SMART
DIGITAL
THERMOMETER
MINI PROJECT REVIEW
SUTEN NAIDU & PAVITHRAN ENGINEERING SYSTEM AND DESIGN MR. MANICKAM
PROBLEM STATEMENT
The
main intention of this project is to build and implement a digital thermometer that will be able to measure the surrounding temperature, for example the temperature of a room and to alert the user if the temperature is higher than the desired temperature.
WHAT IS DIGITAL THERMOMETER?
Digital thermometers are gadgets that are used for measuring temperature. They are generally easier to read than the traditional type of thermometer, and they are more accurate too. Instead of mercury, digital thermometers have built in sensors
DIGITAL THERMOMETER VS MERCURY THERMOMETER
When
talking about delivering accurate readings (figures), digital thermometers are more accurate when compared against mercury thermometers, since the interpretation of digital thermometer readings doesnt require eye straining in an effort to focus on the analog rulerbars typically found on mercury thermometers.
DESIGN DESCRIPTION
To show the accurate surrounding temperature on the LCD Extra features:
Light indicator to show the temperature status. (eg:
Green light-temperature normal, Yellow- moderate, Red-temperature high)
Alarm to warn the surrounding people if the
temperature is higher than desired temperature
TEMPERATURE SENSOR MC
DISPLAY
LIGHT INDICATOR
BUZZER
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.
SOFTWARE
MikroC PRO 4.15 MPLab 8.83. EAGLE CAD 6.4.
WHY CHOOSE PIC16F877A
Peripheral Interface Controller
8MHZ CRYSTAL OSCILLATOR
Standard frequency crystals - use these crystals to provide a clock input to your microprocessor. Since the PIC16F877A doesnt have build in oscillator the 8MHz crystal oscillator is used. Rated at 20pF capacitance and +/- 50ppm stability. A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. This frequency is commonly used to keep track of time, to provide a stable clock signal for digital integrated circuits
WHY LM35 TEMPERATURE SENSOR?
LM35 is a precision IC temperature sensor with its output proportional
to the temperature (in C).
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.
The operating temperature range is from -55C to 150C
OTHER TEMPERATURE SENSORS AVAILABLE IN MARKET
LM335A
TMP36 LM34
- reading range from 40C to 100C.
- gives reading in kelvin - reading range from 50C to 125C. - same as LM35, but the reading is in Fahrenheit
LCD SCREEN
LCD (Liquid Crystal Display) screen is an electronic display module A 16x2 LCD display is very basic module and is very commonly used in various devices and circuits
The reasons of choosing this LCD because of its economical purpose, easily programmable, have no limitation of displaying special and even custom characters (unlike in seven segments), animation and so on.
A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely, Command and Data.
SCHEMATIC
