Voltage Divider Circuit

Voltage Divider Explanation

A voltage divider is a simple circuit made of two resistors connected in series. It is used to scale down a voltage to a desired level. The basic principle is that the voltage is divided between the resistors in proportion to their resistance values.

In your example:

The resistors in the divider are 10kΩ and 20kΩ.
The voltage across the 10kΩ resistor (between GND and GPIO 34) will be your desired measurement.

Formula to Calculate Voltage

The voltage at the GPIO pin (V_out) is determined using the voltage divider formula:

$$
V_{out} = V_{in} \times \frac{R_2}{R_1 + R_2}
$$

Where:

$V_{in}$ is the input voltage (in this case, 3.3V)
$R_1$ is the resistor connected to GND (10kΩ)
$R_2$ is the resistor connected to the GPIO pin (20kΩ)

Substituting the values:

$$
V_{out} = 3.3V \times \frac{20kΩ}{10kΩ + 20kΩ} = 3.3V \times \frac{20}{30} = 2.2V
$$

So, the voltage at GPIO 34 will be 2.2V.

Code to Read the Voltage Using ESP32

You can use the ADC (Analog-to-Digital Converter) feature of the ESP32 to read the voltage at GPIO 34.

Code Example (in Arduino IDE)

#define ANALOG_PIN 34 // GPIO 34 is an input-only pin

void setup() {
  Serial.begin(115200);  // Start serial communication for debugging
  pinMode(ANALOG_PIN, INPUT); // Set GPIO 34 as input
}

void loop() {
  int analogValue = analogRead(ANALOG_PIN); // Read the analog value (0-4095)

  // Calculate the voltage at the GPIO pin
  float voltage = (analogValue / 4095.0) * 3.3; // Map the value to 3.3V range

  Serial.print("Analog Value: ");
  Serial.print(analogValue);
  Serial.print(" --> Voltage: ");
  Serial.println(voltage);

  delay(1000); // Delay for 1 second
}

Code Breakdown:

analogRead(ANALOG_PIN): Reads the voltage on GPIO 34 as a digital value between 0 and 4095, corresponding to 0V and 3.3V, respectively.
Voltage Calculation: The result of analogRead() is mapped to the voltage range of 0 to 3.3V based on the ADC’s 12-bit resolution (0 to 4095).
Serial Output: The calculated voltage is printed to the Serial Monitor for monitoring.

Important Considerations:

Ensure that the voltage you’re measuring doesn’t exceed 3.3V, as ESP32’s ADC pins are not 5V tolerant.
The analog input on the ESP32 uses a 12-bit resolution, meaning values will range from 0 to 4095.

This setup will allow you to measure the voltage at GPIO 34 using the voltage divider circuit and display it on the Serial Monitor.