Fire Alarm System

Fire Alarm System

Fire alarm system is a topic that is always interesting to try. This is because it involves a microcontroller, temperature sensor and smoke and programs in the LCD viewer. This application is a demo of the fire alarm using ATmega AVR Microcontroller 8535, which is already available on-chip 10-bit internal ADC with 8 channels.

Tools required for this application experiment:
1. Smart AVR ATmega AVR 8535 or other sismin already supports serial communication.
2. 2 LM 35 temperature sensor
3. Sensor Smoke / Gas AF30
4. Digital Multimeter
5. 12V adapter
6. Relay Board
7. Buzzer and spray

Block Diagram
We need a measure of the temperature sensor LM35 as a fairly linear from the range of 000-100 degrees Celsius. Two sensors attached to the fruit and PA.2 PA.0 as a demo at the room temperature measurements inside and outside. While the humidity sensor has an analog output type 808H5V5 the range 0.8V – 3.9V connected to PA.1 .. If you want to have a temperature sensor chip cooling, use the type LM35DT.

AVR Atmega 8535-Atmega16 configuration

1 Temperature Sensor LM 35DZ
Smoke Sensor AF30
PA.0 PC & PD
PA.1
PB
AVR 8535
LCD 20×4
Buzzer and water hoses

lm35

TEMPERATURE SENSOR
LM 35 temperature sensor is the most widely used for practice, because besides the price is pretty cheap, linearitasnya pretty good. LM35 does not require external calibration which provides accuracy of ± ¼ ° C at room temperature and ± ¾ ° C in the range -55 to +150 ° C.LM35 is intended to operate at -55 ° to +150 ° C, while LM35C at -40 ° C to +110 ° C, and LM35D at 000-100 ° C. kisran LM35D packages are also available at eight feet and TO-220 package. LM35 sensors will generally increase by 10mV each increase of 1 ° C (300mV at 30 ° C).

AF30 Smoke Sensor

gas sensors configuration

Basically, the working principle of these sensors is to detect the presence of gases which are considered representative of cigarette smoke, ie Hydrogen gas and ethanol. Sensor AF-30 has a high level of sensitivity to two types of gas. If these sensors detect the presence of these gases in the air with a certain concentration level, the sensor will think there is smoke in the air.When the sensors detect the presence of these gases serve targeted the electrical resistance of the sensor will go down as has been discussed in past articles. By exploiting the working principle of this sensor AF-30, the content of these gases can be measured.

sensitivity level sensor AF-30 graphic

From the graph in the image above can be seen that by measuring the ratio between resistance at the time there are gas sensors and sensor resistance in clean air or do not contain these gases (Rgas / Rair), we can know the gas concentration. For example if the sensor resistance (RS) when there is a 1KW and Hydrogen gas sensor resistance (RS) at the time of 10KW of clean air is then:

From the above calculation and according to the graph in Figure 1, if Rgas / Rair = 0.1, the concentration of Hydrogen Gas in air is about 100ppm. To know the size of the sensor resistance (RS) when the air cleaner can be calculated using the formula:

For example if Fout at the time of the clean air is 2.8 V and RL is used then by the formula above 10KW RS is obtained when the air is clean (Rair) is 7857.14 W or 7857W. From the above calculation results obtained by RL = 10KW, RS when the air is clean (Rair) = 7857W, with clean air during Fout = 2.8 V.

By looking at an image graph and the calculation above, then Fout values for each comparison value Rgas / Rair be known so that the level of concentration of these gases is also well known.For example for the Hydrogen gas with a concentration level of 10ppm, from a graphic image Rgas / Rair @ 0.29 then

Rgas / Rair @ 0.29
Rair = 7857W
Rgas = Rair x (Rgas / Rair)
= 7857W x 0.29
= 2279W
From the above calculation results obtained Rgas value at 10ppm Hydrogen gas concentration.Because Rgas is equal to the resistance sensor (RS), then based on the value obtained Rgas, then from the formula to find the value of RS, the value when the concentration of Fout 10ppm Hydrogen can be obtained:

Rgas  = 2279W

Vc     = 5V

RL     = 10KW

Vout = 4,072V

So Fout value when the sensor detects the value of 10ppm Hydrogen concentration amounted to 4.072 V. In the same way can be obtained Fout values for each gas concentration levels of Hydrogen and Ethanol in accordance with a graphic image. From the values are found for table Fout Fout value changes.

the program with BASCOM AVR :

Declare Sub Display()                                     

Config Portb =

Config Lcdpin = Pin , Db4 = Portc.4 , Db5 = Portc.5 , Db6 = Portc.6 , Db7 = Portc.7 , E = Portd.6 , Rs = Portd.7

Config Lcd = 20 * 4

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

Start Adc

Dim W As Word

Dim X As Word

Dim Perc As Word

Dim Volt As Word , Volt_d As Byte

Dim Channel As Byte , I As Byte , Cols As Byte , Cols_d As Byte

Cls                                                  

Cursor Off                                             
Locate 1 , 4                                       

Lcd “Fire Alarm”

Locate 3 , 1

Lcd ” Suhu & Sensor Asap”

Locate 4 , 1

Lcd ” AVR ATmega8535″

Wait 1

Do

W = Getadc(0)                                         
Print W

X = Getadc(1)                                          
Print X                                                
If W <= 78 And X <= 300 Then

Call Display()

Locate 4 , 4

Lcd “Ruangan Aman”                                    

Portb = 0                                             

Waitms 600

End If

If W > 78 And X <= 300 Then                           
Call Display()

Portb = 0

Locate 4 , 4

Lcd “Ruangan Panas”

Waitms 600                                               
End If

If W > 78 And X > 300 Then                        

Call Display()

Portb = 255

Locate 4 , 2

Lcd “Terjadi Kebakaran !”

Wait 2                                                
End If

Loop

End

Sub Display                                              
Cls

Locate 3 , 1

….

Locate 3 , 19

Lcd Chr(223) ; “C”

Volt = W * 5

Volt_d = Volt Mod 10                                     

Volt = Volt / 10

Locate 1 , 1

Lcd Volt ; “,” ; Volt_d

Cols = Volt / 2

Locate 2 , 1

For I = 1 To Cols

Select Case I

….

End Select

Next I

Cols_d = Cols Mod 2

If Cols_d > 0 Then

Lcd Chr(5)

Cols = Cols + 2

Else

Cols = Cols + 1

End If

For I = Cols To 20

Select Case I

End Select

Next I

End Sub

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