Turning on a LED with a LDR can be confusing until thought about logically. Using a 9 volt battery, simple voltage divider, LED with current limiting resistor, and LDR.
The LDR is represented by the resistor connected between the voltage divider and base (middle pin) of the NPN transistor.
Switching the values of R¹ and R² will determine which path the current will take to ground.
** If you have a multimeter you can connect your LDR out of circuit and measure resistance values to chose the best values for your voltage divider. You don't want the light to come on too soon.**
