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Old Aug 30, 2012, 10:59 AM
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FlyBoy20's Avatar
United Kingdom, Wales, Swansea
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Another electronics question..or three

Newbie has three questions..

1) Am I right to assume that an Rx has a transformer built into it to step down the multiple lipos voltage to say, the 6v which most Rx's and servos operate at, or is this the job of the ESC?

2) I was also wondering how many amps a micro-sized servo would pull, and the same question about an Rx at idle?

Manufacturers never seem to mention amperages in this connection.

3) If a10A ESC says it's UBEC is '5v/1A', is this the point at which it cuts the motor?
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Old Aug 30, 2012, 11:33 AM
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United States, FL, Monroe
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Quote:
Originally Posted by FlyBoy20 View Post
Newbie has three questions..

1) Am I right to assume that an Rx has a transformer built into it to step down the multiple lipos voltage to say, the 6v which most Rx's and servos operate at, or is this the job of the ESC?

2) I was also wondering how many amps a micro-sized servo would pull, and the same question about an Rx at idle?

Manufacturers never seem to mention amperages in this connection.

3) If a10A ESC says it's UBEC is '5v/1A', is this the point at which it cuts the motor?
Some info,
http://www.headsuprc.com/servlet/the...scfaq2011/Page
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Old Aug 30, 2012, 12:07 PM
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Thanks, but it says 'This page is not available for the store.'
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Old Aug 30, 2012, 12:46 PM
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United States, WA, Seattle
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The BEC portion of the ESC is what brings the lipo voltage down to 6v for the servos and RX. Battery eliminator circuit - that's what it does, eliminate the need for a separate battery to run those functions like is needed on a nitro plane. Ever wonder what an RX battery is? A small 4 or 5-cell NiXX battery plugged directly into the RX to feed it and the servos.

The ESC portion runs the throttle. This is where the LVC function is located. The LVC never should interfere with the BEC as the power to the RX and servo are ALWAYS needed.

They are 2 separate systems on the same 'board'. Don't get them confused. You can buy ESC with out a BEC, and a (U)BEC without an ESC.
I emphasize, 2 separate functions.

The current draw of servos can vary significantly depending on type and brand. This shows a few examples.
Peak Servo Current Tests
Unfortunately most servo manuf. don't post that info.

The current draw of an RX is very low. (but, leave your battery plugged in indefinitely and you'll still end up with a dead battery).
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Old Aug 30, 2012, 12:51 PM
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Thanks, but it says 'This page is not available for the store.'
Works here...
Are you using a computer?
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Old Aug 30, 2012, 02:21 PM
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The link for Heads Up also works fine for me and is a much more detailed look at the ESC and BEC functions. Well worth reading.
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Old Aug 30, 2012, 06:40 PM
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Yeah a typical ESC contains a BEC (battery eliminator circuit) but the typical BEC uses a solid state regulator, and no transformer. So-called switching BECs will have either an inductor or transformer, and they look about the same -- both have iron or ferrite cores.

You can figure around 0.25 amps for a typical parkflyer servo, but the current waveform is very noisy. .25 amps is the worst-case average, but narrow spikes go higher.
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Old Aug 31, 2012, 03:38 AM
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Originally Posted by FlyBoy20 View Post
Newbie has three questions.. .... 3) If a10A ESC says it's UBEC is '5v/1A', is this the point at which it cuts the motor?
No, it means that the "UBEC" built into the ESC supplies 5v to the receiver and is capable of supplying up to 1A current.

The correct term for the device in the ESC that supplies voltage for the receiver is "BEC", which stands for Battery Eliminator Circuit because it eliminates the need to use a separate 4.8v receiver battery. When a manufacturer calls it a "UBEC" or "SBEC" it generally signifies that it's a switching BEC (though one can never be sure with Chinese devices), which generates less heat while operating than a simpler, cheaper, linear BEC.
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