Light on and off sound buzzer

 

This is a 3 VOLT SYSTEM. Using a (2N 5551 B011 NPN) transistor 

Resistor 1 is 180 ohms and resistor 2 is 90 ohms

The reason I used resistor 2 which is not needed, is that sometimes the bace(B) can get alot of volts which can cause  permanent damage to the transistor.

When light is applied to the photoresistor, the base gets power hence creating a potential deference between resistor 1 and the collector (C) which causes a 0 or on power to the sound buzzer.

But when the light is out, the output is 1 and the buzzer gets power so it produces sound

I used this system on my door. So that when i open the door, the led moves with the door hence coursing the photoresistor to lose light and then it buzzers 



This is the image of the sound buzzer



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