Hi all
I am trying to make security system.
I same thing that all have seen the movies that some important thing is secured by the laser beam and when one try to penetrate to laser beam than alarm blow up.
My concept is to use the LDR (photoresistor) and laser (which is focusing on the LDR).
I want to make it with my system's parellel port {LPT1}.So what i was thinking that untill laser is pointing to LDR is sends 1 and when laser intrupted occur it become 0.
I have experimented by conecting one end of LDR data pin D0 (pin 2) and for voltage i have use 4.5v battery and make it ground to pin 25.I have used lamp instead of laser but the inportb(0x378) gives 0 both time(with light and without light).Code:So my que is that at what voltage does parallel port undersand 0 and 1.
why this happned?