For home security , we can build " Thief Detector " using PIC 18f2550 microcontroller and PIR Motion Sensor . When something will be moving front to the sensor , the thief detector system will give an alarm to us . That's the basic theme of this project .
PIR Motion Sensor :
Actually this sensor is continuously transmitting an Infrared Ray signal and receiving the reflected signal . According to the information of receiving signal it changes it's output signal . You can see the pin out of PIR Motion Sensor .
Generally when something moving in the front of it , the sensor produce 3.3 volt to it's out pin . Otherwise the out pin will be 0 volt . By applying this technique we can get information or status of out doors .
We will get the PIR Sensor connected with ADC(Analog to Digital Converter ) pin of PIC 18F2550 . We will use RA0 as input .
ADC(Analog to Digital Converter ) :
We need a basic knowledge about ADC . Let's take a look at here :
 |
| ADCON1 Register |
Basically ADC is like as voltage divider . According to voltage It produce output .
bit 5 : VCFG0: Voltage Reference Configuration bit (VREF- source)
1 = VREF- (AN2)
0 = VSS or 0 volt
bit 4 :VCFG0: Voltage Reference Configuration bit (VREF+ source)
1 = VREF+ (AN3)
0 = VDD or 5volt
We will set VCFG0[bit 5]=0and VCFG0[bit4]=0 . So we will get highest value 5volt[1023] and lowest value 0volt[0].The ADCON1 is a 10 bit register that means 2 to the power 10 is it's highest counting capacity and result is 1024 . So this register can count from 0 to 1023 . When 0 volt , we get reading at RA0 pin 0 .When 5 volt , we get reading at RA0 pin 1023. It means 5volt equivalent to 1023 .
If 5 volt equal reading 1023 .
So 1 volt equal reading 1023/5 [When something detect PIR Sensor provide 3.3 volt at Output Pin]
So 3.3 volt equal reading (1023/5)*3.3 =675.8 . When we get reading 675 at ADC channel , we understand that sensor detects something . So it make PORTB.F6 pin high and Buzzer turns on .
Circuit Diagram :
Source Code :
void main() {
int input;
CMCON=7;
ADCON1=0x0E;
TRISB.F6=0;
while (1) {
input = ADC_Read(0);
if(input>=675){
PORTB.F6=1;
delay_ms(4000);
}
PORTB.F6=0;
}
}
