Homemade Stir Plate Guide with Pics

So I decided to take the next step and construct my own magnetic stir plate. I didn't want to spend any money on it except for the stir bar. I made it completely from parts laying around the house. If you're not a computer geek you may have to buy some of this stuff.

Parts List:
80mm computer fan (scavenged from an old computer)
2 x rare earth magnets (scavenged from a Western Digital 30gb hard drive)
7.5v AC to DC phone charger (from an old phone I had at one point)
4 x #12 1.25" wood screws (had extra's laying about from a home improvement project)
8"x10" sheet of clear Acrylic (I mod my own computer cases so I have extra laying about)
Backing from an old picture frame (explained below)
Electrical tape

Fan
I started off with a 120mm fan I had laying around but I found out 120mm fans just don't have the rpm's needed to create a vortex so I went out to the garage and pulled an 80m fan off an old P4 system I keep around for parts.

Magnets
I pulled apart a hard drive from an old computer. The rare earth magnets are located in the base of the arm, as seen in the picture.


Insulating the fan hub
I found out that if I just glued the magnets strait to the fan hub the magnets would create enough resistance to cause the fan to slow down and sometimes not start on its own. To remedy this I tried a double layer of some spare clear acrylic sheets I have laying about but evidently clear acrylic doesn't insulate against magnetic forces very well. I wanted to use wood but don't have any spare wood laying about the house so I used the backing of an old picture frame and cut it into circles the same size as the fan hub. I used two layers of it to be safe.


Mounting the magnets
I actually only used one rare earth magnet that I broke in half. I made sure to make sure each piece was facing the right way first before super gluing them to the fan hub insulators. I found that just a little space between them works best.


Power
For some odd reason I've kept every cell phone charger I've ever owned. I think I may be an electronics horder. I pulled the box of chargers out of the garage and sorted through them. I knew from reading web guides, and this forum, that 12v is way to much but 6v isn't quite enough. I found one that was 7.5v and went with it. Probably blind luck, but it works perfectly.


Part 2 incoming:

Splicing
Picture of my epic splicing job, lol.


Flask base
This is one that may not be "free" for some people. I mod my own computers so I have spare sheets of clear acrylic. They are about $3 at Home Depot.


Fine Tuning
I knew that I was going to have to dial in the right distance to get the stir bar working. Really I was just being lazy on this part but it works out surprisingly well. I just found some old wood screws from a home improvement project I did and screwed them into the case fan holes you use to mount the fan to the computer case with. The screws are flat on top so the acrylic sheet lays flat and I can adjust the height with just a few twists.


Finished Product in Action
Here is the finished product in action. The vortex goes all the way down to the stir bar, but it's hard to get a clean picture it. I left it running for a long time. Nothing got hot, or off balance so I'd say it's a success. Stirs 750ml of water with no issues. I'll find out how it does on a starter Tuesday night.

This must be the simplest DIY stir plate design I've seen on here. Good job, buddy!

This thread could not have come at a better time. I just pulled my old computer apart and was thinking about doing the same thing.
Thanks for the boost to do it.

very cool and simple, I been thinking of building one. Where do you get stir bar?

paraordnance said:

very cool and simple, I been thinking of building one. Where do you get stir bar?

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The cheapest stir bars I have found are at www.mcmaster.com . The round ones work great and the octagon ones work but are extremely loud.

paraordnance said:

very cool and simple, I been thinking of building one. Where do you get stir bar?

Click to expand...

Place I order my grain kits from had the 1 & 3/8th stir bar for $4.99. It's the solid one without the bump in the middle. I tossed it in with my last grain order to save on shipping.