By running off mains, the fume extractor can run 2X fans at full power.
And all of the parts are easily available, maybe even stuff you have lying around.
The shell of it is an empty ATX power supply.
I'm keeping it short and simple, because I'm presuming that whoever wants to try this has basic knowledge of electricity.
If you don't know what you are doing, then this project is a bad idea - 220V AC CAN KILL YOU. If you wire it up wrong, you could short circuit to the metal shell and....
Hope you enjoy!
Step 1: Parts
Apart from the box, you'll need:
1x DPDT switch, rated for mains voltage.
1x 220-12V transformer.
2x 3300microF polarised caps, rated for 25Volts or more.
2x 12V fans
1x bridge rectifier, or 4x power diodes.
1x three-prong socket like the one that computers use.
Lots of wire.
Screws, bolts, nuts.
Drill with metal bit.
Clear pieces of plastic for gluing over the openings of the box.
Step 2: The Box
Mark on the shell where you need to drill and cut.
1 hole for the second fan, plus holes for the screws
2 holes to bolt down the transformer. Place it so that it sits on the bottom of the extractor.
1 hole for the switch.
Step 3: Sealing up
You'll use clear plastic to seal up as many of the holes as you can.
I used one of those clear fake CD protectors cut into shards.
This will increase the efficiency of the extrator by quite a bit.
Step 4: The circuit
The live and neutral lines are switched at the DPDT, while the earth is screwed onto the chass to provide protection against short circuits.
The Live and Neutral are stepped down to around 12v at the transformer, then rectified with the bridge. The caps filter it and boost the voltage slightly.
The 2 fans are connected in parallel.
And my drawing is very beautiful, if don't say so myself...