Light/Dark Indicator

In this project, we introduce you to a circuit which has very wide application in our daily lives: a light detection circuit.
Our light detector is, of course, very simple – but you can see variations of this circuit in such things as street light switches, lift door protectors, safe alarms, etc.
Combine this project with the water indicator prescribed in Project 3 and you have the basis of your own electronic weather station: you’ll be able to tell if it is wet or dry as well as light or dark – all electronically!

You will need these components
Resistors:
One 390-ohm (orange – white – brown)
One 33k ohm (orange – orange – orange)
One 1.2k ohm (brown – red – red)
One light dependent resistor (LDR)
Diodes:
One protection diode (1N4002 or similar)
One light emitting diode (LED)
Transistors:
One NPN type DS548 or similar small signal type
Miscellaneous:
One battery clip
5 lengths of tinned copper wire
12 self-tapping screws with washers
Baseboard & project overlay No. 4