reversible permanent magnet

A reversible permanent magnet is a magnet that can be turned on and off and can keep either state without external power.

The video begins with the magnet in "on" mode, that is, it is holding the bar on the bottom against gravity. Note that the power supply is off (as seen in the background).

A charge pulse is applied (by switching the DC power supply on then off quickly) which changes the magnet to "off". The bar on the bottom drops onto the table.

We hold the magnet near the bar and it is not attracted to the magnet. (This could have been done more dramatically in the video).

Next, the polarity of the DC signal is reversed (we reach behind and swap the banana connectors) and again a short DC pulse is applied. The magnet picks up the bar off the table.

Although we don't explicitly show it clearly in the video, the power supply is off with the exception of the short pulses that turn the magnet on or off. The rest of the time the magnet stays in whatever state it is in; that is why it is still called a "permanent magnet". This is also how this differs from a solenoid where the electrical input power must be provided any time the magnetic field is on.




Built by Ara Knaian, video by Amy Sun, both of the MIT Center for Bits and Atoms.

Category:

Science & Technology

Tags:

• magnet
• science
• engineering
• control
• fablab

[100roberthenry]

anymore details on this?

[fablabamy]

@100roberthenry The magnet is called a "reversible permanent" or "electro-permanent" (EP) magnet. It is a permeable material whose flux can be programmed (redirected). Apparently this has been widely implemented since the 60's. The video is our first attempt to see if it'd work!

Ara's thesis (2010) describes the use of EP magnets in a cm-scale stepper motor. Others from Daniela Rus' lab also use the EP as a programmable connector in modular robotics.

[fablabamy]

@100roberthenry It seems I can't paste the URL for the thesis. Try this,

domain: cba.mit.edu

path: /docs/theses/

file: 10.06.knaian.pdf

[100roberthenry]

@fablabamy thanks very much...

[Risenangelicaegis]

This is the concept that makes Steorn's motor work

[dajlrj]

how is this different from an electromagnet?

[TruthNewsTV]

Should be possible to use this in an overunity permanent magnet motor.

[zeropointfuel]

Is this a permanent magnet or a electromagnet? Their is a difference nice work if it is a permanent magnet.

[MrTech40]

Interesting. Very interesting.

[ForteanOrg]

Fascinating. Where can we find the paper that describes this setup/experiment?