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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.

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