Here is another instructable of making a cheap dark sensor from scratch!
Its Cheap and works fine.
No requirement of arduino or Ic's.
Step 1: Items Required
So, For making this basic sensor , you will be required some basic items which can be easily purchased from a local electronics shop for some bucks.
Here are the parts which are required :-
1. 1 X BC547 ( Very Common Transistor)
2. 1 X 5mm LED
3. 1 X 220k Ohm Resistor
4. 1 X 330 Ohm Resistor
5. 1 X LDR (Light Dependent Resistor)
6. Soldering Items and a perfboard
7. Couple of wires
Step 2: Circuit Diagram
Just follow the circuit diagram and you will get your Dark Sensor ready at no time!