In this project we will make Office or home security system. There will be security for LPG gas leakage, intruder, fire and Rain. We will monitor these and control also. For controlling we will use relay for controlling devices and use fan for fire. We will use GSM modem to monitor these. We will send sms on particular nos. when any problem increase above the peak level.
We will use AT commands to send sms from mobile.
ACTION OF STEPS
Micro controller interface
In this sensor unit it is our choice , how many sensor’s we use , IN this project we use two sensor’s, In this project we use two electronics circuit with infra red sensor’s and fire alarm sensor.
In the infra red sensor. We use ic 555 as a main component. Pin no 4 and pin no 8 is connected to the positive supply. Pin no 1 is connected to the negative voltage. One capacitor is grounded from the pin no 5 for noise cancellation. Output is available on the pin no 3. Sensor is connected to the pin no 2.
In the case of infra red sensor. Pin no 2 is negative bias through the 33k ohm resistor and pin no is positively biased through the photodiode. One infra red transmitter l.e.d is focused to the photodiode . Infra red l.e.d is directly connected to the positive and negative supply through the 470 ohm resistor..
In normal stage when light is focus on the photodiode then pin no 2 is positively biased photodiode. If pin no 2 is positive then negative output is available on the pin no 3. Now when any body interrupt the light then there is no light on the photodiode and pin no 2 is now gets its voltage from only 33 k ohm resistor. If pin no 2 is become negative then output is shifted to the pin no 3. when positive output is available on the pin no 3 and with the help of this voltage NPN transistor is on and npn transistor provide a negative voltage as a pulse to the microcontroller.
If we connect two sensor as a input to the microcontroller then we use same circuit with the ic 555 .
Note that microcontroller sense only negative input to the microcontroller.