Wireless Temperature

Sensor and Data Logger

Presented by:Akash gautam

Abhinav saksena

Introduction:- This project deals with a portable wireless data acquisition system for temperature in real time

process dynamics.

Process variables (like temperature, pressure, flow, level) vary with time in certain applications

and this variation should be recorded so that a control action can take place at a defined set

point.

This project uses an 8- bit embedded platform for a sensor and RF communication for data

transmission.

This wireless data logger senses and monitors the variations in the local temperature there by

transmits the data within the range to an assigned embedded processor based server.

Received temperature is displayed on a local liquid crystal display (LCD) on assigned server and

simultaneously on computer.

Temperature

Sensor ADC

Block Diagram

Microcontroller

Microcontroller

Transmitting unit

Receiving unit

LCD

PC

Receiver

Buzzer

Temperature Sensor( LM-35):-

The LM35 series are precision integrated-circuit temperature sensors,

whose output voltage is linearly proportional to the Celsius

(Centigrade) temperature.

The LM35 is rated to operate over a −55° to +150°C temperature

range & it draws only 60 μA from its supply, it has very low self-

heating, less than 0.1°C in still air.

The output voltage varies by 10mV in response to every oC rise/fall in

ambient temperature, i.e., its scale factor is 0.01V/ oC.

The general equation used to convert output voltage to

temperature is:

Temperature ( oC) = Vout * (100 oC/V)

So if Vout is 1V , then, Temperature = 100 oC

The output voltage varies linearly with temperature.

Pin

No

Function Name

1 Supply voltage; 5V (+35V to -2V) Vcc

2 Output voltage (+6V to -1V) Output

3 Ground (0V) Ground

Analog to digital converter:-

An analog-to-digital converter is a device that converts a continuous

physical quantity (usually voltage) to a digital number that represents the

quantity's amplitude.

We know that AVR has a inbuilt ADC. The ADC is multiplexed with PORTC

that means the ADC channels are shared with PORTC.

The ADC can be operated in single conversion and free running more. In

single conversion mode the ADC does the conversion and then stop. While

in free it is continuously converting. It does a conversion and then start next

conversion immediately after that.

The ADC has only four registers.

ADC Multiplexer Selection Register – ADMUX : For selecting the

reference voltage and the input channel.

ADC Control and Status Register A – ADCSRA : As the name says it

has the status of ADC and is also use for controlling it.

The ADC Data Register – ADCL and ADCH : The final result of

conversion is here.

Using the ADC:-

ADMUX Register.

REFS1 REFS0 selects the reference

voltage.

The ADCSRA Register.

uint16_t ReadADC(uint8_t ch)

{

//Select ADC Channel ch must be 0-7

ch=ch&0b00000111;

ADMUX|=ch;

//Start Single conversion

ADCSRA|=(1<<ADSC);

//Wait for conversion to complete

while(!(ADCSRA & (1<<ADIF)));

//Clear ADIF by writing one to it

ADCSRA|=(1<<ADIF);

return(ADC);}

Reading an analog value.

Microcontroller (Atmega 8):-

The AVR is a modified Harvard architecture 8-bit RISC single chip

microcontroller which was developed by Atmel in 1996.

Atmega has 3 GPIO.

IT has 23 I/O pins.

Any I/O pin can be used as an input pin or an output

pin.

Input Pin: A I/O pin configured to work as I/P.

Output Pin: An I/O pin configured to work as O/P.

The configuration of an I/O pin depends on 3

registers,

DDRX: Data Direction Register

PORTX: Data Register

PINx: Port Input pin register.

Controlling Pin behaviorRegister Description Function

DDRX Data Direction

Register

Sets a pin as

Input or

Output.

PORTX Port Data

Register

Assigns a

default value to

an I/O pin.

PINX Data Read

Register

Used to read

the

instantaneous

value of an

Input pin.

To set the first pin of PortB as an input

pin, we would simply write:DDRB.0=0; // Set PB0 as

input pin.

To set it as an output pin, we would

simply replace 0 by 1, DDRB.0=1; //Set PB0 as

an output pin.

Real time clock:-

Atmega 8 has built in RTC registers

void main(void)

{unsigned char h,m,s;

unsigned char date,month,year;

unsigned char h2[3],m2[3],s2[3];

unsigned char

date2[3],month2[3],year2[3],temp[2

];

// Real Time Clock initialization

rtc_init(0,0,0);

rtc_get_time(&h,&m,&s);

rtc_get_date(&date,&month,&y

ear);

WHAT IS RS-232?

The RS-232 standard defines the voltage levels that correspond to

logical one and logical zero levels for the data transmission and the

control signal lines.

Valid signals are either in the range of +3 to +15 volts or the range -3

to -15 volts with respect to the ground/common pin; consequently,

the range between -3 to +3 volts is not a valid RS-232 level.

For data transmission lines (TxD, RxD and their secondary channel

equivalents) logic one is defined as a negative voltage, the signal

condition is called "mark." Logic zero is positive and the signal

condition is termed "space."

RS-232 COMMUNICATION PORT RS-232 is basically to control signals connecting between DTE (data

terminal equipment) and DCE (data circuit-terminating equipment).

Data Lines

RxD (Data receive)

TxD (Data Transmit)

Control Lines RTS (Request to send)

CTS (Clear to send)

DTR (Data terminal ready)

DSR (Data Set ready)

USART Universal Synchronous Asynchronous Receiver Transmitter (USART) is a

highly flexible serial communication device.

It can communicate in synchronous as well as in asynchronous

modes.

Communication may be

simplex (in one direction only, with no provision for the receiving

device to send information back to the transmitting device),

full duplex (both devices send and receive at the same time)

half duplex (devices take turns transmitting and receiving).

UARTs are commonly used in conjunction with communication

standards such as RS-232, RS-422 or RS-485.

The AVR has a full duplex USART with a high resolution baud rate generation

USART DATA FRAME

The idle, no data state is high-voltage, or powered.

Each character is sent as a

logic low start bit +

a configurable number of data bits (usually 8, but legacy systems can

use 5, 6, 7 or 9) +

an optional parity bit +

one or more logic high stop bits.

The start bit signals the receiver that a new character is coming.

The next five to eight bits, depending on the code set* employed, represent

the character

void USART_Init( unsigned int ubrr)

{

/* Set baud rate */

UBRRH = (unsigned char)(ubrr>>8);

UBRRL = (unsigned char)ubrr;

/* Enable receiver and transmitter */

UCSRB = (1<<RXEN)|(1<<TXEN);

/* Set frame format: 8data, 2stop bit */

UCSRC = (1<<USBS)|(1<<USBS)|(3<<UCSZ0);

Interfacing AVR with PC via UART

AVR

MAX-232

LEVEL

SHIFTERTTL over Tx

& Rx

connection

RS-232

Cable

Data

send/receive

from terminal

software

Serial Peripheral Interface Is a synchronous serial data link standard established by Motorola.

Devices communicate using a master-slave relationship in which master initiates the data frame.

Communication is possible in full duplex mode.

SPI signals:

• SCLK : Clock

• MOSI: Master data output Slave data input

• MISO: Master data input, Slave data output

• CSS: Slave select

The below figure shows a single slave configuration.

Typical hardware Setup The bus master first configures the clock, using a frequency less

than or equal to the maximum frequency the slave device

supports. Such frequencies are commonly in the range of 1–

100 MHz.

The master then transmits the appropriate chip select bit for the

desired chip to a logic 0.

During each SPI clock cycle, a full duplex data transmission

occurs:

the master sends a bit on the MOSI line; the slave reads it from that same line

the slave sends a bit on the MISO line; the master reads it from that same line

// I2C Bus

Initialization

i2c_init();

APPLICATIONS OF WIRELESS TEMPERATURE &

DATA LOGGER

In this smart world there are many smart devices which may

measure different variables of environment.

Some of the important applications are-

1.Cold Storage compound.

2.Used in places of Extremes

3. Data acquisition systems

4.Home Automation etc.

Thank you