FPV backpack PCB build

If you've been building electronic bits or modifying stuff you've bought then tell us all about it here. A good place to discuss the installation of 2.4GHz DIY modules too.

Re: FPV backpack PCB build

Postby skelator » Thu Sep 20, 2012 2:36 am

RCModelReviews wrote:The files are now up on the website at:

http://www.rcmodelreviews.com/fpvbackpack02.shtml


sweet! I just ordered some part from my local store, I just need a new 200mw vtx only have 20mw at the moment

Thanks bruce!
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Re: FPV backpack PCB build

Postby tignmeg » Thu Sep 20, 2012 2:56 am

Awesome set of vids Bruce
Maybe a suggestion for V2 would be to hard-wire the BEC as a daughter board on the bottom instead of having it float around
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Re: FPV backpack PCB build

Postby RCModelReviews » Thu Sep 20, 2012 3:33 am

tignmeg wrote:Awesome set of vids Bruce
Maybe a suggestion for V2 would be to hard-wire the BEC as a daughter board on the bottom instead of having it float around

When it's part of the backpack, I hot-glue the UBEC in place so it doesn't float around.

That's coming up in the next Backpack video.
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Re: FPV backpack PCB build

Postby JustinTime » Thu Sep 20, 2012 4:31 am

Is saying here 'I too want a kit' is as good as sending you an email? If yes, than: I too want a kit.

There, now it's official. :D
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Re: FPV backpack PCB build

Postby iflylilplanes » Thu Sep 20, 2012 6:17 am

I have just viewed the two build videos, could you please tell us which receivers will work with the back pack? Please put me on the list for a kit too.
Many Thanks,

Dave W.


Dead Stick Glide Distance: Half the distance from the airplane to the nearest emergency landing field.
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Re: FPV backpack PCB build

Postby rotorz » Thu Sep 20, 2012 8:14 am

RCModelReviews wrote:
rotorz wrote:Looks like half an FPV backpack to me..

Why is the camera being run at lipo voltage, it seems to be missing a whole regulator circuit?

It's actually run at 0.6V less than the lipo voltage -- the diode drops the 0.7V and acts as a charge-pump to reduce the amount of noise that would otherwise come from the pack. When the pack voltage drops due to the load of the FETs switching on in the ESC, it can't drag down the filter capacitor voltage because the diode switches off -- so there's a noticeable reduction in noise on the power-feed to the camera.

Most cameras are now rated at 9V-12V so this means that with a 3S lipo having a useful working voltage of about 12.6V down to 9.9V, the camera will see 12V down to 9.3V -- which is its safe operating range.

I thought the rcmodelreviews wise thing to do was run the camera from 9v or has that all changed now?

I was going to -- but found that the dropout voltage on the regulator was too high and that when the 3S lipo got down to less than 10V, some cameras would stop working -- not a good thing if you're 400 feet up and a mile away at the time :shock:

I also found that some cameras drew so much current that with the (up to) 3.6V drop across the regulator, it was risking going into thermal shutdown if the ambient temperature was over about 35 degrees C. So.. it was better to play it safe and remove the regulator because the alternative would have been a more expensive regulator with a heat-sink or a far more complex switching regulator. KISS won the day!


MMM I'm no expert on these things but .6v headroom doesn't sound a lot.

Has this circuit been tested on anything more powerfull than a Ladybird?

I suppose the proof will be in the pudding, those with cheaper ESC's, (like me), and higher wattage power systems might want to have a separate video battery if noise is a problem.
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Re: FPV backpack PCB build

Postby RCModelReviews » Thu Sep 20, 2012 8:23 am

I've (and others here) have been flying this design for a full season of FPV with no problems at all.

Of course you can use a smaller (450mAH is good) 3S lipo to power the backpack if you want but I've flown FPV for nearly half an hour on my AXN with this setup and it's worked perfectly -- using the SecurityCamera2000 600TVL camera with WDR.
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Re: FPV backpack PCB build

Postby RCModelReviews » Thu Sep 20, 2012 8:25 am

Oh yes, and I've also used it on some long-distance flights with the HK EPP model -- as you can see in this video:

https://www.youtube.com/watch?v=Xga7vaQp9rs

I'm using a 65A ESC in that model and it draws over 500W at full noise.
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Re: FPV backpack PCB build

Postby Mistimeanors » Thu Sep 20, 2012 12:26 pm

Appreciate all your perseverance and dedication. Thanks. I'll have a crack at etching for fun but please put me down for two kits.
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Re: FPV backpack PCB build

Postby icedfusion » Thu Sep 20, 2012 12:32 pm

Put me down for a kit also - this looks fantastic!

ice.
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