Learn to monitor and control your home & environment with self contained, inter-communicating microprocessors. Arduino / Raspberry Pi Applications include ham radio, robotics, weather stations, model railroading, toys and more. - KK4HFJ
A Voltage Divider is a simple circuit for dividing a higher voltage into a lower voltage without cumbersome transformers, etc. The example shows the proper values of two resistors (in ohms) for obtaining 12v from 120v. Using the formula and calculator below, you can adjust the voltage in, and resistance values, to get the output you desire.
If Vin = 120v, R1 = 9000 Ohms, and R2 = 1000 Ohms: