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Old Mar 12, 2012, 01:43 AM
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Discussion

Static in video when servo moves?


Hey, I'm having some issues with my first single battery setup, as my previous planes all had a separate video battery

heres my setup
1.2ghz 1000mw Lawmate tx
IBCRAZY Cloverleaf
TBS 69 Camera
Eagletree OSD, Elogger, Guardian
DPCAV SEPIC Voltage regulator 1-35V
DPCAV LC Filter
Hobbyking UBEC
these are all mounted on a rite wing zep2 with 2x 4s 3000mah Zippy Lipos

The problem is that when i move any of the servos (hs-645mg) or start up the motor lines of static will appear in the video, when i throttle up the osd text will "jump" up, heres the video of it
fpv issue (0 min 22 sec)


Any ideas? Thanks
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Old Mar 12, 2012, 02:18 AM
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What's powering the RC Rx? ESC's BEC, or the HK UBEC?
If the latter, where in the circuit is the UBEC? Before (close to the battery) or after the LC filter?
ET OSD directly links the receiver and the video system so any noise at the Rx (servo noise, or
ESC noise) bypasses your LC filter. With the connections between Rx and OSD, you
may have also created a ground loop.

ian
Old Mar 12, 2012, 02:28 AM
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the RX is powered by the UBEC, the video Signal wire is only connected into the OSD, the power to the vtx and cam comes from the ubec. The ubec is at the ESC end of the elogger, where power is spilt to UBEC, Voltage REG and ESC
Old Mar 12, 2012, 02:31 AM
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Filter the video equipment from all other components.



**EDIT: Oh, I see you did...
Old Mar 12, 2012, 02:35 AM
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torroid on the video line just before the Vtx?

Are you using audio? is the audio wire hanging free? it might be overdriven, or if it's not connected to anything, might want to ground it.


Edit: ninja
Old Mar 12, 2012, 02:36 AM
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I don't see any issues in your circuit. No ground loops, and the one LC filter you have, should
be sufficient (I've never had to add a 2nd closer to the video Tx). What are you doing with the
audio line? Is audio signal clamped to ground, or free floating? Might have noise coming in
there, and that can interfere with video. [edit]pete beat me to it.

ian
Old Mar 12, 2012, 02:42 AM
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Quote:
Originally Posted by Daemon View Post
I don't see any issues in your circuit. No ground loops, and the one LC filter you have, should
be sufficient (I've never had to add a 2nd closer to the video Tx). What are you doing with the
audio line? Is audio signal clamped to ground, or free floating? Might have noise coming in
there, and that can interfere with video. [edit]pete beat me to it.

ian
The audio from the vtx is just free floating, should i try grounding it? thanks
Old Mar 12, 2012, 03:01 AM
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definitely try grounding it.
Old Mar 12, 2012, 11:52 AM
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just tried it, it isn't working, any ideas?
Old Mar 12, 2012, 12:07 PM
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just go to a separate video battery. Yeah I know you know to do that and wanted to avoid the hassle , but it just make sense now.
Old Mar 12, 2012, 12:08 PM
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Can only suggest bypassing OSD with the video line just to see if the noise is coming in there.

ian
Old Mar 12, 2012, 12:55 PM
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Signal come out of the cam and into the OSD and down the OSD's grd. trough the Rx and trough the BEC to finally reach the batts. Problem is your OSD's ground is long and also carry the servo's current. The ground level (0V) of your OSD is not exactly 0V, but change slightly as current from the servos pass. Solution: Feed your servos directly from the Rx, only the signal reaching the OSD.

Good read

-Hugo
Last edited by Hugeone; Mar 12, 2012 at 01:13 PM.
Old Mar 12, 2012, 01:05 PM
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Hugo,
according to this img #4, only + passes through the LC filter, but on my LC filter both + and - passes through. I'm not sure how i should fix this? can you recommend something?

Thanks
Taiping
Old Mar 12, 2012, 01:13 PM
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I highlighted the solution above.
Old Mar 12, 2012, 01:17 PM
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But how would the servos then get power? since power is not passed through the osd?


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