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  1. Introduction
  2. Difference between micro controller and micro processor
  3. Block diagram and kit diagram
  4. Micro controller architecture (AT89C52)
    1. Features of micro controller
  5. Pin diagram and description
  6. Port pin alternate functions
  7. AT89C52 block diagram description
  8. Oscillator characteristics
  9. Stepper motor
    1. Introduction
    2. Variable reluctance motors
    3. Unipolar permanent magnet and hybrid motors
    4. Practical unipolar and variable reluctance drivers
    5. Bipolar motors and H-bridges
    6. Practical bipolar drive circuits
  10. Necessity of regulated power supply
  11. Conclusion
  12. Bibliography

Home security systems provide security from threats such as intruders or thieves, by sounding a siren to grab the attention of the public. Two sensor pairs are placed in the system. Among them one pair of receiver sensors is connected to the entrance of the house and the transmitter is carried by the authorized person. The other sensor pair is placed inside the house. When the authorized person enters the house both the sensors detect the person and don't sound an alarm. When a thief enters the house only one sensor detects the person and sends the signal to the controller. On detecting the signal, it sends an interrupt to sound a siren.

The controller is coded such that whenever the detected signal at the corresponding port enters, the output pin, which is connected to alarm doesn't sound. When a thief enters the house only one sensor detects the person and sends the signal to the controller. On detecting the signal, it sends an interrupt to controller and according to it the siren connected at output pin will sound the alarm. The gate is controlled by using a stepper motor which is connected to one the output ports of the controller through a line driver, L293D. The stepper motor is interfaced such that it opens the gate when there is a detected signal and closes when there is no signal.

[...] Since two machine cycles (24 oscillator periods) are required to recognize a 1-to-0 transition, the maximum count rate is 1/24 of the oscillator frequency. To ensure that a given level is sampled at least once before it changes, the level should be held for at least one full machine cycle UART The UART in the AT89C52 operates the same way as the UART in the AT89C51. Interrupts The AT89C52 has a total of six interrupt vectors: two external interrupts (INT0 and INT1), three timer interrupts (Timers and and the serial port interrupt. [...]

[...] Home appliance REGULATED POWER SUPPLY DESCRIPTION A variable regulated power supply, also called a variable bench power supply, is one where you can continuously adjust the output voltage to your requirements. Varying the output of the power supply is the recommended way to test a project after having double checked parts placement against circuit drawings and the parts placement guide. This type of regulation is ideal for having a simple variable bench power supply. Actually this is quite important because one of the first projects a hobbyist should undertake is the construction of a variable regulated power supply. [...]

[...] Thus it is concluded that ordinary power supply is not suitable for some of the electronic circuits for instance, with such circuits we have to employ a regulated power supply, which gives a fixed output. NECESSITY OF REGULATED POWER SUPPLY The DC level of an ordinary power supply changes due to the following reasons. Variations in AC mains voltage: the permissible variation in the mains voltage as per Indian electricity rules is of its rated value. But in India the variation in voltage is much more than its rated value. [...]

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