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Password based door security system

Published on Mar 02 2011 // 555 Alarm circuits

Password based door security system

The Password based door security system is a high security circuit. It is a double security device. One security is, through the password and other through the reed switch system. This can be used in bank lockers, garages, safes and wherever a high security is required.

Main Components:

The main components in the circuit are listed below:

1. Reed switch
2. Keyless lock IC RS7225
3. 555IC
4. Alarm generator IC KD9561
5. Loud Speaker

Circuit Working:

This circuit can make a door or window to be secured with a double security system. The circuit can be connected to a door in two ways.

At first, the door is connected with a password security system using the IC RS7225. If anyone needs to open the door, they need to enter the correct five digit password in the keypad provided. If the correct password is pressed, the corresponding keys closes. So, it gives the input to the momentary lock output in the 9th pin of IC RS7225 and also, the unlock output, ie the 8th pin. So, the door can be opened now.

If any stranger tries to open the door, or if the password is entered wrongly, then the 5th pin output goes high. This pin triggers the NPN transistor VT2 through D3. The transistor inturn triggers the IC555. Now, IC555 acts as a Monostable multivibrator and gives a pulse to the Alarm generator IC KD9561. The alarm generator generates a alarm sound. This will be a feable sound and hence, it is amplified with the TDA2822M amplifier IC. The amplified alarm sound is heard in the Loud Speaker

As a second security, the door is connected with the reed switch set up. The magnet to the movable side i.e., to the door and the door frame is connected with a Normally Opened reed switch. When the magnet is moved, or else when the door is opened, the reed switch contacts closes. When the reed switch closes, it triggers the NPN transistor VT2. The transistor inturn triggers the IC555. Now, IC555 acts as a Monostable multivibrator and gives a pulse to the Alarm generator IC KD9561. The alarm generator generates a alarm sound. This will be a feable sound and hence, it is amplified with the TDA2822M amplifier IC. The amplified alarm sound is heard in the Loud Speaker