Rare earth magnet for solenoid core

AI Thread Summary
The discussion revolves around designing a water valve using a solenoid coil and a rare Earth magnet to control a plug in a reservoir. The setup involves a magnet that, when powered, lifts the plug to allow water flow, with movement restricted by a string. The user questions the necessity of using a rare Earth magnet instead of a standard ferrous core, noting that the magnet was chosen to achieve greater force with less current. It is explained that using a magnet allows for movement out of the coil rather than into it, and starting with a strong magnet reduces the likelihood of demagnetization. The conversation emphasizes the unique advantages of rare Earth magnets in solenoid applications.
JakesSA
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Hi,

I am trying to design a simple water valve that opens a plug in a small water reservoir until its empty.
So far I have a solenoid coil wound around a hollow core plastic pipe with a cylindrical rare Earth magnet inserted halfway into the pipe with a 'plug' attached to the top of the other half. Switch power on and the magnet pops out lifting the plug allowing water to flow around the magnet core through the pipe. Total movement of the core is restricted by a string attached to the bottom of magnet and plastic pipe. After power shut off the plug just falls back into place sealing the reservoir.

Since everyone else seems to use a standard ferrous material for the movable core, is there actually any point in using a magnet here?

Thanks in advance ..

EDIT: I used the rare Earth magnet in the hopes of obtaining more force for less current ..
 
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If you put an soft Iron core in a solenoid, it will tend to pull inwards to the center of the solenoid when you apply power.

Using a magnet does allow you to get movement out of the coil instead of into it, if you get the polarity right.

That is also how you remagnetize the magnet, so starting off with a very strong magnet will make this less likely.
 
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