Voltage 0-25V Sensor

A precision resistive divider that scales an input of up to 25V down into the 0-5V range an Arduino's analogue input can safely read, at a fixed ratio of 5 to 1. Simple, passive and reliable — it lets you monitor a 12V battery or a 24V supply without damaging the board. Two things to watch: there is no isolation, so both circuits must share a ground, and it is not suitable for measuring mains voltage under any circumstances. Extends Arduino analogue input to 25V safely; Fixed, predictable 5:1 division ratio; Passive design, no power supply needed; Ideal for battery and supply monitoring