I home brew my own beer, and one important tool for brewing is a stir plate. It keeps yeast in suspension and aerates the growth medium for maximum cell count. To purchase one of these stir plates is easily $100 bucks and is probably overkill for my purposes. For around $10 and a few salvaged materials I can have a pretty snazzy stir plate that suits my purposes just fine.

Step 1: Materials

You really don't need much in the way of materials. Once everything is gathered you can knock out the build in less than 30 minutes or so.

Materials List:

Cigar box
Assortment of washers, nuts, and bolts
computer fan
cell phone charger
hard drive magnet
25 ohm rheostat (Radio Shack)
simple on/off switch (Radio Shack)
Knob (Radio Shack)
Some type of spacer material (washer, plastic, cardboard)
resistors (maybe)

Tools you will need:

Drill and assortment of bits
super glue
wire strippers or utility knife
heat shrink
soldering gun

<p>Thanks for sharing. Built one for myself in a couple of days. Works great! </p>
<p>how can I determine the proper rheostat? can I put any kind of rheostat? </p>
<p>Your directions were great once I found a working fan out of an old computer. I also noticed a 2&quot; stir bar works best.</p>
Thanks heaps for the instructable, there are heaps of videos on YouTube but non show the wiring in great detail. This gives me a bit more confidence to wire it up myself.
Thanks for the instructable! Works just as well as a real $150 stir plate. I used 2 store bought rare earth magnets (using only 1 gave an irregular spin to the stir bar) inside a prescription bottle cap (spacer) and gorilla glued the cap to the fan. Also I used wood screws (instead of bolts/nuts) and homemade spacers to mount the fan at optimal distance and cut the screws short so that the top surface of the box was completely flat. My scavenged adapter was 4.5V 400mA DC. The fan was 12V 140mA.
Instead of a computer fan, could I use a motor salvaged from an old R/C car? And instead of a hard drive magnet could I use a powerful neodymium magnet?
I think you can use any type of motor as long as it is DC. Honestly I'm not much of an electrician. Hard Drive magnets are neodymium magnets so if you had one of a more regular shape that may even be better.
This is a neat idea. The magnet you used doesn't seem to appear in any of your pictures. I don't see it in the one of all the parts. And even more surprisingly, there isn't a picture of the magnet glued onto the fan. I might not have noticed but that was the one picture I was specifically looking for. Or am I just blind?
You're right. I'm sorry I neglected this. When I get a chance I'll unscrew the fan and post a picture. Its just a hard drive magnet I had. It's has a banana shape is the best way I can describe how it looks. Kind of makes it difficult to center but you just have to play with it.
Have you got a Teflon-coated stirrer in there?<br> <br> L<br>
Absolutely! Pretty cheap on eBay. I tried using just a metal bar with an o-ring, but the actual stir bar is the way to go for sure.
there's also a few on Amazon, &lt;$5, that qualify for supersaver shipping. If the item is hard to get locally, but the price is reasonable on Amazon, it goes in a queue until I have over $25 worth.
The one on eBay I got was $5 with shipping.
Woot, chemistry! It's awesome to see all of these real-science Instructables coming through. This is nicely put together, with good clear photos. Any chance you might create a short (10 second) video showing the stirring bar a-stirrin'?
How's that?
Your I'ble is chemistry-related. The geodetic scope (protractor and laser pointer) was geometry and geodesy related. The cheap postal scale used physics. Science Is Good :-)<br><br>Or were you asking about how to make a video?
I meant how was the video.

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