Working on a Hexapod...

I hope this is the right part of the forum to post my question... I'm working on a small hexapod project as my first "formal" arduino build.

The basic platform it's going to run 18 servos controlled with a Pololu Micro Maestro and powered by a small 7.4v 1500mah LiPo pack (I'm going to use a step down regulator for the servos adjusted to 5.5 volts, the Micro Maestro can be powered straight from the LiPo).

The main microcontroller will be a Nano powered by a separated small 7.4V 360mah LiPo... for input I'm planning to use a SHARP IR Ranger Sensor (if I can get it to work fine for V2.0 I'm will be using 2 IR sensors to generate a stereoscopic location effect) and 2 micro switches placed at the end of the front legs (to detect any obstacles that maybe are too low for the IR sensor to know that something it's there), for data output I will be using a UART wireless transceiver to connect with the computer and on some point another arduino board on a remote location (second project! some sort of portable terminal that can be used with the hexapod and any other future automatons), and I have a small OLED color display that will provide details on the hexapod status (displaying communication and sensor status, plus possible errors on the micro maestro).

At this point I have already tested the wireless transceiver and the display! I'm going to start working on the connection between Maestro and arduino tomorrow, buuuuuuttt.... there are a couple of questions that I want to check before keep moving forward:

First, can I use my Arduino*UNO* to check all the connections and then when all the details and coding is ready send all to the NANO?

Second, Can I connect the VCC of the display and wireless to the 3v3/+5V pins on the NANO or should I use another step down regulator to power them and let the NANO alone (the microcontroller and this regulator will be powered by the 360mah LiPo)

Third and last question, Did I'm correct to assume the all the GND pins should be common?

Thank you for your advice on my project!

MrFus: First, can I use my Arduino*UNO* to check all the connections and then when all the details and coding is ready send all to the NANO?

Yes, that should work. The Nano 3.1 uses the same ATmega328P processor as the UNO. The SMD version of the chip has two additional analog inputs (A6 and A7) but if you ignore those, the pins are all the same as on the UNO.

MrFus: Second, Can I connect the VCC of the display and wireless to the 3v3/+5V pins on the NANO or should I use another step down regulator to power them and let the NANO alone (the microcontroller and this regulator will be powered by the 360mah LiPo)

You can draw a few hundred mA from the +5V pin without any problem. I'm not sure how much 3.3V power you can get from the Nano's FTDI chip but it is probably down around 50 mA.

MrFus: Third and last question, Did I'm correct to assume the all the GND pins should be common?

Yes.

Nano schematic shows UA78M05 regulator, good for 500mA. Actually achieving that will depend on Vin - I doubt anything over 7.5V in will yield close to 500mA out. FTDI chip is good for 50mA.

Nano can also be bootloaded as an Uno; doing so would make performance identical between the two.