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Thread: EZOSD power/ground problem?

  1. #1
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    EZOSD power/ground problem?

    I'm trying to track down problems in my video system and encountered what I think is a problem with my EZosd.
    I use a Fatshark VTX that runs off the 3s balance plug right off one of my batteries. While looking for a possible ground loop, I disconnected the ground between the VTX and the battery, leaving the + still hooked up, to make sure the VTX didn't have another path to ground. As expected the VTX did not come on when I hooked everything up.

    What surprised me is the OSD did not power up either. My batteries connect to the current sensor, then the bus connects the current sensor to the OSD, then to the VTX. I thought the OSD got its power and ground through the current sensor. But if that's the case the case then that doesn't compute with the OSD not powering up unless the VTXs ground was connected.

    Otherwise everything seems to work great otherwise. All the current data displays just fine on the OSD when the ground is connected.


    What hat clued me in to a possible problem and started me on this wild goose chase is I only get about 1,200 ft before my video cuts out. When the plane is not flying and it's just in the back of my truck, it can get about 1.5 miles down the road befor the signal starts to degrade. I'm not sure if the two issues are related but I think they could be.

    Posting a rough wiring diagram, forgive my poor artwork.
    Click image for larger version. 

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  2. #2
    ImmersionRC Support Guru swillhide's Avatar
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    Why do you have power and group going from the OSD to the Vtx? since your running batteries in parallel you only need a signal from the osd to the vtx then power and ground from the vtx to the battery.

    Got a pic of the rig?
    AMA # 1015480 HAM Callsign # Procrastinating..
    Futaba 9c w/Ezuhf /Skywalker 1880 or anything else that I can Lawn Dart.
    Retired: Disco(Sold), Skywalker 1900(Dirt Nap), Qav540g/Nazav2/Iosd mk2

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    A bit more info after more troubleshooting. No idea if this was something I did or a weird factory defect.

    I removed the current sensor from the plane and hooked a battery to it. I put the ground wire of my voltage tester straight to the battery ground and then started testing the pins on the connectors of the current sensor and found the error.

    Both places voltage leaves the current sensor, not including the big plug to the esc, are shorted somehow. The +5v pin on the ezBus is putting out 12.4v. BUT so is the ground wire. Same on the vtx power supply connector. The + is putting out 12.4v, and so is the ground.

    Miso somewhere on the circuit board the hot and ground are shorted together. That kind of explains why nothing came on unless I hooked the vtx to the balance plug. Without that nothing in the system had a ground as all the connectors on the current sensor were acting as supplies.

    I'm actually surprised everything else worked fine and nothing else seemed to be burned out. The osd worked fine and the current usage displayed properly too. I think it just really hurt my vtx range because the whole video system and all its noise was having to ground through the balance plug fat shark supplies.

    I already ordered a new current sensor. If you guys want me to ship this one someplace to see if it was a production error or something I did that's fine. The only thing that makes me think this may have been a production error is that when I first tried hooking the osd up, I was planning on powering the VTX from the port on the current sensor, but when I plugged it in there nothing happened. Which makes sense if both wires were trying to supply voltage so there was no ground.

  4. #4
    ImmersionRC Support Guru swillhide's Avatar
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    Always start with your retailer, they will be the quickest way to get a replacement.
    AMA # 1015480 HAM Callsign # Procrastinating..
    Futaba 9c w/Ezuhf /Skywalker 1880 or anything else that I can Lawn Dart.
    Retired: Disco(Sold), Skywalker 1900(Dirt Nap), Qav540g/Nazav2/Iosd mk2

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    Quote Originally Posted by swillhide View Post
    Why do you have power and group going from the OSD to the Vtx? since your running batteries in parallel you only need a signal from the osd to the vtx then power and ground from the vtx to the battery.

    Got a pic of the rig?
    as to your specific question. The red and black lines between the osd and the vtx on my drawing are the wires on the 5 wire ezBus. I wasn't sure if those bus wires actually supplied voltage or ground when I drew the diagram. That's why I put question marks by them. Sorry I should have described that part better.

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    For that cable between the osd and the vtx, should the red and black wires be stripped off the bus?

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    Quote Originally Posted by swillhide View Post
    Always start with your retailer, they will be the quickest way to get a replacement.
    Ok I'll do that. I already ordered a replacement, but I'll eventually have multiple planes so I won't mind having extras if they send me a spare.

    When I posted the thread I thought I had a wiring problem, I hadn't found that it was internal to the hardware at that time.

    I like the osd. It supplies all the info I want and surprisingly still worked even though all the ground wires were supplying voltage.
    Last edited by Steel-W0LF; 7th September 2015 at 09:01 PM.

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