Team IOT Project Group 22: Joe Hankins, John Bustle

Published November 23, 2021

Annoying Fridge Alarm

Forgetful roommates who don't close the fridge? Worried about keeping your food (and drinks) thoroughly cooled? Then this device is for you!

BeginnerFull instructions provided144

Things used in this project

Hardware components

Particle Argon

General Purpose Transistor PNP

Maxim Integrated DS18B20 Programmable Resolution 1-Wire Digital Thermometer

Through Hole Resistor, 2 kohm

Adafruit Rotating LED buzzer alarm

Jumper wires (generic)

Software apps and online services

ThingSpeak API

IFTTT Maker service

Hand tools and fabrication machines

Soldering iron (generic)

Solder Wire, Lead Free

Story

This project aims to help solve the problems of forgetful roommates/kids or a faulty fridge. You know how sometimes you can "close" a fridge but it doesn't really close quite all the way? Well that was the main inspiration for this project. Not only will it detect when the door is left even slightly ajar, if this or anything else causes the fridge temperature to fall below a safe temperature, then a second alarm will trigger and its users will be notified of this event. Though many new fridges nowadays have a system similar to this built into it, sometimes you are in a living situation where you either cannot afford these new fridges or where appliances are provided and they are a little out of date. Nobody wants food poisoning, so this project helps ensure safe containment of food. The argons used in this project will not only graph the temperature data in real time, but also communicate when one has an issue and then is able to send the user a message via an IFTTT notification.

1 / 4 • Temperature Sensor

Wiring Diagrams

1 / 2 • Door Sensor Circuit, Red Circle Represents Physical Alarm

The door sensor circuit utilizes a PNP transistor acting as a switch between the digital output from the Argon and the 5 Volts coming from the VUSB pin. This was done due to the voltage requirements needed by the physical alarm. The specific transistor used here could be swapped out with another kind or another component completely, as this component could sometimes get quite hot if the alarm was running for too long. The temperature sensor needed an additional 2kohm resistor across the pins of the sensor board in order to read values from the argon. The temperature sensor also required the use of additional libraries in order to accurately record the temperatures in Fahrenheit.

IFTTT Applets

1 / 8 • Trigger Event

IFTTT applets were made to send both users notifications when either the fridge door was open or when the temperature got too high. This makes it easy to know when things are getting out of line even if you aren't home.

ThingSpeak Integration

Live Data: https://thingspeak.com/channels/1577432

ThingSpeak was used to graph the temperature data over time, so one could look at fluctuations and maybe root out the cause of their food going bad. Using a simple webhook, data from the temperature sensing argon is published to the console, and the webhook finds the specific temperature event and publishes the data to the ThingSpeak graph every 10 seconds.

Communication Flowchart

Video Demonstration

This is a brief video showcasing the circuits used as well as what the alarm looks like in action. Feel free to comment with questions, suggestions, or anything you liked about the project. Thanks!

Code

// This #include statement was automatically added by the Particle IDE.
#include <DS18B20.h>

// This #include statement was automatically added by the Particle IDE.
#include <DS18B20.h>

// This #include statement was automatically added by the Particle IDE.
#include <DS18B20.h>

#include <DS18B20.h>
#include <math.h>

const int      MAXRETRY          = 4;
const uint32_t msSAMPLE_INTERVAL = 2500;
const uint32_t msMETRIC_PUBLISH  = 10000;

const int16_t dsVCC  = D2;
const int16_t dsData = D3;
const int16_t dsGND  = D4;

// Sets Pin D3 as data pin and the only sensor on bus
DS18B20  ds18b20(dsData, true); 

char     szInfo[64];
double   celsius;
double   fahrenheit;
uint32_t msLastMetric;
uint32_t msLastSample;

void setup() {
  Serial.begin(115200);
  
  pinMode(dsGND, OUTPUT);
  digitalWrite(dsGND, LOW);
  pinMode(dsVCC, OUTPUT);
  digitalWrite(dsVCC, HIGH);

  delay(1000);
  Particle.subscribe("Fridge Status: OPEN", myHandler, "e00fce68623c330ea3b4fcc1");
}

void loop() {
  if (millis() - msLastSample >= msSAMPLE_INTERVAL){
    getTemp();
  }

  if (millis() - msLastMetric >= msMETRIC_PUBLISH){
    Serial.println("Publishing now.");
    publishData();
  }
}

void publishData(){
  sprintf(szInfo, "%2.2f", fahrenheit);
  Particle.publish("dsTmp", szInfo, PRIVATE);
  msLastMetric = millis();

}

void getTemp(){
  float _temp;
  String status;
  int   i = 0;

  do {
    _temp = ds18b20.getTemperature();
  } while (!ds18b20.crcCheck() && MAXRETRY > i++);

  if (i < MAXRETRY) {
    celsius = _temp;
    fahrenheit = ds18b20.convertToFahrenheit(_temp);
    Serial.println(fahrenheit);
  }
  else {
    celsius = fahrenheit = NAN;
    Serial.println("Invalid reading");
  }
  msLastSample = millis();
  if(fahrenheit >= 45)
  {
      status = "WARM";
      Particle.publish("WARM", status, PUBLIC);
  }
  else{}
}
void myHandler(const char *event, const char *data)
{
    Particle.publish(event, data, PRIVATE);
    
}

int switchPin = D0;
int writePin = D6;
int alarmPin = D7;
String status;

void fridgeAlarm();
void setup() {
    pinMode(switchPin, INPUT);
    pinMode(writePin, OUTPUT);
    pinMode(alarmPin, OUTPUT);
    Particle.subscribe("WARM", myHandler, "e00fce68391e3538c530f420");
}

void loop() {
delay(5000);
digitalWrite(writePin, HIGH);
digitalWrite(alarmPin, HIGH);

if (digitalRead(switchPin) == HIGH)
{
    delay(5000);
    status = "OPEN";
    Particle.publish("Fridge Status: OPEN", status, PRIVATE);
    while(digitalRead(switchPin) == HIGH)
    {
    digitalWrite(alarmPin, LOW);
    }
}
if (digitalRead(switchPin) == LOW)
{
    digitalWrite(alarmPin, HIGH);
}
else
{
}
}
void myHandler(const char *event, const char *data)
{
    Particle.publish(event, data, PRIVATE);
}

Credits

Joe Hankins

1 project • 0 followers

John Bustle

1 project • 1 follower

Annoying Fridge Alarm