ATMEGA8 Temparature Controller

For More Products Visit Our Website:

www.amateurworld.in

Page 1 of 6 AMATEUR WORLD world of amateur electronics www.amateurworld.in

ATMEGA8 TEMPERATURE

CONTROLLER

Basic object of this project is to control one Heater and one Fan to maintain constant temperature in

an environment. For this we are using ATMEGA8L microcontroller as the main controller and LM35

for Temperature Sensor. One 16X2 LCD is attached with the microcontroller to display the Set

Temperature Value and Present Temperature Value. LCD will also to display the status of Heater and

FAN. For Heater we are using one Relay to control 230VAC Heater Element and we have attached on

12VDC Brushless DC FAN directly with the board.

Working Principal:

Whenever the system is switched ON, LCD will display SV (for SET Temperature Value) and PV

(for Present Temperature Value) at the left side of the display. On the right side we will display the

status of FAN (as FN) and Heater (as HT). We have interfaced three switches with the

microcontroller. Now to change the SV, we have used two switches as UP switch and DWON

switch. One another switch is left unused for further development of this project. Now on pressing

UP switch, value of SV will increase and DOWN switch, value of SV will decrease.

To do the main function of the project, i.e. controlling of FAN and HEATER, we use three compare

functions in our software. To overcome the problem of frequently ON/OFF of HEATER and FAN, we

assume Hysteresis of 10C, i.e. HEATER or FAN status will be changed if PV is out of +_ 10C. So, if PV is

greater than +_ 10C of SV then FAN will be on to cool down the environment and if PV is bellow +_ 1

0C

of SV then HEATER will be ON to increase the temperature of the environment. And when PV is

within +_ 10C of SV, HEATER and FAN will be OFF. This is to note that in a moment either HEATER or

FAN will be ON.


www.amateurworld.in


SCHEMATIC DIAGRAM:

SOFTWARE:

Software is written in BASCOM AVR, Basic language. It is just plain English like language and easy to

understand and easy to write. Bellow is the complete code.

'ATMEGA8 TEMPARATURE CONTROLLER PROJECT

'FOR B.TECH STUDENTS

'CONTROLLER: ATMEGA8

'Dated 20/03/2012

'MAIN OBJECTIVE OF THIS PROJECT IS TO MEASURE AND DISPLAY TEMPERATURE

'AND CONTROL HEATER & FAN TO MAINTAIN SET TEMPERATURE

'FOR TEMPERATURE, LM35 TEMPERATURE SENSOR IS USED

'*********************************************************

'$sim

$regfile = "m8def.dat"

$crystal = 8000000 ' 8 MHz crystal

$swstack = 40

$hwstack = 32

$framesize = 32

'*********************************************************

' CONFIGURE 16X2 LCD

'*********************************************************

Config Lcd = 16 * 2


www.amateurworld.in


Config Lcdpin = Pin , Db4 = Portb.3 , Db5 = Portb.2 , Db6 = Portb.1 , Db7 = Portb.0 , E = Portb.4 , Rs =

Portb.5

Cursor Off 'MAKE CURSOR OFF

'*********************************************************

' CONFIGURE ADC FOR MEASUREMENT OF LM35

'*********************************************************

Config Adc = Single , Prescaler = Auto , Reference = Avcc

Start Adc

'*********************************************************

' DECLARATION OF I/0

'*********************************************************

Config Pind.5 = Input



Menu Alias Pind.5

Up Alias Pind.6

Down Alias Pind.7

Config Portd.3 = Output

Config Portd.4 = Output

Fan Alias Portd.3

Heater Alias Portd.4

Fan = 0 'MAKE FAN OFF

Heater = 0 'MAKE HEATER OFF

'*********************************************************

' DECLARATION OF VARIABLES

'*********************************************************

Dim W As Word , W_single As Single , W_avg As Single

Dim Pv As Integer

Dim Gp As Byte

Dim Sv As Integer , Sv_s As Eram Integer

Dim Hv_h As Integer , Hv_l As Integer

'*********************************************************

Deflcdchar 0 , 4 , 14 , 31 , 14 , 4 , 32 , 32 , 32 ' replace [x] with number (0-7)

Cls 'CLEAR DISPLAY

Lcd "PV=" ; Spc(3) ; Chr(0) ; "C" ; Spc(2) ; "HT="

Lowerline

Lcd "SV=" ; Spc(3) ; Chr(0) ; "C" ; Spc(2) ; "FN="

Sv = Sv_s

Main:

Gosub Measure_lm35

Gosub Check_temp

Debounce Up , 0 , Sv_up

Debounce Down , 0 , Sv_down

Goto Main

'********************************************************

'HEAR WE MEASURE TEMPERATURE FROM LM35 SENSOR

'FIRST WE MEASURE THE ADC COUNT AT 'W'

'AS WE KNOW ADC WILL COUNT MAXIMUM VALUE(1024) AT 5V

'WE CAN PER COUNT VALUE BY THE FORMULA,


www.amateurworld.in


'W_SINGLE=(WX5)/1024=WX0.005

'I.E. EACH COUNT IS EQUAL TO 5mV

'NOW FROM DATA SHEET OF LM35 WE KNOW THAT LM35 WILL

'OUTPUT 10mV PER DEGREE CENTRIGATE

'SO EACH COUNT=W_SINGLE/2 DEGREE CENTRIGATE

'FOR ACCURACY WE TAKE 100 SAMPLE AND THEN TAKE AVARAGE

'********************************************************

Measure_lm35:

W_avg = 0

For Gp = 1 To 100

W = Getadc(0)

'W_single = W * 5 'CHECK MATH FOR LM35

'W_single = W_single / 1024

'W_single = W_single / 2

If W 0 Then

W_single = W / 2

Else

W_single = 0

End If

W_avg = W_avg + W_single

Next Gp

If W_avg 0 Then

W_avg = W_avg / 100 'MAKE AVAGARE OF DISPLAY

Else

W_avg = 0

End If

Pv = W_avg 'TO IGNORE THE FRACTION

Locate 1 , 4 'LOCATE THE DISPALY VALUE LOCATION

Lcd Spc(3) 'ERASE OLD VALUE

Locate 1 , 4 'LOCATE THE DISPLAY VALUE LOCATION

Lcd Pv 'DISPLAY THE CURRENT VALUE

Locate 2 , 4

Lcd Spc(3)

Locate 2 , 4

Lcd Sv 'DISPLAY THE SET VALUE

Return

'********************************************************

'HERE WE INCREASE SET TEMPERATURE VALUE BY 1

'********************************************************

Sv_up:

Incr Sv 'INCREMENT SV BY 1

If Sv > 110 Then

Sv = 0

End If

Sv_s = Sv 'SAVE SV AT EEPROM

Locate 2 , 4

Lcd Spc(3)

Locate 2 , 4

Lcd Sv

Goto Main


www.amateurworld.in


'********************************************************

'HERE WE DECREASE SET TEMPERATURE VALUE BY 1

'********************************************************

Sv_down:

If Sv 0 Then

Decr Sv 'DECREASE SV BY 1

Else

Sv = 110

End If

Sv_s = Sv 'SAVE SV AT EEPROM

Locate 2 , 4

Lcd Spc(3)

Locate 2 , 4

Lcd Sv

Goto Main

'*******************************************************

Check_temp:

Hv_h = Sv + 1 'HYSTERISYS=1

If Pv >= Hv_h Then

Fan = 1 'TURN ON THE FAN

Heater = 0 'TURN OFF HEATER

Locate 1 , 14

Lcd Spc(3)

Locate 1 , 14

Lcd "OFF"

Locate 2 , 14

Lcd Spc(3)

Locate 2 , 14

Lcd "ON"

End If

Hv_l = Sv - 1 'HYSTERISYS=1

If Pv Hv_l And Pv < Hv_h Then

Fan = 0 'TURN OFF FAN

Heater = 0 'TURN OFF HEATER

Locate 1 , 14

Lcd Spc(3)

Locate 1 , 14

Lcd "OFF"


www.amateurworld.in


Locate 2 , 14

Lcd Spc(3)

Locate 2 , 14

Lcd "OFF"

End If

Return

'************************************************************

End 'end program

Documents

ATMEGA8 Temparature Controller