I have bought today, some buck converters instead of obtaining the p rail for the hc05 from the obd2 uart board which is feeding the hc. How can I neatly get the 3.3v from the Uart and is what I am doing better due to the loading of the uart ps? You can see what I am doing from my order for today. I am after a fast answer due to having placed my order.
No we cannot see what you are doing. If you could provide us with the part numbers or names it would really help us out.
I am using the hc-05 Bluetooth connected by jumper to sparkf OBD2-uart board. I am only missing the rail to the hc.
If I understand correctly I think you want a 3.3V step down converter, if you wire this to the 12V battery supply you should get the 3.3V you want.
The HC-05 module I used, had a 5V to 3.3V on board regulator.
If you have 5V available that is all you need.
I then used a SparkFun level shifter to connect 5V Arduino to the HC-05.