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SUTEN NAIDU & PAV
ENGINEERING SYST
DESIGN
MR. MANICKAM
SMART
DIGITAL
THERMOME
MINI PROJECT REVIEW
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PROBLEM STATEMENT
The main intention of this project is to build and implementthermometer that will be able to measure the sur
temperature, for example the temperature of a room and to
user if the temperature is higher than the desired temperature
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WHAT IS DIGITAL THERMOMETER?
Digital thermometers are gadgets that are used for m
temperature. They are generally easier to read than the traditio
of thermometer, and they are more accurate too. Instead of
digital thermometers have built in sensors
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DIGITAL THERMOMETER VS MERCURYTHERMOMETER
When talking about delivering accurate readings (figuresthermometers are more accurate when compared against
thermometers, since the interpretation of digital thermometer
doesntrequire eye straining in an effort to focus on the ana
bars typically found on mercury thermometers.
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To show the accurate surrounding temperature on the LCD
Extra features:
Light indicator to show the temperature staGreen light-temperature normal, Yellow- m
Red-temperature high) Alarm to warn the surrounding people
temperature is higher than desired temperat
DESIGN DESCRIPTION
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MC
DISPLAYTEMPERATURE
SENSOR
BUZZERLIGHT
INDICATOR
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COMPONENTS PIC 16F877A microcontroller.
LM35 temperature sensor.
LM7805 5V voltage regulator.
16x2 LCD.
9V battery.
Resistors: 10K (Fixed and variable), 100 (3 units), 18 (1 unit).
Capacitors: 104F and 33pF (2 units).
8MHz crystal oscillator.
3 LEDs (Green, Yellow, Red)
Connecting wires.
Breadboard.
PIC Kit 2.
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PIC16F877A
Peripheral Interface Controller
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8MHZ CRYSTAL OSCILLATOR
Standard frequency crystals - use these crystals to provide a clock in
your microprocessor.
Since the PIC16F877A doesnt have build in oscillator the 8MHz crys
oscillator is used. Rated at 20pF capacitance and +/- 50ppm stability.
A crystal oscillator is an electronic oscillator circuit that uses the mech
resonance of a vibrating crystal of piezoelectric material to create an signal with a very precise frequency.
This frequency is commonly used to keep track of time, to provide a s
clock signal for digital integrated circuits
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WHY LM35 TEMPERATURE SENSOR
LM35 is a precision IC temperature sensor with its output pto the temperature (in C).
The sensor circuitry is sealed and not subject to oxidation, e
The LM35 generates a higher output voltage than thermocomay not require that the output voltage be amplified.
The operating temperature range is from -55C to 150C
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OTHER TEMPERATURE SENSORSAVAILABLE IN MARKET
LM335A - reading range from 40C to 100C.
- gives reading in kelvin
TMP36 - reading range from 50C to 125C.
LM34 - same as LM35, but the reading is in Fahrenhe
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SCHEMATIC
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