I am just getting started and I want to connect an ultrasonic distance sensor to an Arduino Nano and power it using a rechargeable battery. I've been looking about and there seems to be different options for powering the Nano but I like something like the Adafruit LiIon/LiPoly Backpack. I found this in relation to powering a Pro Trinket here.
The thing I am having trouble understanding is around the supply voltage. The supply from the board to the sensor seems to be 5V and the backpack has 3.3V. I am just making the assumption of using this backpack for illustration at the moment. Do you need a battery that can supply 5V? If so are there any recommendations for one that could fulfill the role?
The Nano needs either a regulated fixed 5v supplied to its 5v pin or around 8-12v on the Vin pin.
You can’t power it off 3.3v and expect to find 5v on the 5v output.
That pack is only suitable for some of the Arduino family that will run off a lower voltage ( such as the Trinket)
If you really need to use that same battery charger module, you would need a boost converter to convert the 3.3V it outputs to 5V for the Nano. The LiPo batteries I have seen are usually ~3.7V.
I understand Adafruit makes similar charging modules with built-in boost converters (like the PowerBoost). I'm sure similar modules are available cheaper online.
Or you could make your life easier and go for a 3.3V Arduino. If you want an easy transition from the Nano's code, you could use a 3.3V Arduino Pro Mini. They use the same chip. If you do plan on taking this approach, make sure your proximity sensor can run on 3.3V.