PASSWORD-BASED DOOR SENSOR ACTIVATION CIRCUIT

GROUP MEMBERS:MUHAMMAD AIZAT BIN SELAMATEE091622THEERAN A/L SHANMUGAMEE091619SECTION NO :05COURSE :DIGITAL LOGIC LAB EEEB161SEMESTER :1ST YEAR 2ND SEMESTER (2013/14)DATE OF SUBMISSION: 8/7/2013OBJECTIVES

Based on the given problem statement, the objectives that need to achieve are:a) To design the password circuit using Alteras Quartus II.b) To verify the functionality of the design using ModelSim-Altera.c) To propose a cost analysis of this design if want to purchase all the chips.

INTRODUCTIONRegarding the few burglary cases that happen in our apartment, we have come out with an idea to design a simple low cost security system for our apartment. This security system consists of a door contact sensor and a loud buzzer. The door contact sensor will be placed on the apartments front door meanwhile the loud buzzer will be installed on the apartments wall. The system operates when the sensor is activated. For example, when someone opens the door, the sensor will transmit a signal to the buzzer. Thus, the buzzing noise will then alert the nearby residents.While creating this security system, we found out that this security system is still not good enough as we need to be able to open the door without triggering the buzzer. Hence, we came up with the idea of adding a password entry system which requires a correct 4-digit password. When a correct password is entered, we can activate and deactivate the sensor as we leave or enter the apartment. The 4-digit password is obtained from the last four digits of our student ID number. In order to enter the password, a 12-button (6x2) matrix keypad is used as inputs to the circuit. Apart from that, we have also included a Sensor Activation (A) as input switch and two LEDs outputs which are green (G) and red (R). When the door is activated by applying logic 1 or deactivated by applying logic 0 to input A, the green LED will light on (logic 1). The green LED must light on (logic 1), indicating the password entered is correct. Otherwise, the sensor will remain its current state. When the door sensor is active, the red LED will light on (logic 1).

METHODOLOGYIn this password-based door sensor activation circuit, there are 3 main parts which are keypad encoder, password comparator and activation circuit. For keypad encoder, the encoder accepts the inputs from K[0] until K[7] which is entered by using the 12-button (6x2) matrix keypad and encodes the 8-bit input to 4-bit output. This can be done by using 16-line-to-4-line encoder by cascading two 74148 chips as demonstrated in the figure 1(result). From figure 1(in result), all the outputs that will be connected to the input of the password comparator are assumed to be encoded into 4-bit codes. Table 1 below shows the input from the keypad encoder and the corresponding encoded output. *Notice that ENT and CLR buttons are encoded to 1011 and 1100 respectively.Keypad ButtonEncoder InputEncoder Output

1101000000001

2100100000010

3100010000011

4100001000100

5100000100101

6011000000110

7010100000111

8010010001000

9010001001001

0010000100000

ENT100000011010

CLR010000011011

Table 1

For the password checker, after the inputs are encoded to 4 bit outputs, the codes will undergo the checking process. Output G will be logic 1 if all the codes match with the default password and in this case, the user will be able to activate or deactivate the door sensor. Otherwise, the output will be 0 and the sensor activation circuit will be disabled. Also, when the CLR button (1100) is pressed, the output G will be changing to logic 0. This process can be done by cascading five 4-bit magnitude comparators (7485), which are four for password checking and another one for ENT and CLR buttons. For the activation circuit, which is the last part of the design where the output from the comparator block, G is used as one of the input of this block. Another input will be the input A, which controls the activation and deactivation of door sensor, provided that the input G is on. As mentioned before, by applying logic 1 to A, will activates the door sensor and output R will be light on (logic 1), meanwhile by applying logic 0 to input A will deactivate the door sensor and output of R will become logic 0. Output R can be obtained by simply adding AND gates at both of the inputs of A and G.

RESULTSEncoder Circuit

Figure 1

Encoder Waveform

Figure 2

Comparator Circuit

Figure 3

DISCUSSION

COMPONENT ANALYSIS

COST ANALYSIS

CONCLUSIONIn a nutshell, we have designed a simple low cost security system for our apartment. By this security system, we can prevent from burglary cases which are increasing drastically in our Amanah apartment. We have come out with sophisticated circuit consisting three main parts which are keypad encoder, password checker and activation circuit. This security system is able to perform its task as it has been verified by using Alteras Quartus II and ModelSim-Altera softwares.