Stirring plate from USB enclosure

[Loreno Minati] built his own stir plate out of a hard drive enclosure. It’s the exact same hack as the one we saw a few weeks ago. A magnet was glued to the center of a computer fan, which causes the magnetic capsule inside the beaker to spin. This creates a vortex, evenly mixing the liquid.

Using a hard drive enclosure is a brilliant idea. It’s designed to sit in plain sight so you get a very nice finished look. It’s also exactly the right size for the fan itself. A potentiometer mounted in the cap of the enclosure allows for variable speeds, and the DC barrel jack is being used for the power source. Now that we think of it, this may be the best use of an external HDD enclosure we’ve ever seen (even eclipsing its original purpose). Check out a video and image gallery of the project after the break.

We’ve categorized this as a beer hack since stir plates are often built by hobbyists for growing yeast starters used in home brewing.

[Thanks Jorge]

Comments

  1. CutThroughStuffGuy says:

    All he has to do now is add a heater :)

  2. marcus says:

    From the picture, it looks like more than just a potentiometer is used for the speed control. Most simple instructions suggest a basic LM317 circuit.

    Also, I wonder what metal this enclosure is made of. Usually diamagnetic materials like aluminum tend to cause the spinning magnet to spin slower due to Lenz’s law.

  3. Goja says:

    If the case is made of alluminium, the idea is not that brilliant, because the eddy-current slows the rotation down.

    http://en.wikipedia.org/wiki/Eddy_current

  4. ehrichweiss says:

    @Goja, yep. There’s a magic trick that uses the eddy current to make for a very magical(and scientific) effect. For the life of me I can’t remember the name of it but I know it contained the word “Newton”…

  5. Jordan says:

    sooo, where do you get the magnetic bars from? I’ve got the rest sitting around….

  6. Jordan says:

    @ehrichweiss: http://tinyurl.com/4z94x9g
    That what you needed?

  7. rwohleb says:

    @Goja, the eddy current will be minimal and is not a big issue. Look at just about any hot plate with integrated stirrer. The top is frequently steel, which will also have eddy currents.

    The brilliant part of this hack is the reuse of materials.

  8. Tom Hargrave says:
  9. Chuckt says:

    Just get a cheap plastic hard drive case and a fan.

  10. Amos says:

    Actually, this and all the “beer” hacks should be in the “chemistry hacks” category.

    The only way to make this better would be to keep the USB connection; allowing a PC to change the speed (or at least just start/stop). It would allow timed stirring cycles. Yes, hotplate functionality would make it better, too, but I doubt if the materials would take much heat, anyway.

  11. Rachel says:

    Eddy currents definitely reduce efficiency. Try holding a magnet over some spinning hard drive platters, and watch it slow down significantly.

    It would also help to break off the blades of the fans.

  12. jaqen says:

    @rachel: keeping the fans will keep the enclosure ventilated though, i suppose even a fan motor will generate some heat, that doesn’t have anywhere to go since it’s enclosed.

  13. echodelta says:

    Try sliding one of those hard-drive magnets down a ramp of aluminum channel. They are small and heavy, but they float down instead of drop. Could a slow enough speed be had with the platter motor in a drive running on a lower 3-phase freq ? If good; then glue magnet on, heat resistors inside, and put cover on. Drives can get hotter than fermentation needs. Put the little tea cozy on the flask, and let a dwino set the temp and rpm 3phase.
    A naked hard drive with a flask whirling away on top is more interesting than the sleek approach.

    Not all beer hacks are chem-related. Keg-fridges and beer ballistiae come to mind. An old advert in the 60’s had a beer company wanting to deliver faster for fresher taste. Things they tried: one, an ICBM (Inter-City Beer Missile) there was another skit I forget. Get hacking. I challenge everyone to send a growler to space and return it safely to earth to get refiled. To send great beer where no beer has gone before. This is not trivial. The first hackers of stone and bone encountered alcohol and wanted more. Thus began farming to get enough grain and staying put to brew and ferment in some of the oldest structures built by man known to exist, in-ground vats!
    Where would we be with the best hack after stone tools? Beer!

  14. Jonathan says:

    The “circuit” looks like just a NPN transistor amp (from the transistor-looking thing’s part#), to avoid burning up the pot.
    I expect the PCB is just there because that’s what was in the case to start with, and has no other components on it.

  15. zipgoods says:

    eheh, very cool!

  16. marcus says:

    @Rachel: If you break off the blades off the fan, and you do it unevenly, you’ll wind up with a big vibrating motor. Better just to keep the fan blades intact.

    Also, be careful with kegkits.com: http://www.homebrewtalk.com/f14/read-before-you-buy-kegkits-com-120110/

  17. Goja says:

    Actually, a throttled fan (closed intake) will run faster, because a lot of the air, that creates friction is pumped out.
    Its not a vacuum, but it makes a noticeable difference.
    So keep the blades in. ;-)

  18. fraguk says:

    Found this similar device using a fan: http://brewiki.org/StirPlate

    I’m actually tempted to make a heated one of these for gravy. Or yeast.

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