Using a photoresistor as a switch

[arhanghel]

Hello,
I want to use a photoresistor (photocell) to hook up an LED or an fluorescent tube when night falls (when night falls they(led or fluorescent tube) must start to illuminate).

Any idea how can I do something like that?

Thanks!

[komaspieler]

You could use the photoresistor to trigger a transistor (for example a MOSFET) to in turn control an opto-coupler that controls a triac to switch your fluorescent tube.. for the LED you can most likely leave out the opto-coupler part as it is only for galvanic separation of the low-voltage circuit to the line voltage circuit.