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Old Oct 06, 2005, 07:50 PM
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I don't know if this is plausible?possibe or already exists


A small receiver for parkflyers with a capacitor that gets charged by the battery pack and holds enough charge to power the servos for 30 seconds to a minute in case your pack gets ejected or the esc fries. It would be like having a receiver pack but without the added weight.

Doable? Practical? Or does it already exist?
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Old Oct 06, 2005, 07:53 PM
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a ParkBEC would work if your ESC fries ($17) but wouldn't help if you eject your battery- Just don't eject your battery and you'll be just fine.

Jim
Old Oct 06, 2005, 08:00 PM
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Good advice but it doesn't tell me if I have invented the next great thing or just had a dumb idea.
Old Oct 06, 2005, 08:06 PM
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I can't imagine there is a big calling for a device to protect against ejecting batteries. The CG issues would probably keep many from landing in one piece anyway. And the burnt up speed controller part as I said could be handled by a ParkBEC if somebody is concerned enough to want to protect against it.
Old Oct 06, 2005, 08:23 PM
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Party pooper. I was going to cut you in for half the profits but now... you're out.
Old Oct 06, 2005, 08:46 PM
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Quote:
Originally Posted by BrunswickOH
. The CG issues would probably keep many from landing in one piece anyway. .
Have you never landed a model with the pack dangling by its leads? The CG is way out of wack but it still controllable.
Old Oct 06, 2005, 09:01 PM
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difference between dangling and OUT OF PLANE
Old Oct 06, 2005, 09:09 PM
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If you really wanted to do this, here's what I'd do.

I can make you a 4.2v ParkBEC. Power your RX from that. Also, take a very small single cell Lipo and add a servo connector. Plug that into a spare channel like you would an RX pack. I'd suggest a Kokam 145. In operation, the parkBEC would keep the Lipo charged, and the lipo would power the servos in the event of a battery ejection. The whole setup would weigh about 11 grams and cost under thirty bucks.
Old Oct 06, 2005, 09:11 PM
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Good idea, Mex!
Old Oct 06, 2005, 09:16 PM
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Quote:
Originally Posted by Comatose
If you really wanted to do this, here's what I'd do.

I can make you a 4.2v ParkBEC. Power your RX from that. Also, take a very small single cell Lipo and add a servo connector. Plug that into a spare channel like you would an RX pack. I'd suggest a Kokam 145. In operation, the parkBEC would keep the Lipo charged, and the lipo would power the servos in the event of a battery ejection. The whole setup would weigh about 11 grams and cost under thirty bucks.
Thanks but that defeats the whole idea of coming up with a brainstorm. I don't want to add a UBEC or a seperate receiver pack. I thought I came up with a good idea. Obviously NOT.
Old Oct 06, 2005, 09:19 PM
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Alternatively one could make a lipo cell that had charge circuitry built in which would run from 5v to keep the single lipo cell charged, and then have a diode or other circuitry to allow the cell to provide power in the event of a power failure. That'd be pretty doable too, but significantly less off-the-shelf than a 4.2v ParkBEC.

Either way what you suggest is both possible and plausible. I'm not sure how often batteries are violently ejected (not often for me, YMMV), but I could see it being saleable as a general purpose safety device in case of any power failure.

*edit*
But you already are adding a separate reciever pack, its just a capacitor instead of a battery. A cap that can power servos for any length of time is going to be heavier and more expensive than carrying around a truly tiny RX pack which wither way would charge from the onboard power just like a cap would. I can see the value of building that into an RX for sure, I just don't make RXes and wouldn't want to have to buy another one to add the feature.
Old Oct 06, 2005, 09:26 PM
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OK, ok. I get it. You are not big fans of my idea,
Old Oct 06, 2005, 09:36 PM
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Actually I liked it. If you think of the little lipo cell as a capacitor, then I'd even consider putting it into production. The problem with a normal capacitor is it just doesn't have enough juice. If you say that "normal" servo current is about 100ma, then the big cap on a castle P25 would give you about 5 milliseconds of servo power. So to do it with a real capacitor would take a quite large cap. Like, five Farads large. For reference, that would be five thousand of the largest capacitor on my desk in parallel.
Old Oct 06, 2005, 09:50 PM
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Deletedfor proving Nauga wrong
there was a case posted of a plane ejecting its battery while set for high throttle... and the windmilling prop had the (brushed) motor acting as a generator... allowing a controlled landing. (fortunately he didn't have a major CG change...)

But.. it really is best to just be CERTAIN the battery can't eject.

If you want a backup power supply.. try a flexible solar cell.
Old Oct 06, 2005, 10:15 PM
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Quote:
Originally Posted by Comatose
Actually I liked it. If you think of the little lipo cell as a capacitor, then I'd even consider putting it into production. The problem with a normal capacitor is it just doesn't have enough juice. If you say that "normal" servo current is about 100ma, then the big cap on a castle P25 would give you about 5 milliseconds of servo power. So to do it with a real capacitor would take a quite large cap. Like, five Farads large. For reference, that would be five thousand of the largest capacitor on my desk in parallel.
Then how about a tiny watch or camera battery?


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