How to Make a Automatic Light

About: I make diy and electronics based projects.

This is a simple automatic light circuit

Step 1: Components Needed


2)12v relay

3)1k resistor

4)100mfd 25v capacitor

5)10mfd 63v capacitor

6)2× in4007 diode

7) BC 547 npn transistor

8) pcb

9) bulb holder

Step 2: Circuit Diagram

Sorry for the bad image

Step 3: After Completing the Circuit

Step 4:

Connect bulb holder to no of relay

Step 5:

Step 6: More Details in Video



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    4 Discussions


    Question 7 months ago on Step 2

    I pretty much understand what you have built and appreciate the tutorial. Is there a simple way to reverse what this does? So that it would turn on a light (or provide power) during the day instead of at night? The only way I've figured out how to do that is a second relay in the circuit and that seems very inefficient. I'm not an electronics guy at all, but trying to learn. Thank you.

    3 answers
    Electro makerWallythecat

    Answer 7 months ago

    Try connecting transistor in reverse but I don't know it's work or not. Thankyou.

    WallythecatElectro maker

    Reply 7 months ago

    I'm wondering if I substitute a 547 pnp transistor for the 547 npn. Trying to puzzle my way through the spec sheets, it seems like that might work. Time to dig out the breadboard and check my component inventory.