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Old Nov 07, 2002, 12:36 PM
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Redmond, WA
Joined Nov 2002
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BEC == Voltage Regulator?

OK, finally received my Voyager, Hacker B40 + Kontronic controller. Reading the Kontronic manual, it says not to use the BEC for cell count of 9 or 10 (which is what I want to run on).

Can I make a BEC out of a voltage regulator?

Specs from a radioshack voltage regulator (from RS site)
"Overload protected. Rated 1 amp (heat sink required). 35VDC maximum input. TO-220 case. Type: 7805; Output: +5VDC"



Also, I hear of a ultimate BEC, uBEC. What does this provide over my idea of building a BEC with a RadioShack regulator?

Thanks in advance!
-Andy
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Old Nov 07, 2002, 01:34 PM
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Mountain View Moffett Fd, California, United States
Joined Apr 2001
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Yep. Most BECs are just 5V regulators.

Although you can use a linear regulator (7805), you need one that can handle more watts. The problem is that if the difference in the regulated voltage (5V) and the supply voltage (12-16V) is too high, the regulator will overheat and shut down. That's why they put a restriction on the number of cells on BECs.

The UBEC uses a much more efficient regulator and doesn't have this problem.

If you want to use a linear regulator, get a beefier one (3A) and be sure to put a good heat sink on it.

BTW, I use a separate 1050mAh NiMH battery on my Voyager.


--jim
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Old Nov 07, 2002, 02:59 PM
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Chicago
Joined May 2002
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Homemade linear reg

If you want to build a linear regulator yourself, here's some instructions; http://www.ikarus-modellbau.de/ubbth...b=5&o=&fpart=1

Greg
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Old Nov 07, 2002, 03:27 PM
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MD
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Andy,

Yes, you can make one. I will be making one from R.S. 7805 (+5V) with the heat sink and two capacitors. I have not yet eitch the pc board; but, I have design a layout on the computer already. It should handle the micro to mini servos plus the receiver without a problem. If you are looking at a higher voltage +6V, use the LM7806.

I am also looking at making the 3A switching voltage regulator.
This is more efficient but, the parts are higher in cost. I don't have the parts yet.

Steve
www.erols.com/onon
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Old Nov 07, 2002, 03:46 PM
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Cary, NC
Joined Sep 2001
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For ten cells, at 1A, you'll have about 5-7W of loss in a linear regulator. That's quite a bit in a TO-220 package unless it has good heatsinking. As Jim suggested - use one with a higher current limit and a higher junction temp rating. And HEATSINK IT. If the regulator shuts down, you'll lose your Rx response.

The UBEC uses a switching supply, which provides better efficiency - probably 80-85%, versus the 30-50% you'd get with a linear supply.

I've designed a 3A (continuous) switching supply for my e-Raptor 50. It's still on paper now, but I'll have the parts and PCB's in a week or so. Aside from the 3A of Rx power, it also provides 0.5A @ 12V for a motor cooling fan. I even added the circuitry to switch the 12V on and off from the Tx. I don't know why I'd want to turn off the cooling fan, but I figured it'd be neat to have the option. Plus - maybe I can power something else from that 12V output on another model. I'll have 9 PCB's, so I'll certainly be able to build more than one of these. I'm anxious to get my "enhanced" BEC together and test it. It oughtta work, since I design power supplies for a living!

KC
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Old Nov 07, 2002, 04:20 PM
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Redmond, WA
Joined Nov 2002
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Thanks for all the info

So it looks like I'll suffer from inefficiency with Radioshack regulators. I'd hate to suck up battery power just to heat up a heat sink.

So, to servos work consistently with different voltages (assuming enough current) on their power leads? i.e. is the turn rate different at 4.5 vs 5V?

-Andy
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Old Nov 07, 2002, 04:42 PM
1.21 Gigawatts!
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Irvine, CA, USA
Joined Oct 2000
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KC,

Any chance of you publishing your design or selling it as a kit for those who likes to tinker?

Thanks,

Stephen
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Old Nov 07, 2002, 07:15 PM
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In Heli Wonderland
Joined Aug 1999
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With a simple BEC, you don't need a CB. Just mount the reg's to a heatsink and solder on the wires and caps.

If you want a really nice BEC, check out the UBEC at

http://www.koolflightsystems.com/ultimatebec.htm
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Old Nov 07, 2002, 08:03 PM
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Cary, NC
Joined Sep 2001
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Quote:
Any chance of you publishing your design or selling it as a kit for those who likes to tinker?
I have a completed schematic, bill of materials and PCB layout - I just need to order the boards and parts, which I'll probably do on Monday. Thus by the following week I should have a board together and running.

Once I'm sure the design works properly (which I'm confident that it will), I'll publish the design for all you electronics geeks out there. There's not much to it really - a couple of buck supplies, some logic, ESD & surge protection and some filtering to mitigate conducted emmissions and susceptibility. And I managed to fit it all onto a 1.1" x 2.5" 2-layer board.

In addition to publishing schematics & such, I'll also be willing to sell off some of the raw PCB's (boards with no parts on them). I have to order a minimum number, so I'll have some extras. I've etched my own boards in the past, but got tired of the hassle. Now I prefer to let someone else make the boards now.

KC
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Old Nov 07, 2002, 08:09 PM
1.21 Gigawatts!
Steph280's Avatar
Irvine, CA, USA
Joined Oct 2000
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Count me in on the PCB, I will try to build a couple.

Thanks.

Stephen
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Old Nov 07, 2002, 10:41 PM
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Cary, NC
Joined Sep 2001
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As soon as I've tested my BEC out, I'll post about it.

And I'll save a couple of PCBs for you, Stephen...

KC
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Old Nov 07, 2002, 10:53 PM
The effect is sadly temporary
Hippo's Avatar
Ann Arbor, Michigan
Joined Oct 2001
1,677 Posts
You guys are doing it the hard way...

Just buy an extra GWS 2 Amp speed control. (They're really cheap, and only weigh 2 grams...) Then just cut off the motor lead. That's it. Done. BEC in one step.

I guess I'm just lazy.
-Dan
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Old Nov 07, 2002, 11:04 PM
2013 GRAND SPORT CORVETTE
Hoverup's Avatar
Golden Gulf Coast
Joined Jul 2002
10,202 Posts
Dan - Seems like the most elegant solutions are often the simplest things right under our noses. Sounds like a great idea. Good on you.
Cheers - Boyd
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Old Nov 07, 2002, 11:13 PM
RPV builder & operator
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Canada, QC, Gatineau
Joined Jan 2001
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Nice try Hippo, but the GWS ESC can only take up to 8 cells.
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Old Nov 07, 2002, 11:18 PM
The effect is sadly temporary
Hippo's Avatar
Ann Arbor, Michigan
Joined Oct 2001
1,677 Posts
Oops.

I guess I should read things a little closer before I open my big mouth.

Sorry.

Good Luck,
-Dan
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