Discussions

12V power for a Tarot Gimbal on 4S

Posted by Justin Hardin on August 16, 2014 at 9:57am

My goal is to get clean 12v power to a Tarot Gimbal from my 4s Lipo Battery.

My Setup:

  1. 3DR Y6 DIY (so doesn't include the voltage regulator in the RTF kit)
  2. 4S Lipo
    1. min voltage is 3.2V/cell, or 12.8V
    2. max voltage is 4.2V/cell or 16.8V
  3. Tarot Gimbal from 3DR
    1. The Tarot Gimbal asks for 7.4v - 14.8v inputs
  4. My first idea was to use a L7812 linear voltage regulator
    1. These regulators have 2V dropout voltage, which means once I get below 14V my output voltage will drop unpredictably under 12V.

My Questions

  1. Does anyone know what voltage regulator setup comes in the 3DR Y6 RTF?
  2. Is the best option a 12V uBEC like this one from hobby king or this one from helipal?
  3. Or a 12V SEPIC step up step down regulator like this?
  4. Or should I go with a 7809 linear voltage regulator and just feed 9V to the tarot? I could have a maximum 7.8V delta with a fully charged battery pulling 500ma, not sure how much heat that would generate.
  5. Or should I go with a lower dropout voltage regulator (.3V @ 500ma) which would mean I'd get clean 12V power until I reach 12.3V, which I should never reach as I'll end all my flights before I reach 3.2v/cell (or 12.8V)
  6. I like the idea of using top end components (quality) and building it myself (learning, make it as small and lightweight as possible)
  7. With all of the above options, I'm assuming the best wiring option would be to splice into the power distribution board +/- ?

So many options! Any help appreciated!

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Tags: 12v, 3dr, regulator, sepic, tarot, voltage, ubec
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Replies

  • Michael Ciurescu August 18, 2014 at 8:40am

    Hi Justin,

     

    I just installed my Tarot T-2D on my F550 a few days ago. I am using this UBEC from HobbyKing, and I also share the power to my FatShark 600mA Transmitter. I also put a 470uF 25V capacitor on the output of the UBEC.

    I did not do a full test yet... I went out this weekend to test my Tarot, and I got good results, but I did not check the video of my FatShark to see if it interferes with it...

    One day I should connect the power output to my oscilloscope and test it, but I don't know when I will have time for that...

    But in theory, everything should work because the Tarot has it's own power regulators, and also the FatShark has to bring down the voltage to 5V, so even if the input power fluctuates, at the end, after the UBEC and also their own regulators, the final output should be a clean power for what they need to do...  So doing anything extra on top of what I already done it does not really make sense...

     

    By the way... if you want to get a ~2V dropout voltage, then you can also use diodes. Most diodes have 0.7 drop voltage, so if you put 4 diodes in serries then it drops 2.8 volts. So when the 4S battery is discharged (about 14V) then you get 11.2V, and when the battery is fully charged at 16.8V, then you get 14V output. And of course, it's always good to put a capacitor on the output of the diodes.

     

    Just remember that the Tarot has it's own voltage regulator, so you don't have to be perfect... the FatShark on the other hand, even though it has it's own regulator, I've read on the forums people complaining about input interference, so I think it is much more important to get a clean voltage on that!

  • Scott Reid August 17, 2014 at 9:03am
    I'd avoid a 78xx regulator, they are very ineffecient. I'd recommend a buck-converter based regulator, like most discrete BECs are. I use one of these to power my gimbal, video tx,, and minimosd from a 4s.
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