Introduction: Darkness Sensor Using OpAmp
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.
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.