1. College of Engineering and Science
Digital Combination Lock System
ELEN 408
Spring 2016
Names:
Dinuka Kuruppuarachchi
Ruzova Dahal
Jayakody Arachchige
Sponsor Details: The Vacant Property Specialist,
Jake Switzer
(District Sale Manager)
800-918-9100
jacob.switzer@vps360.com
email: www.vps360.com
05/16/2016

2. Senior Design Spring Report 16th
May 2016
ELEN 408 Electrical Engineering
Design I
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College of Engineering and Science
Introduction to the Project
This senior design project is carried out for our sponsor company Vacant Property
Security, LLC (VPS) which was founded in 1993. VPS is a trusted leader in securing,
maintaining, and managing vacant properties across a wide range of residential and commercial
sectors. They have locations in Los Angeles, CA, Atlanta, GA, Miami, FL, Chicago, IL, Detroit,
MI, Cleveland, OH, Philadelphia, PA, Newark, NJ, and Dallas, TX. VPS allows customers to
protect their vacant properties against unauthorized access and property decay.
The company’s main goal is to ensure that properties retain their value and provide
customers peace of mind in knowing that their vacant properties are safe and secure. VPS used to
order security doors from a company in UK, which recently stopped manufacturing them. Hence,
our objective was to solve their problem by building a replacement door. The intended purpose
of this project is to build a digital combination lock system that will allow to unlock the door
which will be built by the Mechanical Engineering senior design team for VPS. The door is
made of steel and it features a keypad where codes can be entered to gain access to the property
while providing additional security from intruders. The focus of our Electrical Engineering
Design team was to design and rebuild a door lock system, where we can enter codes that will
interact with the main controller which in turn will interact with the locking mechanism and
allow us to unlock the door. Finally, this digital combination control lock system is mounted on
the door built by the Mechanical Engineering Design team.
Moreover, this electronic lock system works based on combination codes and has a
buzzer attached to it which will further facilitate the customers. These doors are expected to
provide security in the building.
Our Electrical Engineering project team consists of Dinuka Kuruppu, Ruzova Dahal, and
Shakya Jayakody. We were supported by our advisor Dr. Davis Harbour and Dr.Paul Hummel of
Louisiana Tech University in Ruston, Louisiana and also by Mr. Chad Mosley of Vacant
Property Security, LLC in Dallas, Texas. Besides, we planned and worked in collaboration with
the Mechanical Engineering Team throughout the year to successfully complete the project.
according to requirement.

3. Senior Design Spring Report 16th
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Design I
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Customer Requirements
Functional Performance:
- Improved power supply. The electronic release seems to use much more power in the cold
weather. We have most of our dead battery calls in the winter
- Key & Code all-in-one door. The door is designed such that the servo motor is also activated
using a key
- Override key – If the battery dies key will open the door. Battery needs to be replaced
occasionally
- Make door lever recessed. Easier for stacking and transport.
- Recessed pull handle – some folks have issues opening the door using the lever.
- Less force to pull down the open/close handle
- Improved button color longevity
- Login database with all logging details including date, time and password type
Operating Environment
- These doors will be placed on places where security access are required
- The doors are expected to be placed in residential temperatures of about 50-100 F
- Minimal dust
- Able to be operated multiple times a day
Economic
- Should have economic life of more than 5 years
- Should not require disassembly other than changing batteries
- Should be able to safely operate
Maintenance, repair, retirement
- Technician will be needed to install
- Battery supplied for power will be easy to remove or replace and instruction to do so will be
provided
- Contact the local agent during the any faults
Reliability, robustness
- No failure should occur during economic life
- Besides replacing the battery occasionally, no parts should occur

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Safety
- Use of proper tools and safety method to install the system will prevent any injuries
- This door can be safely operated multiple times per day
- Will not catch fire during normal use
Pollution
- Will not create any pollutions
- Will not create noise greater than 40 dB.
Ease of Use
- Can be operated multiple times per day
- Door will be unlocked once the correct code has been entered
- Entering incorrect code for three times will activate the buzzer for security purpose
Human Factors
- No large force required to unlock the door
- Correct code will unlock the door instantly
- Battery can be replaced or removed easily by the operator by following the instruction
provided
- None of the parts are slippery
- Can be accessed by people in wheelchair too
Appearance
- The exterior of the door will be made of steel
- Only the keypad, LED and fingerprint scanner will be seen and accessed from the outside
of the door.
- The main controller, batteries and wires are attached to a board that is mounted on the
door from the interior
- Surface finish will be smooth and easy to clean
- There will not be any sharp metals or edges

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College of Engineering and Science
Company Requirements:
Marketing
- The retail price of the finished door should be less than $4500
Manufacturing
- The final demonstration and presentation was done on May 6, 2016
- Components used in the door are readily available to buy within US
- The components are chosen in the basis of budget and functionality
Financial
- The budget for the entire project is $4500 of which Electrical Engineering Design team
will be using approximately $75
Other
- Production prototype was shown to the Senior Design Professors Dr. Harbour and Dr.
Hummel before the final testing

6. Senior Design Spring Report 16th
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College of Engineering and Science
Project Flow Chart
Figure: Project Flow Chart

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The above flow chart demonstrated the overall working process of the project. We started the
project by the making a timeline in Gantt Chart. We used AT Mega 2560 as our main
microcontroller and Atmel Studio 7 to program it using C programming language. First, we used
a 4 by 4 matrix keypad to enter the password for easiness and later replaced it by 2 by 3 matrix
color coded keypad according to company requirements. After programming for the passwords,
Real Time Clock was implemented and SD card and Buzzer were added.
Technical Details
Block Diagram
Figure: Block Diagram showing inputs and outputs of the system
We used AT Mega 2560 as our main microcontroller and Atmel Studio 7 to program it. The
inputs of the system are sensor, 5 color coded keypad and real time clock. Outputs/results are
obtained in various forms through rotating of servo motor, SD card reader to store and record
time, and buzzer to make alarms.

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College of Engineering and Science
Figure: Layout of System

9. Senior Design Spring Report 16th
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ELEN 408 Electrical Engineering
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College of Engineering and Science
Working Mechanism of servo
When we enter correct set of password, the servo will rotate 17 clockwise to unlock the door.
Similarly, when we lock the door, the servo will rotate 17 anti-clockwise.
Figure: Working mechanism of servo

10. Senior Design Spring Report 16th
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College of Engineering and Science
Mechanism of the controller with LCD
Figure: Layout of system consisting of LCD
Initially and LCD was also attached to the system for easiness and to be able to debug. However,
it was later removed according to company requirements.

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College of Engineering and Science
Microcontroller Programming Flowchart

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Figure: Flowchart showing microcontroller working mechanism
Main Controller
The Arduino Mega is a microcontroller board based on the ATmega2560 using AVR
architecture. It consists of 14 PWM output pins,16 analog inputs, 4 UARTs pins total 54 digital
input/output pins. It runs with a 16 MHz crystal oscillator. This board can operate on an external
supply of 6 to 20 volts. For the stability the recommended range of the supply is 7 to 12 volts.

13. Senior Design Spring Report 16th
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ELEN 408 Electrical Engineering
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College of Engineering and Science
Figure: Arduino Mega
Specifications
Microcontroller - ATmega2560
Operating Voltage - 5V
Input Voltage (recommended)- - 7-12V
Input Voltage (limits) - 6-20V
Digital I/O Pins - 54
Analog Input Pins - 16
DC Current per I/O Pin - 40 mA
DC Current for 3.3V Pin - 50 mA
Flash Memory - 256 KB of which 8 KB used by bootloader
SRAM - 8 KB
EEPROM - 4 KB
Clock Speed - 16 MHz
Figure: Ports on Main Controller

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ELEN 408 Electrical Engineering
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College of Engineering and Science
Five Color Coded Keypad
The flow chart below shows the working mechanism of 5 buttons used to enter the password.
Figure: Working Mechanism of Keypad

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Keypad Design
Requirements
We were required to design and built five button color coded keypad to enter the password.
However, to be able to reset the password without creating conflict of command, we decided to
add a master button.
Process
To add six buttons, we decided to do the PCB design to make the schematic and layout for the
keypad. We used CADSoft Eagle PCB Design Software to do the PCB layout for the keypad.
The schematic was based on 2 by 3 matrix layout design as seen in figure.. We ordered the push
buttons from Digi key and based on the measurements from the data sheet, the schematic was
made using the software. Next, the layout was made using the same software as seen in figure…
Figure: 2 by 3 matrix design Figure: PCB Layout
After making the layout, it was printed on a photo paper using laser printer. By applying heat for
30 minutes, the mirror image of the layout was printed on the copper clad board. The board was
then dissolved into Ferric Chloride solution for 30-40 minutes to fabricate the copper board.

16. Senior Design Spring Report 16th
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ELEN 408 Electrical Engineering
Design I
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College of Engineering and Science
Finally, the PCB layout was ready. Holed were drilled using hand drills. The push buttons were
inserted and were soldered from behind the board. Two wires from the rows and three wires
from the columns of 2 by 3 matrix buttons were soldered and connected to the main controller.
The keypad was then programmed by coding on the Atmel Studio 7.
The process can be seen in pictures below:
Figure: Keypad Design Process
Servo

17. Senior Design Spring Report 16th
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ELEN 408 Electrical Engineering
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College of Engineering and Science
DSS-M15 is a heavy-duty gear standard servo with 180 𝑜
wide angle. high torque power
improved stability and durability.
Figure: Keypad Design Process
Features:
-Operating Voltage range 4.8- 7.2 volts
-Operating speed: 0.18 sec/60 𝑜
-Quiescent current: 80mA
-Stall Torque
-Control signal RC PWM
Buzzer and Bumper switch
A buzzer will notify if the password incorrect/correct and when the door is unlocked/locked.
Bumper switch will detect whether door is closed or open, signal will deliver to the
microcontroller to process.

18. Senior Design Spring Report 16th
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ELEN 408 Electrical Engineering
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College of Engineering and Science
Figure: Keypad Design Process Figure: Keypad Design Process
SD Card reader and Real Time Clock
For our senior design project, the company also required Password tracking device to check who
has enter 5 different passwords on relevant time. To accomplish this task, we include a Real
Time Clock, SD Card Reader and a SD Card.
Figure: SD Card Reader Figure: Real Time clock DS3231
Real Time Clock
Real Time Clock will use to store time. Due to the in build battery, data won’t be loss even when
there is a power outage. RTC and the microcontroller communicate in 𝐼2
𝐶, with in build unique
hex address. RTC maintains seconds, minutes, hours, days, date, month, and year information.
This module also can read the temperature.

19. Senior Design Spring Report 16th
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ELEN 408 Electrical Engineering
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College of Engineering and Science
Features:
-High accurate RTC (±2𝑝𝑝𝑚 from0 𝑜
𝐶 − 40 𝑜
𝐶)
-𝐼2
𝐶Communication methodhas most microcontrollers
-Battery-Backup input for continuous timekeeping
-Standard 3.3V
- Digital Temp sensor ±3.5𝑝𝑝𝑚accuracy
-Two time-of day alarm
Block Diagram:
𝑰 𝟐
𝑪communication method can communicate 100 devices individually, since each device has
unique hex address using bus network. DS3231 also has a unique hex address stored in 𝑰 𝟐
𝑪
Interface And Address Register Decode. Clock And Calendar Registers Store the time and date.
Once the Handshake between microcontroller and the Real Time Clock happen Clock And

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ELEN 408 Electrical Engineering
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College of Engineering and Science
Calendar Registers will send the data to microcontroller using 7 Bytes User Buffer for use full
data.
SD Card Reader
SD Card and SD Card reader will be use to store a database, to check who has open the door
using 5 different passwords. SD card and the microcontroller communicate using SPI
communication method.
Features:
-SDHC Card Reader
-ISP Communication method has most microcontroller
-SanDisk 4GB SDHC Card
-Standard 5V/3.3V
-Size: 5cm x 3.1cm
Cost
ATmega2560 Microcontroller $44
Keypad Build $30
Real Time Clock $2
SD Card $8
SD Card Reader $1
Some of the constraints that applies to our design are as follows:
Economic Constraints
- Economic constraints this particular constraint do not apply
Environmental Constraints
- Environmental constraints this particular constraint do not apply
Political Constraints
$75

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College of Engineering and Science
- Political constraints do not apply
Ethical Constraints
- Ethical constraints constraints do not apply
Health and Safety Constraints
- Health and Safety constraints does not apply
Manufacturability Constraints
- Mechanical and Electrical engineering knowledge will be required apply to manufacture
or modify the system
- PCB design for color coded keypad might have to be done
Sustainability Constraints
- Sustainability Constraints do not apply
Conclusion
We have laid out the company requirements, prepared schedule, built flowcharts, discussed
working mechanism and ordered our main controller. We conducted weekly team meetings and
worked together to design and build the locking mechanism for the door. The first, second and
third project demonstration was done on December 5, 2015, March 16, 2016 and April 28
respectively. The final presentation of the project was done on May 6, 2016.