magnetic stirrer

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pixelhussar

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Hey guys,


Just two questions. I found an old pc fan I can power with my old TT scale train power supply. Housing and everything else is done as well.

Now I have to glue the magnet on the fan and buy that small doodad that spins around.

What is the direction of the magnet's polarities supposed to be? Is it horizontal (90 deg to rotational axis of the fan) or is it vertical (parallel to the rotational axis).

I'd say the first, but I'm not sure.

Won't a strong earth magnet damage the fan or lower it's efficiency?

Thanks!
 
If you're using a hard drive magnet (crescent moon shaped), it won't matter which side is up. Try taping the magnet to the hub first before gluing, and set your stir bar on it to make sure it is centered, otherwise you'll have issues with the stir bar getting kicked off when in your flask. If you're using two small rare earth magnets, then tape them in the same way, make sure they're centered on the outer edges along the hub's diameter and put the stir bar across them to make sure the polarities are correct.

When you first start it up in the flask, you may need to turn the potentiometer (the spinny doo-dad) to high to get the stir bar started and lower it once it does, then increase the speed slowly from there until you find the right amount of force.

I built a stir plate identical to the How-Tos posted on HBT and mine has been working flawlessly. I haven't had any issues with the fan and doubt it will get damaged since the RPMs are much lower than what it was originally designed for, even with the additional magnetic field and load.
 
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