DIY Stir Plate For Under $10

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Ready to take the plunge into creating yeast starters but don't have $75 to spend on a stir plate? Below you'll find instructions on making a stir plate from items you most likely have laying about the house.

Free Salvaged Parts List:
  • Super Glue - (The normal stuff sitting in your desk drawer works great.)
  • Computer Case Fan - (From any computer, even that 1980's one sitting in the garage. A 80mm or 120mm will work.)
  • Old Computer Hard Drive - (Any size, older the better, doesn't have to be functional. Once again, the drive out of that 1980's computer sitting in the garage would work great.)
  • Thick Cardboard - (I used the backing from an old picture frame.)
  • Old Cell Phone Charger - (Any carrier for any phone, around 7.5v, one you don't use any longer.)
  • Four 1-1.5" Screws - (Preferably ones with a flat head.)

Parts you may have to purchase:
  • 5"x7" piece of clear acrylic - Cost around $5 - (Any home improvement store will have them. They are used to replace glass in picture frames.)

Step 1 - Rare Earth Magnets
So you're probably wondering what's up with the hard drive on the parts list. Well hard drives use rare earth magnets to write data to platters spinning around inside the drive. What we are going to do is harvest those magnets to use with our stir plate.

Fist step is to pop the case off the hard drive. Some use normal Phillips head screws, others you need a hex wrench for. After you remove the screws, pop the top of the case off. Inside you will find some circular platters with an arm extending over them. At the base of the arm is where the magnets are located. Here's a picture to help you find them:

DIY Stir Plate For Under $10 - GreenDragon - 1-200.jpg

Step 2 - Preparing the Fan
Now that we have the magnets we need to mount them to the case fan you found. Most case fans use metal ball bearings, however, if we just glued the magnets directly to the fan the magnetic force wouldn't allow it to spin up. What we need to do is add a little insulation to the fan.

In the middle of the fan is a flat circular area where all the fins attach. Grab your thick cardboard and cut a piece out of it that is roughly the same radius as the flat circle in the middle of the fan. Then super glue that piece directly to the fan.

Step 3 - Magnet Time!
Take one of the magnets you harvested from the hard drive. Most of the time they are in a half-moon shape. Grab the magnet with some pliers and snap it in half. The magnets are surprisingly brittle so it shouldn't take much force. What you need to do next is super glue the two pieces to opposite ends of the circular cardboard you glued to the fan. Make sure you check the polarity on the magnets before gluing them so that your stir bar will be attracted to them. Here's a picture of what it should look like after you complete this step:

DIY Stir Plate For Under $10 - GreenDragon - 2-201.jpg

Step 4 - POWER
Your fan should have either a 4-pin molex connector or a 3-pin motherboard plug at one end. Either way, cut off the connector. The only wires we are interested in are the red and black ones. Your fan may also have a white and yellow wire; just tuck those out of the way.

Next, grab your old cell phone charger, make sure it's unplugged, cut off the end that plugs into your phone, and remove the insulation on the end to expose the wires. What you want to do is splice the red wire on the charger to the red wire on the fan, then the black wire on the charger to the black wire on the fan. Be sure to tape up the splice job or use professional ends, either works. Here's a picture of my splice job:

DIY Stir Plate For Under $10 - GreenDragon - 3-202.jpg

Step 5 - Preparing for the Base
Take your four screws and screw them into the fan using the same holes the fan used to mount to the computer case with. You want the head of the screw to be about a quarter inch above the magnets. Here's an example:

DIY Stir Plate For Under $10 - GreenDragon - 4-203.jpg

Step 6 - Finishing Up!
After you have your screws in, just lay your piece of acrylic on top of them. Adjust the screws as needed until you have it pretty level. Example here:

DIY Stir Plate For Under $10 - GreenDragon - 5-204.jpg


That's it. You're all set to go now. Toss your flask on top with a stir bar in it, plug in your stir plate, and watch it spin!

DIY Stir Plate For Under $10 - GreenDragon - 6-205.jpg

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November 8, 2012  •  10:15 PM
Nice alternative for those who don't want to spend the time and effort to make a nicer one. I'm not sure why you snap the magnet in half, just lay it on there, it's already in the right polarity and keeping it whole is easier and less risky. I built my stir plate, which looks like something you'd buy in a store, for around $18.
November 25, 2012  •  02:52 PM
I'd like to see how you did it if you wouldn't mind posting it.


November 29, 2012  •  08:48 AM

Hi what did you use as your stir bar.
I am going to try this thanks for the post
December 5, 2012  •  01:10 PM
I second that question: What did you use as a 'stir bar'?
December 6, 2012  •  09:39 PM
The flask and stir bar you have to buy sorry. I suppose you could try to create your own stir bar, but that would probably require more equipment then I have access to.
December 10, 2012  •  12:44 PM
I made a stir bar out of a McDonald's straw that I repurposed from a wifi antenna hack from a few years ago. I also got some small button neodymium magnets from Hobby Lobby or Michael's Arts and Crafts.

Simply and carefully slide those magnets into the straw and leave about 1mm on the ends. Used some food grade silicone to seal the ends. I made up several sizes all the way up to 1 1/4 inch. They work pretty good!

For the jug, I repurposed a grappa bottle which was repurposed from a 1 gallon glass Hot Wings/Sauce jug which was free.
December 28, 2012  •  04:37 PM
The only phone charger I could find was rated at 12v, is this still ok to use?
December 28, 2012  •  04:55 PM
@HollisBT You can try. If it's too high of voltage the fan will spin too fast and throw the stir bar, if so you can try switching to a 120mm fan and see if that works better.
December 28, 2012  •  07:08 PM
Awesome, thanks for that. I was mostly just concerned about heat/fire lol.
January 12, 2013  •  09:49 PM
or add a rheostat in the workings (about $3) and you can actually dial in the speed. Start slow and then turn it up to create the whirl tornado.
January 13, 2013  •  03:02 PM
Made a stir bar by using a bolt with a nut threaded on the opposite end to counter balance so it looks like an "I---I". Then wrapped the bolt/nut in plastic vapor barrier. Took a heat gun and melted the plastic and while wearing gloves just rolled the bolt smooth into a cigar shape. Attached an O-ring as a spin point and it spins fine. On my homemade stir plate used a 5V charger so to get the liquid to start stirring I had to use a flat bottom glass coffee pot and also center the stir bar in the pot before starting up the fan to spin. If the fan starts up first and i add the stir bar after it will not start the liquid vortex spinning. Also adjust the vertical distance between the glass bottom and the fan magnets by using some plastic CD holders on each side of the fan. FYI, computer fans are usually 12V and some fans will start up with lower voltage, the 80mm fan I used works fine with 5V but some larger fans may not start with only 5V. The 12V would spin much faster and using less fan voltage is a common practice to reduce noise/spin rates in computer cases.
July 10, 2013  •  09:56 PM
Amazon has some pretty good magnetic stir bars and flasks for anyone wanting to buy that part. Just search "stir bar" on Amazon.

I also built my own stir plate with a project box from ratio shack, I added a rheostat and an on/off switch. I had an old 12v power supply so I can feed it full power if needed.
July 11, 2013  •  02:43 AM
saw this and thought "Nice"
also found this
anyone tried?
July 11, 2013  •  01:01 PM
I am making a DIY stir plate atm too... What I have used has also been "laying around the house" except for a few items...
For the box I bought a wooden cigar box from a local store (since I do not smoke cigars)... Total cost $2.49 + tax = $2.66, and I plan on buying the rare earth magnets local too since they are only $2.99 + tax... The rest of the items I had at home (except for the flask and stir bar)... They include an old 120mm computer fan, a Zalman fanmate (to control fan speed), an old phone charger, and the hardware for mounting the fan... So although the Stir Starter is a good product the total cost of my stir plate will be $13.81 ALOT less than the $42.00 listed... So I would say make your own... There are plenty of video tutorials out and about to make it easy going... Cheers!!!
July 12, 2013  •  12:05 AM
I did something similar, but made self contained and easy to store. I mounted the fan under the lid of one of those big Maxwell House coffee containers and ran the power out a small whole in the side. I had an old external 5v PC power supply laying around that uses the old style PC Molex connector, so it detaches from the fan with ease. When I'm not using it, I can detach the power supply and put it inside the container for storage. Total cost for me was about $7 for the stir bar from the LHBS.
July 12, 2013  •  01:03 AM
Thank you for the inspiration! Following your directions, I built a stir plate with what I had on hand. I used a spare 4.5V wall wart, refrigerator magnets, Shoe Goo to attach them, and a square of 1/4" thick plastic for the platform. Long machine screws and a few washers created space at the top and bottom for the fan to cool itself. I have already made several batches of yeast, enough to recoup the cost of the flask and stir bar several times over.
July 17, 2013  •  02:03 AM
I'm working on building a stir plate. Mine will be in a plastic box I bought at the surplus store for $2. If you live in Minneapolis/St. Paul, you've got to love I was able to buy all the parts (including magnets) for about $14.

I have a 12v 500 ma power supply and a 12v .98 amp fan. I wanted to throw in a rheostat to control the speed, but when I wired it up between the fan and power supply the rheostat started smoking and getting hot. The rheostat was just something I had on hand. It's says B10K(Ohm) on the bottom. It does work to control the speed, but it only works in a very narrow band of the rheostat range.

Am I using the wrong rheostat? I do have an assortment of resistors around. Would adding some to the circuit help this work better?

All this is because I have no idea how fast a stir plate should spin. I don't have a stir bar yet, so I haven't tested it. If someone tells me I should just give it a go

Any help would be appreciated.
July 18, 2013  •  11:48 AM
I found another much longer thread that helped me understand this a little better. It referenced this website They use a voltage controller because the potentiometer can't handle absorbing the load. Ordered the controller last night. Got 3 for $.99 on eBay with free shipping.

We'll see how it goes with that.
July 28, 2013  •  04:03 AM
Made mine in about 45 minutes from stuff I already had around the house. Works like a charm. Thanks for the awesome post! I'd been looking to buy one, but had a hard time justifying the $100 price tag for what is basically a glorified electric motor with some magnets glued on. Never crossed my mind to use one of the many small motors and rare earth magnets I have around already!
August 8, 2013  •  10:19 PM
I tried doing a build similar to this for my last batch - it's a PITA. Buy this, save time, get reliability and a good looking effective stir plate complete with stir bar, a retainer magnet so you don't dump your stir bar into your wort and a forever guarantee.
August 8, 2013  •  10:21 PM
the stirstarter is awesome, even can adjust the speed to your liking. it's perfect for HB purposes.
August 19, 2013  •  02:10 PM

You're getting smoke because your variable resistor is too large (50K = 50,000 ohms). A 12v/0.100Amp motor needs a 100 to 200 ohm variable resistor with a rating of 2 watts or greater.

The variable resistor's power rating is for the entire arc of resistive material. You're only using about 1% of the arc. If the power rating is 2 watts (typical), then the 50 ohms being used is rated at 0.02 watts. However, Ohm's and Watt's laws predict you'll need about 0.250 watts of dissipation. You're overheating the resistor by about 10x, which makes some fine smoke.

There are some comments elsewhere oh HBT about wrapping an LM317 voltage regulator around the variable resistor. The LM317 dissipates the power without stressing the resistor.
August 28, 2013  •  04:28 AM
Soooo. I had all this stuff in my house, so I went ahead and tried this. I followed the directions, but I am not getting any whirlpooling. The Stirbar does not even spin. It is definitely attracted to the magnets beneath, because it sits right above them, and if I put the fan really close, the stir bar starts bouncing around a bit. I am not sure what is wrong. Maybe my fan is spinning to fast? I have flipped the magnets several times in different combos to make sure the polarization was not an issue, and I get the same result each time. I am using a laptop fan.
August 28, 2013  •  04:33 AM
Or maybe my fan is too small? I am not sure if it is 80 mm or less. But judging by the pics above, it does not look like those magnets are much, if any, farther apart than my set up.
August 28, 2013  •  03:19 PM
@nolabrew85 if you remove the plexiglass sheet and put the stirbar directly on the magnets does it attach or bounce off?

Also if you are using a 40mm or 60mm fan then they spin at much higher rpm's and I'm not sure the stirbar can keep up.
August 28, 2013  •  05:33 PM
@GreenDragon The stirbar attaches. I think my fan is probably 40mm or 60mm because it looks like it is about 2-2.5 inches, and it spins very fast. I have about 4 broken laptops that I could salvage more fans from, but if they are generally all going to be that small, then I will just buy that $43 stirplate from williamsbrewing instead of wasting my time. What do you think? (I don't have any old desktops at my disposal).
September 3, 2013  •  01:34 PM
I doubt you'll find an 80mm fan in a laptop and if you do it would be one of those thin ones that isn't very well insulated. In your case it may be better to plop down the $$ for a real one.
September 3, 2013  •  09:19 PM
@GreenDragon Really simple way to make a stirbar. Take a cocktail straw, cut it an inch long, cut a nail's head and pointy end off so it's 1" long. squirt some RTV silicone into the cocktail straw, push the nail into it, and then cap both ends. Walla, stirbar. It works great too.
October 7, 2013  •  07:05 PM
Did the same thing except I used legos to build a base up around the fan and get the correct height.
October 7, 2013  •  09:00 PM
Lol, that is awesome! I love legos, I totally should have thought of that.
October 20, 2013  •  09:40 PM
In the "Go Large or Go Home" category, I used the DIY Stir Plate to de-gas a carboy of mead. There is about a quarter-inch of glass on a carboy bottom; the key is to get as much magnetic field as close as possible to the stir bar. It took two stacks of eight rare-earth disk magnets to drive the stir bar. Spun it for several days in various places around the carboy bottom with no problems. The key seems to be to "capture" the stir bar (both ends) with the two magnets, then spin up the motor slowly. After the motor spins up, reduce power slightly so the stir bar doesn't get thrown off.

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