DIY Stir Plate For Under $10

Posted Oct 20th 2012 | By:  

GreenDragon

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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:



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:



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:



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:



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:



Done!

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!

Posted in

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diy, stir plate, stir, plate, tutorial, cheap, budget, ten dollars

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11 COMMENTS

 Leave Comment

J187

Posted: 

November 8, 2012  •  04:15 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.

 

beerFacedotkom

Posted: 

November 25, 2012  •  08:52 AM

I'd like to see how you did it if you wouldn't mind posting it.

Thanks,

Jeff

 

mattyboy

Posted: 

November 29, 2012  •  02:48 AM

[QUOTE="GreenDragon"]1[/QUOTE]

Hi what did you use as your stir bar.
I am going to try this thanks for the post

 

jOitheboat

Posted: 

December 5, 2012  •  07:10 AM

I second that question: What did you use as a 'stir bar'?

 

GreenDragon

Posted: 

December 6, 2012  •  03:39 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.

 

NoTrubble

Posted: 

December 10, 2012  •  06:44 AM

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.

 

HollisBT

Posted: 

December 28, 2012  •  10:37 AM

The only phone charger I could find was rated at 12v, is this still ok to use?

 

GreenDragon

Posted: 

December 28, 2012  •  10:55 AM

@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.

 

HollisBT

Posted: 

December 28, 2012  •  01:08 PM

Awesome, thanks for that. I was mostly just concerned about heat/fire lol.

 

heeler

Posted: 

January 12, 2013  •  03:49 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.

 

fiat84

Posted: 

January 13, 2013  •  09:02 AM

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.