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GoPro H3B...USB vrs MicroHDMI for FPV

Discussion in 'General Discussion' started by Peter Patricelli, Dec 1, 2013.

  1. Peter Patricelli

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    I have read the GP3B manual and can't find an answer. The GPH3B has two video out-ports...a mini-USB port and a micro HDMI port. I have been using the USB port for FPV....but only got video out when I went into RECORDING. I just saw a Youtube video that demonstrated that, through that USB port one can go into live-view without recording by going into Playback mode and pressing the shutter button...canceling review and putting you into live view. That gets me where I sometimes want to go...but with more button switching sometimes with the gimbal activated and twitching....not good.

    My question is....does the Micro-HDMI port work the same?? or Differently? I do have the Tarot cable which uses the HDMI..not the USB port. Does the HDMI give me live view...perhaps automatically....all the time regardless of recording?

    I would have to dis-assemble my FPV-TX off the bird to test it out myself....would like to avoid that if possible unless I'm definitely going to gain something...like continuous live view. Anyone know?

    Thanks.

    I
     
  2. ElGuano

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    The big difference is the USB port outputs composite video (analog) which most FPV systems use. Also, if you use the USB port, there's a special cable mod that has a tiny resistor that forces the GoPro into video-out mode (almost every GoPro cable sold for FPV will have this mod already done to it). This way, as soon as your GoPro turns on, it's outputting composite video through USB, whether it's recording or not. My monitor shows GoPro output as soon as I plug in the battery to my Phantom.

    I don't know how it works with the HDMI port, but presumably you'd need an HDMI INPUT on your vTX accept that signal, as well as a DAC to convert it to analog to transmit to your vRX.
     
  3. Peter Patricelli

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    Thank you. That perhaps clarifies that my USB cord does NOT have that mod to give continuous live-view. That also possibly clarifies a dim memory I have of a video suggesting that the Tarot cable (HDMI) plugging into the Tarot controller (for HDMI to analog conversion?) before going to the FPV-TX. My foggy understanding of that....and lack of clear connection ports and sequence...led me away from using the Tarot cable in the first place.

    Anyone using the Tarot -HDMI port cable? Can you clarify? Do you plug directly into the FPV-TX....or go to the Tarot controller? If that...then where out to the TX? And, do you get continuous live-view?
     
  4. ElGuano

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    I had the Tarot cable for the T-2D 2axis gimbal, it's a USB cable and it has the resistor mod. I plugged it into the vTX directly, no part of it went to the Tarot board. The cable also has a 5v power cable for the GoPro too, which as I understand it is incompatible with the Tarot board if you use an H3B. The one I had is not HDMI and I'm unaware that Tarot makes an HDMI cable/DAC.

    My tarot cable broke at the USB pins - it was plastic and just couldn't take the stress of continually removing/reinserting into the camera. I replaced it with an ebay USB cable with a metal connector.
     
  5. Peter Patricelli

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    El Guano,
    I was hesitant to cut open the package and look at it carefully...a couple of loose small screws in there safer if I leave it sealed....until needed....and looked and looked carefully at it through the plastic assuming it was USB at first, but it didn't look right. However, I suspect you are correct and it is USB.

    You obviously are more experienced and knowledgeable than I, and I am not going to use the power cord, but I do believe 5V is correct for the GP3B. Someone on here fried their GP3 with 11Vs!
     
  6. ElGuano

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    While you're correct that the GoPro requires a 5V input, and the Tarot board outputs 5V from the pins that the USB cable connects to, I understand that the H3B draws in excess of 1 amp, which is significantly higher than the Tarot board can output. There have been some reports that connecting an H3B to the power port causes the Tarot board to eventually fry. I didn't bother testing those reports myself, though!

    YMMV and it may work fine, and maybe non-black edition GoPros may work flawlessly. I do know that my H3B draws a SIGNIFICANTLY more power when it's recording AND outputting composite video to the USB port (a fully charged battery that lasts 1.5 hours drains to zero bars in about 30 minutes when used for FPV), so I'd be especially careful with the power cord if your end goal is FPV. It may be worth it just to run a UBEC from an aux 11v lead for the GoPro if you really want to charge/power it from the flight battery.

    There's a small screw in the package that lets you permanently affix the GoPro cable to the camera tray. I found it unnecessary, especially since the lens ring permanently bolts the camera to the tray already.
     
  7. Peter Patricelli

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    You are right again...it was the charging/amperage issue that caused problems....not the voltage. I just don't want anyone else reading this to get mis-information....from ME. Given the short battery life of the GP3B it is tempting to power it from the bird somewhere....but further drawing battery power away from flying. AND, with the GP3B one MUST have the battery in place to power up the camera (after that apparently you can remove) but that is just too frickin' crazy on the field, fumbling with the camera UNmounted and the bird HOT, loose battery and door, etc.. No thanks, leave the battery in place, doing what it is designed to do.

    Thanks again.
     
  8. ElGuano

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    Yeah, flying separate batteries for different components has never made much sense to me. The argument that you get more flight time by not draining your flight battery for your camera/GPS/gimbal/etc. doesn't quite ring true to me, especially considering the extra weight and overhead you need to keep the other battery aloft. Plus, drawing power from your flight battery is precisely efficient, your aux components draw exactly what they need for that flight, and nothing more. If you're flying a separate 800mah battery to power your gimbal and fpv, and that battery lasts 8-9 flights between charges, then you're not only carrying around the extra weight of that 800mah battery, you're also carrying around a ton of excess you will NEVER use for that flight. And throughout the day you're carrying around 7-8 flights worth of discharged weight that is also doing you no good.

    IMO, unless you're forced to run some kind of uber-ubec that weighs 50g, or there is no other way to power the component from your flight battery, there are very few situations where you're better off hauling a separate battery onboard.