Video Signal Loss
« on: November 07, 2016, 07:50:57 pm »
Having systemic trouble keeping a solid video signal.  Not talking about normal signal quality issues from just poor signal, talking about full "no signal" drops that last around a second or so each while the system restarts.

My on-board equipment is:
-RunCam SkyPlus (configured on 12v feed)
-Eachine 200 mw transmitter
-Min ODS interface

The signal drops can happen at any time, but are predicable any time I increase throttle, sometimes just at takeoff, so I suspect a voltage supply issue.  I tried adding some capacitors into the circuits with a little improvement, but didn't fully resolve.

So I changed my PDB to a "highly recommended" by my LHS:  http://ubuyadrone.com/ubad-mini-pdb/

I configured the camera and TX to 12 volts, and connected the OSD to the 5v circuit.  First flight went fine, but since then I'm back to have significant signal drops.  Makes FPV flying essentially impossible.

I did a test without the OSD and running the camera and TX of a separate battery.  That went fine.   But once I put everything back on the PDB, I'm back to problems.

The only options I see are to:
-Try adding one or more capacitors [again]
-carry extra battery just for video system (weight & room issues)

Any other ideas or suggestions?

Paul

jtrout19

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Re: Video Signal Loss
« Reply #1 on: November 07, 2016, 11:32:42 pm »
I think ive read sbout this being an issue with your grounds. Dont quote me on that but i think thats what ove read. I was having different issue in the past and came across video loss on throttle up before.

jtrout19

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Re: Video Signal Loss
« Reply #2 on: November 07, 2016, 11:34:55 pm »

Re: Video Signal Loss
« Reply #3 on: November 08, 2016, 04:56:39 am »
MICRO MinimOSD Minim OSD-Battery problems

Thanks for the link.... A lot of discussions about grounds and then the confirmed cause was connection of an audio lead to the VTx.  I think I'm good on both of those issues.

I tried installing a capacitor today on the OSD, no change.  Tomorrow I plan to try running test with separate battery for camera and VTx, since I can easily run them on a small 3S setup.


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jtrout19

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Re: Video Signal Loss
« Reply #4 on: November 08, 2016, 05:15:34 am »
Well you could put a voltmeter on your 12v rail and see if the voltage fluctuates when you throttle up. If it does then that is your problem. If it doesnt then you should look elsewhere.

Re: Video Signal Loss
« Reply #5 on: November 09, 2016, 08:24:37 am »
I usually use a small separate 3s lipo for the fpv, but I have also used power from the flight battery.  I got a little bit of wavy screen when using the flight battery, but nothing too bad.

If your wiring is correct (all grounds should be connected together) then I suspect you are getting a big voltage drop on your flight battery when you throttle up.  Either you have a bad battery, bad connections, props too big, loss of ESC sync ...

jdl

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Re: Video Signal Loss
« Reply #6 on: November 09, 2016, 09:58:01 am »
As you tested successfully without OSD, although on separate battery, you can check if MicroMinim OSD Board is causing the signal loss or not. Bypass it: connect camera directly to VTX. If no video loss (using the onboard primary battery) - OSD board is the problem. Make sure that ONLY ONE ground wire is connected to MicroMinimOSD board, preferably the ground wire for OSD power supply. No other grounds from camera or VTX! Otherwise severe ground loop effects occur sometimes. I had a lot of troubles with MicroMinimOSD - loss of OSD overlay and/or flickering of the overlay under normal / heavy throttling, before I disconnected all other grounds from OSD board except one. Also added 470uF capacitor parallel to OSD power wires - this seems to be  mandatory. No problems at all after that.

I also found necessary to add a 150ohm resistor in series between the cam video out and OSD. Without it there were disturbances of OSD overlay in some (maybe too bright? - don't remember) scenes - maybe due to improper output impendance matching of the cameras I used. But this is not related to your problem, I think.

Audio channel from camera to VTX never caused problems for me.

In all my setups I use Eachine VTX200, 600, 600R transmitters and PAL CCD cameras.

Hope this info helps.

Re: Video Signal Loss
« Reply #7 on: November 09, 2016, 04:14:53 pm »
Very helpful, thanks! Yesterday's test with separate battery and no OSD went well.  Next test I plan is camera and VTx on PDB but without OSD, just to make sure the PDB isn't the issue.

I did test with a capacitor on the OSD but it was much smaller than you indicated, so I'll see where I can find the 470uF size. 

So on the grounds, since I'm using the 5v input to the OSD from PDB you are saying I should disconnect the ground wire coming from the Telemetry feed from the FC?

I'll try all the above and report back.  Not much time today, but hopefully can check it out by Thursday/Friday.


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jdl

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Re: Video Signal Loss
« Reply #8 on: November 09, 2016, 06:10:40 pm »
I suppose the OSD board can be your culprit because the MAX7456 (video overlay IC) is quite sensitive to the power supply. Although I haven't had such personal expirience (I mean total video signall loss) I think I've read somewhere about it.

And yes, ground wire to the FC (telemetry link) should also be removed. Together with grounds coming from camera and from VTx to the OSD, if already connected.

470uF is reasonable value for the filter capacitor. I tested with 1000uF but it is too bulky and really not necessary. Good source may be old computer motherboard - you can harvest  470uF/16V or 10V capacitors from it - they are very compact and usually of high quality. But still, test them with capacity meter, if available, sometimes they age without any visual signs (leaks, bombing, etc.). Unusually high readings (for instance 500+uF reading for a 470uF nominal) may indicate a problem - avoid these ones. Also too low readings aren't good.


Re: Video Signal Loss
« Reply #9 on: November 10, 2016, 11:04:29 pm »
Ok... testing completed with very weird results and no combination that actually works.

I have removed all grounds except that to the power feed to the OSD (removed the telemetry ground to FC and the battery ground to the BAT1 connection).

I tested VTx and camera with power from PDB (no OSD).  This is the ONLY combination that works.

I secured a 470uF 10v capacitor and connected it on the 5v feed from the PDB (before the OSD).
The OSD will not even boot in this scenario.  Video feed starts, then drops signal, and then comes back, but no OSD at all.

If I disconnect the feed to the OSD, power up the quad (with the capacitor now "charged") and then connect it to the OSD, the OSD will boot and everything looks good on the ground.  But as soon as I throttle up, I'm back to signal dropping in and out and when the signal comes back, the OSD is gone.

I then tested with the OSD powered from a 4 cell NiMH battery pack.  This is the closest combination to actually working, but the OSD fails to overlay at all while the motors are running, but as soon as I kill motors, the OSD image returns (so it appears the OSD is not dropping out, just failing to integrate on screen when the motorsare running).  The only thing I can therorize is that the battery lead is picking up interference from the motors, and causing the OSD issues.

About to give up on this entirely... which is a shame.

ANYTHING I'm overlooking?

Paul

Re: Video Signal Loss
« Reply #10 on: November 28, 2016, 04:17:23 pm »
All, update is that I have successfully flown now many times with the OSD disconnected and no video signal loss.  That combined with earlier testing certainly points to a voltage issue or some other cause for the OSD dropping out, rebooting, killing the signal in the process.

Since the implementation of a 470uF capacitor made things [slightly] worse than the 220uF, and even the 220uF didn't fully resolve the issue, does anyone have any other recommendations?

I've thought about trying a separate 5v BEC for a dedicated/isolated power source.  Any thoughts about that?  If so, what I should look for in BEC features?

Paul


Re: Video Signal Loss
« Reply #11 on: November 29, 2016, 04:05:56 am »
Does the OSD get hot?  Some OSDs have that problem.

Re: Video Signal Loss
« Reply #12 on: November 29, 2016, 10:57:04 pm »
Can't say that I've tried to check that.  In a 5 minute flight it would typically cycle 3-4 times, but usually coinciding with "throttle up" situations.  How would you define "hot"... just to the touch after landing?  Some other measure?

Re: Video Signal Loss
« Reply #13 on: November 30, 2016, 04:52:24 am »
Ah, your voltage is dropping when you throttle up.  Capacitors won't fix that.

That sometimes means the props are too big or the battery is too old or weak (low C rating).

One solution would be a separate lipo for the FPV stuff.  Another would be one of those "any-volt" regulators that is two regulators so it can regulate up or down or just stabilize.

Re: Video Signal Loss
« Reply #14 on: December 09, 2016, 03:17:13 am »
 FYI, I've got a new 5v BEC coming.  I think I'll try to just wire it up with a small 2c battery pack totally separated.  Fairly new batteries, running 5045 bullnose props on a 4s battery with 2206 motors... Seems to not struggle for power at all, but yes, it is voltage drops to the OSD I believe, Corresponding to time that I "add power".  Will update once I've tried the new solution.


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