Simple system PSU for a robot

[AleRoss]

Hi guys!

First off, this is my first post so, hello world 

I make robots in my school, we design them from the very basics stuff so i was thinking about the power supply unit. The robot should be made of four boards, three of which, stacked together: the bottom unit (which has many sensors and signals), the power supply unit and the logic unit (we use an FPGA module to develop on a zynq platform).
Since we use many expensive components on each of theese two boards, and change often the fourth board (which is on the front), i'd like to make the power supply smart enough to detect shorts and rail voltage. I'd also like to branch the 5v rail in multiple ones, and monitor them.
It is a very ambitious project, especially for a beginner like me, anyone that want's to follow me in this adventure?

So here is what i've thought so far:

The FPGA Module (Microzed) has already all the linear, low-dropout regulators the fpga needs so i don't need to desing such a complicated stuff.
If i make this smart enough, i can report back to the FPGA the status of the rails, so i was thinking about implementing a standalone TI TM4C123GH6PM microcontroller which has plenty fo processing power and memory to accomodate my needs, plus i already own a developement board for it  . This uC has a 12bit 12channel ADC that would be sufficient to read rail voltage and maybe to read the .1 Ohms sense resistors i want to try. About sense resistors, i would really like to avoid opamps, while easy and logic to use here, they would add complexity to the whole thing and i am really trying to to keep it simple. To detect overcurrent i just need to sense .5, 1 and 2 amps on the rails and with a 1v reference, i can go far beyond that. I've made some math on this



The battery im going to use will depend on the voltage of the motors, but i'm planning to use a 3 cell lipo with a voltage of 11.1v. I need 4 rails of 5v@1.5A, so i need to handle 7.5W!!
I really like the easy of use, stability, of the noise-free 78XX regulators, howerver a bit of math reveals to me that i can't power 3 servomotors (for a grabber on top of the robot), the FPGA and all the sensors with thoose. I can source 300mA at 30 °C, 11.1 v in, 5v out, without heatsink. The room for the board is not small, so i can count on a bit of surface, however i might also consider to seal this power supply and i will enclose it for sure, so little airflow is granted.
I don't want to mess around with components i'm not confident about, so i won't design a switching supply. Sparkfun sells a DCDC Converter (https://www.sparkfun.com/products/9370), i might use that, any advice? any other solutions? where can i buy more reliable dcdc converters?

I'm asking myself how to switch the rails when there's a fault condition, maybe i'll have something for tomorrow.. Let me know if this project is interesting and excuse me for the chinglish, i have made tons of errors for sure.

Alessandro,
Italy