Magnetic Stirrer Plate

This is a simple compact magnetic stirrer made to help mixing up photographic chemistry, though it could be used for other chemical mixing purposes. The idea is based on a number of DIY projects seen on YouTube that use an old computer fan and neodymium magnets. 

It is a 3d printed base and magnet holder based around other components I had to hand:

• An 80mm (dia) x 25mm (height) 12V computer fan
• 4 x 9mm (dia) x 3mm (height) neodymium magnets
• Cheap PWM motor controller
• LED + 220ohm resistor
• 2.1mm DC panel mount socket
• 5V wall-wart power supply
• Some 6mm thick MDF

The stirrer is sized for a 1 litre beaker or mixing graduate and works pretty well with a range of speeds from gentle to quite aggressive whirlpool using a 5V supply. The cheap PWM motor control module makes the wiring extremely simple. I only had to buy some 30mm magnetic stirrer bars.

It is printed in PLA - but PETG or ABS is fine. The base plate needs to be heat resistant and strong, so I used an off-cut of 6mm MDF sheet which will be painted.

The fan has its blades cut off using side cutters, and the hub sanded smooth with a Dremel tool. The magnet holder is sized to fit snugly onto the hub of the blade-less fan, held in place with double-sided tape - the magnets are held securely and accurately positioned so the fan doesn't vibrate. 

The original FreeCAD file is included - it was made using the Realthunder fork of FreeCAD, release 2022.11.28. A spreadsheet in the file allows for adjustments of certain parameters, so the model can easily be changed to adapt to different fan measurements or plate sizes. 

Further construction notes are included in the PDF. 

Updated 14/1/23 to move power jack to rear of base