Darkness Sensor Using OpAmp

Introduction: Darkness Sensor Using OpAmp

About: Arduino and electronics projects

I have made a darkness sensor circuit using lots of different things like 555-timer ic, transistor and OpAmp

but the OpAmp circuit most reliable circuit.


1 L.D.R(photoresistor)

2 any OpAmp(741)

3 higher value resistor 100k(approx) I'm using 150k ohm

4 lower value resistor 1k ohm

5 10k potentiometer

current limiting resistor (220 ohms)

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Step 1: Voltage Dividers

1. Construct voltage divider using a resistor(higher value)(100K) and L.D.R

2. Measure the voltage across the L.D.R according to your power supply and note it down.

3.Construct another voltage divider using a resistor(lower value)(1K) and potentiometer(10k).

4. Measure the voltage across the potentiometer and set it to the voltage(noted).

Step 2: OpAmp Circuit

1. Connect Vref(second voltage divider) to the inverting terminal of OpAmp.

2. Connect the first voltage divider node to the non-inverting terminal of OpAmp.

3 .Connect V(+) to Vcc and v(-) to GND.

4. Connect the output terminal to the anode of led and cathode to GND via a 220-ohm resistor.

Step 3:

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