Spin Up a Stir Plate

It is no secret that a stir plate can boost your yeast count when doing a starter, however, one thing that didn't know off the hop was how easy and inexpensive it would be to make one at home.

I will outline how I put together my stir plate, there are many other ways but hopefully, this will give you an idea of exactly how easy it is if you are not currently using one.

Materials:

Rare Earth Magnet (rip apart an old hard drive)
Fan Speed Controller
12V Power Supply (dig around in your old electronics bin, you probably have one)
Case Fan(80mm) (use one from an old computer)
Stir Bar
Wooden Cigar Box (cigar shops usually give these away or sell for $1)
Machine screws (qty 4) and nuts(qty 12) - (any size that can be pushed through the mounting holes on your fan)

Steps:

Glue rare earth magnets on either side of the middle of the computer fan. Ensure you are glueing to the side of the fan that is free spinning. The exposed magnet faces should attract one another (magnet 1 "NORTH" face up, magnet 2 "SOUTH"face up).
Attach the fan to the inside of the lid so the magnets.fan can spin freely without rubbing on the inside of the lid. I used a few extra nuts as spacers.
Drill a hole in the front of the cigar box so you can push the control knob into the wood and it stays put, you can use some super glue at the end of the build to permanently attach it. Note the center shaft should be able to rotate freely.
Drill a hole in the back of the cigar box so you can shove the power cord through.
The power supply I linked comes with an adapter so you do not need to cut the barrel jack of the cord to separate the positive and negative leads. The adapter (with the green terminal block) allows you to plug in the barrel jack have nice screw terminals for positive and negative. If you found your supply at home, or bought one that didn't come with the adapter you will need to cut off the barrel connector and strip back the insulation to reveal the positive and negative wires.

Note: Sometimes cheap power supplies have a center conductor for +12V and use a braided shield around it for GND.
Terminate the wires to the fan speed controller as shown below. If you bought the speed controller I linked at the top of the post then the control knob is already connected to the controller board.
Bam! Stir Plate.