# ESP32 Tutorial 55/55 - How to measure 12V, 24V or 100V DC voltage | SunFounder's ESP32 IoT Learnig kit

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In this video we learn how to measure any DC voltage using ESP32 board. we learn how to use only 2 resistors to be able to safely measure the DC voltage using ESP32.

## Topics in this lesson

Use Chapters from timeline or click on the time

• 00:00 Introduction
• 1:59 Intoduction to the project
• 5:45 Voltage divider
• 7:33 Wiring explained
• 9:14 Arduino Code explained
• 14:45 Selecting ESP32 board and COM Port on Arduino IDE
• 16:27 Measuring 30V using ESP32 Demonstration
• 21:36 Changed the R2 to 330k ohm
• 22:33 Minimum voltage measuremen
``````
/*
Watch video instruction for this code on YouTube https://youtu.be/znBiVlgV9JI
Resource page for this lesson and code:
http://robojax.com/course3

/*
Arduino code for ESP32 to measure any DC voltage
www.robojax.com
Feb 19, 2024
*/
bool debug = false;
const int R1 = 10000;//we read the voltage acrosst this resistor ()
const int R2 = 100000;

const int VinPin = 35; // Potentiometer connected to GPIO14

// PWM settings
const int freq = 5000; // PWM frequency
const int resolution = 12; // PWM resolution (bits)
const int channel = 0; // PWM channel

float VB1;
int mV;

void setup() {
Serial.begin(115200);
// Configure PWM
ledcSetup(channel, freq, resolution);
//calculatResistor(R1, 24);//10000 ohm and 35.0V

}

void loop() {

Serial.print("VB1 Voltage: ");
Serial.print(VB1); // Convert millivolts to volts
Serial.println("V ");

delay(500);
}

{
if(debug)
{
maxVoltage();
Serial.print("PinVoltage: ");
Serial.print(voltage_mV);
Serial.println("mV");
}
mV = voltage_mV;
VB1 = (((float) voltage_mV) / 1000.0)  * (1 + (float)R2/(float)R1);
}

/*
prints maximum volage
*/
void maxVoltage()
{
float maxVoltage = ( 3.1)  * (1 + (float)R2/(float)R1);
Serial.print("****Maximum Voltage: ");
Serial.print(maxVoltage);
Serial.println("V");

}//maxVoltage() end

void calculatResistor(int r1, float voltage)
{
Serial.print("Calculating R2 when R1 is :");
Serial.print(r1);
Serial.print(" Ohms and Maximum Input Voltage is ");
Serial.print(voltage);
Serial.println("V");
Serial.print("***** R2 Should Be ");
float r2 = (voltage - 3.1)/ (3.1/ (float)r1);
Serial.print(r2 / 1000.0);
Serial.println(" kilo Ohms");
while(1);
}

```  ```

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