LOW COST TEMPERATURE SENSOR DEVICE

Guided by:Prof: Rahul Koshti

Presented By: Vimanyu Kachroo (747)

Prateek Dua (723)Sudhanshu Sharma (742)

INTRODUCTION

• The aim of this project is to design an ambient temperature measurement circuit.

• The motivation for doing this project is the fact that temperature measurement has become an integral part of any control system operating in a temperature sensitive environment

• In this project the ambient temperature will be displayed on a LCD and further a fan will be trigged on a specific temp.

• An 8051Microcontroller will be used for handling all the required computations and control.

• A temperature sensor LM 35 is used for sensing the ambient temperature. The system will get the temperature from the IC and it will display the temperature over the LCD.

OBJECTIVE

• There are many aspects that should be considered when measuring temperature. The needs of a home refrigerator are different to those of a commercial furnace, or those for monitoring liquids flowing through pipes in a beverage-processing plant.

• The previous application examples present very different challenges to those encountered when measuring the temperature within the housing of a cell phone or laptop computer.

• While each of these applications need to measure temperature, they all have very different requirements.

BLOCK DIAGRAM

Circuit Description

WORKING

• Resistor R13 and present R14 is used to provide an external reference voltage of 1.28V.

• The step size of the ADC will be 10mV and span will be 0-1 V.

• That is for a 10mV input the digital out of ADC will be 1 (1 in decimal also), For 20mV it will be 10 (2 in decimal) and so on.

• The microcontroller accepts this data and puts it on the seven segment display.

• Digital out of the ADC (D0 to D7) are connected to P1 (P1.0 to P1.7) of the microcontroller.

• The control pins from ADC CS, RD, WR and INTR are connected to P3.7, P3.6, P3.5 and P3.4 of the microcontroller.

• This is the data path through which the microcontroller sends chip select (CS), read (RD) write (WR) signals to the ADC and receives INTR signal from the ADC.

• Data lines (a to h) of the multiplexed seven segment display are interfaced to P0 (P0.0 to P0.7) of the microcontroller.

• Activation signals for the segment driver transistors Q1 and Q2 are available from P3.2 and P3.1 pins of the microcontroller.

PCB LAYOUT

PCB LAYOUT

SIMPLIFIED DIAGRAM

COMPONENT DESCRIPTION

• 8051 MICROCONTROLLERA microcontroller is a single chip that contains the processor (the

CPU), non-volatile memory for the program (ROM or flash), volatile memory for input and output (RAM), a clock and an I/O control unit. Also called a "computer on a chip," billions of microcontroller units (MCUs) are embedded each year in a myriad of products from toys to appliances to automobiles. For example, a single vehicle can use 70 or more microcontrollers. The following picture describes a general block diagram of microcontroller.

• 89s52: The AT89S52 is a low-power, high-performance CMOS 8-bitmicrocontroller with 8K bytes of in-system programmable Flash memory.

• Atmel's AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications.

• The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry.

LM 35 Temperature Sensor

• LM35 is a precision IC temperature sensor with its output proportional to the temperature (in oC).

• The sensor circuitry is sealed and therefore it is not subjected to oxidation and other processes.

• With LM35, temperature can be measured more accurately than with a thermistor

• It has an operating temperature range of –55°C to +125°C and is accurate to ±0.5°C over the range of –10°C to +85°C. It can derive power directly from the data line hence eliminating the need for an external power supply.

• Each LM 35 has a unique 64-bit serial code, which allows multiple LM 35 to function on the same 1-Wire bus.

• Another feature of the LM 35 is the ability to operate at low external power supply.

APPLICATIONS

• Temperature sensors are used extensively in the steel and iron industries to monitor temperatures and chemistry throughout the steel making process.

• Temperature sensors are used in the testing of prototype electrical and mechanical apparatus.

• Temperature sensors are used to monitor and control accordingly the temperature of sensitive devices such as computer CPUs.

THANK YOU.