PIC Thermometer

Original circuit from HAMRADIOINDIA. The circuit there uses two temperature sensors and 3 seven segment displays because of decimal point in the output (e.g. 25.6 Celsius). I modified the circuit and simplified it by removing the spare sensor and using only two display. The reason is when I simulated it in Proteus, the output is somehow wrong. I don't know if the output is right on actual but since I want to make sure with the actual circuit, I followed my schematic that gives the right output on simulation. I did not program the microcontroller. The HEX is from the site and the code is available there.

Motor circuit from NERDKITS. Great explanation of the basic principle of motors.

THERMOMETER:

 

Digital Thermometer using PIC16F877A microcontroller. The circuit uses LM35 as its temperature sensor, and displays the temperature (0-99 Celsius) using the two 7 segment display. 

Input voltage: 9-12V DC
then it is regulated to 5V DC connected to PIN 6 and PIN 1 of the microcontroller and input to the sensor

MATERIALS:

pic16f877a
22pF x 2

10nF
10uF
100nF x 2
10uF electrolytic
470uF electrolytic
7805 voltage regulator
2.2k
10k
470ohms x 8
LM35
BC558 x 2
7 Segment Common Cathode x 2
4 MHz Crystal

DC jack

wires
PicKit2
Pic Programmer

POWER SUPPLY:

The circuit is also programmed to turn on devices using the RC pins. Example: RC0 is ON when the temperature is above 39 Celsius. One application is to turn on a fan when it is already too hot. That's why we included additional circuit for this application

<circuit not shown>

OPTIONAL (MOTOR/FAN):

The output of the RC0 can work like a switch to ON/OFF the motor

Temperature > 39 : turn on the fan

<circuit not shown>

Additional Materials:

Battery holder (2 x AA batteries)

3V DC Motor
1N4003 diode
2N7000 transistor
100k

SNAPSHOTS:

Download program in hex, schematic for $20

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