HOME/ OFFICE SECURITY SYSTEM (8051 BASED)

Securiy is a matter of great concern to all of us in this world. Normally there are four types of security threat to our property. 1 )Thief, an inturder. 2)Fire, so we use fire sensor. 3)Water spilage /over flow, so we use water sensor. 4) Gas leak , we use gas sensor, whenever there is security breach from one of above or any combination of above. The project takes the following action 1) Sounds an ALARM to attract your or public attention . 2) If the reset sw is not pressed within 30 seconds the projects takes further action, 3) It makes an emergency call to deliver an emergency message stored in speech IC. 4) It will make five attempts to call you before it checks the conditions again. The project presented here is based on world’ s most powerful intel’ s mcs-51 family of microcontroller atmel at89c51. CIRCUIT EXPLANATION: This project is based on 8051 microcontroller.(IC2) IC3 and is used as buffer. IC4 is a one time programmable(otp) chip where messages are stored. This is 21 second speech ic where total of 12 messages can be recorded on eight different locations, but total duration should not be more than 21 seconds. Recorded messages can be played back by setting the trigger pin 10 & 11 to high, making these pin low will stop the message, Setting these pin high will repeatedly replay the same message. IC5 is an audio amplifire . Audio output from speech ic(IC4) pin no 7 cout is coupled to this ic on pin no 3 through VR2 volume control and C10. Amplified output from pin no 5 drives the speaker through capacitor C14. R14 and C13 corrects the tone. .C15 and C16 couples the audio message to telephone line.

IC4 needs 3.3v operating voltage .R9 is a voltage dropping resistor, D7 is 3.3v zener diode and C7 is a filter capacitor. These components will always maintain the voltage to3.3v at pin 9,12 of IC4. capacitor C8 is a feed back capacitor.,C9 and R13 connected to pin no 7 of IC 4 are tone corrector.R12 along with the VR1 variable resistor performs the sampling rate adjustment. R10 and R11 connected to pin26 and pin 27 of the microcontroller are voltage dropping resistors. R15 and R16 connected to the base of transister Q1 and Q2 are voltage dropping resistors and drives transistors Q1 & Q2 when set to high logic by microcontroller. Q1 Drives the dial relay RL1and Q2 drives the off-hook relay.RL2........................