When we need to monitor the temperature in an environment close to a heat source, a temperature alarm is essential. This small electronic device can sense the temperature in the surrounding environment, and once it exceeds a predefined value, it emits a sharp sound alarm, alerting you to take necessary actions. In this article, we will create a simple temperature alarm model using Arduino. In this example, when the ambient temperature exceeds 25 degrees Celsius, a buzzer will be triggered, producing a sound warning. Simultaneously, Arduino will output the current temperature value via the serial port, allowing you to monitor temperature changes in real-time.
To obtain temperature readings from the surrounding environment, we need to use a sensor. This sensor acts like a sensory organ, converting physical quantities into electrical signals for transmission. In this project, we have chosen the LM35 temperature sensor, which has lower power consumption and is suitable for a wide temperature range. This is particularly helpful for hobbyists and makers in their projects.
Required Components and Wiring
- 1 × Arduino UNO R3 (with accompanying USB data cable)
- 1 × Breadboard
- 5 × Colored Jumper Wires
- 1 × Buzzer
- 1 × LM35 Temperature Sensor
Arduino Temperature Alarm Project Code
void setup() {
pinMode(10, OUTPUT); // Set the buzzer pin
Serial.begin(9600); // Set the baud rate to 9600 bps
}
void loop() {
int val; // Variable to store the LM35 reading
double data; // Variable to store the converted temperature value
val = analogRead(0); // LM35 is connected to the analog port, read its value
data = (double) val * (5.0 / 1024.0) * 100.0; // Temperature conversion formula
if (data > 25) { // If the temperature is greater than 25 degrees Celsius, activate the buzzer
for (int x = 0; x < 180; x++) {
// Convert the angle of the sine function to radians
sinVal = (sin(x * (3.1412 / 180)));
// Generate the sound frequency using the sine function value
toneVal = 2000 + (int(sinVal * 1000));
// Apply the tone to pin 10
tone(10, toneVal);
delay(2);
}
} else { // If the temperature is less than 25 degrees Celsius, turn off the buzzer
noTone(10); // Turn off the buzzer
}
if (millis() - tepTimer > 500) { // Output the temperature value to the serial monitor every 500ms
tepTimer = millis();
Serial.print("Temperature: "); // Print "Temperature" to the serial monitor
Serial.print(data); // Print the temperature value
Serial.println("°C"); // Print the temperature unit
}
}
Code Explanation
Setup Function:
- pinMode(10, OUTPUT);: Configures pin 10 as an output, which is connected to a buzzer.
- Serial.begin(9600);: Initializes serial communication at a baud rate of 9600 bps for debugging and displaying temperature data.
Loop Function:
- int val; and double data; are variables used to store the LM35 sensor reading and converted temperature, respectively.
- val = analogRead(0);: Reads an analog value from analog input 0, connected to the LM35 sensor.
- data = (double) val * (5.0 / 1024.0) * 100.0;: Converts the analog reading to a temperature value in degrees Celsius. The LM35 outputs a voltage proportional to temperature.
The following block checks if the temperature exceeds 25°C:
- if (data > 25) {: If the temperature is above 25 degrees Celsius:
- A for loop is used to create a sine wave sound with the buzzer, providing an audible signal.
If the temperature is below 25°C:
- else {: If the temperature is 25 degrees Celsius or lower:
- The noTone(10); command turns off the buzzer.
- if (millis() – tepTimer > 500) {: Every 500 milliseconds (0.5 seconds), the code checks and outputs temperature data to the serial monitor.
- tepTimer = millis(); updates a timer variable to keep track of time.
- Serial.print(“Temperature: “); prints “Temperature” as a label.
- Serial.print(data); prints the temperature value.
- Serial.println(“°C”); prints the temperature unit.
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