DIGITAL LOGIC DESIGN LABORATORY

EEEB 161

SEMESTER II (2014/2015)

Password-based Door Sensor Activation Circuit

PUAN YANTI ERANA BINTI JALIL

SECTION 6

DATE : 27 JANUARY 2015

NO NAME ID

1. MOHD AMJAD RIDZUAN BIN RADHI EP095834

2. AZRI BIN ABDUL RAHMAN EP095837

OBJECTIVES :

1. To design the password logic circuits based on given situation and problems using

Aleras Quartus II.

2. To verify of the functionality of the designed system using ModelSim-Altera.

3. To gain the wave from the password comparators and the activation sensor circuit.

4. To propose a cost analysis of the design for components purchase.

INTRODUCTION :

Problems with burglary cases in Amanah apartment has made us realized that we need

to design a low cost Password-based Door Sensor Activation Circuit security system to be

installed in the apartment. The system has three phase which consists of a 12 segment matrix

keypad and a sensor placed on the apartments front door, and a loud buzzer, which is installed

on the apartments wall.

When the sensor is activated and someone opens the door, the sensor will transmit a

signal to the buzzer. The buzzing noise will then alert nearby residents.

The sensor can be activated or deactivated if the password is correct. Only the residence

of the apartment will know the input password. One room has two people, so two password

will be needed to activate or deactivate the door sensor

In addition, a Sensor Activation (A) input switch with two LEDs; Green (G) and Red

(R). The door sensor can be activated by applying logic 1 to input A, and deactivate by applying

logic 0. The Green LED will light on (logic 1) when the correct password is entered, while the

Red LED will light on (logic 1) when the door is activated.

DESIGN METHODOLOGY :

The design of the Password-based Door sensor Activation Circuit are based on three phase

which is :

1. 6x2 Keypad Encoder.

The keypad input are design by using 8-to-3 encoders and some logic gates to change from

decimal based numbers to binary numbers. The encoders used in the design is active low,

therefore the input and output of each encoder is based on the following truth table

The 10 key outputs varies from K[7] to K[0] with different combination. Each key will give 2

different logic 1 inputs to the encoders. The key inputs must be inverted to make it enable the

active low encoder.

The keypad circuit encoder is as given figure :

2. Password Comparator

Our password has 4 numbers, so each number must have one comparator. In our design we

want the password comparator to accept 2 password. So eight IC comparators (7485) will be

used because we have 8 number digits. Each comparators are connected by the A=B enable,

and each B-input comparators is set as our password binary number and each A-input is

connected to by the outputs of the encoder.

This means that, when the first comparator has an output of A=B (logic 1) it can be

connected to the second comparator, and if the second comparator does not have an output of

A=B then the third comparator will not be connected.

The designed password comparator is based on the given diagram :

The Password for the comparator circuit is:

1) Comparator1 ; 5 = 01012 Comparator2 : 8 = 10002 Comparator3 : 3 = 00112

Comparator4 : 4 = 01002

2) Comparator5 ; 5 = 01012 Comparator6 : 8 = 10002 Comparator7 : 3 = 00112

Comparator8 : 7 = 01112

3. Activation Circuit

From the password comparators, if the input is logic 1 and the enter button is pushed it can

activate the green light which means that the password entered by the user is correct.

In the designed circuit, the enter button is also connected to a comparator so that it can give

an output logic 1 ( A=B).

The output 1 will turn ON the Green LED. The output of the password comparator will also

connected to a switch sensor (Activation/Deactivation Switch) with an AND gate.If the

Activation switch is ON then the Red LED will be ON. The activation circuit is given based

on figure below :

RESULT :

For the first part, input was inserted by user in decimal from the keypad then was converted

into BCD by the Keypad Encoder Circuit. The input comprises a combination of 8 pins, K[7]

to K[0]. The combinations are as follow:

DECIMAL K[7] K[6] K[5] K[4] K[3] K[2] K[1] K[0]

1 1 0 1 0 0 0 0 0

2 1 0 0 1 0 0 0 0

3 1 0 0 0 1 0 0 0

4 1 0 0 0 0 1 0 0

5 1 0 0 0 0 0 1 0

6 0 1 1 0 0 0 0 0

7 0 1 0 1 0 0 0 0

8 0 1 0 0 1 0 0 0

9 0 1 0 0 0 1 0 0

0 0 1 0 0 0 0 1 0

ENT 1 0 0 0 0 0 0 1

CLR 0 1 0 0 0 0 0 1

Encoded Binary Number:

DECIMAL BINARY

P[3] P[2] P[1] P[0]

0 0 0 0 0

1 0 0 0 1

2 0 0 1 0

3 0 0 1 1

4 0 1 0 0

5 0 1 0 1

6 0 1 1 0

7 0 1 1 1

8 1 0 0 0

9 1 0 0 1

Output Wave form of keypad encoder

Output Password Waveform : Password correct, Activation is ON

Password is correct, Activation is OFF

Password is incorrect

Second Password input, Activation is ON

DISCUSSION :

I) COMPONENT ANALYSIS

In this project, the components used are:

# COMPONENT UNIT

1 ENCODER (74148) 2

2 COMPARATOR (7485) 9

3 AND GATE (7408) 1

4 OR GATE (7432) 1

5 NAND GATE (7400) 15

II) COST ANALYSIS

For this project, a few low cost components have been used to create a cost effective

security system. Listed below is the overall cost of this project.

# COMPONENT UNIT PRICE/UNIT (RM) PRICE (RM)

1 ENCODER (74148) 2 1.00 2.00

2 COMPARATOR (7485) 9 0.98 8.82

3 AND GATE (7408) 1 1.49 1.49

4 OR GATE (7432) 1 2.70 2.70

5 NAND GATE (7400) 15 2.51 37.65

TOTAL 52.66

CONCLUSION :

For the conclusion :

1. The main purpose, in which to a Password-based Door sensor Activation Circuit can be

applied by the following logic circuit.

2. The schematic diagram of the circuit can be applied to Quartus II and we can get the

waveform by using ModelSim-Altera

3. Based on the waveform the circuit, the output of the door sensor design circuit can be

determined and verified.

4 From the designed circuit, we can determined the how many logic gates that are needed to

build the circuit

5. The cost the design circuit is RM52.66. This means that the designed circuit is affordable

and can be used for safety measures.