21-05-2012, 05:45 PM
PIC16F877A-based Temperature Monitoring System
PIC16F877A-based Temperature.pdf (Size: 403.54 KB / Downloads: 199)
Hardware description
the circuit of the temperature
monitoring system. The
circuit mainly consists of the LM35
temperature sensor, PIC16F877A microcontroller
and HD44780 controller
based 16×2 LCD.
Software description
The software code is written in ‘C’
language and compiled using Hitech
C cross compiler in MPLAB IDE. The
software performs the following operations
in an infinite loop:
1. Initiate analogue-to-digital conversion
and obtain the result
2. Calculate the equivalent voltage
value from the ADC result
3. Calculate the temperature in degree
Celsius from the voltage value
4. Display the temperature on the
LCD
The voltage output (in volts) of the
sensor is:
Construction
A single-side, solder-side PCB layout
of the temperature monitoring system
is shown in Fig. 4 and its component
layout in Fig. 5.
A 230V AC primary to 0-9V AC
secondary step-down transformer is
used to step down the 230V mains
supply. The output of the transformer
is rectified using a bridge rectifier
consisting of diodes D1 through D4
and regulated to 5V using 7805 voltage
regulator. The glowing of the LED
(LED1) indicates the presence of 5V
supply in the circuit.