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Old 07-01-2014, 04:14 PM   #1
geb
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Default voltage regulator for retracts

Greetings,

I am considering a pair of E-flite 10-15 size electric retracts for use in a Spitfire project. The retract specs limit their voltage to 7.4 (I.E., a 2 cell battery) and (of course) I had been planning on using a 3 cell battery (11.1 volts) for the additional power and weight. Is anyone aware of a convenient, ready made voltage regulator to use between a 3 cell battery and the retracts so they get their required diet of 7.4 volts?

Thanks for any help offered.

Gary
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Old 07-01-2014, 04:18 PM   #2
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Originally Posted by geb View Post
Greetings,

I am considering a pair of E-flite 10-15 size electric retracts for use in a Spitfire project. The retract specs limit their voltage to 7.4 (I.E., a 2 cell battery) and (of course) I had been planning on using a 3 cell battery (11.1 volts) for the additional power and weight. Is anyone aware of a convenient, ready made voltage regulator to use between a 3 cell battery and the retracts so they get their required diet of 7.4 volts?

Thanks for any help offered.

Gary
any cheap BEC should do it, would limit the voltage to normal sevo output and for the amount of time you are going to run them should be fine. Other wise if you don't want ready made you could wire up some voltage regulators pretty easily into the power line

http://www.headsuphobby.com/3-Amp-Un...UBEC-G-150.htm
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Old 07-01-2014, 04:49 PM   #3
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Or just use a UBEC, like from Castle Creations. I never thought UBECs that way, but that's all they are is voltage regulators.
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Old 07-01-2014, 05:48 PM   #4
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Originally Posted by geb View Post
Greetings,

I am considering a pair of E-flite 10-15 size electric retracts for use in a Spitfire project. The retract specs limit their voltage to 7.4 (I.E., a 2 cell battery) and (of course) I had been planning on using a 3 cell battery (11.1 volts) for the additional power and weight. Is anyone aware of a convenient, ready made voltage regulator to use between a 3 cell battery and the retracts so they get their required diet of 7.4 volts?

Thanks for any help offered.

Gary
Out of curiosity, what are you using for receiver/servo power? If your BEC uses a switching (uBEC or SBEC) type of regulator, that should power both the receiver/servos and your retracts just fine.

DennyV
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Old 07-02-2014, 03:31 PM   #5
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Default Voltage reg,/ retracts

I had planned on using an Electrifly Rimfire .10 paired up with their 35 Amp ESC,which apparently contains a "BEC", and a 2200 Mah 3 cell pack. I had planned to use a Spektrum AR6210 receiver. As I am rather new to electric flying, I had not fully considered the functions of the ESC in regulating the voltage to the receiver.
So it looks like the retracts should be fully protect from excess voltage by the BEC within the ESC.
Thanks to all for your responses. Very helpful.

Gary
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Old 07-02-2014, 05:07 PM   #6
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Originally Posted by geb View Post
I had planned on using an Electrifly Rimfire .10 paired up with their 35 Amp ESC,which apparently contains a "BEC", and a 2200 Mah 3 cell pack. I had planned to use a Spektrum AR6210 receiver. As I am rather new to electric flying, I had not fully considered the functions of the ESC in regulating the voltage to the receiver.
So it looks like the retracts should be fully protect from excess voltage by the BEC within the ESC.
Thanks to all for your responses. Very helpful.

Gary
Can someone answer if the electrify BEC uses a linear regulator?
if so IMHO a linear regulator might be marginal in this application.

Thanks

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Old 07-02-2014, 11:00 PM   #7
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My Parkzone Spitfire MkIX uses those retracts. Each one has a standard servo plug and connects to the receiver, using a Y cable.
The voltage they receive, will be the same as for any other servo, from your Rx.

The BEC in most ESC's, is designed to drive 3 servos. By adding electric retracts, you are asking it to drive the equivalent of 5 (or more).

My own retracts proved problematic with the original ESC, possibly due to insufficient power.
Retract spec states current draw @ 5mA (idle), 200mA (stall), which actually sounds reasonable - although that is doubled for 2 wheels.
The Spitfire BEC (EFLA1030) is rated at 700mA, so with retracts, that only leaves 300mA for driving the 4 servos onboard.

I recently bought a 6A UBEC to provide more power, to avoid receiver brownouts.
Havent had a chance to fit it yet but should be trying it this summer.
I just need to decide whether to use a separate Rx battery, or wire it to the main LiPo.

Current hangar: Cessna 182, Cessna Skymaster, PZ Spitfire MkIX. ASW-17, Kalt Whisper.
Micro: Blade mSR, Blade mCPx, Sukhoi 26XP, T-28 Trojan, Beast, Stryker, Carbon Cub, Spitfire, Mustang.
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Old 07-04-2014, 03:37 PM   #8
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Default Retracts / Voltage Reg.

Sparky 1963,

Thanks for your response re: your experience with the ParkZone Spitfire. I would be very interested in hearing how the 6A UBEC works. My Spit is still under construction. I had been waiting to join the wing panels to the center section pending a retract decision, I.E; determining dihedral angle to work with the selected retract. These retracts (E-flite) seem like the best option when considering the difficulty of duplicating the real thing.
I got interested in the E-flites after speaking with a U-control flyer this winter who used them very successfully on several stunt ships.
B.T.W., how does the ParkZone Spitfire provide cooling air to the motor and ESC? As you are no doubt are well aware of, the Spitfire had a very,very aerodynamically clean fuselage, thus leaving no opportunities for cooling air intakes, but oh, what a beautiful aircraft!!

Thanks for your input,

Gary
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Old 07-04-2014, 08:52 PM   #9
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Originally Posted by geb View Post
...I would be very interested in hearing how the 6A UBEC works...
Gary
In gas engined models, a dedicated receiver battery provides the correct voltage and adequate current, for receiver and servos.
With an electric model, having a BEC (Battery Eliminator Circuit) built into the speed controller, eliminates the need for a separate receiver battery,
by providing a regulated supply - but is usually limited in how much power is available.

A universal BEC does the same job but it is a separate item, not built into the ESC.
In addition to providing a reduced/regulated voltage for the receiver, it can provide higher current, to drive more, or bigger, servos.

Apart from weight considerations, there's nothing to stop you using a dedicated Rx pack, in addition to the flight pack.
You only need a UBEC, if you want to power the receiver from your flight battery, where the voltage needs to be dropped.
When you use a UBEC, it needs to get power from somewhere. This can either be a separate LiPo pack, or connected to the ESC battery wires.

Where the servo wire runs from ESC to receiver, you need to cut the red wire (or pull out the pin and insulate it), so there's no conflict between the 2 devices.

*
Originally Posted by geb View Post
B.T.W., how does the ParkZone Spitfire provide cooling air to the motor and ESC?
...no opportunities for cooling air intakes, but oh, what a beautiful aircraft!!
Gary
Certainly is a nice looking aircraft.. the pride & joy of my collection
A decent model spitfire has been on my wishlist, since I could say 'airplane' - lol.

The cowl behind the spinner, is completely open. There isnt much of a gap but it should be enough to allow some air movement, to cool the motor.
However, there is a solid bulkhead between motor compartment and radio bay, so none of that air will reach the battery/ESC.

I was initially concerned about lack of cooling but I trust that Horizon did their maths (and product testing) properly and got the ratings right.
Even so, I would be unwilling to fly around at full-throttle, and risk heat-related consequences.

ESC is tucked tightly into the surrounding foam, under forward turtledeck - and sitting directly above the battery (the last place you really want a toasty hot-spot).
There's very little option for providing cooling in that position, without ruining the appearance of the model.
The ESC is a small flat PCB, wrapped in sleeve, with no apparent means of disssipating heat (heatsink fins etc).
The motor wires are long enough to move the ESC back into the radio bay, rather than stuck in an insulated hole.

You could create an air inlet, by drilling thru the battery bay floor, into the small scoop under the wings - this mod wouldnt be visible externally.
It probably wouldnt help though, without a corresponding outlet for airflow - which would mean piercing the fuselage somewhere.
I'd be worried about increased air pressure conceivably blowing the hatch off.

Current hangar: Cessna 182, Cessna Skymaster, PZ Spitfire MkIX. ASW-17, Kalt Whisper.
Micro: Blade mSR, Blade mCPx, Sukhoi 26XP, T-28 Trojan, Beast, Stryker, Carbon Cub, Spitfire, Mustang.
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Old 07-04-2014, 10:58 PM   #10
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Originally Posted by geb View Post
Sparky 1963,

Thanks for your response re: your experience with the ParkZone Spitfire. I would be very interested in hearing how the 6A UBEC works. My Spit is still under construction. I had been waiting to join the wing panels to the center section pending a retract decision, I.E; determining dihedral angle to work with the selected retract. These retracts (E-flite) seem like the best option when considering the difficulty of duplicating the real thing.
I got interested in the E-flites after speaking with a U-control flyer this winter who used them very successfully on several stunt ships.
B.T.W., how does the ParkZone Spitfire provide cooling air to the motor and ESC? As you are no doubt are well aware of, the Spitfire had a very,very aerodynamically clean fuselage, thus leaving no opportunities for cooling air intakes, but oh, what a beautiful aircraft!!

Thanks for your input,

Gary
In case you are interested in the "Linear vs Switching" type of BEC's (Battery Elimination Circuits), take a look:

BEC Linear Current Rating
http://www.wattflyer.com/forums/showthread.php?t=63779

As quoted from the above thread, those switching type voltage regulators are exactly that. These units are used all over the place, from cell phone chargers, computer power supplies, a number of "Wall Wart" chargers, televisions, the list goes on and on.

"How these uBEC's work is a little involved, but basically their internal parts are never in their "linear mode". Just think of taking a toggle switch, put it in series with a 20 Volt battery and a light bulb. Then switch it on and off with exactly a 20% on, 80% off cycle. At 100,000 times per second. (Difficult with a toggle switch, easy with electronic switching) So, with a little electronic smoothing circuitry, your output voltage would be that 20 VDC times 20/80 or 5 VDC. That switch will never get hot, since it is either a dead short (no heat) or open circuit (again no heat)".

DennyV
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