Hi guys,
it's been a long time when i posted a instructables so i am making this simple but great dark detector for you.

I made this also for my younger sister who need some light in her room while going to sleep.

Step 1: List of Parts

Parts Required are :-

1x Ldr [Light Dependent Resistor]
1x Bc547 Transistor
1x 220K Ohms Resistor
1x 100 Ohms Resistor [ Read Next Step for Other Colors of Led]
1x 10mm White Led
1x Battery Clip
1x 9v Battery

That's All.

Step 2: Schematic

How it Works :- An Led is Illuminated when it will detect no light. An LDR (Photoresistor) is used in this circuit for sensing the light and dark conditions, and transistor bc547 is working as a switch. When the LDR will detect no light it will open the transistor bc547 due to which the LED will light up. And The 100 ohms resistor is used to protect led from direct contact to 9v Supply.

Step 3: Assemble the Components

Assemble the Components according to Schematic and Remember the pinouts of bc 547.
Solder the Components Firmly :)

Step 4: Finishing Touches....

Now Solder the Battery Clip to the Wires as shown in schematic and Hot Glue whole Board to the battery.

Connect the Battery Clip to Battery.
And Test it.

Please Vote This Instructable in Contests.
Hope i could get something for my little sister's Birthday.