Magnetic Stirrer

As I was looking through my junk laying around the room I noticed the old USB cooler fan which I have no use for. Then I thought of what I could possibly use it for and I remembered of the magnetic stirrers I have seen used in chemical labs. Unsurprisingly the idea to use a CPU cooler fan to make a stirrer wasn't new and already existed on many online DIY websites, but I decided to make it anyway to show how electronics can be reused in other fields.

Materials:

• CPU cooler fan 5V
• Magnets
  • 2 magnets to mount on the fan
  • 2-4 round magnets or 1 magnet stir bar
• Glue gun
• Various non-metal materials for a case
• Container (e.g. plastic cup)

First I took apart the housing to get the fan itself. It is a standard 5V fan with a USB power supply; if necessary you can also use batteries to power it.

Next step was to find some magnets. I found smaller magnets lying around, but they were a bit weak. Luckily I also found a pair of old broken headphones, so I opened them up and obtained a pair of stronger magnets. Now the magnets were a bit too strong that when attached to the fan they would attract the magnets used inside the fan motor itself, thus, preventing the fan from spinning. As a solution, I used a small plastic piece to create space between the fan and batteries.

After gluing the magnets to the fan, I used the original cooler fan housing and some plastic pieces to create a cover stand on which we could place the container for stirring. This step can be done in many different ways so feel free to experiment.

As a stirrer magnet I used the weaker magnets. Classic way is to use a magnetic stir bar, but unfortunately I wasn't able to find one. I used the weaker magnets I had already and they worked quite well, but for real chemical uses I would search for a better stirring bar.

So finally I added some water in the cup, threw in the magnets, and put it on the stirrer. As fan started spinning the magnets started stirring and we got a little whirlpool going. Success!