
>      Steffen
> 
> 
> 
> Am 13.07.2011 21:47, schrieb Christophe De Wagter:
> > Dear Stephen,
> >
> > We have had one plane with a tiny autopilot that had significant 
> > jitter just after power-up and the jitter dissapeared after a while or 
> > after moving the sticks in manual. This was quite some time ago so I 
> > should check but I think we just powered the servo's from the ESC 
> > instead and replaced the jittering servo with a better quality one and 
> > it was solved. Now I'm just not sure anymore which of both actions 
> > actually solved it. I do remember checking that the pulse to the servo 
> > was perfectly good after power-up so it was not code but some 
> > interference/power supply servo interaction. Powering servo's other 
> > than at most 2 micro servo's in a very small MAV from the tiny supply 
> > is not recommended at all if you ask me.
> >
> > -Christophe
> >
> >
> >
> > On Wed, Jul 13, 2011 at 6:02 PM, Steffen Spies <address@hidden 
> > <mailto:address@hidden>> wrote:
> >
> >     Hi,
> >
> >     I checked my files and I can clearly say, that I don't use you
> >     airframe file, Christophe. Also the define is not part of my
> >     airframe config.
> >
> >     My receiver is a 35MHz ACT DSL4top "MK", which I also use on my
> >     Mikrokopter. It already sends all channels, so no PPM Encoder is
> >     needed.
> >
> >     Powersupply: the jitter appears with only one Servo connected and
> >     the supplied voltage is perfectly stable.
> >
> >     I took a screenshot of my scope. The signal on the top is channel
> >     3 output of the Tiny board. The signal at the bottom comes from
> >     the rc-receiver.
> >
> >     http://gallery.derspies.de/main.php?g2_itemId=1122
> >
> >     The signals "stay" perfectly - no jitter.
> >
> >     Steffen
> >
> >     Am 13.07.2011 08:47, schrieb Christophe De Wagter:
> >     > 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?
> >     > -Christophe
> >     >
> >     >
> >     >
> >     > On Wed, Jul 13, 2011 at 7:18 AM, Steffen Spies
> >     <address@hidden <mailto: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
> >     >
> >     >     Steffen
> >     >
> >     >     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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> >
> >
> >
> >
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