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Re: [Paparazzi-devel] Question regarding servo motor
From: |
Aka |
Subject: |
Re: [Paparazzi-devel] Question regarding servo motor |
Date: |
Wed, 13 Jul 2011 22:40:42 +0200 |
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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> >
> >
> >
> >
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>
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Re: [Paparazzi-devel] Question regarding servo motor, Long Di, 2011/07/13