Thermal Sensor

7/28/2019 Thermal Sensor

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Jesmine GandhiB.Tech (ECE) Sem-8

Presented By :


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A sensor (also called detector) is a converter that measures a

physical quantity and converts it into a signal which can be read byan observer or by an (today mostly electronic) instrument.eg.

Thermal Sensors, Humidity Sensors, Light Sensors, Motion Sensors

etc.

For accuracy, most sensors are calibrated against knownstandards.

A sensor is a device which receives and responds to a signal. A

sensor's sensitivity indicates how much the sensor's output

changes when the measured quantity changes.

A device that detects temperature is called a Thermal Sensor.

Thermal sensors are found in many laptops and desktop PCs in

order to sound an alarm when a certain temperature has been

exceeded.


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A Thermal Sensor which transmits temperature wirelessly is called awireless thermal sensor.

It converts the measured temperature into voltage values which is

used to drive the circuit.

The Wireless Temperature sensor is a battery operated digital

temperature sensor with a microprocessor controlled 434 MHz. FCC

certified radio transmitter.

The sensor needs to be calibrated for perfect measurement and

efficiency.


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The ATMEGA 32 based Thermal Sensor measures the temperature, converts

it into analog voltage values and the analog voltage values are in turn

converted to digitized form using the controller

An RF Tx/Rx pair is used to wirelessly transmit the digitized voltage over the

media.

It displays the temperature of the object or environment from the sensor in

form of ranges defined during programming on a 16x2 LCD Screen.


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ATMEGA32 Development Boards- (2)

An RF Tx/Rx pair(RF 434)- (1)

Breadboard- (2)

LM35( Temperature sensor IC)- (1)

16X2 LCD Display- (1)

Small Coil Antennas- (2)

Flash Programmer- (1)

Battery and Connection Wires


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LM 35

(Temp. Sensor)

Controller1

Transmitterequipment

Receiverequipment

Controller 2 LCDModule


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You can measure temperature more accurately than a using a thermistor.

The sensor circuitry is sealed and not subject to oxidation, etc.

The LM35 generates a higher output voltage than thermocouples and may not

require that the output voltage be amplified.

It has an output voltage that is proportional to the Celsius temperature.

The scale factor is .01V/oC

The LM35 does not require any external calibration or trimming and maintains an

accuracy of +/-0.4 oC at room temperature and +/- 0.8 oC over a range of 0 oC to +100oC.

Another important characteristic of the LM35DZ is that it draws only 60 micro amps

from its supply and possesses a low self-heating capability.


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It is a 3 pin IC; the extreme pins are forVccand Ground while the middle terminal

gives the output voltage.

Calibrated directly in Celsius (Centigrade)

Linear + 10.0 mV/C scale factor

0.5C accuracy guaranteeable (at +25C)

Rated for full -55 to +150C range

Suitable for remote applications Low cost due to wafer-level trimming

Operates from 4 to 30 volts

Less than 60 A current drain Low self-heating, 0.08C in still air

Nonlinearity only C typical

Low impedance output, 0.1 Ohm for 1 mA load


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The controller used in this project is ATMEGA32 which is a 40

pin controller.

The controller is pre-mounted on a Development Board which

provides it with the required resistances and capacitances.

We basically use the ADC pins (PORT A) for analog to digital

conversion and vice versa of the sensor output.


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The high-performance, low-power Atmel 8-bit AVR RISC-based

microcontroller combines 16KB of programmable flash memory, 2KB

SRAM, 1KB EEPROM, an 8-channel 10-bit A/D converter, and a JTAG

interface for on-chip debugging.

The device supports throughput of 16 MIPS at 16 MHz and operates

between 4.5-5.5 volts.

By executing instructions in a single clock cycle, the device achieves

throughputs approaching 1 MIPS per MHz, balancing power

consumption and processing speed.

It is enabled with dual programmable USARTs which are used to

translate data between parallel and serial forms.

In the current project, the USART is made to work in Asynchronous

Mode.


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Peripheral Features

- On-chip Analog Comparator

- Programmable Watchdog Timer with Separate On-chip Oscillator

- Master/Slave SPI Serial Interface

- Two 8-bit Timer/Counters with Separate Pre-scalar, Compare

- One 16-bit Timer/Counter with Separate Pre-scaler, Compare and

Capture mode

- Real Time Counter with Separate Oscillator

- Four PWM Channels

- Programmable Serial USART

- 8-channel, 10-bit ADC- Byte-oriented Two-wire Serial Interface

- Four PWM Channels

- Dual Programmable Serial USARTs


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The MAX232 is an integrated circuit that converts signals from an RS-232serial port to signals suitable for use in TTL compatible digital logic circuits.

The MAX232 is a dual driver/receiver and typically converts the RX, TX,CTS and RTS signals.

The drivers provide RS-232 voltage level outputs (approx. 7.5 V) from asingle + 5 V supply via on-chip charge pumps and external capacitors. Thismakes it useful for implementing RS-232 in devices that otherwise do notneed any voltages outside the 0 V to + 5 V range, as power supply designdoes not need to be made more complicated just for driving the RS-232 inthis case.


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It is a Transmitter- Receiver pair module operating at a frequency of 434

MHz.

RF 434/315 MHz ASK TRANSMITTER MODULE

The TX434 is an ASK Hybrid transmitter module. TX434 is designed by the Saw

Resonator, with an effective low cost, small size, and simple-to-use fordesigning.

Frequency Range : 315 / 433.92 MHZ.

Supply Voltage : 5V.

Output Power : 4~16dBm

The receiver module works at a frequency of 434/315MHz. We can interface

this directly with microcontroller or we can use it with the help of encoder


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RF 434/315 MHz ASK RECEIVER MODULE

RX434 is an ASK receiver module. The MO-RX3400-A is based on a single-conversion ,super-heterodyne receiver architecture and incorporates anentire Phase-Locked Loop (PLL) for precise local oscillator generation. It can

be used on wireless security system or specific remote-control function andothers wireless system

Operation voltage : 5 VoltsAvailable frequency : 315/434 MHz

The transmitter module works at a frequency of 434/315MHz. we caninterface this directly with microcontroller or we can use it with the help ofdecoders


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LCD (Liquid Crystal Display) screen is an electronic display moduleand find a wide range of applications.

A 16x2 LCD display is very basic module and is very commonly usedin various devices and circuits

A 16x2 LCD means it can display 16 characters per line and there are2 such lines.

In this LCD each character is displayed in 5x7 pixel matrix. This LCD

has two registers, namely, Command and Data.


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The command register stores the commandinstructions given to the LCD.

A command is an instruction given to LCD to doa predefined task like initializing it, clearing itsscreen, setting the cursor position, controllingdisplay etc.

The data register stores the data to bedisplayed on the LCD.

The data is the ASCII value of the character tobe displayed on the LCD


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LM 35 or Temperature Sensor IC, measures the environmental orexternal temperature, and converts it into corresponding voltagelevel. With every degree change in temperature voltagecorresponds to 10mV.

The voltage levels are now transferred to the first microcontrollerwhich is mounted on the development board.

MAX232 IC steps down the external voltage, to the 5 volt levelrequired for functioning of USART in the controller.

The sensor output is connected to the first pin of the ADCport(PORT A) of ATMEGA 32(microcontroller).The Analog signals are

sampled, quantized and finally digitized.

Since we are using a 8 bit ADC, therefore we need 256 quantizationlevels. For calibration of microcontroller and Thermal Sensor, weneed to divide entire span of 1.5 volts over 256 quantization levels.


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The Potentiometer knob is rotated until we get the output across

GND pin and output pin of thermal sensor as 1.5 volts.

The USART present inside controller(ATMEGA 32) has a protocol

of converting digits into characters. For this purpose we need towrite the code such that characters are assigned temperature

values.

The digitized sensor output(from PORT D) in the form of

characters is transmitted by the transmitter of RF434.

The receiver intercepts the signal, transmits it into the

microcontroller and as per our code the characters are converted

back into temperature values .The temperatures are in turn

transmitted to the 16x2 LCD and displayed.


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Control can be centralized or decentralized and data can becollected and analyzed in real time or later using

readily available personal computers.

Escape from the entanglement in this tyranny of wires that we

face in our day-to-day work.

Makes the system more reliable and efficient.

Needs less maintenance and human intervention.

Makes the system secured and robust.


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Used in industrial furnaces.

Employed in Automobile Industry.

In power Plants and industrial boilers.

For detecting emergency in an industrial system if the temperature goes

above a prescribed limit.

Forest Fire Detection.

Detection of Greenhouse gases.

Can be employed in Aircrafts and Submarines


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We have programmed our project and it works successfully over an

operating temperature of 25 51 degrees Celsius.

We have used the 26 lower case alphabets to encode the range of

temperature(26 degrees).

The project is found to display the room temperature effectively

and when a burning match stick is brought near Sensor IC, we

observe a corresponding increase in temperature.


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THANK YOU

Thermal Sensor

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