basic electronics power question

hey guys im trying to follow the steps in this instruct-able in this circuit design he I think uses 2 different power sources one for the motors one for the board

So I was hoping to use 2 3.6 volt batteries in Series to power it all im wondering what the best way is to then split that power for the arduino the motor drivers ?

The problem with motors is that they generate interference that can reset the Arduino. One way to reduce the interference getting into the Arduino is to have separate power supplies. Another way is with proper supply decoupling.

Hint:- never try and learn stuff off an Instructables they are mainly crap. Unless you can spot the author's mistakes then steer clear of them.

if I have two different power supplies do I join there grounds or not ?

if I have two different power supplies do I join there grounds or not ?

Only join the grounds if you want it to actually work.

thanks one other question if I needed say a 3.7 volt battery to do something is there any reason that using 3 in parallel in series is a bad idea hoping to increase range and time between recharging is needed ?

When you say 3.7V I assume you are wanting to use LiPo's. If so I would forget the circuit and take a serious read on the safety side and charging of Lipo's before you decide how to connect them

Was planning to use one of these

Im aware i should charge each one separately