Figure shows the connection diagram ! its a 311 opamp with 4 th terminal gnded R2 is an LDR whose dark resistance is greater than 10kohm A laser torch can be used to power the ckt which is directed at the LDR ! when the light is falling on the LDR its resistance will be less than 10k ohm,then the voltage drop across the resistance will be less ! hence the o/p voltage of the opamp will be 0.When the light is interrupted the resistance of the LDR increases hence droping more voltage ,and the o/p will be approximately supply voltage .The o/p can be connected across a buzzer and can be connected to a relay if the alarm ,we want is of non stoping .ie ,it can be turned of only by another process not by turning the light again. the pin out of the 311 However the sytem provides no other extra security! becoz if someone shows a light on the ldr and intrudes the laser then the system may not be able to realise wat happened !So we must use some extra security tecniques ! Those includes 1)f...
Innovation is not the product of logical thought ,even though the final product is tied to a logical structure