>
> Yes, I am referring to the PPM signal from the RC receiver to PPZ.
>
> It was pretty clear that the fault was due to an overloaded 5V supply.
> On the ground I was able to faithfully re-create the AP crash conditions
> simply by rapidly exercising all the servos. I also did fairly extensive
> testing to debug this problem, including measuring current drain with
> all servos operating, which is what clarified the issue.
>
> I have suggested in the past that PPZ be updated with a higher capacity
> 5V converter, and given what you wrote below, it might also be a good
> thing to source the 3.3v line off the battery, rather than the 5V
> supply. However, the "temporary" solution is to simply use a separate 5V
> supply for external devices like servos, modems, etc.
>
> Adam Spence wrote:
> > John, what are you referring to with the RC RX cable? Is this the PPM
> > cable attaching the receiver to PPZ?
> >
> > There's been a couple of crashes like this discussed on IRC recently.
> > I'm not sure if the fault was identified but the overloading of the 5v
> > PSU was suggested. This could easily happen when the servos are driven
> > to the limit and stall due to the hardware set up. Where ever possible
> > the currents drawn by the servos need to be measured when all control
> > surfaces are at the limit. If there are any stall conditions the setup
> > needs to be adjusted either physically on the air frame or by reducing
> > the control throws in the config file.
> >
> > The 5V PSU is not only responsible for supplying the servo power but
> > also the 3v3 regulators power! Therefore if the 5v line drops due to too
> > much current being drawn then it may take out the main CPU. For my
> > particular setup with an 868 modem, the CPU, GPS and Modem can take upto
> > 500mA of current. The limit of the 5V PSU is 2.25A so roughly there may
> > be something in the region of 1.75A left for all of the servos. That
> > only needs a couple of servos to stall and you could be in trouble.
> >
> > Due to the above, I will be removing the 5V connection to the servos and
> > providing another regulated 5v directly from the battery. This will have
> > a limit of maybe 5-10A which is complete over kill.
> >
> > I've just noticed the current-limiting switch on the hardware, this
> > means the servos can only draw 1A and then the switch kicks in and
> > notifies the CPU using GPIO. Does anyone know what the firmware does in
> > this instance? That therefore means that there's even less current
> > available for the servos and anything else which you may have connected
> > on the 5v rail... hmmm. I see this can trigger from 0.5A to 1.25A,
> > anyone ever tested this? I'm wondering now what would happen if this
> > were to fire, the servos would be left in their current position (or
> > driven back slightly from mechanical pressure). The AP might (depending
> > on what the GPIO signal does) try and keep driving the servos at their
> > current position which would mean that when the current limiter recovers
> > it then goes straight to the limit again?
> >
> > Anyway I've rambled enough this morning!
> >
> > Adam
> >
> > 2009/8/9 John Burt <
address@hidden <mailto:
address@hidden>>
> >
> > Martin,
> >
> > I crashed an Easystar just like that during early flight testing.
> > The AP (Tiny 2.11) went nonresponsive and dived into the ground,
> > despite my having immediately flipped the switch to manual. It would
> > seem that the AP processor just locked up - truly a worst case
> > scenario. The cause of the behavior was an undervoltage spike
> > condition due to sourcing the four servos and RC RX off the 5V
> > supply. In case you haven't already, you should always power your
> > hardware off a separate BEC (which begs the question of why the AP
> > has a 5V source anyway).
> >
> > AP generated noise on the ground wire was other cause of bad AP
> > behavior that I experienced. This causes glitching and reduced RC
> > range. It has been covered ad nauseam in other posts, but I'll
> > repeat it: it's especially helpful to put an RF choke on the RC RX
> > cable. Try to wrap the wire 4+ times around the choke.
> >
> >
> > Martin P wrote:
> >
> > Hello everyone!
> > Last weekend I had a good AUTO1 flight with my Minimag. It
> > reacted to pitch and roll commands, and I was able to control
> > the throttle. I had an attitude command in my flightplan which
> > was never left (as I know now).
> > Yesterday I tried again, without the attitude statement and
> > without a holding point block.
> > In AUTO1, it killed the throttle. Switched to manual and landed
> > to change battery because it was not fully charged.
> > Took off again. Switched to AUTO1 and it immediately stabilized
> > the plane. Strangely, this time it did not react to the roll
> > command. I flew around using the rudder. When I used the
> > elevator stick, the autopilot controlled the throttle. Good, so
> > far.
> > Suddenly the plane dived down vertically from an altitude of
> > roughly 40m. No reaction, just kept going vertical and slowly
> > spinning around the longitudinal axis until it crashed.
> > There was not as much damage done as I expected. These foamies
> > are awesome. All RC components including Tiny and Xbee are OK.
> > Except for the Lipo which is badly bent out of shape and will be
> > replaced for safety reasons.
> > Unfortunately I can't see much from the log as I had lost the
> > link probably minutes before. I was in stage "HOME" because I
> > had left the fly-too-far circle before and came back manually.
> > The switch was on manual so I probably tried to rescue. The Tiny
> > was unplugged which can have happened at the crash or before.
> > One aileron was ripped off and the horizontal IR was missing (I
> > found it in the grass).
> > So far, my report. The Minimag is already repaired and I'll keep
> > trying.
> > Greetz, Martin
> >
> >
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