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Author Topic: "Quivering servo"  (Read 3967 times)

Rhys

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"Quivering servo"
« on: May 24, 2017, 03:39:03 pm »

I am sorry if this is covered somewhere, but a lengthy search failed me.
I have a model which has yet to hit the water. Major part of the reason is that one of the servos quivers without any inputs. I have tried pretty much every suggestion offered. Re-routed the wires, fresh batteries, changed servos and it still continues. All the gear is Turnigy 2.4. I hope someone can help.
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Martin (Admin)

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Re: "Quivering servo"
« Reply #1 on: May 24, 2017, 03:54:02 pm »


Have you checked for ANY metal to metal contacts?
Eg. Rudder links, loose nuts / bolts, loose rigging.....   :-)
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Netleyned

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Re: "Quivering servo"
« Reply #2 on: May 24, 2017, 04:03:41 pm »

Sounds like a dodgy channel connector
on the rx.
Can you change the rx?
If not try changing the offending
servo to a spare set of pins.
Check the pins on the offending
channel where they go into the
rx board for a bad solder joint.


Ned
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craggle

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Re: "Quivering servo"
« Reply #3 on: May 24, 2017, 04:20:53 pm »

Do you have a spare servo you could plug in to the same channel to test it?

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Netleyned

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Re: "Quivering servo"
« Reply #4 on: May 24, 2017, 04:35:00 pm »

Done that in first post %)


Ned
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Martin (Admin)

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Re: "Quivering servo"
« Reply #5 on: May 24, 2017, 04:37:05 pm »


Yes, remove all connections, expect power, check with a known good servo on one channel at a time.

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HMS Invisible

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Re: "Quivering servo"
« Reply #6 on: May 24, 2017, 04:46:21 pm »


Same applies with other electrical problems: tell us what you are using!

If your supply voltage is unstable then add a supply capacitor https://www.youtube.com/watch?v=NA-OXTGZR5c
You don't get a lot of supply line capacitance in small 2.4G receivers because it is a bulky component. A problem you are not likely to get with an old 2ch 27MHz am bec receiver

If you have a touch of overshoot then add a dampener or just ignore it since it is not a problem in normal use. https://www.youtube.com/watch?v=GNI7TaK5POc
A servo is a closed loop system which is prone to overshoot if you crank up the power with no load. Metal gears have a greater inertia than the plastic equivalent.

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Rhys

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Re: "Quivering servo"
« Reply #7 on: May 24, 2017, 05:48:33 pm »

Thank you all. All the servos, RX and TX are brand new. There are no connections of metal of any sort, I tried a number of different servos, (all of them if memory serves me right), tried all alternatives for for plugging into the RX.
Thanks for the link on you tube. Perhaps the issue was because the servo was not connected to anything? I was just trying the system before final assembly. Now watching another it suggests a "?" core to be wrapped into the lead, but I failed to pick up what he said, or where you get them. Help again please.
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Re: "Quivering servo"
« Reply #8 on: May 24, 2017, 06:04:30 pm »

Is it just the one channel that the servo twitches on?
Even brand new gear can be faulty.
Ned
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Rhys

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Re: "Quivering servo"
« Reply #9 on: May 24, 2017, 06:16:46 pm »

I'm sorry Ned, I don't know how to explain more clearly, but see if this clarifies. One of the 2 servos flutters/twitches, whatever we want to call it. If I unplug and switch their source plugs, it's still the same one, on the other channel. If I swap servos from any of the ones I have, the problem persists.
These are on a large model Landyacht, but as I said above it was just under test. One channel serves as steering, one as a lever arm sail winch, as suggested by the guy who has built a good number of these, components as suggested and used in almost all of the landyachts. (Not a BAT).
It seems to me that the best solution offered on the videos is a ferrite core, now where do I get a couple, as I have a few models to get working.
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T33cno

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Re: "Quivering servo"
« Reply #10 on: May 24, 2017, 06:37:20 pm »

Do you mean it is actually moving or just chattering in centre neutral position? Noise is normal especially when new.
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Rhys

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Re: "Quivering servo"
« Reply #11 on: May 24, 2017, 06:38:17 pm »

It moves through an arc of about 10 degrees each way.
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T33cno

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Re: "Quivering servo"
« Reply #12 on: May 24, 2017, 06:42:32 pm »

It moves through an arc of about 10 degrees each way.
Yes that isn't normal but I have no solution.
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unbuiltnautilus

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Re: "Quivering servo"
« Reply #13 on: May 24, 2017, 07:17:53 pm »

Is it the steering servo or winch arm servo causing the problem? Are both servos identical or is the winch arm one a high torque or larger type of servo? What supply voltage are you using to drive the servos? Rechargeable or disposable batteries?
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Rhys

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Re: "Quivering servo"
« Reply #14 on: May 24, 2017, 07:42:48 pm »

Steering one is the one fluttering.
Power supply linked to the battery pack for the RX. Off the shelf, not re-chargeables.
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g6swj

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Re: "Quivering servo"
« Reply #15 on: May 24, 2017, 10:55:22 pm »

Might be worth posting a pic of your setup.

Your last post made me wonder about your power supply configuration - almost reads that you have more than one route for the power (power supply linked to battery pack for RX) rather than just plugging the servo into the RX for both signal and power - on the other hand could just be misreading your post!

Also what batteries are you using ("off the shelf")  4 x 1.5v=6v which should be fine BUT could this be part of the problem as rechargeable would be 4.8v most BEC's are 5 volt - RX should be ok to approx 6.5v

Regards
Jonathan
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Rhys

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Re: "Quivering servo"
« Reply #16 on: May 25, 2017, 08:07:24 am »

I do appreciate all the input. Please remember that I am completely new to RC so I am likely to be saying things that you guys know in a different way.
What has me so puzzled is that I very carefully followed the (limited) instructions with the RC gear from the manufacturers, and also the better ones from the maker of the model.


Jonathan, yes the servos are just plugged into the RX for both signal and power. The RC gear suggested using 1.5v x 4 so hopefully that isn't the issue. Someone somewhere else suggested low voltage might be the issue.
I will try to post a pic. Have I enough posts to be allowed to do that? Most forums need many more than I have yet.
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malcolmfrary

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Re: "Quivering servo"
« Reply #17 on: May 25, 2017, 09:56:04 am »

Quote
One of the 2 servos flutters/twitches, whatever we want to call it. If I unplug and switch their source plugs, it's still the same one, on the other channel. If I swap servos from any of the ones I have, the problem persists.
If the problem moves with the servo, its a dud servo.  If it stays with the channel, suspect the radio (but make sure that the receiver has a signal to receive, unexpected things happen when they have to make it up without instructions from the transmitter).  A servo tester is a really cheap item these day, every home should have one.  Settles a lot of questions.
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g6swj

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Re: "Quivering servo"
« Reply #18 on: May 25, 2017, 10:01:52 am »

Rhys,

Don't worry about "lost in translation" - just plug away with what you observe and for sure the problem will be identified eventually. Malcolm's comments make a lot of sense as always....

Slightly different attack - if you plugged the 2 servo's into say channel 3 & 4 what happens?

Can you control the servo's from the stick/control relating to channel 3&4?

Do you get the same quivering movement on Ch3 &4?

Also is the movement continuous or just one cycle at power on and then it stops?

Regards
Jonathan
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HMS Invisible

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Re: "Quivering servo"
« Reply #19 on: May 25, 2017, 11:13:13 am »


Steering one is the one fluttering.
Power supply linked to the battery pack for the RX. Off the shelf, not re-chargeables.

That is the kind of relevant information asked for.
Servo timing is the issue but you want a more stable voltage supply to fix it.
Four NiMH cells in your existing wiring harness is nearly one order of magnitude better than what you have and it may suffice.
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chas

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Re: "Quivering servo"
« Reply #20 on: May 25, 2017, 11:26:38 pm »

I've just re read this thread to check, you don't say that the quivering is happening when the transmitter is switched on. I'm sure it is but thought I had better check as most installations will quiver if no tx signal is being received.

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nemesis

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Re: "Quivering servo"
« Reply #21 on: May 26, 2017, 08:14:55 am »

Had this problem years ago, turned out to be a  faulty pot in the servo, nemesis
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Martin (Admin)

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Re: "Quivering servo"
« Reply #22 on: May 26, 2017, 10:27:11 am »

I've just re read this thread to check, you don't say that the quivering is happening when the transmitter is switched on. I'm sure it is but thought I had better check as most installations will quiver if no tx signal is being received.

Very good point!   :-))
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Rhys

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Re: "Quivering servo"
« Reply #23 on: May 26, 2017, 10:35:07 am »

Yes, turned on. Martin, any idea why I can't post a pic of the set up?
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Martin (Admin)

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Re: "Quivering servo"
« Reply #24 on: May 26, 2017, 11:19:50 am »


We had to introduce size limits to Mayhem quite some time ago ( photo folder now up to 8Gb! ).

For now, Email any photos to and I will resize and post for you! - Mayhem!

You can also use any of the image hosting sites,

https://photos.google.com/
Microsoft photos App (win10 ),
https://cubeupload.com/
http://imgur.com/https://imgbb.com/
http://tinypic.com/
https://imageshack.us/

... also see:
http://www.modelboatmayhem.co.uk/forum/index.php/topic,23.msg595782.html#msg595782
http://www.modelboatmayhem.co.uk/forum/index.php/topic,23.msg579912.html#msg579912
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