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. [...]
[...] To solve for the size of the capacitor, we equate the two formulas for the stored energy in a resonant circuit: P = C V2 / 2 P = L I2 / 2 Where: P stored energy, in watt seconds or coulomb volts C capacity, in farads V voltage across capacitor L inductance of motor winding, in henrys I current through motor winding Solving for the minimum size of capacitor required to prevent overvoltage on the switch is fairly easy: C > L I2 / (Vb - Vs)2 Where: Vb the breakdown voltage of the switch Vs the supply voltage Variable reluctance motors have variable inductance that depends on the shaft angle. [...]
[...] XTAL2 Output from the inverting oscillator amplifier AT89C52 BLOCK DIAGRAM DESCRIPTION A map of the on-chip memory area called the Special Function Register (SFR) space is shown in Table 1. Note that not all of the addresses are occupied, and unoccupied addresses may not be implemented on the chip. Read accesses to these addresses will in general return random data, and write accesses will have an indeterminate effect. User software should not write 1s to these unlisted locations, since they may be used in future products to invoke new features. [...]
[...] In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE- disable bit has no effect if the micro controller is in external execution mode. [...]
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