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anonymous /gist:5d4b430ded3ab24a1f65 Secret
Created Feb 25, 2015

What would you like to do?
Tilt activated alarm
Fake Hide-A-Key Rock Intruder Alarm
written for an Arduino Uno
by Sarah Pavis
// include the LCD screen library code
#include <LiquidCrystal.h>
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
// fix the pin numbers for the tilt switch pin and reset button
const int tiltPin = 6;
const int alarmPin = 7;
// variables to hold the states of the tiltPin
int tiltState = 0;
int prevTiltState = 0;
// variable for the alarm reset buttoon
int alarmButton = 0;
// time check variables for determining LED blink
unsigned long currentTime;
long prevTime = 0;
long blinkRate = 200;
// the pin locations of the LEDs
// could be called out below but it's easier to change the program later on
// if the locations are kept as variables up here
int upperLight = 9;
int lowerLight = 8;
// variables to hold the high or low LED states
int upperLightState;
int lowerLightState;
// a variable to hold the time the alarm was first activated
long alarmTime;
// 30 sec alarm duration after which it resets to standby mode
long alarmLength = 30000;
// a flag variable to be activated the first time the tilt switch changes state
boolean intruder = false;
void setup() {
// open the serial port for debugging and alarm logs
// set the LED pins as output
pinMode(lowerLight, OUTPUT);
pinMode(upperLight, OUTPUT);
// set the tilt switch and button pins as an input
pinMode(tiltPin, INPUT);
pinMode(alarmPin, INPUT);
// clears anything previously on the LCD
// establishes the LCD screen as 16 columns by 2 rows
lcd.begin(16, 2);
// initial screen before thee alarm is activated
// ideally the LCD would be off completely
// but it's useful to have a neutral message here
// for clarity and debugging
lcd.print("Alarm is in");
lcd.setCursor(0, 1);
lcd.print("standby mode.");
void loop() {
// checks the states of each sensor and
// sets the values to variables
tiltState = digitalRead(tiltPin);
alarmButton = digitalRead(alarmPin);
// if the device has been tilted
// then register that there is an intruder
if (tiltState != prevTiltState) {
intruder = true;
// alarm routine
if (intruder == true) {
lcd.setCursor(0, 0);
lcd.print("Intruder Alert");
lcd.setCursor(0, 1);
lcd.print("Alarm Activated");
// get the current time and set it
currentTime = millis();
// this should set the current time as the start of the alarm
// but it resets the variable every time it loops
// i need to refactor this so that alarmTime is constant
alarmTime = millis();
// blink the LEDs without delaying the program
if ((currentTime - prevTime) > blinkRate) {
if (upperLightState == HIGH) {
lowerLightState = HIGH;
upperLightState = LOW;
else {
lowerLightState = LOW;
upperLightState = HIGH;
digitalWrite(upperLight, upperLightState);
digitalWrite(lowerLight, lowerLightState);
prevTime = currentTime;
// if the reset button is pushed or the alarm goes off for too long
// then reset the alarm
if (alarmLength <= currentTime - alarmTime || alarmButton == HIGH) {
intruder = false;
// alarm reset sequence
if (intruder == false) {
lcd.begin(16, 2);
lcd.print("Alarm is in");
lcd.setCursor(0, 1);
lcd.print("standby mode.");
digitalWrite(upperLight, LOW);
digitalWrite(lowerLight, LOW);
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