My shamelessly cheap $12 DIY stir plate

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CS223

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Thanks to Flomaster and his thread

I picked up a Thermatake USB desk fan from Amazon

It's a 3" fan with a retracting USB power cord and a speed control.

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The first thing I did was take it apart. Removed the 4 screws and the little stand. I moved the screws around to serve as legs & swapped sides with the fan guards.

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I took the guard with the Thermatake logo and cut the center out by clipping the 4 wires. In retrospect, I wish I had used the other guard instead as it would have allowed the magnet to be a little closer to the flask as it is offset less, not that it mattered. Just a minor detail.

Next I scrounged a fender washer from the junk box, I peeled the label off the fan hub, cleaned the hub & washer with solvent and set the washer in place. I gently spun the fan with my finger and eyeballed the washer to center it. It didn't take long nudging and spinning to get it where it was centered with no visible runout. At that point I dropped some super glue into the center of the washer and let it set.

The washer is important to shield the motor from the effects of the strong magnet. If you don't use a washer, then you need to space the magnet(s) some distance away to prevent them from interacting with the magnetic field of the motor.

While the glue was setting, I tore apart a 3-1/2" HDD to rob the magnet from it. I could have used some spiffy disk magnets but I didn't have any and I'm cheap and wasn't about to spend $10 on magnets. I liberated the magnet from the HDD & cleaned the old adhesive from it.

I placed the magnet on the washer and used a 6" machinist scale to get it centered on one axis, I put the stir bar on the magnet and found it's neutral happy spot. I then nudged the magnet in the other axis until the stir bar was centered on the fan axis. All this was done by eye and by gently spinning the fan by hand.

Once I was satisfied with the magnet position, I put a bead of superglue around the magnet and let it set.

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I scrounged a few 6-32 screws and attached the cut out fan guard to the top and that was it.

I used my iPhone wall charger, set the flask directly on the guard and away it went. I need to find some rubber feet/caps to go on the end of the screws to keep from scratching the counter, maybe some caps used for spare ports on aquarium air lines should work. It's a nice compact, easy to stow stir plate, my storage space is very limited. The 1L flask was from Stirstarters.com $12 delivered.

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Here's it's chugging away with some washed US-05 in 800ml of DME

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Thanks Flomaster and thanks Homebrewtalk!

:mug:
 
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Very nice! That is the cheapest stir plate I have seen.....just my style. At $11.73 plus free shipping if you order $25 or more from Amazon how can you go wrong? For another $14.28 I can order a 2000mL borosilicate Erlenmeyer flask from Amazon and get my order over that $25 threshold to get free shipping. With all the old usb cell phone chargers we have lying around the house I am set for my power supply, but if I didn't there are tons USB wall chargers for cheap on Amazon too. Yeast starters here I come!
 
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Nice! What's nice about this is that you don't have much work to do other than mount the magnet AND you have speed control :) For my fist stir plate I just harvested a pc fan and slapped it on a variable transformer, both of which were dumpster parts. This is much cleaner!
 
Nice! Looks like I'm going to be building one of those soon, already looking at the fan on Amazon.
 
Ordered the fan and a flask off amazon the other day. Can't wait for it to arrive and try it out! I've got several old crap hard drives I'm planning on tearing apart to get the magnets. Always knew they'd come in handy for something some day...
 
Anybody want to throw a magnet in an envelope and send it to me for a couple bucks?? Can't find an old hard drive and would rather not drop $10 on one. Anywhere else to salvage a cheap magnet beside a hard drive?
 
cbehr said:
Anybody want to throw a magnet in an envelope and send it to me for a couple bucks?? Can't find an old hard drive and would rather not drop $10 on one. Anywhere else to salvage a cheap magnet beside a hard drive?

You can use two small disk magnets as well. You just have to make sure the N pole is up on one and the S pole is up on the other. I think Ace hardware carries the disks, Amazon does as well.
 
Home Depot sells magnets in different sizes. I don't remember what the cost but they were around 3 or 4 bucks for a package.
 
What I wonder is if you could use a different fan with the USB to 3 pin (or is it a 4 pin plug) if the thermaltake fan goes out. That would also be really helpful as those little 120mm fans can get pretty cheap.
 
Thanks for posting this thread...

My fan just arrived in the mail, now it is time to turn it into a stir plate! Sure beats paying big bucks for one or getting involved with circuitry work! Best part if the fan dies I can buy a new fan and still be saving money!
 
Does it matter if i buy the Thermatake USB desk fan 11 or the Thermatake USB desk fan 12? they are about a $5 difference.

thanks
 
djelemenohpee said:
which one did you buy? the 11 or the 12?

I bought the 11, I think either would work fine though. The 12 is bigger, but I'll try the smaller first, then decide if I need to go bigger.
 
Where can u get one of those magnets if u don't have an old hard drive? All the ones on eBay do not look like the ones you guys are using.
 
I got my 11 today and if I could do it again I'd get the larger one. The 11 will be fine for my 2000ml flask but I wanted this one for my 5000ml. I may order the order also.
 
DakotaRules said:
I got my 11 today and if I could do it again I'd get the larger one. The 11 will be fine for my 2000ml flask but I wanted this one for my 5000ml. I may order the order also.

How about your magnet for the fan. Where did you get that?
 
DakotaRules said:
I got my 11 today and if I could do it again I'd get the larger one. The 11 will be fine for my 2000ml flask but I wanted this one for my 5000ml. I may order the order also.

I retract my statement about the size of the fan, this thing rips! No need for the larger sized fan at all!
 
All my materials are in, going to put this together tonight. Just thinking about the washer being used. Curious is the washer needed, it is said to be used to shield the field from the fan motor. Won't the magnetic field pass through the washer and still make it to the fan? With the magnets I bought, the field can pass through my finger and attract each other, very strong magnets.

Has anyone tried not using the washer?
 
Anyone wondering the quality of these fans, I have two that I have been using in my entertainment center for 4+ years with no issues.
One is on 24/7 to exhaust air from around my DVR and the other comes on automatically with my PS3.

I would buy these fans again in a heartbeat.
 
Curious is the washer needed, it is said to be used to shield the field from the fan motor. Won't the magnetic field pass through the washer and still make it to the fan? With the magnets I bought, the field can pass through my finger and attract each other, very strong magnets.

Has anyone tried not using the washer?

You definitely need the washer or some ferrous material to shield the motor. If you have disk magnets you could use a flat bar. Or you can space the magnets above the motor some distance using a plastic spacer of some sort. That's how Stir Starters makes theirs. If you're using two individual magnets, be sure you have one with the N pole up and the other with the S pole up.
 
I bought one of these awesome thermaltake fans from Amazon (free shipping with prime) and was able to convert it into a stir plate with just a single trip to the hardware store.

For all those who are curious, I couldn't get my hands on a hard drive, but Lowes had a pack of magnets for $2.50 that work just fine. I've doubled them up on each side, but it would also work to just use one on each side.

I glued the washer to the back of the fan, but as of now, I am just letting the magnets sit freely on the washer. They're strong enough to hold themselves in place. (I was too afraid to glue them because if they were out of place it would be hell to remove and re-attach them.)

I just took the back grill off completely instead of bothering to cut the wire.

Here's a video of my awesome 'shamelessly cheap' stir plate in action: http://www.youtube.com/watch?v=LN0Xi0ymSH8&feature=youtu.be

As you can see, I don't have a frame or box so for the time I'm using two books. This fan moves really fast, It's way more than I need for a 1L flask.

This took less than 3 hours including ordering, trips to the hardware store, etc. Thanks for the great idea.
 
http://www.amazon.com/gp/product/B001LIHGFC/?tag=skimlinks_replacement-20

This laptop cooling pad may also be an option. Same price point as the Thermaltake. Likely significantly lower quality, but might be a good option to adapt to stir plate duties.

I'm planning to switch my stir plate from the current monstrosity of a project box to something compact like this.
 
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