Temperature sensing
In an industry will have to use electronic circuit to run a machine.When the machine is used to operate in a very long time, the circuit will definitely heat. When the temperature is increased the circuit will be at risk of suffering damage or fire.Therefore to solve the problem,temperature sensor is designed to prevent and reduce the cost of maintenance.
Thursday, 17 May 2012
Sunday, 25 March 2012
HARDWARE
This project
will require following hardware:
a)
1
x PIC16F873A
b)
1
x PJT 11 Printed Circuit Board (PCB)
c)
1
x LCD
d)
1
x Buzzer
e)
2
x Temperature Sensor (LM35)
f)
Other
related electronic component
Interface PIC16F873A with Temperature
Sensor (LM35)
Signal pin
(Vout) from LM35 can be connected to either one of analog input pin (AN0-AN4)
except AN3 (pin 5) but make sure the ADC configuration is correct. In fact, pin
5 (Vref+)from PIC should be given for 1V but it may has offset, so a variable
resistor (VR1) was installed for voltage adjusting. For more stability, user is
recommended add a capasitor (104) between the analog signal and GND for every
analog input such as signal from LM35 and variable resistor (VR1).
Interface PIC16F873A with LCD
The 16
header pin should be soldered to the LCD first. The following table shows the
LCD (2X16 character) connection:
PIN
|
PIN NAME
|
FUNCTION
|
CONNECTION
|
1
|
VSS
|
Ground
|
GND
|
2
|
VCC
|
Positive
supply for LCD
|
5V
|
3
|
VEE
|
Contrast
adjust connected to a preset for contrast adjusting
|
|
4
|
RS
|
Select
register, select instruction or data register
|
RA2
|
5
|
R/W
|
Select
read or write
|
GND
|
6
|
E
|
Start
data read or write
|
RA5
|
7
|
DB0
|
Data bus
pin
|
RC0
|
8
|
DB1
|
Data bus
pin
|
RC1
|
9
|
DB2
|
Data bus
pin
|
RC2
|
10
|
DB3
|
Data bus
pin
|
RC3
|
11
|
DB4
|
Data bus
pin
|
RC4
|
12
|
DB5
|
Data bus
pin
|
RC5
|
13
|
DB6
|
Data bus
pin
|
RC6
|
14
|
DB7
|
Data bus
pin
|
RC7
|
15
|
LED+
|
Backlight
positive input
|
5V
|
16
|
LED-
|
Backlight
negative input
|
GND
|
TABLE 1
FEATURES
Power Transistor (BD135)
-BD135 is
used for controlling the DC brushless fan with sufficient current.
Temperature Sensor (LM35)
-In this
project, two LM35s are used for two difference temperature. Vs of the LM 35 are
given 5v and the Vout pins are
connected to AN0 and AN1 (PIC16F873A) separately.
PIC16F873A (Microcontroller)
This
powerful (200 nanosecond instruction execution) yet easy-to-program (only 35
single word instructions).CMOS FLASH-based 8-bit microcontroller packs
Microchip’s powerful PIC® architecture into an 28-pin package and is
upwards compatible with thePIC16C5X, PIC12CXXX and PIC16C7X devices. The
PICF873A features:
·
256
bytes of EEPROM data memory
·
Self
programming
·
An
ICD
·
2
Comparators
·
5
channels of 10-bit Analog-to-Digital (A/D)converter
·
2
capture/compare/PWM functions
·
The
synchronous serial port can be
configured as either 3-wire Serial Peripheral Interface(SPI™) or the 2-wire Inter- Integrated
Circuit (I²C™) bus
·
A
Universal Asynchronous Receiver Transmitter (UART)
All of these
features make it ideal for more advanced level A/D applications in automotive,
industrial, appliances and consumer applications.
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