Creating A Cold Coffee Alarm Device using Arduino

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1const int sensorPin = A0; // connects the temperature sensor to an analog pin
2const int buzzerPin = 8; // connects the piezo buzzer to a digital pin
3const float baselineTemp = 25.0; // the base temperature to compare with what the sensor detects

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1Serial.begin(9600); // opens a serial port
2// sets the LEDs (connected to pins 2, 3, 4) as output
3for(int pinNumber = 2; pinNumber < 5; pinNumber++){
4    pinMode(pinNumber, OUTPUT);
5    digitalWrite(pinNumber, LOW);
6}
7pinMode(buzzerPin, OUTPUT); // sets the buzzer pin as an output

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1// determines the value of the sensor, this will be used to compute the voltage output
2int sensorVal = analogRead(sensorPin);
3
4// outputs the sensor value on the Serial Monitor for checking
5Serial.print("Sensor Value: ");
6Serial.print(sensorVal);
7
8float voltage = (sensorVal/1024.0) * 5.0; // converts the ADC reading to voltage
9
10// outputs the voltage reading on the Serial Monitor for checking
11Serial.print(", volts: ");
12Serial.print(voltage);
13
14// converts the voltage to temperature in degrees Celcius
15float temperature = (voltage - 0.5) * 100;
16
17// outputs the temperature on the Serial Monitor for checking
18Serial.print(" , degrees C: ");
19Serial.print(temperature);
20
21// will be used to print the status on the Serial Monitor
22String tempStatus = "";

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1// determines if drink is COLD
2if(temperature < baselineTemp) {
3    // if temp is less than 25 C, turn the blue LED on
4    digitalWrite(2, HIGH); // blue
5    digitalWrite(3, LOW);  // yellow
6    digitalWrite(4, LOW);  // red
7
8    tempStatus = "COLD :("; // sets the status to print on later
9
10    // turns the buzzer on
11    digitalWrite(buzzerPin, HIGH);
12    tone(buzzerPin, 1024, 3000); // (pin, frequency, duration)
13    // the duration is the same as the delay time for the loop to mimic continuous buzzing sound
14}
15// determines if drink is WARM and getting cold
16else if(temperature >= baselineTemp && temperature < baselineTemp + 3){
17    // if temp is 25 C to 27 C, turn the yellow LED on
18    digitalWrite(2, LOW);  // blue
19    digitalWrite(3, HIGH); // yellow
20    digitalWrite(4, LOW);  // red
21
22    tempStatus = "Still WARM but GETTING COLD!"; // sets the status to print on later
23
24    // turns the buzzer on
25    digitalWrite(buzzerPin, HIGH);
26    tone(buzzerPin, 1024, 1000); // (pin, frequency, duration)
27    // the duration is less than the delay time to mimic a warning alarm sound
28}
29// determines if drink is still HOT
30else if(temperature >= baselineTemp + 3 && temperature < baselineTemp + 8){
31    // if temp is greater than 27 C but less than 35 C, turn the red LED on
32    // I need to set a cap at 35 C because the temp reads very high when there's no subject to test on
33    digitalWrite(2, LOW);  // blue
34    digitalWrite(3, LOW);  // yellow
35    digitalWrite(4, HIGH); // red
36
37    tempStatus = "Still HOT :)"; // sets the status to print on later
38}
39// if there is no mug present on the pressure plate, do nothing
40else{
41    digitalWrite(2, LOW); // blue
42    digitalWrite(3, LOW); // yellow
43    digitalWrite(4, LOW); // red
44
45    tempStatus = "Missing subject"; // sets the status to print on later
46}
47
48// prints the status of the temperature
49Serial.println(" , Status: " + tempStatus);
50
51// three-second gap for each check
52delay(3000);