Inside a magnetically coupled fermentation agitator

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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