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OVER LIGHT SENSOR ALARM CIRCUIT










OVER LIGHT DETECTOR


Here i am going to Introduce you an Excess light Detector or sensor circuit.

The sensing component used in this circuit is LDR (Light Dependent Resistor).

LDRs are sensitive, inexpensive and readily available device. They posses good power and voltage handling capacity similar to an ordinary resistor.


CIRCUIT DIAGRAM OF OVER LIGHT DETECTOR


simple over light alarm circuit diagram




Components required to wire up this circuit


1. LDR
2. R - 1K
3. SCR
4. Buzzer
5. 5V BATTERY



WORKING PRINCIPLE OF OVER LIGHT DETECTOR

The LDR is a variable resistor whose resistance decreases with increase in light intensity. When the light falling on an LDR has normal intensity, its Resistance is large enough and the voltage across R is insufficient to trigger the SCR. However, when light falling on LDR is of large intensity, the Resistance of LDR falls and voltage drop across R becames large enough to trigger the SCR. Consequently the buzzer sounds the alarm. It may be noted that if the strong light disappears the buzzer continues to sound the alarm. It is because once the SCR is triggered the gate loses its control.

You can use this circuit as LIGHTNING DETECTOR AND ALARM



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