Powering the Video Transmitter

[linuxslate]

I am trying to set up my Quad for FPV.

I am spending a lot of (too much) mental effort on how to power the Video Transmitter. (Fat Shark 250mW 5.8GHz -- Needs 12 volts for rated output).

I do not want to power it from the main battery balance leads as Fat Shark suggests due to the following disadvantages:

-- More connections to change LiPo Packs - Just inconvenient for a number of reasons.
-- Un-regulated voltage = Less than rated transmitter output. Output changes as battery discharges.
-- Reduced flight time. Transmitter adds > 350 ma load.

I ordered some small boost converters that will give me a regulated, adjustable output from as low 5V in, so I considered running from the UBEC output, but that is the same 5V that runs the FC. If I over-load/over-temp/glitch that, I loose the FC, so I decided not to do that.

Other options:

-- Power it off the flight battery, but connect it directly instead of to the balance leads.
-- Separate 2S LiPo (Only provides 7.4v to the transmitter).
-- Separate LiPo with the Boost converter.

Thoughts? Suggestions?

[Noctaro]

Hi linuxslate!

I use the option to power my whole FPV system from a 2. 2S Lipo .
I like this method as i got some horrible interferences from running motors if i connect it to flightbattery. (Connected 2 elkos, nearly still same. So its really hard to filter.)
As far as i know the transmitter regulates itself to 5v, so you should not have any range decrease. Even better, it should not heat up that fast. (I did not have any decrease vs 3s lipo but i dont use fatshark transmitter)
My 2s lipo has 700mah, so its not too heavy (~60g), but can power my cam and transmitter for around 3 hours.

Hope this helps a bit.

Greetz Noc

[linuxslate]

The Transmitter produces a Regulated +5V for the camera (and, in my case for the video half of a MinimOSD), but I believe that at least portions of it run on the Input voltage.

Most other Video transmitters, except very low power ones, use more than 5V.

In experience, and in what I have read, RF power output is very dependant on voltage in put in these small transmitters.

I don't have a 5.8GHz power meter, or even FS meter to test, so I cannot be sure.

Never the less, I do agree that a separate 2S Lipo is probably the way to go. I was shopping for a ~700mah 2S LiPo when I saw your reply. Thanks.

[rizky_p]

My Video Tx is connected seperate batre 3s 700mah batre. It is better not onnecting it to flight battery as the noise from the motor will somewhat effect the video quality.

[rizky_p]

My Video Tx is connected seperate batre 3s 700mah batre. It is better not connecting it to flight battery as the noise from the motor will somewhat effect the video quality.

[Nicksdesign]

How certain is it that the Fatshark Predator V2 transmitter is producing reduced power if run on a 2S source? There is nothing in my user manual to that effect.

Nick

[haydent]

i also use a secondary 800mah 3s battery

[linuxslate]

Thanks for all the replies. I have temporarily ended up using a separate 430mah 2S Lipo.

I only purchased that battery because it was what the local hobby shop had on the shelf.

It works, but the 250mW Fat Shark Transmitter/Camera/MinimOSD drains it pretty fast. The 430mah battery is inadequate for what I would call a typical "flying session".

Transmitter power seems good with the 2S battery. With no obstructions, I start getting a lot of video static/drops at about what I think is the limit of the RC transmitter.

I'll have to look at the MinimOSD distance to home next time, but I can tell you that one time in an unexpected breeze, my Quad almost got away from me.

It was a tiny dot in the sky, and there was no way that without FPV I could have known my orientation. Video in the Fat Sharks was very broken, but It was good enough to get me back over the field I took off from. Beginning to panic, I landed, and took a walk to get the quad.

Aside: (I did try RTH, but it was initially having some problems fighting the wind. That's when I "panicked", and set her down where she was. In hindsight, or perhaps with a little more presence of mind, I should have had more faith in RTH. I'm sure that if I had given it just a few more seconds, I would have seen that RTH was flying it back to me.)

The point is that range is pretty good with a 2S battery (stock antennas, too!), but 430mah is too little capacity.

I think a 3S lipo will probably cause the transmitter to run hotter, (and add weight) without a significant increase in video signal range.

I'll keep the 430 mah battery for now, but I will order a higher capacity 2S Lipo next time I place an order from hobbyking/DX/rctimer/whoever.

[haydent]

interesting. ive had my quad not be able to overcome wind in rth and get carried away.

[linuxslate]

Wow. Maybe I did the right thing then.

Another 50m or so downwind, and it would have been in dense tall trees and Florida thicket. It would have been very difficult to retrieve.

[Nicksdesign]

I came across a Fatshark support post where the Fatshark guy stated that the transmit power is the same regardless a 2S or 3S battery is used to supply the power.

Nick

[scrat]

I came across a Fatshark support post where the Fatshark guy stated that the transmit power is the same regardless a 2S or 3S battery is used to supply the power.

Nick

It has the same transmit power regardless 2S, 3S or 4S.