1-project box (can be had at radioshack for ~6$)
1-12v-dc computer fan
1-9v plug(you can use different voltage adapter so long as it powers the fan)
1-rheostat (can be had at radioshack for ~3$)
1-knob (for rheostat)
Start off by drilling a hole in the back of your project box big enough for your adapter wire to feed through. Then of course, feed the adapter wire through the hole.
Locate the positive wire on the adapter and connect it to the rheostat. (Usually the wire with the white stripe is the positive). But you can determine it by using a volt meter.
Connect the power wire from the fan to the the rheostat and connect the ground wire directly to the ground on the fan side.
Next dab a little super glue on the underside of the fan and mount it in place. Depending on the strength of your magnets you may need to secure them in place as well. The magnets i used were out of throttle units for a volvo. They are extremely strong rare earth magnets so no glue was necessary.
Put on the top of your project box and you’re done. Now test out your brand new stir plate. And enjoy the savings!
Here we have a video of the stir plate in action.