How to Make an Light Sensor and Dark Sensor


Introduction: How to Make an Light Sensor and Dark Sensor

Hi Everybody... , and this is my second instructable so please give me advise and point out the areas in which i can improve.

Please after looking to my project give an honest rating.

Step 1: Things That You Will Need

1)LM358 IC
2)LM7805 IC
3)2 LEDs
4)2 LDRs
6)3 9v batteries
7) wires
8)Two variable resistors of 10K

Download the data sheet of LM358 and LM7805 IC.(You may need it !)
Link of LM358-
Link of LM7805-

Step 2: Circuit Diagram

Remember that the LDR doesn't have a negative or positive terminal !
Connect the first terminal of the LDR to positive and second terminal through variable resistor to negative.Then start varying and when you get a vary for example(.58 v to 1.1v) or If the vary is of good range ,then also the circuit will work.After that take a wire in between from LDR & variable resistor and put in the third pin of the LM358 IC.

Please make the circuit given in the diagram.
The circuit should be made in a good light.

Step 3: How the Circuit Looks

Step 4: How It Works

In my circuit the left LDR is light sensor and the right LDR is Dark sensor.When you put hand on left LDR the 1st led stops glowing.
And when you put your hand on right LDR the 2nd led starts glowing.

Comment if you guys have any problem !




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    9 Discussions

    Please use a program to draw the circuit. Like a Multisim, for example.
    It is much easier to analyze.


    1 reply

    The IC LM358 is a 'dual comparator'. Its much like the LM741 IC, instead the 358 can compare two separate pair of volatges simultaneously and give two respective output voltages simultaneously. In this case one of the comparators is used for the dark sensor, while the other is used for the Light sensor.

    Hey, this is Akshay.... studying engineering!
    i made the exact copy of the breadboard connection in the pic. of ur.....
    i din get any light illuminating from my led's....
    but wen i made my own connections by looking at the circuit diagram u've put, both my led glows! no matter wat u do i'm not getting the proper thing over this!!!


    Use Fritzing to mock this up, Its a great circuit and you explain it well, but yeah, the schematics are a bit rough.

    Fritzing is drag and drop, very easy and no crazy variables like spice etc

    I agree with dmartins, using any sort of circuit CAD software makes it much easier to follow. Multisim for example is a very easy software to jump into. As well as Pspice.