Regardless whether you live in a gated community or in an apartment complex; establishing a sincere feeling of security in your home is important to your overall health and well being. Protecting your home provides peace of mind whether you are away on vacation or just relaxing on your living room couch. Undeniably the most important security product to protect your home with is a home security alarm. A home security alarm will alert the home owners when an intruder is on the premises or trying to enter the home. It is a Microcontroller based home security system.
It consists of laser sensor,detector,RF transmitter and receiver module, microcontroller and phone circuit. When the signal is being interrupted, the Microcontroller starts working as per the program burnt into the erasable programmable read only memory(EPROM) and controls the siren and telephone. Block Diagram: Circuit description: 1. Sensor Circuit : LASER beam is used to make the sensor circuit. There is always a continuous beam emitting from a LASER source. The LASER source is placed in such a way that if someone wants to enter the room he must have to cut the beam.
This cutting of LASER beam is sensed by LDR based LASER detector circuit. A laser is a device that emits light(electromagnetic radiation) through a process of opticl amplification based on the stimulated emission of photons The term “laser” originated as an acronym for Light Amplification by Stimulated Emission of Radiation. The emitted laser light is notable for its high degree of spatial and temporal coherence. (LASER light used in our circuit ) 2. 2. LASER Detection : 2. 3. 1. LASER Detection Circuit: 2. 3. 2. Circuit Description:
This results in logic 0 at output pin 1. When there is an object between LDR and light source, LDR offers high resistance, making the voltage drop across R1 lower than Vref, output goes to high. 2. 3. 3. Components Description: 2. 3. 4. 1. LDR: A photo resistor or light dependent resistor (LDR) is a resistor whose resistance decreases with increasing incident light intensity; in other words, it exhibits photoconductivity.
It can also be referred to as a photoconductor or CdS device. A photo resistor is made of a high resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron (and its hole partner) conduct electricity, thereby lowering resistance.