If you’ve spent much time in a chemistry or biology lab, you’ve probably seen a magnetic stirrer. This is a little table that you put a beaker on. A little bar (often called a flea or a pill) goes in the solution and spins to stir the beaker’s contents. Simple versions are not that expensive, but nicer ones can cost a bit. [John] decided to build his own using 3D printing and the design is delightfully simple.
The electronics is nothing more than a PC fan, an off-the-shelf fan controller with a display, and a 3D printed bracket with some magnets. The flea is also 3D printed, although we’d probably buy cheap commercial fleas since they are usually coated with Teflon or some other non-reactive substance. Depending on what you are stirring, the reactivity of your 3D printed plastic and its porosity could be a concern. In addition, a commercial flea has a pivot ring that helps it spin smoothly, although we are sure the 3D printed one will work in most cases.
The 3D printed parts are on Thingiverse. Using the fan as a motor makes things simple. The controller and fan plug together, so there’s nothing to solder. If you do go with the 3D printed flea, [John] suggests using friction welding to seal the two halves, although you could use glue as long as you aren’t planning on stirring anything that would attack the glue.
We’ve seen stirrers before but this one is cheap, easy, and looks good. This would be a great project for a school or home lab that already has a 3D printer. Some stirrers have hot plates integrated and depending on the plastic you use, this might be a good upgrade.