04-06-2012, 12:55 PM
Temperature controlled Fan (AT89C52)
Temperature controlled Fan.doc (Size: 507.5 KB / Downloads: 74)
INTRODUCTION:
This Project is used to control the Fan speed according to the temperature and it also indicates the temperature. The system will get the temperature from the IC (LM35) and it will control the speed according the values stored by the user.
The System is fully controlled by the microcontroller AT89C52. It is a popular 8 bit microcontroller. The circuit consists of four switches, in which two buttons are used to increment and decrement the temperature value and the next button is to edit the temperature values stored it in the memory and the other button is cancel button.
EMBEDDED SYSTEMS:
DEFINITIONS:
Embedded system is a combination of hardware and software, it is also named as “Firm ware”.
An embedded system is a special purpose computer system, which is completely encapsulated by the device it controls. It is a computer-controlled system
An embedded system is a specialized system that is a part of a larger system or machine. As a part of a larger system it largely determines its functionality. Embedded systems are electronic devices that incorporate microprocessors with in their implementations. The main purpose of the microprocessors are simplify the system design and improve flexibility. In the embedded systems, the software is often stored in a read only memory (RAM) chip.
MICROPROCESSOR AND MICROCONTROLLER
Microprocessors and microcontrollers are used in embedded system products. An embedded product uses a microprocessor (or microcontroller) to do one task and one task only.
Microprocessor as the term come to be known is a general purpose digital computer central processing unit. Although popularly known as a "computer on chip", the microprocessor is in no sense a complete digital computer.
Microprocessor CPU contains Arithmetic Logical Unit, a program counter, a stack pointer, some working registers, a clock timing circuits and interrupt circuit.
To make complete microcomputer memory must add, usually Read Only Memory, Random Access Memory, memory decoders and an Input/Output devices. In addition special purpose devices such as interrupts, counters may be added to relieve the CPU from time consuming counting or timing chores.
Operating Procedure
AC 230 Volts 50Hz is connected to the primary. Secondary of transformer is a 12-0-12V. A rectifier converts AC to DC, but the DC output is varying. There are several types of rectifiers; here we use a bridge rectifier. here the bridge rectifier is connected to transformer . For smoothing d.c a capacitor is connected with transformer .Regulator eliminates ripple by setting DC output to a fixed voltage .Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or variable output voltage these are connected to the transformer.
LM35 is the temperature sensor used to sense the temperature .The ADC0804 IC is used which is an analog-to-digital converter in the family of the ADC800 series from National Semiconductors. It works with 5V and as a resolution of 8 bits in addition to resolution; conversion time is another major factor in judging an ADC .these are connected to the power supply
AT89C52 is used here which provides the following standard features: 8Kbytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16-bit timer/counters, six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry Serial communication between PC and microcontroller is done by using MAX232.Here the connections are given as per circuit diagram shown in 2.2 When the power supply is on at a particular temperature of 45 degrees motor start rotating .when the temperature increases fan speed increases.