Here is a Simple Temperature Display Circuit using LCD (Liquid Crystal Display). For Heat Sensor we have used IC LM35 (Precision Centigrade Temperature Sensors) whose Output voltage is linearly proportional to the Celsius (Centigrade) temperature. Output of LM35 IC is 10mv/degree centigrade for eg if temperature is 35 degree, then the output of sensor will be 350mv or 0.35V
For working with LCD it is necessary to have Microprocessor. We have used Arduino Controller Board, which is AN OPEN-SOURCE ELECTRONICS PROTOTYPING PLATFORM.
Output of LM35 is feed to Arduino Analog input pin 0.
Further Data is Processed by the C Program. Output of Micro-controller is connected to the 16X2 LCD
Picture of Digital Thermometer
Below is the Simple Programme which is used here :-
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
const int inPin = 0;
int x = analogRead(inPin);
float millivolts = (x / 1024.0) * 5000;
float celsius = millivolts / 10;
lcd.print((celsius * 9)/ 5 + 32);
Circuit Diagram of Digital Thermometer
If you are new to Arduino, then follow below Instruction while making this Project :
1. After Buying Arduino Controller Board. Make sure it is working correctly. You have to Install Drive and application Software. You may need to do Jumper Setting on some board to switch between USB and External Power Source. Download arduino 1.0.5 for windows
Download CP2102 USB to UART Bridge Controller Driver.
2. After above steps, open Arduino Software and select correct board type and COM Port (Very Imp) from Menu Tools -> Board . You can identify your Arduino Board by reading main IC number.
3. To make sure above step is completed and all are functioning well, upload a simple Basic programme from the Arduino Library Examples. You have to add one resistance and LED. for eg you can do Blink Programme ( Turns on an LED on for one second, then off for one second) or LED Fade Programme.
4. Next Connect your Arduino Kit to 16X2 LCD. Here you have to add one more part, which is 10K Variable Resistance. You will get absolutely nothing character displayed on LCD if 10K preset is not adjusted correctly. If you are not sure, then adjust it near about .5 Volt and latter it can be fine tuned for better contrast.
5. For easy connection and Preset soldering I recommend use of PCB. which is shown below. You can save this for printing on copper clad Board. You can make your own PCB by Heat Transfer method or by screen printing method otherwise use Dot Matrix Board or Bread Board. This PCB will help you in all projects which used 16X2 LCD by reducing LCD Pin from 16 to 8 for easy connection.
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