Circuit Documentation

Summary

This circuit is designed to control an LED using an ESP32 microcontroller via Bluetooth signals from an Android cell phone. The circuit includes a 5V battery for power, a rotary potentiometer for adjusting brightness, a pushbutton for manual control, and a resistor to limit current through the LED.

Component List

1. 5V Battery

   • Description: Provides power to the circuit.
   • Pins: Positive, Negative

2. ESP32 38 PINS

   • Description: Microcontroller used for controlling the LED and handling Bluetooth communication.
   • Pins: GND, 23, 22/SCL, 1, 2, 21/SDA, 19, 18, 5, 17/TX2, 16/RX2, 4, 0, 15, D1, D0, CLK, 3V3, EN, VP, VN, 34, 35, 32, 33, 25, 26, 27, 14, 12, 13, D2, D3, 11, 5V/VIN

3. PR-Rotary Potentiometer

   • Description: Used to adjust the brightness of the LED.
   • Pins: GND, OUT, VCC

4. LED: Two Pin (red)

   • Description: Indicates the status of the circuit.
   • Pins: Cathode, Anode

5. Resistor

   • Description: Limits the current through the LED.
   • Pins: Pin1, Pin2
   • Properties:
     • Resistance: 200 Ohms

6. Pushbutton

   • Description: Provides manual control for the LED.
   • Pins: Pin 3 (out), Pin 4 (out), Pin 1 (in), Pin 2 (in)

Wiring Details

5V Battery

• Positive: Connected to ESP32 pin 5V/VIN
• Negative: Connected to ESP32 pin GND

ESP32 38 PINS

• 5V/VIN: Connected to 5V Battery Positive
• GND: Connected to 5V Battery Negative, PR-Rotary Potentiometer GND, LED Cathode, Pushbutton Pin 4 (out)
• 23: Connected to Resistor Pin2
• 18: Connected to Pushbutton Pin 1 (in)
• 3V3: Connected to PR-Rotary Potentiometer VCC
• 25: Connected to PR-Rotary Potentiometer OUT

PR-Rotary Potentiometer

• GND: Connected to ESP32 pin GND
• OUT: Connected to ESP32 pin 25
• VCC: Connected to ESP32 pin 3V3

LED: Two Pin (red)

• Cathode: Connected to ESP32 pin GND
• Anode: Connected to Resistor Pin1

Resistor

• Pin1: Connected to LED Anode
• Pin2: Connected to ESP32 pin 23

Pushbutton

• Pin 1 (in): Connected to ESP32 pin 18
• Pin 4 (out): Connected to ESP32 pin GND

Code Documentation

/*
 * This Arduino Sketch controls an LED connected to pin 23 of an ESP32
 * microcontroller via Bluetooth signals from an Android cell phone.
 * The LED can be turned on or off based on the received Bluetooth commands.
 */

#include <BluetoothSerial.h>

BluetoothSerial SerialBT;
const int ledPin = 23; // Pin connected to the LED

void setup() {
  pinMode(ledPin, OUTPUT); // Set the LED pin as an output
  SerialBT.begin("Svetlo_pico"); // Initialize Bluetooth with a name
  Serial.begin(9600); // Initialize serial communication at 9600 baud rate
  Serial.println("The device started, now you can pair it with Bluetooth!");
}

void loop() {
  // Waiting for command from mobile
  if (SerialBT.available()) {
    String command = SerialBT.readStringUntil('\n'); // Read command
    command.trim(); // Remove whitespace characters (e.g., \r or space)

    if (command.startsWith("SET ")) {
      int brightness = command.substring(4).toInt(); // Get value after "SET "
      brightness = constrain(brightness, 0, 255); // Limit value to range 0–255
      analogWrite(ledPin, brightness);
      SerialBT.println("Brightness set to " + String(brightness));
    }

    if (command == "ON") {
      digitalWrite(ledPin, HIGH); // Turn on LED
      SerialBT.println("LED ON");
      Serial.println("LED ON");
    } else if (command == "OFF") {
      digitalWrite(ledPin, LOW); // Turn off LED
      SerialBT.println("LED OFF");
      Serial.println("LED OFF");
    } else {
      SerialBT.println("Unknown command. Use ON or OFF.");
      Serial.println("Unknown command.");
    }
  }
}

This code initializes the ESP32 microcontroller to control an LED via Bluetooth. The LED can be turned on or off based on commands received from a paired Android cell phone. The code also allows for setting the brightness of the LED using a "SET" command followed by a value between 0 and 255.