Voltage divider

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Calculate the output voltage from two resistors in series, or find R2 given the desired Vout. Shows total current and power dissipated.

Vout = Vin × R2/(R1+R2) Find R2 from Vout E12 recommended

Parameters

Modes

Input voltage Vin (V)

R1 (upper)

R2 (lower)

12V → 3.3V (ESP32)

R1=68k, R2=27k → Vout = 12×27/(68+27) = 3.41 V. Close enough. Current: 126 µA, negligible.

Battery voltage sensor

Batteria 4.2 V LiPo, ADC max 3.3 V. R1=10k, R2=22k → Vout = 4.2×22/32 = 2.89 V. Dentro range.

Digital volume potentiometer

With fixed R1+R2 and variable wiper you simulate the divider. Output voltage proportional to position.

What is a voltage divider?

Two resistors in series between Vcc and GND. Output: Vout = Vcc × R2/(R1+R2).

How to divide 5V to 3.3V?

Ratio = 3.3/5 = 0.66. With R1=10kΩ: R2 ≈ 19.4kΩ → use 18kΩ (E24).

How to divide 12V to 5V?

Ratio = 5/12 ≈ 0.417. With R1=15kΩ: R2 ≈ 10.7kΩ → use 10kΩ or 11kΩ (E24).