This document contains the code for a smart door knocker based on an Arduino UNO board. The code includes functions for detecting knocks on a sensor, validating the detected knock pattern against a stored secret code, triggering door unlocking if the code is validated, and allowing the secret code to be programmed. It uses LEDs, a buzzer, and a servo motor to control the door lock. The system listens for a series of knocks and compares the timing of the detected knocks to the secret code to unlock the door only if the proper code is entered.

1. Listing Program for Smart Door Knocker based on Arduino UNO R3
/* SecretDoor KnockDetectingDoorLock
OriginallyfromSteveHoeferhttp://grathio.comVersion0.1.10.20.10
Updatesby Lee Sonko
LicensedunderCreativeCommonsAttribution-Noncommercial-Share Alike3.0
http://creativecommons.org/licenses/by-nc-sa/3.0/us/
(Inshort: Do whatyou want,justbe sure to include thisline andthe fourabove it,anddon't sell it
or use it inanythingyousell withoutcontactingme.)
Modifiedby:DindaEkaPratiwi (RefrigerationandAirConditioningCollager,PolytechnicState of
Bandung) (November2015)
*/
#include <Servo.h>
Servomyservo;
const intknockSensor=0;
const intprogramSwitch= 3;
const intlockMotor= 6;
const intredLED = 4;
const intgreenLED= 5;
const intbuzzer= 2;
const intthreshold=50;
const intrejectValue=25;
const intaverageRejectValue=15;
const intknockFadeTime =150;
const intlockTurnTime =650;
const intunlockTime =5000;

2. const intmaximumKnocks=20;
const intknockComplete=1200;
// Variables.
intsecretCode[maximumKnocks] ={50, 25, 25, 50, 100, 50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
intknockReadings[maximumKnocks];
intknockSensorValue =0;
intprogramButtonPressed=false;
voidsetup() {
myservo.attach(lockMotor);
pinMode(lockMotor,OUTPUT);
pinMode(redLED,OUTPUT);
pinMode(greenLED,OUTPUT);
pinMode(programSwitch,INPUT);
pinMode (buzzer,OUTPUT);
Serial.begin(9600);
Serial.println("Programstart.");
digitalWrite(greenLED,HIGH);
}
voidloop() {
knockSensorValue =analogRead(knockSensor);
if (digitalRead(programSwitch) ==HIGH) {
programButtonPressed=true;
digitalWrite(redLED,HIGH);

3. } else {
programButtonPressed=false;
digitalWrite(redLED,LOW);
}
if (knockSensorValue >=threshold) {
listenToSecretKnock();
}
}
voidlistenToSecretKnock() {
Serial.println("knockstarting");
inti = 0;
for(i = 0; i < maximumKnocks; i++) {
knockReadings[i] =0;
}
intcurrentKnockNumber=0;
intstartTime = millis();
intnow= millis();
digitalWrite(greenLED,LOW);
if (programButtonPressed==true) {
digitalWrite(redLED,LOW);
}
delay(knockFadeTime);
digitalWrite(greenLED,HIGH);
if (programButtonPressed==true) {

4. digitalWrite(redLED,HIGH);
}
do{
knockSensorValue =analogRead(knockSensor);
if (knockSensorValue>=threshold) {
Serial.println("knock.");
now= millis();
knockReadings[currentKnockNumber] =now - startTime;
currentKnockNumber++;
startTime = now;
digitalWrite(greenLED,LOW);
if (programButtonPressed==true) {
digitalWrite(redLED,LOW);
}
delay(knockFadeTime);
digitalWrite(greenLED,HIGH);
if (programButtonPressed==true) {
digitalWrite(redLED,HIGH);
}
}
now = millis();
} while ((now - startTime <knockComplete) &&(currentKnockNumber<maximumKnocks));
if (programButtonPressed==false) {
if (validateKnock()==true) {
triggerDoorUnlock();
} else {

5. Serial.println("Secretknockfailed.");
digitalWrite(greenLED,LOW);
for (i = 0; i < 4; i++) {
digitalWrite(redLED,HIGH);
delay(100);
digitalWrite(redLED,LOW);
delay(100);
digitalWrite(2,LOW);
delay(1000);
digitalWrite(2,HIGH);
delay(1000);
}
digitalWrite(greenLED,HIGH);
}
} else {
validateKnock();
Serial.println("New lockstored.");
digitalWrite(redLED,LOW);
digitalWrite(greenLED,HIGH);
for (i = 0; i < 3; i++) {
delay(100);
digitalWrite(redLED,HIGH);
digitalWrite(greenLED,LOW);
delay(100);
digitalWrite(redLED,LOW);
digitalWrite(greenLED,HIGH);

6. }
}
}
voidtriggerDoorUnlock(){
Serial.println("Doorunlocked!");
myservo.write(0);
delay(lockTurnTime);
delay(unlockTime);
myservo.write(180);
for(inti = 0; i < 5; i++) {
digitalWrite(greenLED,LOW);
delay(100);
digitalWrite(greenLED,HIGH);
delay(100);
}
}
booleanvalidateKnock(){
inti = 0;
intcurrentKnockCount=0;
intsecretKnockCount=0;
intmaxKnockInterval =0;

7. for(i = 0; i < maximumKnocks;i++) {
if (knockReadings[i] >0) {
currentKnockCount++;
}
if (secretCode[i] >0) {
secretKnockCount++;
}
if (knockReadings[i] >maxKnockInterval){
maxKnockInterval =knockReadings[i];
}
}
if (programButtonPressed==true) {
for (i = 0; i < maximumKnocks;i++) { // normalize the times
secretCode[i] =map(knockReadings[i],0,maxKnockInterval,0,100);
}
// Andflashthe lightsinthe recordedpatterntoletus know it's beenprogrammed.
digitalWrite(greenLED,LOW);
digitalWrite(redLED,LOW);
delay(1000);
digitalWrite(greenLED,HIGH);
digitalWrite(redLED,HIGH);
delay(50);
for (i = 0; i < maximumKnocks;i++) {
digitalWrite(greenLED,LOW);
digitalWrite(redLED,LOW);
if (secretCode[i]>0) {
delay( map(secretCode[i],0,100, 0, maxKnockInterval));
digitalWrite(greenLED,HIGH);

8. digitalWrite(redLED,HIGH);
}
delay(50);
}
returnfalse;
}
if (currentKnockCount!=secretKnockCount) {
returnfalse;
}
inttotaltimeDifferences=0;
inttimeDiff =0;
for(i = 0; i < maximumKnocks;i++) { // Normalize the times
knockReadings[i] =map(knockReadings[i],0,maxKnockInterval,0,100);
timeDiff =abs(knockReadings[i] - secretCode[i]);
if (timeDiff >rejectValue){ //Individual value toofaroutof whack
returnfalse;
}
totaltimeDifferences+=timeDiff;
}
if (totaltimeDifferences/secretKnockCount>averageRejectValue) {
returnfalse;
}
returntrue;
}