Hi Guys & Girls. Here is my version of a 3D Printed "Super Slimline Magnetic Stirrer", created for the "Magnets contest". It has 3x speed settings, (Low, Medium & High) made from an old computer fan and controlled with an Arduino Nano.

Minimal materials have been used here, and so it's a pretty easy and cheap project to complete.

Use it in the kitchen to achieve those Perfect Throffy Coffee or Hot Chocolates :-)

KEEP READING FOR THE PERFECT HOT CHOCOLATE RECIPE...

Supplies

Arduino

Computer Fan (4-Pin)

4x M5 30mm Hex Bolts

Power Switch

3x 6mm Micro Switches

2x Magnets

Power Jack

TOOLS:

3D Printer

Soldering Iron

Screwdrivers

Hot Glue Gun (Advised)

Step 1: Gather Your Materials

Arduino Nano (or Aftermarket)

https://www.amazon.co.uk/gp/product/B07WPK49V2/ref...

70mm 4pin Fan

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksi...

4x M5 30mm Hex Bolts

https://www.ebay.co.uk/itm/M4-M5-M6-M8-A2-STAINLES...

12v Rocker Switch

https://www.ebay.co.uk/itm/On-Off-Round-Rectangle-...

3x 6mm Tactile Micro Switch

https://www.ebay.co.uk/itm/6mm-x-6mm-x-9mm-Momenta...

2x Neodymium Magnets 10-20mm

https://www.ebay.co.uk/itm/small-large-NEODYMIUM-M...

12v Jack

https://www.ebay.co.uk/itm/One-Pair-Male-Female-So...

Step 2: 3D Printing Your Parts

Here are the 4 parts you will need to print. They have all been designed in TinkerCad with most walls being 1.2mm or 2.4mm, so be sure to set your hotend nozzle to print @ 0.6mm for a nice fast print time. Also I printed these with an Infill of 100% as they're mostly hollow prints anyway.

Step 3: Uploading Code to Arduino Nano

Okay, so here is the code used to control this project. Simply connect your nano, and compile the sketch.

Magnetic_Stirrer_Code.ino
Download

Step 4: Soldering Your Circuit

So now we can start soldering our circuit into the main 3D Printed Shell. The best way to do this is to solder all cables to the switches, and power jack, leaving the Arduino until last. Hot glue is perfect to hold all components in place and also adds a layer of electrical insulation to all connections.

Once you have this done, take your fan and hot glue your magnets to the fan blades about 25mm apart, keeping them as centrally balanced as you can. Place your fan into the centre space and screw down tightly.

Next is to Solder everything to your arduino. Follow the wiring diagram in the photos, and then carefully push it into the space "to the left of the fan".

Step 5: Fan + Magnets

Okay, So here we have our PWM Fan. Normally a 4pin fan used to cool
your computers CPU. You will have 12v Positive, Ground, Tach (Tachometer, which will tell the computer how fast the fan is turning), and PWM/Signal wire. "Tach" wont be used here, and so we can cut it off. PWM is the one we want (Pulse Width Modulation). A quick google on your fan model and you should be able to work out what wires are for what. (PinOut Diagram)

This type of fan is perfect for our project as it uses a very small current to control the 12v fan. We can do this from our Arduino data pins. However, if we were to connect the fans 12v supply cable to one of these data pins on the Arduino, you will most likely fry the board. It will draw too much current (So please double check your fans wiring)!

So, as for magnets... Most magnets will do, but a nice strong "Neodymium" magnet is preferred. I made a spacer from corrugated cardboard to raise the magnets closer to the top on the unit. You may need to do the same, but for design purpose, I have left enough space so you can use slightly thicker magnets if you wish. Hot Glue or Super Glue should be fine...

Step 6: The Pill

Once you have printed both halves of your "Pill", you will see a 20mm x 8.5mm void as to which you can fill with any magnetic material you wish. Luckily I already had some 8mm threaded rod so I used that, but I was also considering cutting an old screwdriver or drill bit to use for this. Like I say, anything magnetic will do... (chopped Nails?)