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Old Jul 16, 2014, 04:31 PM
Smasher of foam
FunkeyMonk's Avatar
United States, OH, Stow
Joined Sep 2012
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My MinimOSD blacks/browns out during flight.

I'm having trouble with my MinimOSD, and I can't seem to find any helpful information written in the past 12 months. Who's an MOSD genius who wants to help?

I've not yet had a single flight with my two-week-old MinimOSD which didn't have a problem during flight. When I'm flying, after 2-3 minutes, the MinimOSD will first stop displaying, and then blacks out my video entirely. Thank goodness for RTL!

I'm flying an APM 2.6. Currently, I have the MinimOSD running off separate 5v and 12v power. It's connected directly to the APM's telemetry port, since I don't have a telemetry radio.

My Wiring Right Now:
5v side: Connected from APM telemetry port to Minim's Tx, Rx, +5v, Gnd.

Power connector pads on board are de-soldered. Ground connector pads on back of the board are soldered.

12v side: Running an ImmersionRC 600mhz 5.8ghz. Video in/out connected between camera and vTx. 12v and Gnd in/out connected between battery and vTx.

What I've tried:
1. Initially, the board came from ReadyToFly Quads with the power connecting pads pre-soldered. I ran the board from only the 5v side, and on the 12v side I connected only the video wires. This had problems with interference from motors, so I added the grounds on the 12v side. Interference was gone, but I still had to plug/unplug the battery several times before every flight to get the Video or OSD or both to display. Then, I'd get video to show up, and I'd have to reset the OSD a few times to get the data to display, too. But during flight, the OSD will blank out, and then, usually while I'm flying back home, the video goes black, too.

2. I desoldered the board blobs and rewired for separate 5v and 12v power. Got the same motor interference problem again, so I re-soldered the ground pads on the back of the board to connect the 5v ground to the 12v ground. Fixed the interference problem (again), but I still have trouble getting the OSD/Video to boot when I connect the battery. (Although it's at least less problematic to get the OSD to boot up and display. If I get any video to display through the minim, it now also pulls up the OSD info almost every time.) And the OSD still cuts out during the flight, and then the video blacks out after.

3. I've tested for loose wires on the vTx, camera, APM, MinimOSD, etc. I can't reproduce the problem through any amount of wiggling, tugging, smushing, etc. The wiring seems good.

My guesses at the problem:
* Unstable voltage coming from the APM? I'm not sure how I'd test this. I can't find my multimeter, and it'd be pretty tough to use it during normal flight conditions, anyway.

* MOSD is overheating? I know the "older" models had problems overheating on the 12v side, but I'm having the same results whether I power it from 5v or 12v or both.

* MOSD is just "bad?" <-- seems the most likely candidate to me, but maybe I'm missing some important step somewhere.
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Old Jul 16, 2014, 07:16 PM
flying ninja!
ican3d's Avatar
Joined Jun 2011
845 Posts
Sound like "Ground loop". Had that issue before. Go check out "Ground Loop" threads.
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Old Jul 16, 2014, 08:24 PM
Smasher of foam
FunkeyMonk's Avatar
United States, OH, Stow
Joined Sep 2012
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Quote:
Originally Posted by ican3d View Post
Sound like "Ground loop". Had that issue before. Go check out "Ground Loop" threads.
Yes, I do think I may have a ground loop, only because I've connected the 5v and 12v grounds on the mOSD.

(The ground could loop in a circuit: from 12v > vTx > Battery > APM > 5v > 12v) but that's a pretty big loop with a power filter in between, in the vTx. But maybe that power filter makes no difference in the case of a ground loop. I dunno.

I can break that loop by de-soldering the ground connector on the mOSD, but then I get interference from the motors. (So bad that it completely obliterates the image.)

I've also tried breaking that loop by simply disconnecting the black ground wire from the APM to the mOSD. It doesn't help.
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Old Jul 17, 2014, 10:12 AM
Smasher of foam
FunkeyMonk's Avatar
United States, OH, Stow
Joined Sep 2012
207 Posts
YES! It's fixed now. Last night I found an old ESC laying around so I hooked it up and just used its BEC to power the mOSD. Problem solved. So I must've been getting bad/dirty/inconsistent/noisy power from the APM. But I have none of the old problems. The OSD boots up immediately when I connect power, and everything works during flights. Ran two batteries through it this morning without problems. Now I just need to buy a real dedicated BEC and I guess I'm all set. (But this makes me wonder about the quality of the power going from the APM to my receiver.... maybe that accounts for the brownout I had a few weeks ago.)

For what it's worth, I've left the 5v and 12v sides powered separately, since I'm just too lazy to bother rewiring them again. But I suspect it would work fine if I went back to powering the whole board off the 5v side, now that I'm using a dedicated BEC.
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