6)chapter 3 updt

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CHAPTER 3

METHODOLOGY

3.1 Basic Operation of the Magnetic Door Lock System using the Electronic

Combination Lock Based on PIC16F877A.

In building this project, there were several steps taken. This project is a combination of

different phases in completing of the project due to requirement.

3.2 Circuit Analysis

Figure 3.1

Referring to figure 3.1, this EMF door lock is operated only when the correct combination is

keyed in on the Key-Pad. If wrong combination is keyed, the EMF lock does not operate. The

system will activate the relay and buzzer if the password keyed in which is preset in the

program is correct. The whole system is connected to the Peripheral Interface Controller

also known as PIC. Whereby, the PIC is programmed with HEX code which is converted

from a simple C-language programming to function. Based on this project completed, the PIC

used was PIC16F877A which is a 40 pin PIC as mentioned in the Literature review. The

whole project was initially built on a breadboard before connecting it to the Printed Circuit

Board (PCB).


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The process of connecting to the components onto the Breadboard is to troubleshoot

problems by simply disconnecting and reconnecting the component without going through

hassle. P-Spice was also used to simulate the circuit to check for errors.

3.2.1 Methods taken in Connecting the Circuit

Powering it

Electronic parts mostly all use 5V. 5V is obtained by using the LM7805 voltage

regulator chip. What the 7805 chip does, it takes a higher DC voltage, between 6V and 30V,

and turns it into almost 5V on the output. The measured value and the theoretical measure

vary. It is also important to put a capacitor between the output and ground to make the

voltage smooth. Otherwise there will be small high-frequency oscillations in the power,

which can mess up circuits. For building and testing a circuit, a DC power supply is used.

The EMF lock requires a 12V supply. Therefore, a 12V supply will be supplied to the whole

circuit whereby the voltage regulator regulates at almost a constant 5V to its components and

the EMF lock will receive a 12V supply.

As shown in figure 3.2, user can choose either use the AC to DC adaptor or 12V

battery to power up the circuit. Higher input voltage will produce more heat at LM7805voltage regulator, therefore a heat sink can be used. Typical voltage is 12V. Anyhow,

LM7805 will still generate some heat at 12V. There are two type of power connector for the

circuit, DC plug (J1) and 2510-02 (JP1). Normally AC to DC adaptor can be plugged to J1

type connector. Shown in Figure 3.2, the diode D3 is use to protect the circuit from wrong

polarity supply. Capacitors C1 and C7 is use to stabilize the voltage at the input side of the

LM7805 voltage regulator, while the capacitors C2 and C8 is use to stabilize the voltage at

the output side of the LM7805 voltage supply. DS4 is green LED to indicate the power status

of the circuit. R2 is resistor to protect DS4 from over current that will burn the DS4.

Figure 3.2


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Interface PIC with Keypad

In this project, the keypad consists of 8 pins as shown in figure 3.3. The 8 pins

remaining are separated into 2 groups, 4 pins (K1- K4 in the Figure below) connect to the

input of microcontroller and 4 pins (K5-K8 in Figure 7) connect to the output. User can

decide any digital I/O pin for the input and output. Input must be pull high to 5V using a

resistor and this configuration will result an active-low input.

Figure 3.3

Push Button as input for PIC microcontroller

One I/O pin is needed for one push button as input of PIC microcontroller. The

connection of the push button to the I/O pin is shown in Figure 3.4. The I/O pin should be

pull up to 5V using a resistor (with value range 1K-10K) and

this configuration will result an active-low input. When the

button is being pressed, reading of I/O pin will be in logic 0,

while when the button is not pressed, reading of that I/O pin

will be logic 1.

Figure 3.4


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Interface PIC16F877A with LCD (2 X 16 character)

In Figure 3.5, it is a 2X16 character LCD. LCD connection pins and function of each pin are

shown in table below:

Figure 3.5

Table 3.1 shows the description of the LCDs pins.

Table 3.1

Pin Name Pin function Connection

1 VSS Ground

2 VCC Positive supply for LCD

3 VEE Brightness adjust Connected to a preset to

adjust brightness

4 RS Select register, select instruction or data

register

RC0

5 R/W Select read or write GND

6 E Start data read or write RC1

7 DB0 Data bus pin RD0








15 LED + Backlight positive input VCC

16 LED - Backlight negative input GND


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LED as output for PIC microcontroller

Figure 3.6

One I/O pin is needed for one LED as output of PIC microcontroller. The connection

for a LED to I/O pin is shown in figure 3.6. The function of R10 is to protect the LED from

over current that will burn the LED. When the output is in logic 1, the LED will ON,

while when the output is in logic 0, the LED will OFF.

Relay as output of PIC microcontroller

Figure 3.7

The relay used for the project consists of 5 pins, 2 pins is the 2 end of the coil, 1 is

COM, 1 is NO and 1 is NC as shown in Figure 3.7. One end of the coil is connected to 9V

and another end is connected to an NPN transistor to amplify the small IC current to larger

value required for the relay coil. COM pin is connected to 9V and NO is connected to a 2510

2-pin connector which is provided to locate the door magnetic lock.

9VDC


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ICSP for loading program

ICSP stands for In Circuit Serial Programming and describes the serial programming

interface for PIC microcontroller. ICSP gives user a convenient way of programming PIC

Microcontroller without removing the chip from the development or production board. User

needs a programmer that provides the ICSP connector.

Figure 3.8

Referring to figure 3.8, MCLR, PGC and PGD needs to be connected to the ICSP box header

to program the PIC microcontroller. At the same time, RB3 need to be pull down to 0V to

disable low voltage programming, because the programmer is using high voltage

programming.

Buzzer as output of PIC microcontroller

Figure 3.9

Buzzer can be connected to any I/O pin as output.


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3.3 Overall Schematics

Figure 3.10


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3.4 Breadboard Construction

The circuit was built on the breadboard as a trial board to test the connectivity of the

components as shown in figure 3.11.

Figure 3.11

3.5 Programming the PIC

An ICSP port was installed, as it has been stated, to program the PIC without removing it.

The PIC needs to be program in order to activate the combination circuit before testing the

project. The software used to program the PIC is WinPIC 8000 or PICkit2 using MPLab.

The process of programming the PIC16F877A using WinPIC 8000 as shown below.

Figure 3.12


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The initial process is by doing a hardware test as shown in figure 3.12.

Figure 3.13

A prompt on the Hardware is ok will appear as shown in figure 3.13.

Figure 3.14

Insert the microcontroller into the ZIF socket of the USB programmer. Click on

the Detect Pic icon to detect the microcontroller shown in figure 3.14.

Then select the source code which is in HEX format.

Figure 3.15


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Click on the Erase button to erase any remaining program in the microcontroller. As

shown in figure 3.15

Figure 3.16

Click on the Program All button to program the select hex file into the microcontroller.

After finish downloading the hex file, click on Accept button. Refer to figure 3.16.

Figure 3.17

To read back the program which is downloaded into the microcontroller, click on the Read

All button as shown in figure 3.17.


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3.6 RIMU and GERB TOOL Artwork

After completing the experimental test, the circuit was drawn by using software

named RIMU. From there, it will be transferred to GERB TOOL software to produce a

printed circuit board (PCB) for the circuit as shown in figure 3.18.

Figure 3.19


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3.7 PCB Lab Work

At this stage, the GERB TOOL printed artwork is laminated together with copper

board using a film and kept under a UV machine. To avoid the damage of the film, the

laminating and UV process needs to be done in a special room. Then, the board is transferred

to two machines. First machine is to develop the circuit and strip off the film from the board

as shown in figure 3.20. This process is called developing. The second machine is to etch

copper from the board and the process is called etching, refer to figure 3.21. After all this is

done, the board is cleaned with water and lastly placed into a container filled with a required

chemical to strip off the remaining copper. The final step is the drilling process as shown in

figure 3.22.

Figure 3.20: Developing process Figure 3.21: Etching process


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3.9 The Prototype

The prototype is built with a simply, mobile and cost efficient material. At the outer

part of the casing, some holes was drilled according to the required size to fit in the Key-pad,

the LEDs, Push button, and the LCD as shown in figure 3.24. The PCB was placed inside the

casing. The PCB is shown in figure 3.25.

Figure 3.24

Figure 3.25

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