Magnet which loses its magnetic grip when current passes through

  • #1

Main Question or Discussion Point

Problem
Traditional electromagnets create a magnetic field when current passes through them.

What I need is a magnet that loses its magnetic grip when current passes through.

Is there a particular name for these kind of magnets / systems?

Application
I want the magnet to hold a metal object (no energy should be consumed). With a push of a button (current applied) magnet should release the object.
 

Answers and Replies

  • #2
Mech_Engineer
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What about a rare earth magnet in front of an electromagnet? When you turn on the electromagnet, it is at the reverse polarity of the rare earth magnet and cancels (or at least weakens) the magnetic field holding the part.
 
  • #3
Averagesupernova
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You can do this by heating a permanent magnet with a heating element. It is not instantaneous at all. Another way would be to wind a coil around a bar magnet and appply the current to oppose the bar magnets field (cancellation). As the bar magnet ages and its field weakens you may need to adjust the current.
 
  • #4
Mech_Engineer
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You can do this by heating a permanent magnet with a heating element. It is not instantaneous at all.
Doesn't that permanently demagnetize it?
 
  • #5
S_Happens
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My first thought would be to have a solenoid actuate movement of a permanent magnet, either through direct mechanical motion or pneumatic/hydraulic. Have the permanent magnet retract from the object when energy is applied to the solenoid. Obviously you'd need something for the permanent magnet to retract into/prevent object from following the permanent magnet, but that's just as easily done as setting up any of this.

Edit- We use solenoid valves to apply/remove pneumatic pressure from certain process valves where we need on/off capability instead of precise control.
 
  • #6
Averagesupernova
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Heating a magnet does not necessarily permanently demagnetize it. Some weller soldering irons use a magnet in the tip that turns on and off a reed switch. This is what regulates the temp. If you want a different temp just change out the tip.
 
  • #7
All the ideas are very interesting.

Heating up the magnet is an original one, however, a combination of a permanent magnet / solenoid seems more elegant.

Further research showed that these are called electropermanent magnets. Here is a short description: http://walkermagnet.com/hagou/magnetic_handling/electro-permanent-magnet.html" [Broken].

Will try to contact several magnet manufacturers to see if an off the shelf version is available.
 
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