Before I burn up another one of these things, can I power a camera and transmitter off of a 3S LiPo battery?  The specs for the camera say 9 - 12.6v and the specs for the transmitter say 8 - 12v.

I tried using a 3S on another camera and transmitter and wound up with a small cloud of smoke and no video.  It is my understanding that the 3S produces 11.1v which should be fine.  As for AMP's, the devices will only draw what they need correct?

Figured I would ask the community before I fry this new FPV system that just arrived (I have another on order just in case).

Thank you in advance!

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Dan.
Again you are right in a perfect world, however overvolt can happen.
I gave a very good charger with balance, But sometimes I do not use the balance as its not important to do it every time. Sometimes I charge packs in parallel to save time (at the field. If I get a bad cell then the other pack Will overcharge

I use a class b lipo to power my transmitter and camera in parralel, i do not bother with a diode after a fresh charge ect because the voltage drops instantly to around 12V

these things have built in regulators so its not a big deal is its 12.6v

Now you have a diode there is no reason to change them out, but for future reference, the things will run fine.

However it also depends on battery size because that determines the voltage drop, i use a 1000mah but a 2200mah would likely not drop for a while and cause problems.

If you are charging your 3S lipo to >13v, then I would be more worried about not burning down the house then what happens with the camera and transmitter..

Using switched DC-DC regulators on FPV camera and transmitters can lead to problems with video noise and reduced range. Not always, but often. I always make sure the camera and transmitter works on 12V so that I can use a 3S lipo directly. The simplest way to get a good robust FPV system is keeping it simple and using a separate FPV battery from the R/C power system since motors and ESC's generate a lot of noise.

Right! Bruce from RC model Reviews has some interesting stuff concerning this discussion http://www.youtube.com/watch?v=NeFW-B42HCg

I usually agree with Bruce, but this time he's overcomplicated it in my opinion. He's using two linear regulators to try and block the noise from the UBEC/system, instead of just feeding a dedicated battery directly to the camera and a linear regulator for the 3.3V device.

He's probably trying to make is so that you can use one battery for the entire system, but you almost always end up with video noise that way since analog video signals are very sensitive, and motor & esc's generate a lot of electrical noise.

No need to complicate matters. One battery, if a 3S, works fine. As has been said, with a correctly operating charger, the fully charged 3S should not exceed 12.6 V and that won't stay there for long. LiPo's have a relatively flat discharge curve except at beginning and end. Your battery will be at 12V before you know it. If you saw magic smoke, more than likely you reversed polarity somewhere. If you are worried about video noise, add a common mode filter. Want to read more, go to FPV Labs...

Short answer is yes you can. i do it myself on 2 of my FPV crafts. No need to complicate issues and make more potential failure spots in your circuit , not to mention the extra interference from any more electronic voltage switchers.

Happy flying.

What I found works best for my FPV quads and airplanes:

A 3s 1300 / 12v direct to FPV cam and transmitter, and a Y split to a UBEC or SBEC with 5 V jumper setting for the simple OSD/Telemetry and Transmitter.

Then a separate power source going to the ESC(s).

Hope this helps.

All the best.

Daniel

i use a 3s for video tx and camera, no probs for the TX, but my particular camera starts to fall over very quickly at under 11.5, i get ghosting, graininess then just dark....

I have used 3S lipos directly to power camera and Tx a number of times without any smoke issues.  One thing nobody has mentioned is brown-out performance.  Your main battery pack voltage is going up and down a lot in direct  proportion to your throttle stick.  Although you may land with >11V you will definitely have excursions much lower than that.  I happen to have a nice power supply and tested my particular Tx and camera combos.  I had one set that would brown out at ~8.5V which was probably fine but another one worked well down to 6V and then carried on in wobbly black and white down below 5V.  Both were 12V devices. If you cannot find a good power supply to test with, record your video while running your battery down as low as you normally dare and then with the quad (or whatever) on the ground give it a few short full bursts of throttle and check that the video stays on.

Luckily these are still analogue devices and they power up quickly once voltage returns.  There would be nothing worse than losing video while still flying just due to brown-out.

As far as a UBEC is concerned I normally use CastleCreations 10A peak BECs.  While they work great in airplanes, they need to be away from the APM.  I had one hexa noticeably twitching in one axis when I relocated the BEC closer to the APM, moving it cured the problem.  A linear regulator should not have this issue as there is no switching going on.

There are some goofy 5 volt cameras and video tx's out there, but this works just fine.  If you need to go the extra mile, get (whatever you call it) that takes in your 10-13 volts and just outputs 12. 

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