Temperature Alarm With Arduino

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After experimenting with the LED Real Time Clock shield from PMD Way, I've started to come up with some useful projects that can be demonstrated with it. One example is a temperature alarm - you set a low and high temperature, and if the ambient temperature is below or exceeds the range - the buzzer will sound. .

Once you have the shield, it's very easy to do as everything is assembled. First, install this library into your Arduino IDE. Then plug the shield into your Arduino Uno or compatible board, then upload the sketch below:

#include "TTSDisplay.h"

#include "TTSTemp.h"

TTSTemp temp; TTSDisplay rtcshield;

boolean alarmOnOff = false; int highTemp = 40; int lowTemp = 10; int currentTemp;

void LEDsoff() { // function to turn all alarm high/low LEDs off digitalWrite(2, LOW); digitalWrite(4, LOW); }

void setup() { // initalise digital pins for LEDs and buzzer as outputs pinMode(2, OUTPUT); // LED 1 pinMode(3, OUTPUT); // LED 2 pinMode(4, OUTPUT); // LED 3 pinMode(5, OUTPUT); // LED 4 pinMode(6, OUTPUT); // buzzer

// initalise digital pins for buttons as inputs // and initialise internal pullups pinMode(9, INPUT_PULLUP); // button K1 pinMode(10, INPUT_PULLUP); // button K2 pinMode(11, INPUT_PULLUP); // button K3 }

void loop() { // get current temperature currentTemp = temp.get();

// if current temperature is within set limts // show temperature on display

if (currentTemp >= lowTemp || currentTemp <= highTemp) // if ambient temperature is less than high boundary // OR if ambient temperature is grater than low boundary // all is well { LEDsoff(); // turn off LEDs rtcshield.num(currentTemp); }

// if current temperature is above set high bounday, show red LED and // show temperature on display // turn on buzzer if alarm is set to on (button K3)

if (currentTemp > highTemp) { LEDsoff(); // turn off LEDs digitalWrite(4, HIGH); // turn on red LED rtcshield.num(currentTemp); if (alarmOnOff == true) { digitalWrite(6, HIGH); // buzzer on } } }

// if current temperature is below set lower boundary, show blue LED and // show temperature on display // turn on buzzer if alarm is set to on (button K3)

if (currentTemp < lowTemp) { LEDsoff(); // turn off LEDs digitalWrite(2, HIGH); // turn on blue LED rtcshield.num(currentTemp); if (alarmOnOff == true) { digitalWrite(6, HIGH); // buzzer on } } } // --------turn alarm on or off----------------------------------------------------- if (digitalRead(11) == LOW) // turn alarm on or off { alarmOnOff = !alarmOnOff; if (alarmOnOff == 0) { digitalWrite(6, LOW); // turn off buzzer digitalWrite(5, LOW); // turn off alarm on LED } // if alarm is set to on, turn LED on to indicate this if (alarmOnOff == 1) { digitalWrite(5, HIGH); } delay(300); // software debounce } // --------set low temperature------------------------------------------------------ if (digitalRead(10) == LOW) // set low temperature. If temp falls below this value, activate alarm { // clear display and turn on blue LED to indicate user is setting lower boundary rtcshield.clear(); digitalWrite(2, HIGH); // turn on blue LED rtcshield.num(lowTemp);

// user can press buttons K2 and K1 to decrease/increase lower boundary. // once user presses button K3, lower boundary is locked in and unit goes // back to normal state

while (digitalRead(11) != LOW) // repeat the following code until the user presses button K3 { if (digitalRead(10) == LOW) // if button K2 pressed { --lowTemp; // subtract one from lower boundary // display new value. If this falls below zero, won't display. You can add checks for this yourself :) rtcshield.num(lowTemp); } if (digitalRead(9) == LOW) // if button K3 pressed { lowTemp++; // add one to lower boundary // display new value. If this exceeds 9999, won't display. You can add checks for this yourself :) rtcshield.num(lowTemp); } delay(300); // for switch debounce } digitalWrite(2, LOW); // turn off blue LED } // --------set high temperature----------------------------------------------------- if (digitalRead(9) == LOW) // set high temperature. If temp exceeds this value, activate alarm {

// clear display and turn on red LED to indicate user is setting lower boundary rtcshield.clear(); digitalWrite(4, HIGH); // turn on red LED rtcshield.num(highTemp);

// user can press buttons K2 and K1 to decrease/increase upper boundary. // once user presses button K3, upper boundary is locked in and unit goes // back to normal state

while (digitalRead(11) != LOW) // repeat the following code until the user presses button K3 { if (digitalRead(10) == LOW) // if button K2 pressed { --highTemp; // subtract one from upper boundary // display new value. If this falls below zero, won't display. You can add checks for this yourself :) rtcshield.num(highTemp); } if (digitalRead(9) == LOW) // if button K3 pressed { highTemp++; // add one to upper boundary // display new value. If this exceeds 9999, won't display. You can add checks for this yourself :) rtcshield.num(highTemp); } delay(300); // for switch debounce } digitalWrite(4, LOW); // turn off red LED } }

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Step 1: Operating the Temperature Alarm

Operating instructions:

  • To set lower temperature, – press button K2. Blue LED turns on. Use buttons K2 and K1 to select temperature, then press K3 to lock it in. Blue LED turns off.
  • To set upper temperature – press button K1. Red LED turns on. Use buttons K2 and K1 to select temperature, then press K3 to lock it in. Red LED turns off.
  • If temperature drops below lower or exceeds upper temperature, the blue or red LED will come on.
  • You can have the buzzer sound when the alarm activates – to do this, press K3. When the buzzer mode is on, LED D4 will be on. You can turn buzzer off after it activates by pressing K3.

Display will show ambient temperature during normal operation.You can see this in action via the video.

We hope you enjoyed this simple and useful project.

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