Simple Thermometer

Components:

1) Arduino uno
2) LCD display (16X2)
3) Thermistor
4) 220 ohm resistor
5) Male to male probes

Method:

LCD:

• The LCD consists of 16 pins. Starting from the leftmost pin, the first one VSS (gnd), VDD( vcc), VO, RS, RW, E, D0- D7, A, K
• The VSS and VDD goes to GND and 5V supply from the arduino respectively V0 goes to the potentiometer centre. RS stands for register select. It is connected to one of the digital pins of the arduino.
• When it is low the LCD accepts commands like clearing, etc. Whereas when it is high the LCD accepts text from the program to the display.
• RW stands for read/write operation when it is low the LCD is taken for write operation. It is very rare that the program reads data from the LCD, so it is always connected to the ground.
• The next pin is enable (E). This is a control line used to tell the LCD that you are sending it data. It is attached to one of the digital pins of the arduino.
• The pins D0 to D7 are used for the 7 segments usually you pass only four segment pins from D4 to D7 for using simple alphabets and numbers. It is only then when you need special characters you connect all 8 pins and define the shape of the character.
• The last 2 pins of the LCD are not necessary and remains unconnnected.

THERMISTOR:

Then comes the thermistor the analog input is accepted from the thermistor divider circuit as shown along with the 220ohm resistor.
This raw analog input is caliberated and processed using the program following code:

double Thermistor(int RawADC)
{
  double Temp;
  Temp = log(10000.0*((1024.0/RawADC-1)));
  Temp = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp ))* Temp );
  Temp = Temp - 273.15;        
  return Temp;

}

This function is used to caliberate the analog signal which we get from the thermistor. It varies with differemt resostors.

Easy schematic of the circuit