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This question already has an answer here:

A new project I'm working has to be highly modular. All the electronics will be hidden in a case, so I was wondering if there's any way to use magnets and pass current through them for the project?

It's well known that neodymium magnets could lose their magnetic capabilities in extreme heat, so simply soldering wires to the magnets is out of the question. Is there anything I could do to solve this problem?

Also the magnets might need to run close to 4 Amps of current, which shouldn't be a problem if the metal coating on the magnet is good.

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marked as duplicate by Dave Tweed Jun 23 '17 at 11:55

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • \$\begingroup\$ Spot weld the cables to them. That's the only solution. \$\endgroup\$ – Passerby Jun 23 '17 at 3:04
  • \$\begingroup\$ Might want to look into a method like this one: shop.littlebits.cc/collections/kits \$\endgroup\$ – Jay Jun 23 '17 at 4:05
  • \$\begingroup\$ I'm not sure how they're manufactured, but for an example of a commercial product that uses magnetic conductive contacts, see InfiniiMax III QuickTips. Only three small magnets, but they have quite a bit of pull. The InfiniiMax connector is not suitable for high current and not very rugged (I think they use gold-plated magnets?), but is a neat example of a commercial product. \$\endgroup\$ – uint128_t Jun 23 '17 at 5:16
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    \$\begingroup\$ Repeat of How to bond wires to neodymium magnets. It's getting harder and harder to be original! \$\endgroup\$ – Transistor Jun 23 '17 at 6:16
  • \$\begingroup\$ neodymium magnets are about 7000 times more electrically resistive than copper. Something to bear in mind when using them as part of a circuit. \$\endgroup\$ – crobar Jun 23 '17 at 10:40
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I would use a method that does not rely on the magnet as a conductor. Use the magnet to hold a conductor against another. This brings a number of advantages that result from isolating the requirements of conductive connector components from the properties of the magnet. This eliminates the need for coating a magnet with gold, much easier to coat the contact itself. Magnets tend to be fragile, and the conductor can be very slightly sprung; enough to soften impacts (which also cause de-magnetisation if I'm correct) and may help with connection reliability.

Otherwise, I would still use a simple mechanical method for connecting to a magnet. For example, wedge a wire between the magnet and enclosure. Very low cost to implement. It may even be stronger than any soldering/welding technique since some coatings on magnets have quite a weak bond.

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  • \$\begingroup\$ This is a good idea. The magnets could be used to hold modules together while some type of connector could bridge the gap. \$\endgroup\$ – user33335 Jun 23 '17 at 6:38
  • \$\begingroup\$ Don't forget to pay Apple for the privilege of using magnetic connections... \$\endgroup\$ – Majenko Jun 23 '17 at 11:15
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You could use a pressure contact or a spring clip of some kind- or spring-loaded pins such as "pogo pins" used in test fixtures or the type used for battery packs. You might be able to use a low temperature solder- if you can find one that is usable below the maximum working temperature of the magnet, which is actually quite low for the neodymium types, less than 100 degrees C, much less than the >300 C Curie point of the magnet- so I am guessing that won't work without degrading the magnets.

Another option would to use a nickel plated ferromagnetic chunk of metal with a wire soldered to it or held with a cross hole and set screw, and let the other end of the magnet glomp onto it.

Or try to spot weld the wire as @Passerby suggests, the heat should be localized and will not demagnetize the magnet.

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    \$\begingroup\$ Amazing idea. I found these cfconn.com/product-show_13460 \$\endgroup\$ – user33335 Jun 23 '17 at 6:48
  • \$\begingroup\$ @user2900812, nice find. That kind of thing would be useful in a Production or Test environment. \$\endgroup\$ – Wossname Jun 23 '17 at 7:38
  • \$\begingroup\$ @user2900812 Interesting product, thanks for the link. \$\endgroup\$ – Spehro Pefhany Jun 23 '17 at 12:23
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Neodynium magnets fall apart after snapping together a few too many times. I have some which have never had much use, but they have crumbled from being snapped together, pulled apart, snapped together, pulled apart... The Nickel casing flakes away first, followed by chunks of magnet.

I offer you a related, but alternate approach.

  • clamp and bond two magnets to the inside of the case, either side of contacts, one with north facing away from your assembly and one with north facing into your assembly
  • attach metal connectors on the outside of the chassis, which will make the electrical circuit. I'll leave it to your choice as to the connector/ terminal.
  • On your complimentary module (which connects to this one), create a similar assembly, but reverse the polarity of the magnets.

When you push the two modules together,

  • The like poles will repel preventing misalignment, but dissimilar poles will attract causing alignment.
  • The magnetism forces should hold the equipment together.
  • The Magnets will not suffer compression & shock forces of snapping together and should enjoy a longer lifespan.
  • You will not encounter heating issues through solder, welding, or passing high current through the magnets they will be isolated from the rest of the circuit.

Rudimentary Diagram (drawn in gimp)

Here the

  • individual magnets are represented by a north (red) and south(blue) poles
  • Thin yellow strips with dark grey on them represent isolated terminals, i.e. not able to conduct into a metal chassis.

Assembly diagram

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Look at the the design of the macbook power connector - called magsafe contacts and magnetic and comes apart with sufficient applied force.

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  • \$\begingroup\$ "All the electronics will be hidden in a case" indicates that he doesn't want an exposed connector. The MacBook connector doesn't use the magnet to pass the current, only to make sure the conducting metal connector stays in contact. \$\endgroup\$ – pipe Jun 23 '17 at 10:34
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I have had this on my CNC router Z-probe for a few years now, used to temporarily connect the measurement wire to the cutting tool shaft:

Wire soldered to magnet

That is simply a wire soldered to a 5 mm diameter neodymium magnet. It also has a coat of epoxy, which originally also covered the wire insulation and was supposed to protect the "fragile" solder joint. But it turns out that the epoxy has wore out while the solder joint is holding up just fine.

The magnet might have been slightly damaged due to soldering, but it is still pretty strong. But one difference from your situation is that the current I'm using is only a few milliamperes.

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The neodymium magnet materials are crumbly, usually there's a nickel plating over them. While you COULD make contact with the nickel, it'd be easier to just use the magnet to attract a slug of iron. Then a set of electrical contacts that is pinched between the magnet and the iron will be pressed together. You could get elaborate, and hide the contacts inside a slot in the case, knowing that they will be extended only in response to the (magnet) connector or cradle.

Imaginative mechanical connections ought not to preclude unsafe conditions if hazardous voltage and current levels are involved, of course.

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