Circuit Documentation

Summary

This circuit is designed to control a DC motor using an Arduino Uno R3 microcontroller in conjunction with a relay module and an HC-SR04 ultrasonic sensor. The motor is powered by an 18650 Li-ion battery and is switched on and off based on the proximity of an object detected by the ultrasonic sensor. A 9V battery powers the Arduino, and a rocker switch is used to control the power supply to the Arduino.

Component List

Arduino Uno R3

• Microcontroller board based on the ATmega328P
• It has 14 digital input/output pins, 6 analog inputs, a USB connection, a power jack, an ICSP header, and a reset button.

Relay Module 1 Channel

• A module that can be used to control high power/high voltage devices safely.
• It has a single channel and can be driven by the Arduino to switch devices on and off.

HC-SR04 Ultrasonic Sensor

• An ultrasonic distance sensor that can measure distances from 2cm to 400cm with an accuracy of 3mm.
• It has four pins: VCC, TRIG, ECHO, and GND.

DC Motor

• A simple electric motor that converts electrical energy into mechanical energy.
• It has two pins for connecting to a power source.

18650 Li-ion Battery

• A rechargeable battery that provides a power source for the DC motor.
• It has a positive and a negative terminal.

9V Battery

• A standard 9V battery used to power the Arduino Uno R3.
• It has a positive and a negative terminal.

Rocker Switch (SPST)

• A single pole single throw (SPST) switch used to control the power supply to the Arduino Uno R3.
• It has two terminals for connecting the power source and the load.

Wiring Details

Arduino Uno R3

• Power Jack connected to the positive terminal of the 9V Battery through the Rocker Switch (SPST).
• IOREF connected to the 5V pin of the Relay Module.
• 5V connected to the VCC pin of the HC-SR04 Ultrasonic Sensor.
• GND connected to the GND pin of the Relay Module and the GND pin of the HC-SR04 Ultrasonic Sensor.
• Pin 11 (relayPin) connected to the S pin of the Relay Module.
• Pin 10 (echoPin) connected to the ECHO pin of the HC-SR04 Ultrasonic Sensor.
• Pin 9 (trigPin) connected to the TRIG pin of the HC-SR04 Ultrasonic Sensor.

Relay Module 1 Channel

• 5V connected to the IOREF pin of the Arduino Uno R3.
• GND connected to the GND pin of the Arduino Uno R3.
• S connected to pin 11 of the Arduino Uno R3.
• COM connected to the negative terminal of the 18650 Li-ion Battery.
• NO connected to pin 1 of the DC Motor.

HC-SR04 Ultrasonic Sensor

• VCC connected to the 5V pin of the Arduino Uno R3.
• TRIG connected to pin 9 of the Arduino Uno R3.
• ECHO connected to pin 10 of the Arduino Uno R3.
• GND connected to the GND pin of the Arduino Uno R3.

DC Motor

• Pin 1 connected to the NO pin of the Relay Module.
• Pin 2 connected to the positive terminal of the 18650 Li-ion Battery.

18650 Li-ion Battery

• Positive terminal connected to pin 2 of the DC Motor.
• Negative terminal connected to the COM pin of the Relay Module.

9V Battery

• Positive terminal connected to the Power Jack of the Arduino Uno R3 through the Rocker Switch (SPST).
• Negative terminal connected to terminal 2 of the Rocker Switch (SPST).

Rocker Switch (SPST)

• Terminal 1 connected to the positive terminal of the 9V Battery.
• Terminal 2 connected to the negative terminal of the 9V Battery and the Power Jack of the Arduino Uno R3.

Documented Code

#define trigPin 9
#define echoPin 10
#define relayPin 11

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(relayPin, OUTPUT);

  // Set the relay pin to HIGH by default to keep the motor off initially
  digitalWrite(relayPin, HIGH);

  Serial.begin(9600);
}

void loop() {
  long duration, distance;
  
  // Send the ultrasonic pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Read the echo time
  duration = pulseIn(echoPin, HIGH);

  // Calculate distance in cm
  distance = (duration / 2) / 29.1;

  // If an object is within 10 cm, turn on the fan
  if (distance <= 10) {
    digitalWrite(relayPin, LOW);  // Activate the relay (assuming it's active LOW), turning on the fan
  } else {
    digitalWrite(relayPin, HIGH);  // Deactivate the relay, turning off the fan
  }

  // Print the distance to the serial monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  delay(100);  // Small delay for stability
}

The code is written for the Arduino Uno R3 and is responsible for controlling the relay module based on the distance measured by the HC-SR04 ultrasonic sensor. The relay, in turn, controls the power to the DC motor. When an object is detected within 10 cm of the sensor, the motor is turned on; otherwise, it remains off. The distance is also printed to the serial monitor for debugging purposes.