Arduino Smoke Alarm Interface

1/*
2   Example Program to
3        Monitor Modified Smoke Alarm
4        Activate Smoke Alarm Remote Buzzer
5        Show status LED when running  or alarm sounding
6
7    Hardware Schematic, PCB file and assembly Instructions  for this code is here:
8    http://Tek4um.com/smokeAlarm
9
10    Release:
11      10 May 2021 v1.0 Initial version
12
13
14
15  © karl grabe Tek4um.com  2021 www.tek4um.com
16  For personal use only.
17*/
18
19#define SMOKE_ALARM_INPUT_PIN  2    // connect to R3 (see circuit diagram)
20#define BUZZER_OUTPUT_PIN 3   //  connect to R4
21#define SMOKE_ALARM_LED_STATUS 4   // on if Smoke Alarm input is  active
22#define SMOKE_ALARM_TEST_BUTTON 5  // for testing
23#define HARDWARE_SERIAL_BAUD  115200
24#define On true
25#define Off false
26#define TEST_TIME_DURATION 1000    // Time duration in ms to sound buzzer and status led for testing
27
28
29void  setup() {
30  pinMode(SMOKE_ALARM_INPUT_PIN, INPUT);    // Connected to the modified  Smoke Alarm
31  pinMode(BUZZER_OUTPUT_PIN, OUTPUT);  // Connected to the Remote  Buzzer, active LOW
32  pinMode(LED_BUILTIN, OUTPUT);
33  pinMode(SMOKE_ALARM_LED_STATUS,  OUTPUT);         // active HIGH
34  pinMode(SMOKE_ALARM_TEST_BUTTON, INPUT_PULLUP);  // active LOW
35
36  Serial.begin(HARDWARE_SERIAL_BAUD);
37  delay(500);
38  Serial.println(F("Monitoring Smoke Alarm... "));
39
40  // Test: Turn on the  remote buzzer & Status LED briefly on startup
41  setBuzzer (On);
42  setStatusLED(On);
43
44  delay(TEST_TIME_DURATION);
45  
46  setBuzzer (Off);
47  setStatusLED(Off);;
48  delay (100);                     // Allow C1 capacitor to discharge, otherwise  a false alarm on startup
49}
50
51void loop() {
52  boolean testButtonState  = !digitalRead(SMOKE_ALARM_TEST_BUTTON);  // read the test button, active LOW so  invert it
53  if (testButtonState) {  // if test button presses sound buzzer and  LED on the PCB
54    setStatusLED(On);     // turn on LED
55    setBuzzer (On);       // turn on transistor Q1 to sound buzzer via cable
56    delay (TEST_TIME_DURATION);
57    setStatusLED(Off);    
58    setBuzzer (Off); 
59  }
60
61  // Check if  the smoke alarm is triggered, print it's state to serial monitor
62  boolean smokeAlarmState  = digitalRead(SMOKE_ALARM_INPUT_PIN);  // true: alarm is on so it's triggered (e.g.  Fire!!)
63 
64 if (smokeAlarmState) { 
65  String AlarmStateText = smokeAlarmState  ? "On" : "Off";    // get text of smoke alarm state, true: On, false: Off
66  Serial.print(F("A Smoke Alarm is: "));
67  if (testButtonState)
68    Serial.print  (F("(test button)"));                      // test button is pressed
69  Serial.println(AlarmStateText);
70  setStatusLED(smokeAlarmState); // status led is on when smoke alarm is on
71  delay (500);
72  return;
73}
74
75// *** to do: add background timer to flash  LED
76  delay(100);         // delay before repeating messages
77  flashStatusLED  ();  // show program is running
78  delay (100);
79}
80
81
82
83void setBuzzer  (boolean state){            // pass true to sound buzzer
84  digitalWrite(BUZZER_OUTPUT_PIN,  !state); // active low
85}
86
87void setStatusLED(boolean state) {        //  pass true to turn on LED
88  digitalWrite(SMOKE_ALARM_LED_STATUS, state);  
89}
90
91void  flashStatusLED(){                    // flip the status led
92    digitalWrite(SMOKE_ALARM_LED_STATUS,  !digitalRead(SMOKE_ALARM_LED_STATUS));
93}
94