This instructable shows us how to make a magnetic stirrer, that can be used in your home lab, from the following items:

An old 3" PC fan
A dead hardrive
A 12v ac adaptor
A paperclip

Tools:

Hotglue gun
Screwdriver
Superglue
Misc Items depending on your taste for getting things done :)

Read on, and enjoy.
Not my original IDEA

Step 1: Set Up Your PC Fan.

Find your self a working PC fan.

I used a 3" fan that I salvaged from an old PC I had laying around

1. Pull the black end off of the cables.
2. I did this carefully to keep the metal contacts in place, otherwise you'll be working with bare cables.
3. Optional : Clean the fan of all dust, I did this with a Q-Tip soaked in alcohol, just to make it look pretty :)

Step 2: Connect Power Supply

Here you'll want to find a 12v AC adaptor

MAKE SURE ITS 12 VOLTS OUTPUT! or else you'll burn out your fan before you even get to test it out.

I used regular tape, just to keep it simple.

1. Put the red cable inside the little socket, this is your positive.
2. Put the black cable on the outside of the plug, this is your negative.
3. Grab your tape and tape these connectors nice and tight so it doesn't shift during use.
4. After the connecters are taped, give it a little tug to make sure they'll stay in place.
5. Plug in adaptor to the wall, and make sure it works.
6. Now unplug your power, and secure the wires to the fan. I used a hot glue gun and put a couple drops to hold the cables down.

Ready? NEXT STEP PLEASE!

Step 3: Salvage the Magnet.

Sorry I dont have pictures for the steps on how to extract the magnets.

1. Get the old harddrive and remove the screws from the casing.
2. Locate the magnets and unscrew them from the casing.
3. Use pliers to hold the piece of metal attached to the magnet, the magnets have some kind of glue holding them down, adding to amazing strength these little things have.
4. What you want to do is bend in two directions so that the magnet comes off the base.

Step 4: Position Your Magnet.

Now you are going to position your magnet

1. Place your magnet on the center of your fan.
2. Plug in your fan. BECAREFUL if you didnt position it right you have a high risk of it flying out.
3. If it wobbles, reposition, repeat.
4. After you are satisfied with your magnets position, trace the outline of the magnet onto your fan.
5. Glue it down and repostion your magnet.

NEXT!

Step 5: Housing for Your Fan.

This is where you can get crafty.

I used the fan guard that the fan was in when I removed it from the PC
You can fashion one out of a wooden base, and a CD cover for the top of the fan.

My guard had little waves on the top, I got my rotary tool and evened it out.
Then I put my fan inside and secured it with some more hot glue.

Step 6: Making a Stir Bar

This is what will go inside your container that will spin the fluids.

I had a broken CD-ROM laying around, so I decided to take it apart and see what I can get from it.
I found that the little platform that the disc sits in had a metal bar in the center, so I took that out.
WORKED GREAT!

You can make it from a paper clip, or any other thick wire.

I found that anything larger than one inch wont work too well, anything smaller, and it wont mix at all.

Experiment with different sizes, what ever fits your needs/likes. I also found that the longer the bar is, the more it will rattle and make ALOT of noise.