Simple stir plate
thingiverse
This is a super-easy, super-cheap stir plate with a 120mm case fan wired directly to a 12v power supply. I cut up some refrigerator magnets and they stick without glue. I use it with a large stir bar in a 5L Erlenmeyer flask. I'm not sure of the smallest flask this would take but it's pretty simple. You may have to resize based on the fan you use because the lip has to sit just above the magnets.
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