Temperature and Pressure Sensor part1

05:51:00 Unknown 1 Comments

Introduction:
Fahrenheit and Celsius scale digital thermometer is a temperature indicator which displays temperature in both Fahrenheit and Celsius scale. The temperature sensed in Celsius scale in the Celsius scale thermometer project is converted into the Fahrenheit scale temperature just by using the Celsius to Fahrenheit conversion formula.
We are using pressure sensor that is MPx2100.The MPx2100 series devices silicon pressure sensors providing a highly accurate and linear voltage output directly proportional to applied pressure. The sensor Is single, monolithic silicon diaphragm with the strain gauge and thin-film resistor network integrated on chip. The chip is laser trimmed for precise span and offset calibration and temperature compensation.
Description:
          A digital thermometer can be easily made by interfacing a temperature sensor to the microcontroller PIC18F452.The temperature sensor used in the project is LM35. The LM 35 generates a 10mV variation to its output voltage for every degree Celsius change in temperature. The Output of the temperature sensor is analog in nature so we need an analog to digital convertor for converting the analog input to its equivalent binary output.
            The ADC has 10-bit resolution with a maximum of 1024 steps and the LM35 produces 10mV for full scale output. Now, if we use the step size of 2.5 mV, the Vout  will be 1024 x 2.5 mv = 2.56 V for full scale output.
We are using pressure sensor that is MPx2100.The MPx2100 series devices silicon pressure sensors providing a highly accurate and linear voltage output directly proportional to applied pressure. The sensor Is single, monolithic silicon diaphragm with the strain gauge and thin-film resistor network integrated on chip. The chip is laser trimmed for precise span and offset calibration and temperature compensation.
Components:
1.      LM35
2.      LCD
3.      PIC18F452
4.      Potentiometer
5.      MPX2100
6.      Oscillator , capacitors
7.      4x3 keypad
8.      Buzzer
9.      Regulator
10.  PCB

Components Description:
            Here is the brief description of components used in this project.

MICROCONTROLLER: PIC18F452:
There are 40 pins. 33 pins are set aside for 5 ports. PORTA, PORTB, PORTC, PORTD, PORTE.
The rest of pin are designated as Vdd(Vcc),Vss(GND),OSC1,OSC2,MCLR(reset). In addition to being used for simple I/O, each port has some other functions such as ADC, timers, interrupts, and serial communication pins.
LM35:
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 also possess low self heating and does not cause more than 0.1 oC temperature rise in still air.   

The operating temperature range is from -55°C to 150°C. 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.
ü  Calibrated directly in Celsius
ü  Linear + 10.0 mV/C scale factor
ü  0.5 C accuracy guarantee able (at +25 C)
ü  Rated for full -55 to +150 C range
ü  Suitable for remote applications
ü  Low cost due to wafer level trimming
ü  Operates from 4 to 30 volts
ü  Less than 60 microA current drain
ü  Low self-heating, 0.08 C in still air
ü  Nonlinearity only .25 C typical
ü  Low impedance output 0.1 ohm for 1 mA load
LCD:
LCD (Liquid Crystal Display) screen is an electronic display module and find a wide range of applications. A 16x2 LCD display is very basic module and is very commonly used in various devices and circuits. These modules are preferred over seven segments and other multi segment LEDs. The reasons being: LCDs are economical; easily programmable; have no limitation of displaying special & even custom characters (unlike in seven segments) 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 The command register stores the command instructions given to the LCD. A command is an instruction given to LCD to do a predefined task like initializing it, clearing its screen, setting the cursor position, controlling display etc. The data register stores the data to be displayed on the LCD. The data is the ASCII value of the character to be displayed on the LCD.
ü  The declining prices of LCDs
ü  The ability to display numbers, characters, and graphics. This is in contrast in LEDs, which are limited to numbers and a few characters.
ü  Incorporation of a refreshing controller into the LCD, thereby relieving the CPU of the tas of refreshing the LCD. In contrast, the LED must be refreshed by the CPU to keep displaying the data
ü  Ease of programming for characters and graphics.
There are two ways to send characters
Use a delay before sending the next one
Use the busy flag to see if the LCD is ready for next one

Pressure Sensor:
We are using pressure sensor that is MPx2100.The MPx2100 series devices silicon pressure sensors providing a highly accurate and linear voltage output directly proportional to applied pressure. The sensor Is single, monolithic silicon diaphragm with the strain gauge and thin-film resistor network integrated on chip. The chip is laser trimmed for precise span and offset calibration an temperature compensation.
            Some important features are
ü  Temperature compensated over 0 to 85 0C
ü  Easy to use chip carrier option
ü  Available in absolute, differential and gauge configurations
ü  Ratiometric to supply voltage
ü  ±0.25% Linearity


I am Mechatronics and Control Engineer from UET, Lahore. Helping Engineering students gives me pleasure.

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