Power output of brushles ESC BEC circuit? (castle creations tbird, if need specific)

[jafoca]

Hey,

I am about to start a DIY Radio System using XBee modules and arduino clones (ATMegas)

I want to power the arduino and Xbee from the BEC of the esc, but I can't find any kind of datasheet that says exactly what voltage is output from this circuit.

For my plane I am currently using an off-brand ESC, but if a specific one is needed, to know the exact output voltage, I have a Castle Thunderbird 36.

So... What is the voltage out from the BEC generally? My micro will be running at 3.3v so I need to interface between the two.

Thanks!

[Tomapowa]

Regardless what the ESC's BEC outputs, you will need a 3.3v regulator (output most likely is 5-6 volts.. normally closer to 5v... heck... measure it! :) ).

How much current do you need to power that "3.3v" device and it peripherals ?

How do you plan on powering your servos? (most need ~4-5 volts)

What distance (range) you plan to cover with this system?

Are those Xbee or Xbee Pro modules you are using...? ;)

[jafoca]

The device ;) has a built in regulator - my concern was that the output from the BEC would be too low, and then the on-board reg would have a voltage drop, which would result in feeding the micro and Xbee < 3.3v they need to run at.

I am not totally sure what current the device will draw, but I am using xbee pro which has a draw of ~300Ma at Tx - I am not too worried about this as the T-Bird's manual says it can source 3 Amp max.

I am planning to power the servos off of the BEC circuit too, before it is plugged into the micro-board.

I am hoping to get pretty good distance with it, 1km+, using external antennas. I am buying some cheapish 3.2 dBi rubber duckies to start with - possibly going patch down the line.

[Tomapowa]

The device ;) has a built in regulator - my concern was that the output from the BEC would be too low, and then the on-board reg would have a voltage drop, which would result in feeding the micro and Xbee < 3.3v they need to run at.

What has a built-in regulator? Your micro/board?
The ESC's BEC regulates its input to around 5 volts, so unless your micro/board has a built-in 3.3V reg, you'll need to add one. If your micro/board indeed has an onboard reg, then you'll have to check (specs) to see what's being used (reg chip type) and determine its minimum input voltage for supplying 3.3v on it's output. Most 3.3v regs should be able to output 3.3v consistently with an input of 5 volts.

[jafoca]

Yes, it is my micro / board that has a 3.3v reg built in.

To be specific, I am going to use this board as the xbee carrier / transceiver on both ends: http://www.nkcelectronics.com/funnel-io-remixed.html

I think that board is near perfect form factor for this application, aside from not having built in servo headers....

[jafoca]

Here is my RX / TX ;)

Nice and small, need to break out a magnifying glass to see what chips are on it tho!
http://jafoca.com/wp-content/uploads/2009/06/img_0274.jpg

[Tomapowa]

Cool gadgets! :D I forgot to mention.. I dug up the schematic for that carrier board and of course... the one part of concern (3.3v reg) does not have a part# near it... all the other parts are identified though... go figure (designator was either U2 or U3... or something like that). They also had some downloadable Eagle files (brd and schematic) but my version of Eagle appears to be too old so I can't review. Most likely it's something like this (good for 400-500mA): http://www.national.com/mpf/LM/LM2937-3.3.html

[jafoca]

Hehehe - it is cool, I was surprised about small it was.

Now I am trying to decide if I want to get a servo-shield PCB manufactured, or if I should just try to getto rig it with a breadboard....