Introduction: Computer Fan Magnetic Stirrer

About: My name is Logan Carlson, I am a recent graduate of Florida Polytechnic University with a degree in Computer Engineering. I try to build all the time and post my projects, but it is time consuming so I have no…
For this magnetic stirrer/mixer I used a variety of different items and materials to make it. The main piece is a large computer fan that I re-wired to make it USB enabled. In the image I added some vegetable oil to a cup of water so that it would show the affect of the stirring and the whirlpool that's made from the magnet. The materials and tools I used for making it were the following:

- Computer Fan
- Small Circular Magnets
- Bucky ball magnets
- Polymorph
- Plastic CD Cases
- Plastic nuts for a screw(Plastic so it doesn't interfere with magnets)
- USB Cord (Can be from an old mouse, keyboard, or anything with a male USB on it.)
- Spray Paint (Any color but I used black)
- Hot glue
- Soldering Iron, and solder
- SPDT switch

Many of these materials are available at Radioshack such as the magnets, switch, and computer fan. 

Here is a video of the final product:

Step 1: Add Magnets and Make Spinner

For this step you will need the computer fan, the bucky balls (or other small magnets), two circular magnets, and polymorph or another form of moldable plastic. Tools that you will need will be glue of some form (hot glue, superglue, etc.), and access to hot water, preferably near boiling. To add the magnets to the computer fan you take two of the circular magnets and glue them to individual fan blades on opposite sides of the fan. Then that part is done, and you need to make the spinner. 

To make the spinner you need some small magnets, preferably spherical, to wrap in a thin layer of moldable plastic. I got a cube of spherical magnets for Christmas last year, a bucky ball-type magnet, and I took some to test as the spinner. For me, 4 of the bucky balls worked the best and spun in the water perfectly. So then once I knew they would work I melted some polymorph and tried multiple times to get the right amount of it. The best worked when I had a very thin amount of the polymorph and wrapped it around the four magnets. This caused the best spin, least noise, and biggest whirlpool in the cup.

Refer to the images for more information on putting it together.

Step 2: Making the Connections and the Switch

To make the connections just take the red and black wires from the computer fan and strip them to expose the wire. Then, also take the USB cable and strip its outer casing to expose the four wires within. Any wires other than red and black are unnecessary so just cut them. The black cables of both the fan and the USB cable need to be soldered together. and the red wires have another step. They need to be connected to the switch instead of one another. So solder them to the required leads of your switch, and then it is all done. 

This is USB powered but I have not yet tried plugging it into my computer. I have been using an apple USB charging cube to power it. If you use it on your computer I am not responsible for any damage done to the device or  the computer, if any is done. Be careful in making sure that your connections are put together correctly so there aren't any shorts.

Step 3: Making the Outer Case for the Fan

For making the outer case I used two plastic CD cases, one for the top and one for the bottom. And then for the sides I used polymorph that I molded into walls. When you make the top you want to use the plastic nuts as spacers between the CD case and the fan, this way it doesn't interfere with the fans turning and doesn't make an annoying scratching sound. Glue the spacers down to the four corners of the computer fan and then glue the CD case on top of the spacers. Then on the bottom just glue the CD case straight to the bottom of the fan. For the sides you want to do the one that you are going to put the switch into first. This way you have room to reach in and glue it. Then you want to do the other three sides. To do this I melted polymorph, stretched it out flat, and then put it against the top and bottom edges of each side. The plastic will start to cave inward so put it upside down on something like parchment paper so the polymorph won't stick. Then once all three walls are done you can glue the wiring to the bottom of the case and push the rest out one side so that the soldered wires aren't exposed. Then you are all done, unless you want to paint it. Put some water in a cup, drop in the spinner, plug in the fan, and turn it on. It should work. If you have any problems just comment and I will try to help you as best as I can. 

If it does work and the whirlpool is visible, you can add some vegetable oil to the water in the cup and let it sit until it is all rested at the top. Then turn on the fan and the whirlpool will be even bigger and more visible. 
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