26-05-2012, 11:37 AM
TEMPERATURE INDICATOR USING AT89C52
[attachment=23113]
Here’s a microcontroller-based temperature
indicator that displays the
temperature in the range of –55°C
to 125°C. Besides AT89C52 microcontroller,
it uses a temperature sensor chip and an
LCD module. The indicator outputs the
calibrated data in digital form. The program
for the microcontroller is written in C and
not in Assembly language. Since C program
has well-defined syntax.
The circuit
Fig. 1 shows the block diagram
of the temperature indicator
using microcontroller
AT89C52. The power supply
for the circuit is regulated
by IC 7805 and supplied
to different parts of the
unit. DS1621 is the temperature sensor
chip. The microcontroller unit (MCU) reads
the temperature from the sensor. The temperature
data is compared with certain
user-defined temperature values and processed
inside the MCU as per the program
and then sent to the LCD for display.
The program
The C-language program for
microcontroller AT89C52 is compiled using
cross-compiler C51 Version 7.10 from
Keil Software. The demo version of this
compiler is available for free on the
Website ‘www.keil.com.’ It can compile
programs up to 2 kB only, which is sufficient
for writing most programs.
For testing the display, the program
Hello.c is given here. This program, when
loaded to AT89C52, displays “Hello! How
R U?” on the LCD. The Hello.c program has
nothing to do with temperature. It just
guarantees a perfect communication between
the LCD and the microcontroller.
For temperature indication, the program
Temp52.c is used. The programs Hello.c
and Temp52.c, along with the hex files, are
given at the end of this article.
LCD
For display, a Lampex make 16x1 LCD
(model GDM1601A) was used. Pin connections
of this LCD are given in Table II. Pins
15 and 16 haven’t been used. Pin 3 is
connected to the circuit ground through a
1-kilo-ohm preset that is used to control
the light intensity of the LCD. Note that the
Hitachi make 16×1 LCD (HD44780A00)
will not work in this project.
Construction
The circuit of this temperature indicator
using microcontroller AT89C52 can be assembled
on any general-purpose, singleside
PCB. The microcontroller chip and
the temperature sensor chip are mounted
on the respective IC bases. Ensure a proper
contact between pins of the IC bases and
the solder points on the PCB. Capacitors
C3 and C4 must be connected near IC2
and IC3, respectively. The actual-size,
single-side PCB layout for the circuit and
its component layout are shown in Figs 6
and 7.
[attachment=23113]
Here’s a microcontroller-based temperature
indicator that displays the
temperature in the range of –55°C
to 125°C. Besides AT89C52 microcontroller,
it uses a temperature sensor chip and an
LCD module. The indicator outputs the
calibrated data in digital form. The program
for the microcontroller is written in C and
not in Assembly language. Since C program
has well-defined syntax.
The circuit
Fig. 1 shows the block diagram
of the temperature indicator
using microcontroller
AT89C52. The power supply
for the circuit is regulated
by IC 7805 and supplied
to different parts of the
unit. DS1621 is the temperature sensor
chip. The microcontroller unit (MCU) reads
the temperature from the sensor. The temperature
data is compared with certain
user-defined temperature values and processed
inside the MCU as per the program
and then sent to the LCD for display.
The program
The C-language program for
microcontroller AT89C52 is compiled using
cross-compiler C51 Version 7.10 from
Keil Software. The demo version of this
compiler is available for free on the
Website ‘www.keil.com.’ It can compile
programs up to 2 kB only, which is sufficient
for writing most programs.
For testing the display, the program
Hello.c is given here. This program, when
loaded to AT89C52, displays “Hello! How
R U?” on the LCD. The Hello.c program has
nothing to do with temperature. It just
guarantees a perfect communication between
the LCD and the microcontroller.
For temperature indication, the program
Temp52.c is used. The programs Hello.c
and Temp52.c, along with the hex files, are
given at the end of this article.
LCD
For display, a Lampex make 16x1 LCD
(model GDM1601A) was used. Pin connections
of this LCD are given in Table II. Pins
15 and 16 haven’t been used. Pin 3 is
connected to the circuit ground through a
1-kilo-ohm preset that is used to control
the light intensity of the LCD. Note that the
Hitachi make 16×1 LCD (HD44780A00)
will not work in this project.
Construction
The circuit of this temperature indicator
using microcontroller AT89C52 can be assembled
on any general-purpose, singleside
PCB. The microcontroller chip and
the temperature sensor chip are mounted
on the respective IC bases. Ensure a proper
contact between pins of the IC bases and
the solder points on the PCB. Capacitors
C3 and C4 must be connected near IC2
and IC3, respectively. The actual-size,
single-side PCB layout for the circuit and
its component layout are shown in Figs 6
and 7.