Resources · Interactive tool

Voltage Divider Designer

The turbidity sensor produces a nominal 0–4.5V signal. An ESP32-S3 uses a nominal 3.3V supply, but GPIO input tolerance and the usable ADC measurement range are different limits. Explore the ideal divider equation below: VOUT = VIN × R2 ⁄ (R1 + R2). The 3.3V line is a reference, not an instant-damage threshold.

Try the presets to compare voltage ratio, current draw and the simplified input-loading model. This simulator does not certify a real circuit as safe or predict calibrated ADC accuracy.

TURBIDITY OUT 4.50V R1 10.0 kΩ DIV R2 20.0 kΩ GND VOLTS 0 5 VIN 3.3V REF VOUT 3.00V ESP32-S3 GPIO2 · ADC MODEL ONLY
STEP 1

Sensor output — VIN

4.50V

The turbidity sensor outputs 0 – 4.5V. Slide to simulate murkier water.

Resistors

R1 10.0 kΩ
R2 20.0 kΩ

Live math

3.00 V at the divider point

Try these

Same ratio → same ideal voltage. Compare divider current and illustrative noise; no preset is a verified hardware design.

Simulated ADC · GPIO2

Teaching model: ideal 0–3.3V scaling and illustrative jitter, not measured ESP32-S3 ADC performance. Check attenuation, calibration, supply and resistor tolerances before connecting hardware.

-- sampling --
Challenges
  • Prove that only the ratio sets the voltage — find three different pairs that all give 3.00V.
  • Find a pair below the 3.3V reference that draws a large current. What is the current in mA?
  • Increase both resistors without changing the ratio. Observe the simulated jitter and explain why source impedance can affect sampling.
  • Set VIN to 3.0V and make VOUT ≈ VIN. Explain why a nominal reading alone cannot establish worst-case pin tolerance or measurement accuracy.
Why 10k + 20k

With R1 = 10kΩ and R2 = 20kΩ, the nominal ⅔ ratio gives 3.00V at a 4.50V input and about 3.33V at 5.00V. These are ideal calculations, not a safety guarantee. Resistor tolerances, the actual sensor and supply voltages, and power sequencing must be included in the real worst-case check. Keep the established hardware unchanged until the teacher has reviewed the actual board and sensor specifications.

The ESP32-S3 datasheet lists a GPIO high-input maximum of VDD + 0.3V under its stated conditions: 3.6V for a powered 3.3V domain. This is not the ADC measurement range, nor a promise that a pin instantly fails just above 3.3V. Do not apply the powered-rail limit to an unpowered board.

Espressif's Arduino documentation lists an ESP32-S3 ADC measurement range up to about 3.1V at maximum attenuation. Its datasheet specifies calibrated error over a narrower range, up to 2.9V at ATTEN3. A 3.33V input is outside those documented measurement ranges and can produce saturated or unreliable readings even without immediate pin damage. Input tolerance and measurement accuracy must be checked separately.

At a nominal 4.5V input, this divider draws about 0.15mA and has a source resistance of about 6.7kΩ. Actual loading, filtering and ADC performance still need validation; the jitter display here is an illustrative model. The resistor values and physical circuit have not been redesigned.

Sources: ESP32-S3 datasheet, tables 5-4 and 5-6; Espressif Arduino ADC documentation.