The Metal sheet came from a Computer power supply, glued to the plywood. The plywood was needed to keep the surface level. The magnets are strong enough to stay stuck without glue. 
The Metal sheet came from a Computer power supply, glued to the plywood. The plywood was needed to keep the surface level. The magnets are strong enough to stay stuck without glue.
It was not needed to connect the ground wire, it is not used. 
I also connected a single RED LED which takes 2 Volt. Spinning the rotor at around 650 rounds per minute generates 2 Volt at a current of 0.0265 Ampere, which is enough to light up the LED. Thus, the alternator can supply up to 0.0265 Amps at 2V DC, and power up to 0.0265 Watts(VA).
http://www.instructables.com/id/DIY-1000-watt-wind-turbine/ http://www.supermagnete.ch/eng/data_sheet_Q-25-06-02-SN.pdf (datasheet of magnets) http://www.powersem.net/Three_Phase_Bridges/Standard_Diodes/Baseline/PSD%2025.pdf (datasheet of rectifier)