I got this unit a very long time ago. I think it was being sold by one of the surplus companies that advertised in electronics magazines.
The design is very simple. A mains voltage synchronous motor with no gearbox, and a custom plastic component that couples it loosely to a metal bar with a magnet at each end. The loose coupling is to avoid loading the motor at start-up as synchronous motors are quite weak when starting up.
I wonder why the units were being sold off. Maybe because it has a slight tendency to lose the spinner in the jar and make loud rattling noises.
The concept is useful to know though, as magnetic coupling has many uses where you wish to induce rotation in a liquid without worrying about a liquid tight seal.
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15 thoughts on “Inside a magnetically coupled fermentation agitator”
  1. Avataaar/Circle Created with python_avatars riorcp says:

    I used to repair automatic washing machines and these motors were commonly used on the old electro mechanical timer switches used. If you take the motor apart you will find a pawl which determines the rotation of the motor, which is uni rotational.

  2. Avataaar/Circle Created with python_avatars Leslie Franklin says:

    That's similar to stirrers used by chemists to stir solutions.

  3. Avataaar/Circle Created with python_avatars Tom Jacobs says:

    I too get agitated by magnetically coupling my fermentator.

    i'll see myself out now.

  4. Avataaar/Circle Created with python_avatars Dancing with the Dogs DJ says:

    Do you ever rest?! Love your stuff and I've just felt the need to remind you lately on quite a few videos lol But it IS absolutely well deserved…. You're just awesome to watch or listen to…. Take care and have a wonderful day!!!!

  5. Avataaar/Circle Created with python_avatars Venena Religio Est says:

    They cannot apply for a patent on existing technology Clive, unless it is used for a radically new purpose altogether.
    Note: it is illegal to put ‘patent pending’ or ‘patent applied for’ if you haven’t applied for one.

  6. Avataaar/Circle Created with python_avatars David Bone says:

    A very good Monday morning to you all from Wellington Somerset

  7. Avataaar/Circle Created with python_avatars spookanide says:

    The packaging is quite something

  8. Avataaar/Circle Created with python_avatars L Duncan Shortridge says:

    Built my own years ago with a scavenged 4-wire PC fan and a 4-wire pwm controller module (YouTube doesn't allow links but if you Google "instructables Quick 'n Dirty Magnetic Stirrer lairdkelly" it should be the first result… The module I used is now unobtainium but there are a number of somewhat larger modules on eBay and Amazon from unenclosed boards to a packaged unit like the Noctua NA-FC1 (basically a 555 or dedicated PWM chip with a hex inverter or MOSFET buffer to generate the PWM clock signal for the fan) Much better than the unreliable chinesium stirrers with a cheap brushed toy motor and rheostat (or home-made ones with a two-wire fan and rheostat "fan controller") and cheaper than lab-grade stirrers based on a mains-power universal motor and a triac or quadrac PWM lamp dimmer/motor controller.

  9. Avataaar/Circle Created with python_avatars Jonny Duncan says:

    Looks like the same synchro motor's, that are in Honeywell/Corgi 2/3 port diverter valves in central heating systems, here in the UK

  10. Avataaar/Circle Created with python_avatars Mark Fergerson says:

    Would someone please explain to this non-drinker what a vodka wash is, and why you can't just stir one with a spoon?

  11. Avataaar/Circle Created with python_avatars John Tickle says:

    is that a microwave oven turntable motor or are they too slow.? Thanks for the video great work.

  12. Avataaar/Circle Created with python_avatars HimmelsDaemon says:

    Speaking of magnets and waterproof, if no-one knows of the "BrickExperimentChannel" then that might be of interest. Specifically of the lego submarine, which is exactly that concept.

  13. Avataaar/Circle Created with python_avatars Cenneth Adameveson says:

    It's just a cheap knock-off laboratory magnetic stirrer. The agitator (flea) is a magnet usually coated in plastic and comes in various sizes. Lab stirrers have a variable speed selector, too fast and the flea does its little dance. There are also heater-stirrers, never seen inside of those and the ones in work seem quite robust even when heated fails they still stir.

  14. Avataaar/Circle Created with python_avatars Mikey C says:

    Gotta love nice, simple gadgets.

  15. Avataaar/Circle Created with python_avatars John DoDo Doe says:

    I'm guessing the unidentified plastic adapter is a generic item glued to the metal bar. The washer that holds it is completely standard for holding on plastic wheels like that.

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