Wiring 7.4V LiPo, 5V UBEC and motor controller

I'm building an arduino UNO R3 based robot.

Based off a great recommendation I received off this forum I've ordered a 4000mah LiPo battery to power the bot.

I plan to split the LiPo output into two branches.
a. Full LiPo voltage to Vbatt on my motor controller.
b. input to 5A, 5V UBEC

Then from the 5V UBEC output I supply two different busses:
a. Sensor/servo bus powering two servos and a ping sensor
b. Vcc bus powering the Arduino and the motor controller

In order to avoid inefficiencies of the onboard Arduino linear voltage regulator I plan to wire the 5V Vcc bus into the Arduino 5v pin (thanks cr0sh).

As I've started to think about the build I'll be making this weekend I'm wondering if I need any conditioning circuitry before i wire power into the Arduino 5v pin. With the servo power demand constantly changing I'm wondering if this will/could cause voltage variances for the Vcc bus.

What do you guys think, and do you have any recommendation for a power conditioner if you think it's required?

Just for clarity I've added the "ASCII graphic" of my circuit

2S LiPo------------------------------motor cont
|
|
5V UBEC
|
|-----------------Vcc bus
|
|----------------servo bus

zacstaples:
What do you guys think, and do you have any recommendation for a power conditioner if you think it's required?

At most you will need an additional decoupling capacitor(s) across 5V/GND on the Arduino. ~47uF electrolytic, but don't be afraid to play with other values.

http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

Is the BEC switch mode or linear?

I'd strongly advise against sharing power between servos and Arduino, provide the LiPo
voltage to the power jack on the Arduino and use the BEC for just the servos. The on-board
5V regulator on the Arduino can power the ping sensor I think (check the numbers though).

I'd also add a suitable fuse between LiPo and Arduino (fast blow). Check if the BEC has an
input fuse too.

LiPo's can generate HUGE currents, fuses are important.

Chagrin, I appreciate the link for de-coupling the power supply. You recommend the 47uf electrolytic which the link explains will cut out the low frequency noise.

I'm not sure what kind of noise the servos will create, but do you think I need to worry about the high freq noise too?

MarkT,
the UBEC is switch mode. I'll include the fuse as you recommend.

The UBEC is (or should be) already designed to keep noise on its outputs to a minimum. If additional decoupling is needed you're only going to be able to figure that out by experimenting.

Chagrin...good point. The need to experiment is what is supposed to make this hobby fun, right?

I'll run the output from the UBEC into an ADC for a while and take some logs to make sure it keeps right at 5V before I used the output to power the Arduino. I'll repost here to let you know how it goes.

I appreciate the quick support. I hit you with a karma point.

Zac