Arduino Nano ESP32 - Measure Voltage

In this guide, we will learn how to use an Arduino Nano ESP32 to measure voltage between 0V and 25V with a voltage sensor. We will explain:

Arduino Nano ESP32 voltage sensor

Hardware Preparation

1×Arduino Nano ESP32
1×USB Cable Type-C
1×Voltage Sensor
1×Jumper Wires
1×(Optional) 9V Power Adapter for Arduino Nano ESP32
1×(Recommended) Screw Terminal Adapter for Arduino Nano

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
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Overview of Voltage Sensor

A Voltage Sensor is a device that already has a voltage divider circuit built into it, using very accurate resistors to help measure voltage easily. It includes two resistors: one is 30 KΩ and the other is 7.5 KΩ. If the ADC uses a 5V reference voltage, this sensor can check voltages from 0 to 25V DC. When the reference voltage is 3.3V for the ADC, the sensor can check voltages from 0 to 16.5V DC.


A voltage sensor comes with two groups of pins:

  • Input Interface (connect it where you need to measure voltage):
    • VCC pin: Connect this positive pin to the higher voltage point.
    • GND pin: Connect this negative pin to the lower voltage point.
  • Output Interface (connect it to the Arduino Nano ESP32):
    • Vout pin (S): Connect this pin to an Arduino Nano ESP32 analog pin.
    • NC pin (+): Do not connect this; leave it free.
    • GMS pin (-): Connect this to the Arduino Nano ESP32's GND (0V).
    Voltage Pinout
    image source:

Wiring Diagram

The wiring diagram between Arduino Nano ESP32 and voltage sensor

This image is created using Fritzing. Click to enlarge image

Arduino Nano ESP32 Code

/* * This Arduino Nano ESP32 code was developed by * * This Arduino Nano ESP32 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * */ #define ANALOG_IN_PIN A7 // The Arduino Nano ESP32 pin connected to voltage sensor #define REF_VOLTAGE 3.3 #define ADC_RESOLUTION 4096.0 #define R1 30000.0 // resistor values in voltage sensor (in ohms) #define R2 7500.0 // resistor values in voltage sensor (in ohms) void setup() { Serial.begin(9600); } void loop() { // read the analog input int adc_value = analogRead(ANALOG_IN_PIN); // determine voltage at adc input float voltage_adc = ((float)adc_value * REF_VOLTAGE) / ADC_RESOLUTION; // calculate voltage at the sensor input float voltage_in = voltage_adc * (R1 + R2) / R2; // print results to serial monitor to 2 decimal places Serial.print("Measured Voltage = "); Serial.println(voltage_in, 2); delay(500); }

Detailed Instructions

To get started with Arduino Nano ESP32, follow these steps:

  • If you are new to Arduino Nano ESP32, refer to the tutorial on how to set up the environment for Arduino Nano ESP32 in the Arduino IDE.
  • Connect the Arduino Nano ESP32 to the voltage sensor.
  • Connect the Arduino Nano ESP32 board to your computer using a USB cable.
  • Launch the Arduino IDE on your computer.
  • Select the Arduino Nano ESP32 board and its corresponding COM port.
  • Copy the above code and paste the code into the Arduino IDE.
  • Press the Upload button in the Arduino IDE to transfer the code to the Arduino Nano ESP32.
  • Test by measuring 5V and 3.3V outputs on the Arduino Nano ESP32.
  • Check the results on the Serial Monitor.
Measured Voltage = 4.96 Measured Voltage = 4.96 Measured Voltage = 4.96 Measured Voltage = 4.96 Measured Voltage = 3.39 Measured Voltage = 3.39 Measured Voltage = 3.39 Measured Voltage = 3.39
Autoscroll Show timestamp
Clear output
9600 baud  


The value measured can change because the standard voltage reference is 5V. This might not be stable and can vary with the power supply.

Video Tutorial

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