Dark Activated Switch Circuits
Showing posts with label dark. Show all posts
Showing posts with label dark. Show all posts
Wednesday, June 12, 2013
Thursday, April 11, 2013
Light and Dark Dependent Circuir
This is the circuit of a simple buzzer
that is activated by darkness, the buzzer is off when theres light and
on when it is dark. A general-purpose operational amplifier, the 741, is
used as a comparator that determines whether it is dark enough to turn on a self-oscillating piezoelectric buzzer.
Its inverting input is connected to a photoresistor,
that is activated by darkness, the buzzer is off when theres light and
on when it is dark. A general-purpose operational amplifier, the 741, is
used as a comparator that determines whether it is dark enough to turn on a self-oscillating piezoelectric buzzer.
a component whose resistance decreases as more light shines on it. Its
non-inverting input, on the other hand, is connected to an almost fixed
voltage, i.e., a proportion of the supply voltage as set by timmer
resistor R2.
Figure 1. Darkness-Activated Buzzer Circuit Diagram.
If there is ample light shining on the photo-resistor, the buzzer is quiet. As less light shines on the photo-resistor,
its resistance increases and causes the voltage across R1 to decrease.
At a certain level of lighting, the voltage across R1, which is also
the voltage at the inverting input of the 741, becomes smaller than the
voltage at the non-inverting input. At this point, the 741 is triggered
to output a high level, turning on Q1. Q1 then activates the
self-oscillating piezoelectric buzzer.
its resistance increases and causes the voltage across R1 to decrease.
At a certain level of lighting, the voltage across R1, which is also
the voltage at the inverting input of the 741, becomes smaller than the
voltage at the non-inverting input. At this point, the 741 is triggered
to output a high level, turning on Q1. Q1 then activates the
self-oscillating piezoelectric buzzer.
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