ATtiny13a Fridge Alarm

Was in the process of designing my own fridge alarm from ATtiny85 when I saw Ralph Bacon take the challenge of making one from an ATtiny13. I contacted Ralph and picked on him about mentioning "Alexa" on his channel.. Because it my Alexa kept trying to order stuff he would say :) . But  I had to try this challenge. I  had some difficulty. I then tried his and still has some difficulty and with mixing the two I got it to work but I just chose a single tone.  Its been working now since February 2021.

Update June 2022:

This has worked so well I ended up doing a PCB from Oshpark and using this on any external door for my home. It works Great!!

https://oshpark.com/profiles/shermluge

UPDATE May 2023:

Ported to Microchip Studio:

works better and lower current

/*

Arduino version: 

Sherm, new fridge alarm inspired from Ralph Bacon...

for ATtiny13 

trying at 1.2MHz

with MiniCore/MicroCore (MCUDude / Nerd Ralph)

Serial at 19200 baud.

 2021-2-26 

 Tested and works as of 2021-2-27

*/

#include <avr/io.h>

#define DEBUG

// constants won't change. Used here to set a pin number:

#define ledPin PB4    

#define buzzer PB3

#define door   PB2

#define stealth     PB1

#define TX     PB0

// Variables will change:

int ledState = LOW;             // ledState used to set the LED

bool doorClosed = 0; //pulled to ground

bool doorOpen = 1; //high

bool doorStatus = doorClosed;

bool prevDoorStatus = doorOpen;

uint8_t WarnCount = 0;

uint8_t AlarmCount = 0;

// Generally, you should use "unsigned long" for variables that hold time

// The value will quickly become too large for an int to store

unsigned long previousMillis = 0;        // will store last time LED was updated

// constants won't change:

const int Second = 1000;           // interval at which to blink (milliseconds)

const int ThreeSeconds = 3000;

const int WarnTimeSeconds = 15000;

const long Minute = 60000;

const long FiveMinutes =240000;

const uint8_t MaxWarn = 8;

const uint8_t MaxAlarm = 20;  

//functions

bool isDoorOpen();

void beep();

bool stealthMode();

void doorClosedSound();

void doorOpenSound();

void setup() {

  // set the digital pin as output:

  //pinMode(ledPin, OUTPUT);

  //pinMode(buzzer, OUTPUT);

  DDRB |= (1 << ledPin);  //set for output

  DDRB |= (1 << buzzer);  //set for output

  //pinMode(door, INPUT);

  #ifdef DEBUG

    // Note that any baud rate specified is ignored on the ATtiny13. See header above.

    Serial.begin();

  #endif

  beep();

  beep();

}

void loop() {

  // here is where you'd put code that needs to be running all the time.

  // check to see if it's time to blink the LED; that is, if the difference

  // between the current time and last time you blinked the LED is bigger than

  // the interval at which you want to blink the LED.

  if(isDoorOpen()==doorOpen){

    unsigned long currentMillis = millis();

    #ifdef DEBUG

      if(!((currentMillis-previousMillis)%100)){

      //  Serial.print(currentMillis-previousMillis);

        Serial.println(F("  in loop"));

      }

    #endif

    //Warn door is open every so many seconds.

    if(WarnCount <= MaxWarn && currentMillis - previousMillis >= WarnTimeSeconds){ 

      #ifdef DEBUG

        Serial.println(F("Warn"));

      #endif

             // save the last time you blinked the LED

      previousMillis = currentMillis;

      //ledState=ledState ? HIGH:LOW;

      WarnCount++;

      for(uint8_t i=0;i<=WarnCount;i=i+2){

        beep();  

      }

    }//if warn

    //Alarm, beep every so many seconds

    if(WarnCount >MaxWarn && currentMillis - previousMillis >= ThreeSeconds){ 

      #ifdef DEBUG

        Serial.println(F("Alarm"));

      #endif

      beep();

      // save the last time you blinked the LED

      previousMillis = currentMillis;

      AlarmCount++;

      //doorIsOpen = doorStatus ? true : false;

    }//if alarm

    //Max Alarm sound after so long on normal alarm.

    if(AlarmCount >MaxAlarm && currentMillis - previousMillis >= Second){ 

      #ifdef DEBUG

        //Serial.println(F("Alarm MAX"));

      #endif

      beep();

      // save the last time you blinked the LED

      previousMillis = currentMillis;

      //doorIsOpen = doorStatus ? true : false;

    }//if alarm  MAX

  } //isDoorOpen()

}

bool isDoorOpen(){

  doorStatus=digitalRead(door);

  if (doorStatus!=prevDoorStatus){

    if(doorStatus==doorOpen){

      #ifdef DEBUG

        Serial.println(F("Door Open"));

      #endif

      doorOpenSound();

    }else{

      #ifdef DEBUG

        Serial.println(F("Door Closed"));

      #endif

      doorClosedSound();

      AlarmCount=0;

      WarnCount=0;

    }    

    prevDoorStatus=doorStatus;

    previousMillis=millis();

  }

  _delay_ms(20);

  return doorStatus;

}

bool stealthMode(){

  return digitalRead(stealth);

}

void doorOpenSound(){

  if(!stealthMode()){

    PORTB |= (1 << buzzer);      //replaces digitalWrite(buzzer, HIGH);

    delay(10);

    PORTB &= ~(1 << buzzer);    //replaces digitalWrite(buzzer, LOW);

    delay(20);

    PORTB |= (1 << buzzer);      

    delay(10);

    PORTB &= ~(1 << buzzer);    

    delay(20);

    PORTB |= (1 << buzzer);      

    delay(10);

    PORTB &= ~(1 << buzzer);    

  }

  PORTB |= (1 << ledPin);      

  delay(80);

  PORTB &= ~(1 << ledPin);    

}

void doorClosedSound(){

  if(!stealthMode()){

    PORTB |= (1 << buzzer);      

    delay(20);

    PORTB &= ~(1 << buzzer);    

    delay(150);

    PORTB |= (1 << buzzer);      

    delay(10);

    PORTB &= ~(1 << buzzer);    

  }

  PORTB |= (1 << ledPin);      

  delay(80);

  PORTB &= ~(1 << ledPin);    

}

void beep(){

  if(!stealthMode()||AlarmCount >MaxAlarm){

    PORTB |= (1 << buzzer);      

    delay(20);

    PORTB &= ~(1 << buzzer);    

  }

  PORTB |= (1 << ledPin);      

  delay(80);

  PORTB &= ~(1 << ledPin);    

}

Posted this in November so its been working solid for  over 8 months now and no issues.. 

Links:

• Ralph Bacon Attiny13 fridge alarm

• MCUDude excellent Attiny13 library

• A great source for Attiny13 info https://blog.podkalicki.com/