Knock detecting door lock.

Group members

D.G.U.I Wickramarathna 100590G

D.G.C.D Wijerathna 100596F

Y.M.S.N Wijayarathna 100597J

W.M.N.C Wijebandara 100598M

Abstract

The project idea was to build a knock detecting

door lock which can identify the specific knocking

pattern and unlock the door if the pattern is

correct. This door locking system provides much

security than systems which are currently using.

When there are many users who use the door,

problems may occur because there is only one key

to open the door. But here in this door locking

system this kind of problems may not occur

because the users who know the knocking pattern

can open the door any time without a key.

Introduction

Background

Door lock is use in doors to lock the door, it is a

security strategy use for avoiding to open the

door. Only rightful person can open the door.

There are many type of door locks currently use

in the world. Key door lock is the most common

one among them. In high security systems it uses

electronic door locks. Electronic door lock is

locking device which operate with the means of

electricity. More often electronic door locks are

connected to an access control.The advantages

of an electric lock connected to an access control

system include: key control, where keys can be

added and removed without re-keying the lock

cylinder; fine access control, where time and

place are factors; and transaction logging, where

activity is recorded. Numerical codes,

passwords, passphrase, Security tokens,

biometrics, Finger prints, Face recognition etc.

are some types of electronic locks.

In building knock detecting door lock we used

micro controllers, pattern detecting algorithms,

touch sensor circuit and password detect system.

At the first we use a Guitar Pick (microphone

used in guitars) and detect the sound appears

when knocking the door, but later we change it so

it detect pattern by touch sensing.

Problem

Key door lock is the most common door lock we

see in homes and many other buildings. Mostly

one key is use for one door so when many users

use door problems may occurs. And also

security problems may occur if the keys can be

duplicated.If the key is lost door can’t be opened

by the user and it can be found by someone else.

And also door opening should be very simple

and user doesn’t like to spend more time in front

of the door opening the door. So face

recognition, eye detecting door lock also have

some problems. Passcode door locks have

security problems in if someone can fetch the

password by looking user typing the password.

Objective

We thought about the above mentioned problem

and try to find a solution and a way to improve

the security. So knock detecting door lock is the

idea we came up. Here door user can assign

specific knocking pattern to the door lock (can

be a music pattern of a song or a simple pattern)

so only the person who know the pattern and

who can knock that pattern in certain accuracy

can open the door. So only having one key

trouble may not occur with this door lock.

Because any user who use the door should know

the knocking pattern and they can open the door

any time they want. Further development and

higher security we thought about having a

password or face recognition. But it will take

much money for the equipment so we decide

only to build the knock detecting part. And also

we thought about farther development by

connecting the door lock with a mobile phone

via blue tooth. It increase the security and if user

forgot the knock pattern only the specific user is

able to connect the door lock.

Methods

march April May June

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

Identifyin

g the

Project

Research

Making

the project

Proposal

and cost

estimation

Design

Making

Prototype

Implement

ation

Testing

and Finish

Project

Document

ation

Research

As mentioned in Introduction first we identified

the need of a door locking system that reacts to

knocking.

In our research period first we studied about

how to get sound of knocking. Getting noise free

sound, how to recognize patterns using suitable

algorithms, connecting system with users mobile

phone via internet, Arduino Programming are

the thing we researched in this period in purpose

of coming up with a better solution for the

problem we identified.

Then we identified the most suitable way to

reach our solution.

Design

The first design we came up with is to identify

correct knock by identifying sound made at the

knock. This is the design we came up to give

that kind of solution.

Microphone

Signal Amplifier

Analog to Digital

Converter

Signal Processing

Unit

Door Lock

In this first design we used a guitar pick-

up(microphone used in guitars) (Figure 1) as the

microphone. We used it because it can be

attached to wood, here to door so it only get the

sound come along the timber without any noise.

This microphone doesn’t accept any sound other

than sound of knocking.

Figure 1 :Guitar pick-up

From microphone we get a current signal that is

proportional to the energy of the sound wave

received by the microphone.

Then this signal is send to the signal amplifier.

This circuit amplifies the weak signal from

microphone so it can be used in processing.

Then the amplified signal is send into the

Analog to Digital Converter circuit. In that part

analog signal is sampled at foscillator/64 rate. Then

average voltage of each sample is compared

with reference voltage and output 1 or 0 for each

sample. Then the output from ADC is a 1, 0 bit

pattern.

This bit stream is send into the processing unit.

In processing unit this bit pattern is compared

with the saved bit pattern, which is

corresponding to the correct knock. If the

difference between 2 bit patterns is less than pre-

defined percentage, the knock is accepted as

correct. Otherwise it is considered as wrong. An

output will be send in to the door lock which

will be opened only if the knock has accepted.

There were few drawbacks of this design.

1. The PIC we planned to use 16F877A

has less performance than we expected.

2. Pattern recognition algorithms are too

much complex.

3. Even though we use a Guitar

Microphone which reduces the noise,

noise still have a big impact on results.

Because of these issues we had to go to an

alternate solution to the problem.

To avoid these problems we do certain changes

in our design. We decided get pattern of the

knock by using touch sensing other than getting

sound input. This avoids problems occurred due

to noise.

We replaced PIC with an Arduino Mega 2560

development kit. Since it has more processing

power and memory, we could solve the

problems occurred due to law performance of

PIC.

Implementation

Touch triggering switch

Touch-triggering switch is a circuit which gives

digital output, it returns +5V when touch is

present and 0V when no touch present. So the

output of this part will be a digital signal

depending on knock.

Touch-triggered

switch

Signal Processing

Unit

Door Lock

We identified three types of touch switches.

Resistance touch switch

Hum touch switch

Capacitive touch switch

Resistance touch switch (Figure 2) is the most

basic type of touch switch it is based on the fact

that human tissues,have a great amount of water

and salt, something that makes it conductive.

Figure 2 :Resistance touch switch

This is not very flexible design and it needs two

electrodes, and not suitable for exposed to

environment very much because it can make a

conductivity between two electrodes with the

time.

Hum touch switch(figure 3) is An Hum touch

sensor uses a high gain amplifier such as a

Darlington pair to amplify this parasitic voltage.

Here is a basic circuit with such a sensor:

Figure 3: Hum touch switch

We identified that this type of switch is more

suitable for our device so we designed a switch

using this type.

So we used ne555 touch circuit which is a type

of Hum touch switch also have some deviation

from it.

This circuit returns a digital signal

corresponding to the knock made. This signal is

send into the signal processing unit.

Figure 4 : ne555 touch circuit

Signal Processing Part

Figure 4 : Circuit Schematic diagram

In signal processing unit, digital signal

corresponding to knock made at door is

compared with knock patterns which are saved.

Signal processing is done by ATMEGA328

micro controller. We used Arduino Uno circuit

which ATMEGA328 is connected.

Programming

Arduino board was programmed using C

language.

In the program, first we save 3 sample knocks in

processing unit. We have to knock 3 times while

pressing a button, so 3 knocks will be saved.

What is saved here is the time gaps between two

+5V pulses in the signal. It is a quality depends

on the pattern of the knock. When somebody

knocks the door its pattern is compared with

these saved patterns. If it is matched with any of

the saved patterns it will be considered as a

correct knock and signal is send to lock to open.

Even though in beginning there are only 3

samples, when times goes on number of samples

is increased up to 20. When door knock occur it

is given a priority value according to how many

saved patterns it matched with. If it is a correct

knock it is saved with its priority value. So when

number of times knocks has made is increased,

the accuracy of the algorithm will also increase.

Door lock

Electronic door locks use magnets, solenoids

and motors to actuate the lock by either

supplying or removing power. Operating the

lock can be as simple as using a switch, for

example an apartment intercom door release, or

as complex as a biometric based access

control system.

In Magnetic Lock a large electro-magnet is

mounted on the door frame and a corresponding

armature is mounted on the door. When the

magnet is powered and the door is closed, the

armature is held fast to the magnet. Mag locks

are simple to install and are very attack resistant.

But the problem with this lock is this needs a

large current and it cannot be supplied by a

battery. This current has to be given in main

supply, and when there is a power cut this lock

will not work.

In our design we used motor actuated door lock.

In this door lock there is a motor which can

rotate both ways. The lock is connected via a

lever to this motor. When motor is rotated to a

one side, door lock locks and when motor

rotated to other side it will unlock.

Here we used a servo motor for the door lock.

Figure 5: Servo motor

Power Supply

Power is supplied to the system is by a 12V

power pack. And also here we have used a

backup power plan that will work under a power

cut using a 9V rechargeable battery.

Figure 6

Here 12V supply and 9V supply has connected via 2

diodes. When 12V supply is present D2 will reverse

biased and no current will be taken from battery. D2

will be forward biased only when 12V power supply

is unavailable and then current will be taken from

battery.

Bluetooth module

We used Blue tooth module in order to advance

the security of the door lock. Here a specific

person can unlock the door using his phone. This

facility can be provided as the interest of the

customer. If it is very high security door , door is

unlock when the both knock pattern is correct

and correct phone is near the door. And also it

can be provided as if the specific person forgot

the knock pattern he can unlock the door using

his phone.

Phone has a specific Bluetooth app and it sends

serial data which attach the MAC address of the

phone and receiving the data Bluetooth module

check that MAC address with saved MAC

address if both are the same door will be

unlocked.

Figure 7: Bluetooth module

Results

Knock detecting door lock is an advance door

lock which can identify specific knock pattern

and figure out it is correct or not. If the knock

pattern is correct lock will be opened. Specific

knock pattern is assigned by the user.

There is a metal plate in the door where we

should knock and only the finger should use to

knock because as earlier mentioned in the

methods when the finger touches the metal small

current is grounded through the body and it is

appears as a digital 1 voltage.

User can press and hold the assign button and

knock the door in whatever pattern he likes and

it should be remembered very carefully by all

users who use the door. It is very hard to knock

in specific pattern 100% exactly twice. So we

have to save same knock pattern 3 times. Those

are three sample patterns.. That knocking pattern

will be saved in the EEPROM. Saved pattern

will not be erased even the power is not in the

system. And we use the concept of learning

algorithm. When the user knocks the door it is

compare with the saved samples and calculate

the similarity percentage if it is more than 95%

user can open the door. And that knock pattern

will be saved as a sample pattern so when this

implement door lock pattern is adopt to the users

pattern changes. And these changes are not big

differences with the original samples but very

small changes which can’t be figure by ears.

Discussion

We thought about how to develop this door lock

with more features. For farther security here we

can assign more than one knock pattern so every

member who use the door has specific knock

pattern for each of them. And there may have a

main user. Each member should well remember

there knock pattern and they can open the door.

When someone opens the door automatically

SMS is sent to the main user’s mobile phone via

a GSM module informing which user opens the

door at the time. And also we can assign a

password for the user so he have to knock the

door correctly and if it is accepted SMS is sent

to particular user’s mobile phone requesting the

password , user have to give the correct

password to open the door. This will increase the

security level much high.

There are few limitations of this design too.

Touch triggered switch is working by leaking

some current through human body. So to proper

working, knock should be only made by human

hand. If the knock is made by wood or any

insulator it won’t work properly.

Also user has to make knock on the circuit part,

if it is made on wrong place of the door it won’t

recognize as a knock. There is an advantage of

this also. Unauthorized person who is trying to

open the door must know the correct place of the

door to know with the correct knock pattern.

In the earlier design with knock detection by

sound, these problems were not present.

Acknowledgment

First on foremost, we would like to thank Miss. Ashanthi Maxworth who guided us through doing this

project. Provided important advices, helped us in difficult periods and giving us necessary information.

And motivate us to do the project well.

And honorable thanks to Prof. (Mrs.) Indra Dayawansa for spend her valuable time forguide us to

improve the device and solving its problems. Provide important advices.

We also thank Mr. ArunaUpul Undergraduate at Department of Electronic and Telecommunication

Engineering for helping us with his knowledge to successfully finish our project.

Also an honorable mention goes to our families and friends for their understandings and supports on us in

completing this project. Without helps of the particular that mentioned above, we would face many

difficulties while doing thisAt last but not in least we would like to thank all who helped and motivated

us.

Reference

http://en.wikipedia.org/wiki/Touch_switch

http://www.arduino.cc/en/Main/ArduinoBoard

Mega2560

http://en.wikipedia.org/wiki/Servo_motor