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Spektrum flap system freeze

fluffpilot

Active member
#1
Alright so, I'm stumped.

Transmitter is my reliable DX6e, receiver is a brand new AR620. Plane is a Storch, servo extensions in use but just plain wires (no amplifiers or weird junk).
Still currently bench testing (with the prop off).
Running all six channels with ailerons on separate channels and flaps on a Y harness. Problem only seems to occur when the flaps are activated. I've got them on a three position switch with zero, half and full programmed. Haven't even gotten into aileron/flap mixing and don't plan to just yet, so the switch is flap only.
What I'm getting is sometimes when the flaps are active, and sometimes while they're activating/returning everything but the throttle control will freeze. For instance flaps down, move the rudder and suddenly it goes full to one side and stops and nothing responds. Flaps active and move ailerons, same deal whatever was moving goes full in one direction or other and nothing responds except the throttle.
Sometimes when you move the flaps, same thing they just go full one direction and everything but the throttle locks up.
Sometimes it all works fine for a while and I can move just about every single servo at once with no issue and sometimes I plug it in and it moves once and quits.

When this happens, if I reach in and unplug two servos (usually the flaps because they're handy) everything will start responding again without even disc/reconnecting the battery. Plug the flaps in again, everything works great until I move them and something else and it goes full lock again. If it's frozen and I unplug the battery and reconnect, everything stays frozen until I unplug a couple servos.
I've tried it on three different batteries (all 3S but different mAh & C ratings) and that doesn't change anything.

I can get video if needed, but dang it's driving me up the wall and I have no idea what's doing it.
 

Hai-Lee

Old and Bold RC PILOT
#2
Alright so, I'm stumped.

Transmitter is my reliable DX6e, receiver is a brand new AR620. Plane is a Storch, servo extensions in use but just plain wires (no amplifiers or weird junk).
Still currently bench testing (with the prop off).
Running all six channels with ailerons on separate channels and flaps on a Y harness. Problem only seems to occur when the flaps are activated. I've got them on a three position switch with zero, half and full programmed. Haven't even gotten into aileron/flap mixing and don't plan to just yet, so the switch is flap only.
What I'm getting is sometimes when the flaps are active, and sometimes while they're activating/returning everything but the throttle control will freeze. For instance flaps down, move the rudder and suddenly it goes full to one side and stops and nothing responds. Flaps active and move ailerons, same deal whatever was moving goes full in one direction or other and nothing responds except the throttle.
Sometimes when you move the flaps, same thing they just go full one direction and everything but the throttle locks up.
Sometimes it all works fine for a while and I can move just about every single servo at once with no issue and sometimes I plug it in and it moves once and quits.

When this happens, if I reach in and unplug two servos (usually the flaps because they're handy) everything will start responding again without even disc/reconnecting the battery. Plug the flaps in again, everything works great until I move them and something else and it goes full lock again. If it's frozen and I unplug the battery and reconnect, everything stays frozen until I unplug a couple servos.
I've tried it on three different batteries (all 3S but different mAh & C ratings) and that doesn't change anything.

I can get video if needed, but dang it's driving me up the wall and I have no idea what's doing it.
It sounds like a common problem!

When you are operating the flaps the current drawn from the BEC is too much and the voltage supply to the Rx is dropping below what the Rx needs to operate, (properly). Nett result is all of the servos can either start moving in directions not commanded or just stop all together.

You need to ensure that all of the control surfaces are free and not resistive or binding. You also need to check what sized BEC your ESC has on-board. It is possible that the total current your plane needs to draw from the 5-Volt rail is more than the BEC can supply.

If your total current required by the servos is too high for the BEC you can either replace the ESC with a version that has an adequate current rating or fit an additional stand alone BEC to share the current!

Lucky you found it on the ground because it definitely is a problem that kills planes quite often.

Have fun!
 

fluffpilot

Active member
#3
You need to ensure that all of the control surfaces are free and not resistive or binding.
I think that's likely a lot of it, I've meddled with some things and now as long as nothing *else* is moving when the flaps are in motion it seems pretty stable. However if I pin a control stick one way or another and move the flaps, it quits. I was starting to suspect a voltage drop and it sounds like you just confirmed it. All the equipment is new, all 8.5g FT servos and a Power Pack C motor with an FT 35A esc. I may have to re-bend some wires (I have a newfound hate for cheap linkage stoppers) and loosen everything up, and try again. For now it's getting late so I'm gonna finish charging all the stuff for the planes that actually fly so I can get a little wing time tomorrow.

Meantime here's a picture of another junk pile I threw together and fully expect to beat to death in the morning (and have a lot of fun in the process, yes those are flaperons)
 

Attachments

fluffpilot

Active member
#4
Right so.
Got all the servos free, everything moves easily. Plugged everything in, moved everything around, throttled up, got it off the ground and was in the air for maybe fifteen seconds before everything went completely to crap. Had just gotten it straight and level and was going to start climbing when everything locked up again. It spun out so I killed the throttle to minimize the impact. Broke the prop but no other damage.
Had a fresh 2200mAh 3S 30C battery on board, so we know what it isn't. The ESC is also programmed, so that wasn't it either. Maybe I got a junk ESC brand new out of the box? 35A does seem a little weak for that big Power Pack C motor and six 8.5G servos.
Gonna put a 60A ESC into it and give that a whirl.
 

Arcfyre

Well-known member
#5
I was having the almost identical problem on my father's Bixler. Any time you pinned the control sticks in any direction, the RX would brown out. The cause ended up being the cheapo batch of 30A ESCs that I got from Amazon. I can use them on flying wings or 3ch planes without a problem (only 2 servos there) but on anything with more channels, you need a decent BEC. In your position I would either get a standalone BEC to power your RX and servos (the Storch has the payload for an extra battery, no problem) or get a different ESC with a decent BEC. Hobbyking has some really nice & cheap speed controllers with a built in switching UBEC. I highly recommend them. Here's a link: Hobbyking ESCs
 

fluffpilot

Active member
#6
Disappointing that the PP C comes with an ESC that won't run the whole plane.
Oh well.

Those HK controllers look pretty nice, and at $20 a pop for a 40A I'll order in a couple just to have spares in the tool kit. Thanks!
 

skymaster

Active member
#8
ok here it is have the same set up same transmitter. on rx you should have rudder to rudder, elevator to elevator. Y harness on ailerons and asign a channel to gear which should be flaps which should be right flap and then asign a channel to aux1 flaps left. mine are asign to channel G. and i also have 1@0 2@50% 3@100% and speed at 3.0s wich is kind of slow so the plane does not jerk when flaps are coming down. good luck
 

fluffpilot

Active member
#9
All the servos are brand new and move fine.
There is nothing binding, everything moves properly, flaps are at 2.0s & I don't recall the positions but it's roughly zero, half, and 5% away from binding at full droop. Ailerons aren't mixed yet but I need to add a little elevator if I can get it to stop konking out. Also flaps are on a Y and ailerons are on individually so I can use them to mix crow braking.
But when you run the motor up and do anything it browns the system out, or running more than three servos at once and same result. So problem number one is it's losing power. Gonna throw a bigger ESC with a better BEC in it and see what it does.
 

skymaster

Active member
#10
You might be right if all servos draw power at the same time it might cause a brown out. so i was wondering if there is a way to make a pdb board that you can power the servos separately and hook up all the data cables together kind of like you run out of gas but you still have control over you steering. you can also just buy a separate BEC. https://www.motionrc.com/products/c...MImbr_uaKH5QIVDNvACh1DMgloEAQYASABEgIsHPD_BwE
 

fluffpilot

Active member
#11
For now I've got some 40A ESCs coming in, so I'm gonna try that first. I don't mind taking the plane to the airfield a few times because I'll bring a couple that do fly and have a great time while I'm there even if the test plane eats dirt on the first launch, lol.

I'm also wondering if putting a bigger battery with more voltage would solve the problem or just blow the 35A ESC apart. Except I've only got 3S and 6S batteries around and I'm not risking an $80 6S to see if blows up midair.
So for now I'm just gonna shove a bigger ESC in it and see what it does, and if that doesn't work I'll hang a standalone BEC in it. Unless I find myself at the hobby shop sometimes during the week in which case I'll grab one of their cheap BECs while I'm there and put that in with the bigger ESC while I've got the power pod apart.
 

FDS

Well-known member
#12
The ESC will have a maximum voltage just like it has a maximum amp capacity. A bigger battery won’t push more current, it will obviously operate at a higher voltage. The motor will spin faster, thus drawing more peak current with the same prop vs a lower voltage.
More voltage in won’t alter the Bec performance, it will still put out the same 5v and only take the same load. Unless your current battery is getting really bad voltage sag I would say that it’s not having any effect on the brown out.
 

fluffpilot

Active member
#13
Makes sense.
So if the bigger ESC doesn't do the trick, then it's time for an external BEC. I was thinking maybe more input voltage would allow for some proverbial "breathing room" before system brownout under load.
For the record I tried it with three different 3S (20-50C) batteries, so pretty much eliminated that as a possible cause.
I'll check back in here with results when some hardware comes in and I can try again.
 

Hai-Lee

Old and Bold RC PILOT
#14
Beware. To many persons the plane failing to respond is almost always blamed on a "Brown out" whereas from my own investigations the majority of such occurrences is the responsibility of Poor Rx antenna placement causing a LOS, (Loss Of Signal).

Now having said that there may be a secondary cause I will delve a little deeper into a true Brown Out.

Firstly when it comes to the BEC which is integral to many ESCs there are 2 basic types, They are a SBEC of a UBEC. The SBEC uses a serial voltage regulator and the UBEC uses a switched mode voltage regulator. Both work well but the UBEC cost more and for a good reason.

With a serial voltage regulator the battery input current to the SBEC is near identical to the output current drawn. Now the power is simply the voltage multiplied by the current so a 3A SBEC can supply 3A at 5V and so supply a total of 15 Watts BUT the battery supply to the SBEC is supplying, (at 12V -3S), 36 Watts! The difference of 21 Watts is dissipated as heat by the BEC regulator. A larger battery voltage just makes the problem far worse!

Now here is the problem with a SBEC! The heatsinking on most SBEC regulators, (used for RC model aircraft) is minimal or poor AND each SBEC regulator has a temperature and over current protection circuit. This means that when you draw too much current the regulator shuts down its output to protect the regulator and the same action is taken when the regulator becomes too hot. In addition the regulator in on the same circuit board as the Motor control circuitry and this adds another dimension as the motor drive circuit can add heat to the regulator and cause the temperature protection circuitry to be tripped shutting down the 5V to the receiver and everything goes dark!

Now a UBEC is a switch mode regulator and could be better considered as a voltage converter rather than a regulator. Effectively the Battery supplied power is converted in voltage and supplied at 5 V to the Rx. There are a few losses in the process but the heat dissipation is far far less and so for most considerations can be considered as negligible. So with a UBEC a 5 V 3A output translates to a 12 V 1.25A battery draw.

Now for the servos I allow 700mA for each 9 G servo I fit and 500mA for each 500 Gram servo I use. Those numbers may seem a little high to some but a little safety margin is included in my assumptions and so I do not suffer from "Brown Outs" with a good ESC.

A 1A BEC is only good for effectively light weight wings and RET models , (2 servos), a 2 Amp BEC is ok for a 3 channel RET or AET planes and of course larger flying wings. 3A is ok for 4 channel builds or lighter draw full house builds. Beyond that I either supplement the ESC fitted BEC or replace it entirely with a separate UBEC of suitable current capacity.

Just what works for me and based upon many crash investigations!

Have fun!
 

fluffpilot

Active member
#15
Let me address signal loss real quick. The same TX was both before and after the attempt successfully staying in touch with planes at high altitude at the far end of the field, with similar model receivers. The TX is known good.

The plane locked up the first time on the bench due to servo binding. I went through and corrected all the servo problems and it performed flawlessly, on the bench.

Everything seemed good, so I took it to the field. At the field I did a few motor run-ups on the ground and everything was good, got about 10 seconds in the air and everything locked out. It hit the ground with everything still powered, and all the servos maxed out in one direction or another and still pushing. Unplug the battery, plug it back in and everything is still doing it. Pop the wing off and unplug a couple servos (literally any two servos) with the battery connected and everything resets.

A 1A BEC is only good for effectively light weight wings and RET models , (2 servos), a 2 Amp BEC is ok for a 3 channel RET or AET planes and of course larger flying wings. 3A is ok for 4 channel builds or lighter draw full house builds. Beyond that I either supplement the ESC fitted BEC or replace it entirely with a separate UBEC of suitable current capacity.
The only thing I can think of is that either the ESC is dropping voltage and scrambling the receiver, or the receiver itself is junk, or both? Now with everything you said I'm thinking I'll probably re-rig my battery hold-down to accept my 5000mAh batteries, dunk the 35A ESC into the trash, drop in a 40A ESC and add a UBEC just to be on the safe side.
If it still does it with a 3S 5000mAh battery, a 40A ESC, and a UBEC I'll see about trying to RMA the receiver.
 
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Hai-Lee

Old and Bold RC PILOT
#16
Let me address signal loss real quick. The same TX was both before and after the attempt successfully staying in touch with planes at high altitude at the far end of the field, with similar model receivers. The TX is known good.

The plane locked up it the first time on the bench due to servo binding. I went through and corrected all the servo problems, and it performed flawlessly, on the bench.

Everything seemed good, so I took it to the field. At the field I did a few motor run-ups on the ground and everything was good, got about 10 seconds in the air and everything locked out. It hit the ground with everything still powered, and all the servos maxed out in one direction or another and still pushing. Unplug the battery, plug it back in and everything is still doing it. Pop the wing off and unplug a couple servos (literally any two servos) with the battery connected and everything resets.



The only thing I can think of is that either the ESC is dropping voltage and scrambling the receiver, or the receiver itself is junk, or both? Now with everything you said I'm thinking I'll probably re-rig my battery hold-down to accept my 5000mAh batteries, dunk the 35A ESC into the trash, drop in a 40A ESC and add a UBEC just to be on the safe side.
If it still does it with a 3S 5000mAh battery, a 40A ESC, and a UBEC I'll see about trying to RMA the receiver.
Seriously the whole problem can be rather confusing! I feel for you as I remember my early struggles and the real lack of informed suggestions. I crashed almost everything I built for the first 12 months and then I did my research and the mist started to lift. Now I teach others to fly and do maidens for others. Apart from my stark reduction in crashes I also have saved many others from repeating my mistakes!

Good luck with your fixing the issue as there are so many things that can cause the same result, (a loss of response followed by a crash). I look forward to seeing your flying videos in the future!

Have fun!
 

fluffpilot

Active member
#17
Good luck with your fixing the issue as there are so many things that can cause the same result, (a loss of response followed by a crash). I look forward to seeing your flying videos in the future!
Thanks! This one will be getting a maiden flight video for sure. Or a maiden crash video, we'll see. Either way next time I try to put it in the air there will be a camera rolling. As for other videos, I did spend some quality time working my new Carbon Cub SS out and that got recorded. It's over in the videos section.
 

FDS

Well-known member
#18
I wouldn’t put a bigger battery in. More weight is always bad, it won’t help the power management of the servos and will badly mess up the CG.
 

Bricks

Well-known member
#19
When purchasing your new 40 amp ESC did you look at the out put 2amp, 3amp ,4 amp if the 40 amp ESC is the same BEC output it will not help your problem. A higher amperage ESC does not always correlate to higher BEC output.
 

Merv

Well-known member
#20
I agree with @Bricks, If you look at 10 brands of 35A ESC, some will have a larger BEC than others. It's the amp rating of the BEC that may be letting you down not the total rating of the ESC.

However if I pin a control stick one way or another and move the flaps, it quits.
Question, When you pin the control sticks, are your servos making a lot of noise?