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Old Jan 29, 2013, 05:03 AM
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mdem's Avatar
Australia, VIC, Carrum Downs
Joined Oct 2012
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Help!
¿?Servo stutter question¿?

Hello everybody, quick background:
- Just got 9xR this morning
- Installed Orange DMS2 module
- Using DMS2 LemonRX
- HXT900 servos (also tried HXT500)
- 2s LiPo as RX battery

So today I got my 9xR in the mail, installed the Orange DMS2 Module, upgraded to latest er9x firmware via USBasp.

Wanted to see if my RXs worked that I ordered from LemonRX (I wanted very small ones for a small glider).
They did work after I noticed I needed to change the channel settings in er9x.

I used a 2s LiPo as the RX power since I that’s what I had on hand, it was at 7.65v, the R can handle upto 10.2v, so there shouldn’t be a problem as far as I can see on that front.


Got everything working but my servos keep stuttering/fluttering/jittering, whatever you want to call it.
It does it pretty much on any channel and on any servo I use. Not 100% of the time, but enough for me not to use them in any plane.
Anyone have any ideas, maybe I’m doing something wrong I don’t see?


I took some quick videos of my binding process and the stuttering itself so you know what I’m trying to say, along with pictures of the setup I used, battery (on a checker), and spec sheet of the RX in use.

Any help would be great.
-Thanks
mdem

RX specs:
https://www.dropbox.com/s/0bro5jp9o8...RX%20specs.jpg

RX1/2:
https://www.dropbox.com/s/8njmx0si5nnkyne/RX%201.JPG
https://www.dropbox.com/s/knfm085iupefezj/RX%202.JPG

Setup picture:
https://www.dropbox.com/s/wyg6mpl31a8wc97/Setup.JPG

Module:
https://www.dropbox.com/s/rv5r49ce58...X%20module.JPG

Battery check:
https://www.dropbox.com/s/jmd5g4o2at...ry%20check.JPG

Bind process + stutter:
(video)
https://www.dropbox.com/s/2hglvf7bth...%20stutter.avi

Stutter again:
(different servos)
https://www.dropbox.com/s/7qq6ybsojc...%20stutter.avi
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Old Jan 29, 2013, 05:17 AM
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Here's a foolproof trouble shooting guide.

Q: Did you buy the servos from Hobbyking?
A: If yes, they're essentially crap servos.

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Old Jan 29, 2013, 05:42 AM
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dingo's Avatar
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Quotte
I used a 2s LiPo as the RX power since I that’s what I had on hand, it was at 7.65v, the R can handle upto 10.2v, so there shouldn’t be a problem as far as I can see on that front

I`m not sure what your saying here . You used a 2s lipo at 7.65 volt for your reciever power . But your R ( assuming this is your transmitter ) is ok for 10.2 volt . Most servo`s don`t handle much more than 6 volts .
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Old Jan 29, 2013, 06:04 AM
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Quote:
Originally Posted by dingo View Post
Quotte
I used a 2s LiPo as the RX power since I that’s what I had on hand, it was at 7.65v, the R can handle upto 10.2v, so there shouldn’t be a problem as far as I can see on that front

I`m not sure what your saying here . You used a 2s lipo at 7.65 volt for your reciever power . But your R ( assuming this is your transmitter ) is ok for 10.2 volt . Most servo`s don`t handle much more than 6 volts .
+1. You're lucky the servos are still working at all - at least they were unloaded. They get whatever voltage is applied to the Rx bus, in this case the full 7.65V from the 2S pack. Good thing it wasn't fully charged at 8.4V. Unless a servo is rated as high voltage, assume a max of 6.0V. And for cheapies, assuming 5V is probably safer.

Some folks get away with 2S LiFe unregulated at 7.2V max for Rx and standard voltage servos,, but not 2S LiPo.
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Old Jan 29, 2013, 06:07 AM
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Quote:
Originally Posted by dingo View Post
I`m not sure what your saying here . You used a 2s lipo at 7.65 volt for your reciever power . But your R ( assuming this is your transmitter ) is ok for 10.2 volt . Most servo`s don`t handle much more than 6 volts .

Oh I see, yeah I used a 2s LiPo as my receiver power pack, thinking the LemonRX could handle it no problem, but I forgot the servos can only handle 6v..

Do you think pushing 7.65v through the RX into the servos would be causing the problems I'm having?
I don't have any other batteries on hand, I'll have to use power supply at brothers house next time I go.

Thanks again
mdem
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Old Jan 29, 2013, 06:11 AM
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Quote:
Originally Posted by scirocco View Post
+1. You're lucky the servos are still working at all - at least they were unloaded. They get whatever voltage is applied to the Rx bus, in this case the full 7.65V from the 2S pack. Good thing it wasn't fully charged at 8.4V. Unless a servo is rated as high voltage, assume a max of 6.0V. And for cheapies, assuming 5V is probably safer.

Some folks get away with 2S LiFe unregulated at 7.2V max for Rx and standard voltage servos,, but not 2S LiPo.
Ok, I understand where I went wrong haha. Honestly just went over my head, to check what the servos are rated for.

So I'm guessing the excessive voltage is the reason for the stuttering from what you guys are saying.

Ha, well that's why I asked, I'm still new to this and I will make mistakes

Thanks for the heads up.
Will have to go through and check all my servos in case I did any damage to them before I use them for anything.
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Old Jan 29, 2013, 06:12 AM
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I`d try a normal 4 cell rx pack & try outdoors away from tin sheds etc & see what happpens .
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Old Jan 29, 2013, 06:22 AM
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Quote:
Originally Posted by dingo View Post
I`d try a normal 4 cell rx pack & try outdoors away from tin sheds etc & see what happpens .
I Don't have a 4cell RX pack, never needed one before so never though to buy one, although I might since they are good for test beds.

I'll just have to go to brothers house, he have a power supply with a variable voltage output.
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Old Jan 29, 2013, 06:39 AM
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Have you got an ESC handy that you can run through the rx then the servos on the rx aswell? The ESC's UBEC should do the trick for you.
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Old Jan 29, 2013, 06:50 AM
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Originally Posted by Teamsherman View Post
Have you got an ESC handy that you can run through the rx then the servos on the rx aswell? The ESC's UBEC should do the trick for you.
Yeah I have a few spare ESCs handy but none of them have any connectors on them.
I'm in no rush, waiting on another order from HK with parts that were missing in my little glider anyway, so cant build. Have some time.

I'm just happy I found out what I was doing wrong so I can avoid it next time.
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Old Jan 29, 2013, 07:00 AM
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Quote:
Originally Posted by AussieNewbie View Post
Here's a foolproof trouble shooting guide.

Q: Did you buy the servos from Hobbyking?
A: If yes, they're essentially crap servos.

That's not at all true btw. When value and number of planes in the air because of that value are factored into the equation, the HXT900 is probably the best servo on Earth.

They're strong, robust, and a little power-hungry, which is understandable given the high-range strength. Hitec HS-55s are at least 4 times the price, and they're not better in any quantifiable way.
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Old Jan 29, 2013, 09:59 AM
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Quote:
Originally Posted by mdem View Post
Oh I see, yeah I used a 2s LiPo as my receiver power pack, thinking the LemonRX could handle it no problem, but I forgot the servos can only handle 6v..

Do you think pushing 7.65v through the RX into the servos would be causing the problems I'm having?
I don't have any other batteries on hand, I'll have to use power supply at brothers house next time I go.

Thanks again
mdem
try it with a bec
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Old Jan 30, 2013, 03:01 PM
Cliff
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Quote:
Originally Posted by dingo View Post
I`d try a normal 4 cell rx pack & try outdoors away from tin sheds etc & see what happpens .
What dingo said.
Cliff

HXT900 and HXT500 are excellent servos
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Last edited by 16141; Jan 30, 2013 at 03:05 PM. Reason: servo part
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Old Jan 30, 2013, 03:58 PM
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HTX 900 must be ok If used in smaller DS planes and wings.
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Old Jan 30, 2013, 05:07 PM
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Hmm, I don't think I use anything but HXT servos. My parachutist has metal gears and the FunCub too but the rest are HXT.
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