Using analog pin to read voltage > 5v

Projects General Guidance
1

Hey guys

I want to make a battery voltage reading device for my model aircraft batteries using an arduino pro mini.

Iv made a voltage sensing unit before but for obvious reasons it cannot take readings above 5v. Great for checking where my single cell 4.2v/3.7v batteries are at but that's about it!

What sort of circuit would I need in front of an Analog pin to allow me to take readings between 0v and 18v?

What other considerations would I need to make when making this device?

Thanks!

Jasper

2

You could use a R voltage divider to tap off a max of 5v when peak voltage is applied.

Weedpharma

3

Hi Horendus.
You talk about 18volt, so I assume you have a 4-cell LiPo battery. 4x4.2volt = 16.8volt max.
A simple two-resistor divider, e.g.10k to ground and 24k to +batt, does the trick.
Make sure you disconnect this circuit from the battery when not in use, otherwise it will drain the battery over time.
Leo..