A magnetic stirrer is a great improvement in your workshop whatever the craft you plan to focus on. Actually I use it for paint, varnishes, resin, chemicals and even for parts or brushes cleaning ! Just turn it on and do something else. In contrast to myself it never get bored stirring.
Initially I found a lot of DIY instructions online. But most of them seems to me over-complicated with sometimes voltage regulator modules, and needed a dedicated +12v power supply unit. I did not have all that fancy parts on the shelf and did some investigations.
To stir well, a 12v fan should be powered between 4 (light stir) to 6v (hard core stir). Slower motion is probably not needed except for fine chemical purpose, and faster motions makes the magnetic attraction of the stir bar problematic. So what you really need is a power around 5v. Good news ! Like me you probably have a lot of 5v sources everywhere in the house, neither it's cheap adapters or USB ports. So you can really build a simple magnetic stirrer with a limited amount of parts :BOM :
1x enclosure (printed or DIY)
1x Power Switch 6mm 3P
1x USB-A inlet
1x 60mm fan (12v)
1x 5mm led (optional)
1x 180 ohms resistor (optional)
5x 6x8mm neodymium magnets : 2x for the rotor, 3x for the stir bar (flea)
or 2x 6x8 neodymium magnets for the rotor + 1x stir bar (20>30mm or +-1")
This is a <5€/30mn project.
NOTE : all these parts are really common, you can use reclaimed ones. The minimal requirement is a 5v source, a 12v fan and magnets. Basic.
Watch the embed video for the building instructions.
The printable enclosure can be downloaded for free at : Thingiverse ; thing #2220363