By David Sandoval
Updated Aug 30, 2022
In electronics, a simple voltage divider can safely step a 12‑volt supply down to 5 volts. By applying Kirchhoff’s Voltage Law, the voltage drops across each resistor sum to the supply voltage, allowing you to extract the desired level.
Cut two pieces of insulated wire. Strip about ½ inch of insulation from each end. Confirm that the power supply is switched off before proceeding.
Twist one end of the first wire to one lead of the 1.4 kΩ resistor. Connect the free end of this wire to the positive terminal of the power supply.
Twist the free lead of the 1.4 kΩ resistor to one lead of the 1 kΩ resistor. This junction will become the 5‑volt output.
Twist the free lead of the 1 kΩ resistor to one end of the second wire. Connect the loose end of this wire to the negative terminal of the power supply. Double‑check all connections before powering the circuit.
Turn on the power supply. Set your voltmeter to DC volts. Place the black probe at the junction between the 1 kΩ resistor and the second wire, and the red probe at the junction between the two resistors. You should read approximately 5 V, confirming the divider works as intended.
The output voltage is calculated by the divider formula:
Vout = Vin × R2 / (R1 + R2)
With 1.4 kΩ for R1 and 1 kΩ for R2 and Vin = 12 V, the result is 5 V.
Choosing high‑accuracy metal‑film parts ensures the output stays close to the intended 5 V even with power‑supply variations.
Always disconnect the power before making or altering connections. Verify the output voltage before connecting sensitive electronics.
A 1.4 kΩ and 1 kΩ resistor pair form a simple, accurate 12 V to 5 V divider. Metal‑film resistors keep the tolerance within 1 %. Follow the steps to safely build and test the circuit.
