Arduino Car Temperature Monitor – Prevent Heat Stroke in Children

The Life Saver is a DIY Arduino-based device that continuously monitors the interior temperature of a vehicle and notifies caregivers when the temperature exceeds a safe threshold. By displaying the current temperature on an LCD screen and sounding an audible alarm, it provides an early warning to prevent heat‑stroke incidents among children left in hot cars.

Step 1: Gather Components

• Arduino Uno
• LCD Keypad Shield
• 11 male‑to‑female jumper wires
• 7 male‑to‑male jumper wires
• DHT11 temperature sensor
• Large breadboard
• Small breadboard
• Passive buzzer (5 V)
• Green LED
• Red LED
• 2 × 330 Ω resistors

Step 2: Connect the LCD Keypad

1. Insert the Orange wire into LCD Keypad pin 5 (top right) and connect the other end to pin 4 on the Arduino.

2. Insert the Red wire into LCD Keypad pin 6 (top right) and connect the other end to pin 5 on the Arduino.

3. Insert the Blue wire into LCD Keypad pin 7 (top right) and connect the other end to pin 6 on the Arduino.

4. Insert the Pink wire into LCD Keypad pin 8 (top right) and connect the other end to pin 7 on the Arduino.

5. Insert the Grey wire into LCD Keypad pin 9 (top right) and connect the other end to pin 8 on the Arduino.

6. Insert the White wire into LCD Keypad pin 10 (top right) and connect the other end to pin 9 on the Arduino.

7. Connect the White wire to the LCD Keypad pin 9 (bottom right) and route the other end to the negative rail of the breadboard.

8. Connect the Grey wire to the LCD Keypad pin 10 (bottom right) and route the other end to the positive rail of the breadboard.

Step 3: Wire the Passive Buzzer

1. Connect the Grey wire to the “SIG” pin of the buzzer and the other end to pin 3 on the Arduino.

2. Connect the Blue wire to the “UCC” pin of the buzzer and the other end to the positive rail of the breadboard.

3. Connect the Purple wire to the “GND” pin of the buzzer and the other end to the negative rail of the breadboard.

Step 4: Install the DHT11 Temperature Sensor

1. Insert the sensor into the breadboard slots H14‑H17.

2. Connect the Orange wire to the sensor’s VCC pin, then to the negative rail of the breadboard.

3. Connect the White wire to the sensor’s DATA pin and route the other end to Arduino pin A0.

4. Connect the Grey wire to the sensor’s GND pin and route the other end to the positive rail of the breadboard.

Step 5: Attach the LEDs

1. Insert the Green LED’s anode into breadboard position D28 and cathode into D29.

2. Insert the Red LED’s anode into breadboard position D25 and cathode into D26.

3. Place a 330 Ω resistor across the Green LED: one leg in position B29, the other leg in the negative rail.

4. Place a 330 Ω resistor across the Red LED: one leg in position B26, the other leg in the negative rail.

5. Connect a Grey wire from position B28 on the breadboard to Arduino pin 13.

6. Connect a Green wire from position B25 on the breadboard to Arduino pin 12.

Step 6: Power Connections

1. Run a Yellow wire from the breadboard’s positive rail to the Arduino GND pin.

2. Run a Yellow wire from the breadboard’s negative rail to the Arduino 5 V pin.

Step 7: Upload the Firmware

#include <LiquidCrystal.h>   // LCD library
#include <dht.h>               // DHT11 library

#define TempSen A0           // Temperature sensor connected to A0
#define redLED 12            // Red LED on pin 12
#define greenLED 13          // Green LED on pin 13
#define speakerPin 3         // Buzzer on pin 3

dht DHT;

const int rs = 8, en = 9, d4 = 4, d5 = 5, d6 = 6, d7 = 7;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

void setup() {
  pinMode(redLED, OUTPUT);
  pinMode(greenLED, OUTPUT);
  pinMode(speakerPin, OUTPUT);
  Serial.begin(9600);
  lcd.begin(16, 2);
}

void loop() {
  DHT.read11(TempSen);
  Serial.println(DHT.temperature);
  lcd.setCursor(0, 0);
  lcd.print("Temp = ");
  lcd.print(DHT.temperature);
  lcd.println("C ");
  delay(50);

  if (int(DHT.temperature) >= 35) {
    digitalWrite(redLED, HIGH);
    digitalWrite(greenLED, LOW);
    int temp = DHT.temperature;
    tone(speakerPin, 1 * temp);
    delay(50);
    noTone(speakerPin);
  } else {
    digitalWrite(redLED, LOW);
    digitalWrite(greenLED, HIGH);
  }
}

Source: Life Saver