Circuit Documentation

Summary

The circuit in question is designed to measure distance using an HC-SR04 Ultrasonic Sensor and display the measurement status through a set of three LEDs (red, yellow, and green). The Arduino UNO microcontroller is used to control the sensor and LEDs, as well as to manage the power-saving mode of the system. The circuit includes resistors to limit the current through the LEDs, ensuring their safe operation.

Component List

LEDs

• Red LED: A two-pin red LED used to indicate a certain range of distance as part of the measurement feedback.
• Yellow LED: A two-pin yellow LED used to indicate a different range of distance as part of the measurement feedback.
• Green LED: A two-pin green LED used to indicate another range of distance as part of the measurement feedback.

Resistors

• 220 Ohm Resistor: Three resistors each with a resistance of 220 Ohms, used to limit the current through the LEDs.

Microcontroller

• Arduino UNO: A microcontroller board based on the ATmega328P, used to control the LEDs and the ultrasonic sensor, as well as to process the distance measurements.

Sensor

• HC-SR04 Ultrasonic Sensor: An ultrasonic ranging module used to measure distances by emitting ultrasonic waves and measuring the time taken for the echo to return.

Wiring Details

Red LED

• Cathode: Connected to the GND pin on the Arduino UNO.
• Anode: Connected to one end of a 220 Ohm resistor, whose other end is connected to pin D5 on the Arduino UNO.

Yellow LED

• Cathode: Connected to the GND pin on the Arduino UNO.
• Anode: Connected to one end of a 220 Ohm resistor, whose other end is connected to pin D6 on the Arduino UNO.

Green LED

• Cathode: Connected to the GND pin on the Arduino UNO.
• Anode: Connected to one end of a 220 Ohm resistor, whose other end is connected to pin D9 on the Arduino UNO.

HC-SR04 Ultrasonic Sensor

• VCC: Connected to the Vin pin on the Arduino UNO.
• GND: Connected to the GND pin on the Arduino UNO.
• TRIG: Connected to pin D13 on the Arduino UNO.
• ECHO: Connected to pin D12 on the Arduino UNO.

Documented Code

#include <LowPower.h>

const int TRIG_PIN = 13;
const int ECHO_PIN = 12;

#define depthOfTote 100

long duration;
float distance, distanceTot, distanceAvg, speedOfSound;
int count;

int red_led = 5;
int yellow_led = 6;
int green_led  = 9;

void setup() {

  Serial.begin(9600);

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  pinMode(red_led, OUTPUT);
  pinMode(yellow_led,  OUTPUT);
  pinMode(green_led, OUTPUT);

}

float readDistance() {

  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  duration = pulseIn(ECHO_PIN, HIGH);
  return duration;
}

void measurementCycle(){
  count = count + 1;

  if  (count < 5){
    //int temperature = dht11.readTemperature();
    speedOfSound = 343; //+ (0.6 * temperature);

    duration = readDistance();
    distance = duration * (speedOfSound/10000) / 2;
    delay(500);

    Serial.print("Distance: ");
    Serial.println(distance);
    Serial.println(count);
    distanceTot = distanceTot + distance;

  } else if (count == 6) {

    count = 0;
    distanceAvg = distanceTot / 5;
    
    Serial.print("Distance Average: ");
    Serial.println(distanceAvg);

    distanceTot = 0;
    if (distanceAvg > 68){
      digitalWrite(green_led, LOW);
      digitalWrite(yellow_led, LOW);
      digitalWrite(red_led, HIGH);

      LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
      LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
      

    } else if (distanceAvg > 40 && distanceAvg < 68){
      digitalWrite(green_led, LOW);
      digitalWrite(yellow_led, HIGH);
      digitalWrite(red_led, LOW);
      
      LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
      LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
      

    } else if (distanceAvg < 40){
      digitalWrite(green_led, HIGH);
      digitalWrite(yellow_led, LOW);
      digitalWrite(red_led, LOW);

      LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
      LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);

  }
}

}

void loop() {
  measurementCycle();
  delay(100);

}

The code provided is for the Arduino UNO microcontroller. It initializes the pins connected to the HC-SR04 sensor and LEDs, reads the distance measurements, and then lights up the corresponding LED based on the average distance measured. It also includes a power-down feature to save energy between measurements.