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Project Documentation

Arduino-Controlled Ultrasonic Sensor Relay for Automated Lighting

Image of Arduino-Controlled Ultrasonic Sensor Relay for Automated Lighting

Circuit Documentation

Summary

This circuit is designed to utilize an Arduino UNO microcontroller to control a relay module based on the distance measured by two HC-SR04 Ultrasonic Sensors. The relay module then switches a bulb on or off. A potentiometer is used to adjust the contrast of an LCD Display 16x2, which is likely used to display information. A resistor is connected in series with an LED to limit the current through the LED.

Component List

Bulb

Description: A simple light bulb.
Pins: positive, negative

HC-SR04 Ultrasonic Sensor

Description: An ultrasonic sensor for measuring distance.
Pins: VCC, TRIG, ECHO, GND

Potentiometer

Description: A variable resistor typically used for adjusting levels such as volume or, in this case, contrast for an LCD.
Pins: GND, Output, VCC

Relay Module 2 Channel

Description: A module with two relays that can control the high power circuit with a low power signal.
Pins: GND, IN1, IN2, VCC, NC1, COM, NO1, NC2, NO2

Arduino UNO

Description: A microcontroller board based on the ATmega328P.
Pins: UNUSED, IOREF, Reset, 3.3V, 5V, GND, Vin, A0-A5, SCL, SDA, AREF, D0-D13

LED: Two Pin (red)

Description: A basic red LED.
Pins: cathode, anode

Resistor

Description: A passive two-terminal electrical component that implements electrical resistance as a circuit element.
Properties: 200 Ohms

LCD Display 16x2

Description: A liquid crystal display capable of displaying 16 characters per line across 2 lines.
Pins: LEDK, LEDA, DB0-DB7, E, RW, RS, VO, VDD, VSS

Wiring Details

Bulb

positive: Connected to Relay Module 2 Channel NO1
negative: Connected to Relay Module 2 Channel GND, Arduino UNO GND, LCD Display 16x2 LEDK and VSS

HC-SR04 Ultrasonic Sensor

VCC: Connected to LED: Two Pin (red) anode, Potentiometer GND
TRIG: Connected to Arduino UNO D12 (for one sensor) and D10 (for the other sensor)
ECHO: Connected to Arduino UNO D11 (for one sensor) and D9 (for the other sensor)
GND: Connected to Resistor pin1, Potentiometer VCC

Potentiometer

GND: Connected to HC-SR04 Ultrasonic Sensor VCC
Output: Connected to LCD Display 16x2 VO
VCC: Connected to HC-SR04 Ultrasonic Sensor GND

Relay Module 2 Channel

GND: Connected to Bulb negative, Arduino UNO GND, LCD Display 16x2 LEDK and VSS
IN1: Connected to Arduino UNO D8
VCC: Connected to Arduino UNO 5V, LCD Display 16x2 VDD and LEDA
NO1: Connected to Bulb positive

Arduino UNO

GND: Connected to Relay Module 2 Channel GND, Bulb negative, LCD Display 16x2 LEDK and VSS
5V: Connected to Relay Module 2 Channel VCC, LCD Display 16x2 VDD and LEDA
D12: Connected to HC-SR04 Ultrasonic Sensor TRIG (for one sensor)
D11: Connected to HC-SR04 Ultrasonic Sensor ECHO (for one sensor)
D10: Connected to HC-SR04 Ultrasonic Sensor TRIG (for the other sensor)
D9: Connected to HC-SR04 Ultrasonic Sensor ECHO (for the other sensor)
D8: Connected to Relay Module 2 Channel IN1
D7-D2: Connected to LCD Display 16x2 RS, E, DB4-DB7 respectively

LED: Two Pin (red)

cathode: Connected to Resistor pin2
anode: Connected to HC-SR04 Ultrasonic Sensor VCC

Resistor

pin1: Connected to HC-SR04 Ultrasonic Sensor GND
pin2: Connected to LED: Two Pin (red) cathode

LCD Display 16x2

LEDK: Connected to Relay Module 2 Channel GND, Bulb negative, Arduino UNO GND
LEDA: Connected to Relay Module 2 Channel VCC, Arduino UNO 5V
DB7-DB4: Connected to Arduino UNO D2-D5 respectively
E: Connected to Arduino UNO D6
RW: Not connected
RS: Connected to Arduino UNO D7
VO: Connected to Potentiometer Output
VDD: Connected to Relay Module 2 Channel VCC, Arduino UNO 5V
VSS: Connected to Relay Module 2 Channel GND, Bulb negative, Arduino UNO GND

Documented Code

#define TRIGGER_PIN  12  // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN     11  // Arduino pin tied to echo pin on the ultrasonic sensor.
#define MAX_DISTANCE 200 // Maximum distance we want to ping for (in centimeters). Maximum sensor distance is rated at 400-500cm.

#define RELAY_LINE1_PIN 8

#include "NewPing.h"
NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance.

unsigned int critical_distance_cms = 50;  // Cutoff distance at which the light will switch
bool state = 0;

void setup() {
  Serial.begin(9600); // Open serial monitor at 115200 baud to see ping results.
  pinMode(RELAY_LINE1_PIN, OUTPUT);
  digitalWrite(RELAY_LINE1_PIN, HIGH);  // Turn the light off
}

void loop() {
  delay(50);                     // Wait 50ms between pings (about 20 pings/sec).
  unsigned int distance = readDistance(); // Current distance of any object facing the ultrasonic sensor

  Serial.print("Ultrasonic: ");
  Serial.print(distance); // Send ping, get distance in cm and print result (0 = outside set distance range)
  Serial.println("cm");

  // Someone is near the door
  if (distance < critical_distance_cms)
  {
    while (distance < critical_distance_cms)
    {
      // Check if they moved away
      distance = readDistance();

      delay(5); // Do nothing until the person moves away from the door
    }

    state = !state; // Change the state of the relay

    if (state)
    {
      Serial.println("Door Open!");
      digitalWrite(RELAY_LINE1_PIN, LOW); // Turn the light on
    }
    else
    {
      Serial.println("Door Closed!");
      digitalWrite(RELAY_LINE1_PIN, HIGH);  // Turn the light off
    }
  }
}

// Updates the value of the Ultrasonic reading
unsigned int readDistance()
{
  // Read 7 values from the ultrasonic and get the median value (median filter)
  // Gets rid of noisy reading
  unsigned int distance = sonar.convert_cm(sonar.ping_median(7));

  // The value 0 indicates that the ultrasonic sensor is reading nothing in front of it
  // Set this distance to max distance so the light doesn't switch unnecessarily
  if (distance == 0)
  {
    distance = MAX_DISTANCE;
  }
  
  return distance;
}

This code is designed to read the distance from the HC-SR04 Ultrasonic Sensor and toggle the state of a relay when an object is detected within a critical distance. The relay then controls the power to a bulb. The LCD display is likely used to show status or distance information, but the code for the display is not included in the provided code snippet.