magnet

119 Articles

You Can 3D Print Yourself Some Simple Magnetic Switches

August 22, 2024 by 9 Comments

Permanent magnets aren’t typically switchable. They’re always doing their magnet thing. However, if you align them with a bunch of other magnets in just the right way, you can create a permanent magnet that you can effectively switch on and off. [Andrew Klein] has done just that with his 3D-printed magnetic switch design.

The concept is simple enough. The design consists of a 3D-printed housing in two parts, top and bottom. When set into one orientation, the housing holds two arrays of magnets in opposite orientations. This effectively cancels out their magnetic fields and allows you to move the assembly around as if it’s pretty much not magnetic at all. However, rotate the device to its alternative orientation, and the magnets poles are aligned. This effectively combines their magnetic fields and makes the assembly act as one big large magnet.

These devices are useful if you want to create magnetic clamps or fixtures that can be attached and detached at will from ferrous surfaces. Being able to effectively “switch the magnet off” is much easier than trying to wrench a powerful magnet from a metal plate, after all.

You can do something similar with electromagnetic techniques, too! Video after the break.

Continue reading “You Can 3D Print Yourself Some Simple Magnetic Switches” →

Print Your Own Magnetic Connector

July 27, 2024 by 22 Comments

If you have a late-model laptop, you’ve probably seen how the chargers magnetically snap into place. In theory, this should be easy to recreate for your own purposes. But why reinvent the wheel when [DarthKaker] has already done the work for you — assuming you only need two conductors.

The 3D-printed shells take the usual round magnets. Obviously, the north pole on one part should point to the south pole on the other part. In addition, if polarity matters, you should also have each housing contain one north-facing and one south-facing magnet so that the connectors will only mate one way.

It appears the project uses wires soldered or spot welded to the magnets. Heating magnets sometimes has bad effects, so we might try something different. For example, you could solder the wires to thin washers affixed to the magnets with epoxy, perhaps. Or use the magnets for alignment and make a different arrangement for the contacts, although that would take a different shell design.

We have talked about magnet soldering for connectors before. Don’t forget that you can build magnets into your prints, too.

Electromagnetic Actuator Mimics Muscle

July 26, 2024 by 11 Comments

Most electromagnetic actuators are rotating motors, or some variation on the theme, like servos. However, it’s possible to do linear actuation with electomagnetics, too. [Adrian Perez] demonstrates this with Linette, his design of a linear actuator that he was inspired to build by the structure of our own muscles.

The design uses a coil of copper wire in a 3D-printed plastic housing, surrounded by a claw full of strong magnets. When the coil is activated, the magnets are pulled towards the coil. When the coil is not energized, the magnets fall away. [Adrian] demonstrates the actuator under the control of an Arduino, which switches power to the coil to move it up and down.

He also notes that the design is similar solenoids and voice coil style actuators, though unlike most his uses discrete magnets rather than a single monolithic magnet. It’s possible to get more capacity out of the Linette design through stacking. You can parallelize the actuators to get more pulling force, with neighboring coils sharing the same magnets. Alternatively, you can stack them in series to get longer stroke lengths.

[Adrian] hasn’t put the design to a practical application yet, but we could see multiple uses for robotics or small machines. We’ve seen some other neat DIY magnetic actuators before, too. Video after the break.

Swapping Vinyl For Cardboard With This ESP32 Turntable

June 30, 2024 by 15 Comments

Cardboard is a surprisingly durable material, especially in its corrugated form. It’s extremely lightweight for its strength, is easy to work, can be folded and formed into almost any shape, is incredibly inexpensive, and when it has done its duty it can be recycled back into more paper. For these reasons, it’s often used in packaging material but it can be used to build all kinds of things outside of ensuring that products arrive at their locations safely. This working cardboard record player is one example.

While the turntable doesn’t have working records in the sense that the music is etched into them like vinyl, each has its own RFID chip embedded that allows the ESP32 in the turntable’s body to identify them. Each record corresponds to a song stored on an SD card that instructs the ESP32 to play the appropriate song. It also takes care of spinning the record itself with a small stepper motor. There are a few other details on this build that tie it together too, including a movable needle arm held on with a magnet and a volume slider.

As far as a building material goes, cardboard is fairly underrated in our opinion. Besides small projects like this turntable, we’ve also seen it work as the foundation for a computer, and it even has the strength and durability to be built into a wall or even used as shelving material. And, of course, it’s a great material to use when prototyping new designs.

Continue reading “Swapping Vinyl For Cardboard With This ESP32 Turntable” →

Spinning Magnets Do Your Dice Rolling For You

June 28, 2024 by 6 Comments

Dice are about the simplest machines possible, and they’ve been used since before recorded history to generate random numbers. But no machine is so simple that a little needless complexity can’t make it better, as is the case with this mechanical spinning dice. Or die. Whatever.

Inspiration for the project came from [Attoparsec]’s long history with RPG and tabletop games, which depend on different kinds of dice to generate the randomness that keeps them going — that and the fortuitous find of a seven-segment flip-dot display, plus the need for something cool to show off at OpenSauce. The flip-dot is controlled by an array of neodymium magnets with the proper polarity to flip the segments to the desired number. The magnets are attached to an aluminum disk, with each array spread out far enough to prevent interference. [Attoparsec] also added a ring of magnets to act as detents that lock the disk into a specific digit after a spin.

The finished product ended up being satisfyingly clicky and suitably random, and made a good impression at OpenSauce. The video below documents the whole design and build process, and includes some design dead-ends that [Attoparsec] went down in pursuit of a multiple-digit display. We’d love to see him revisit some of these ideas, mechanically difficult though they may be. And while he’s at it, maybe he could spice up the rolls with a little radioactivity.

Continue reading “Spinning Magnets Do Your Dice Rolling For You” →

Sort Of Electromagnet Attracts Copper, Aluminum

March 27, 2024 by 10 Comments

It is a common grade school experiment to wind some wire around a screw, power it up, and watch it pick up paper clips or other ferrous materials. It is also grade school science to show that neither an electromagnet nor a permanent magnet will pick up nonferrous items like copper or aluminum. While technically not an electromagnet, it is possible to build a similar device that will weakly pull on copper and aluminum, and [Cylo] shows us how it works in a recent video you can see below.

The device sure looks like an electromagnet made with magnet wire and a steel core. But when he shows the ends of the core, you’ll see that the side that attracts aluminum has a copper ring embedded in it. The coil is fed with AC.

The magnetic field from the coil induces an opposite field in the copper ring that is out of phase with the exciting field. The two fields combine to produce a force on the metal it interacts with. This is often referred to as a shaded pole, and the same technique can help AC motors self-start as well as hold in relays driven by AC. If you want to see much more about aluminum floating on a magnetic field, check out the 1975 video from [Professor Laithwaite] in the second video below.

You probably have a shaded pole AC motor in your microwave oven. Or, maybe,your old 8-track player.

Continue reading “Sort Of Electromagnet Attracts Copper, Aluminum” →

3D Printing Improves Passive Pixel Water Gauge

November 8, 2023 by 9 Comments

Here at Hackaday, we feature all kinds of projects, and we love them all the same. But some projects are a little easier to love than others, especially those that get the job done in as simple a way as possible, with nothing extra to get in the way. This completely electronics-free water gauge is a great example of doing exactly as much as needs to get done, and not a bit more.

If this project looks a bit familiar, it’s because we featured [Johan]’s previous version of “Pixel Pole” a few years back. Then as now, the goal of the build is to provide a highly visible level gauge for a large water tank that’s part of an irrigation system. The basic idea was to provide a way of switching a pump on when the tank needed filling, and off when full. [Johan] accomplished this with a magnetic float inside the tank and reed switches at the proper levels outside the tank, and then placed a series of magnetic flip dots along the path of the float to provide a visual gauge of the water level. The whole thing was pretty clever and worked well enough.

But the old metal flip dots were getting corroded, so improvements were in order. The new flip dots are 3D printed, high-visibility green on one side and black on the other. The only metal parts are the neodymium magnet pressed into a slot in the disc and a sewing pin for the axle. The housing for each flip dot is also printed, with each module snapping to the next so you can create displays of arbitrary height. The video below shows printing, assembly, and the display in action.

[Johan]’s improvements are pretty significant, especially in assembly; spot-welding was a pretty cool method to use in the first version, but printing and snapping parts together scales a lot better. And this version seems like it’ll be much happier out in the elements too. Continue reading “3D Printing Improves Passive Pixel Water Gauge” →