Magnetic Stirrer plate

[Havor]

Hi i am a poor Dutch chemistry student, and i and a other student want to make a couple of magnetic stirrer plate, for home project/study, but the even cost a bout $50 secondhand.

Now i want to make one my self, and have all the parts (about $20 in parts per plate), but only have to decide on the type of Neodymium magnet i should use.

This is the stir bar i gone use.

But i am wondering what the best magnet type would be?
Use 2x round disk type 15x5 and having them facing up and down, and i think having the center of the magnets around the ends of the stir bar.
Or 1x bare type 30x10x5.

And a question, if i would use a longer bar type magnet, could i use longer stir bars later on if i need them, or would 6 disk type magnets work better, paired 30, 45 and 60mm spaced from one and other.
A other question i have about the bar type, am i assuming correct that the poles are on the end of the bars?

 

[Compositepro]

There are many stirrers available really cheap on Ebay and other auction sites, particularly ones where universities dispose of old assets. As far as education goes you will learn more by taking apart or repairing a commercial unit than you will from building one from scratch.

 

[Havor]

We looked at those, and all are way more expensive then when we build our own, we need 5 in total, and that will cost us around €70 in parts, including water proof boxes and PWM voltage/speed regulation, etc etc.

Mainly postage is killing us, new or used, even if we buy them from Aliexpress, there we can have 5 for about €120, the transport cost is about a other €100.

I looked at many YouTube films how they make them, i just wane be sure what type of magnet we should use:
[ul][li]What would be better, the bar of the coin type.[/li]
[li]And if i am correct if the ends are the poles of the magnet.[/li]
[li]For a bar type what length we could use, if longer bars will give us more freedom of type stir bars we use.[/li]
[li]And for the coin type, if adding more magnets whit different spaces could do the same thing?[/li][/ul]

 

[EdStainless]

no heat right? Just stir.
Don't use neo, use ferrite magnets. They are a fraction of the cost and will work fine.
You need something non-magnetic and non-electrically conductive for the top plate.
I have seen two types.
One just had a long bar magnet (magnetized length wise) in an Al holder fastened to the motor shaft. The length was just a little longer than the stir bar.
The other style had a set of small button magnets (6 or 8) mounted to an Al plate in alternating polarity. You could make this stronger by adding iron bars between the back side of pairs.

Many older ones used motors with multiple sets of windings. By switching between them you could get 3 to 5 different fixed speeds. But it takes the right motor to do this.

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P.E. Metallurgy, Plymouth Tube

 

[Havor]

no heat right? Just stir.

Correct

Don't use neo, use ferrite magnets. They are a fraction of the cost and will work fine.

I was thinking of using these Neodymium magnets, at €6.50 for 5, they are a steal.

You need something non-magnetic and non-electrically conductive for the top plate.

Yeah i got waterproof junction boxes for that.

The other style had a set of small button magnets (6 or 8) mounted to an Al plate in alternating polarity. You could make this stronger by adding iron bars between the back side of pairs.

I could make a steal disk, and stick the coin like magnets on to that one.

I i woeld use coin type, hat pattern would be best?

And what material should i then make the disk from? (plastic, aluminum or steel)

For the bar type i would use just a strip of plexi, a little larger, so i can grind i bit of for balancing it.

 

[EdStainless]

So your boxes are plastic, correct?
Ferrite magnets would be 5/euro.
The simple way is to get ferrite bars, just make sure that they are magnetized length ways.

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P.E. Metallurgy, Plymouth Tube