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Old Dec 28, 2008, 04:27 PM
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Spektrum receiver with futaba servos

I'm just getting into RC and will be buying my first radio, receiver and servos soon. I don't know much about this stuff yet.


I'm going to be buying a Spektrum DX6i because its tested to work with an endurance PCTx.
Being that I see that Futaba offers a lot more servos. Is there a bottle neck going with Spektrum because of the servos or can I just use any of Futaba servos including the digital ones using a Spektrum receiver AR7000 DSM2 or AR9000 DSM2.

Sorry for the stupid questions... If im asking them.
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Old Dec 28, 2008, 04:36 PM
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Sunnyvale, CA, USA
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Futaba servos will work just fine. You will have to trim a little plastic off the connectors to get them to fit - that's all.
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Old Dec 28, 2008, 04:38 PM
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This thread might be of some assistance.

Bill
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Old Dec 28, 2008, 08:43 PM
John,not Zerts.JOHN, NOT Zerts
USA, AZ, Chandler
Joined Nov 2007
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I tried Futaba S3114's instead of Hitec HS-55's but the have a jittering problem occasionally...but not bad enough to cause any crash yet. I am going to stick with Hitec in the future.
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Old Dec 28, 2008, 11:40 PM
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Triming tabs

Thanks for the great reply everybody... Trimming the tabs sound like a good plan...

Ok...one more rookie question regarding system power.

I've looked at combo packages that have a motor, controller, and battery pack. This sounds fine "but" and this sounds dumb... does the receiver and servos typically draw there power from one main battery pack or are systems separated by main motor, receiver and then servos.

Thanks again...
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Old Dec 29, 2008, 12:43 AM
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Sounds like you are going to use an electric motor for the power plant.

The controller, usually called the ESC (Electronic Speed Control) most often has a circuit called the BEC (Battery Eliminator Circuit). The BEC reduces motor battery voltage to (usually) 5 volts and powers the receiver and servos through the throttle port on the receiver.

But, (don't you love the buts? ) most BECs are inefficient linear regulators and, depending on the battery voltage, can only handle a limited number of servos. Because the excess voltage is dissipated as heat, the higher the battery voltage, the fewer servos allowed. The ESC spec sheets will tell you what they can handle. Most park flyers and small models use the ESC BEC for RX and servo power.

In your OP you indicated you will be using AR7000 and AR9000 RXs which suggests that you are considering larger models with heavy servo current demands. In that case, you probably should use a separate 5 cell NiMh RX battery or a separate switching BEC. Switching BECs are more efficient and can handle greater loads than the BEC typically found on the ESC. An example of a separate BEC is the Dimension Engineering Sport BEC. There are others, of course.

Bill
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Last edited by ebill3; Dec 29, 2008 at 12:48 AM.
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Old Dec 29, 2008, 11:06 AM
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Thanks ebill3.

Ok I think I understand... "depending on the ESC" I might be able to get 2 servos. With a separate BEC I could use one battery to drive the motor, receiver, and servos? I don't expect to have more than 4 servos. The other way is to use a separate 5 cell NiMh RX battery, which will just power the receiver and servos?

Ok, this is starting to get clear...however, how would you recommend I address the total power system. I'll most likely have 4 servos, one gyro. One FMA Co-Pilot, a video downlink like a black widow and one Blip camera controller.

I know it depends on the draw all these components have... But it's more of a general methodology that I'm looking for. I think I'll have the main battery driving the motor and one battery for the rest of the gear?

Am I correct? Is there a online tool that I can input all the power demands, to kick out the best match for battery model, size and brand?

Thanks again everybody.
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Old Dec 29, 2008, 03:17 PM
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Quote:
Originally Posted by GradGuy
Thanks ebill3.

Ok I think I understand... "depending on the ESC" I might be able to get 2 servos. With a separate BEC I could use one battery to drive the motor, receiver, and servos? I don't expect to have more than 4 servos. The other way is to use a separate 5 cell NiMh RX battery, which will just power the receiver and servos?
Yes.
Quote:
Ok, this is starting to get clear...however, how would you recommend I address the total power system. I'll most likely have 4 servos, one gyro. One FMA Co-Pilot, a video downlink like a black widow and one Blip camera controller.
A 2400 mAh 5 cell NiMh battery or Castle Creations BEC.
Quote:
I know it depends on the draw all these components have... But it's more of a general methodology that I'm looking for. I think I'll have the main battery driving the motor and one battery for the rest of the gear?
Your choice. Some opt for the separate battery, others for a BEC. I prefer the separate battery, but there are pros and cons for both.
Quote:
Am I correct? Is there a online tool that I can input all the power demands, to kick out the best match for battery model, size and brand?
Not that I am aware of.

Bill
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Old Dec 29, 2008, 08:16 PM
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Thanks...

How does one go about calculating / figuring the total power draw to select a battery? I.E. what reading on the equipment do need to know volts, amps... and how do I total their values so it relates to the meaningful demand on a battery?
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Old Dec 29, 2008, 09:20 PM
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Thanks...

How does one go about calculating / figuring the total power draw to select a battery? I.E. what reading on the equipment do need to know volts, amps... and how do I total their values so it relates to the meaningful demand on a battery?
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Old Dec 30, 2008, 08:21 PM
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The problem is, almost nobody publishes normal and stall current ratings for servos. So you end up having to go with other peoples experiences or buidl your own.

Rxs draw max 500 mA.

Something like an Eagle Tre logger can measure actual current draw during flight.
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