For quite a few of the Ellentriek#11 projects, participants wanted to connect Arduino to the main current system: 220 Volt.
As this can be tricky, it’s good to look for solid solutions.
I have found a relay set-up which is safe to use with 220 volt and arduino (yeay!).
This is the little board:
and you need of course to add all the components. The transistor and diode are essential for safety (making sure that the current only goes into one direction).
There is a tutorial on how to build it:
I buy all my Sparkfun stuff here, which makes sure that you avoid the international shipping costs and the US taxes.
(I got the relay specs here)