Hovering Questions About Magnetic Levitation

Who doesn’t love magnets? They’re functional, mysterious, and at the heart of nearly every electric motor. They can make objects appear to defy gravity or move on their own. If you’re like us, when you first started grappling with the refrigerator magnets, you tried to make one hover motionlessly over another. We tried to position one magnet over another by pitting their repellent forces against each other but [K&J Magnetics] explains why this will never work and how levitation can be done with electromagnets. (YouTube, embedded below.)

In the video, there is a quick demonstration of their levitation rig and a brief explanation with some handy oscilloscope readings to show what’s happening on the control side. The most valuable part, is the explanation in the article where it walks us through the process, starting with the reason permanent magnets can’t be used which leads into why electromagnets can be successful.

[K&J Magnetics]’s posts about magnets are informative and well-written. They have a rich mix of high-level subjects without diluting them by glossing over the important parts. Of course, as a retailer, they want to sell their magnets but the knowledge they share can be used anywhere, possibly even the magnets you have in your home.

Simpler levitators can be built with a single electromagnet to get you on the fast-track to building your own levitation rig. Remember in the first paragraph when we said ‘nearly’ every electric motor used magnets, piezoelectric motors spin without magnets.

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Electronifying A Horror Fraught Hydraulic Press

[Josh] is replacing the springs in his car’s suspension. He wanted to know the travel rates of these springs, but apparently, this is a closely guarded trade secret in the industry. One company did manage to publish the spring rates, but they weren’t believable. Instead of taking this company’s word, [Josh] built a spring tester.

The theory behind a spring tester is pretty simple: apply a force to a spring, measure it, then measure how much the spring has traveled. Or compress a spring an inch or so, measure the force, and compress it some more. Either gets you the same data.

This spring tester is built around a Harbor Freight hydraulic press. Yes, the spring is completely captured and won’t fly out of the jig if you look at it wrong. The bottom of the press contains a few load cells, fed into an ATmega8, which displays a value on an LCD. For the displacement measurement, a ruler taped to the side of the press will suffice, but [Josh] used a Mitutoyo linear scale.

What were the results of these tests? You shouldn’t buy coils from Bilstein if these results are correct. The rates for these springs were off by 70%. Other springs fared better and won’t bind when going over bigger bumps. That’s great work, and an excellent application of Horror Fraught gear.

Tank tread robot build aims for a smooth ride

There’s all kinds of interesting things going into this tank robot build, but that beautiful suspension system immediately caught our eye. It helps to protect the body of the robot from being shaken apart when traveling over rough surfaces. Make sure to check out the four parts of the build log which are found on the left sidebar at the post linked above.

This a Master’s thesis project and has been built from common parts. The motors for the treads are pulled from a pair of cordless drills, with some capacitors added to help combat the draw when they start up. The treads themselves are each made from a pair of bicycle chains connected with numerous PVC pipe segments. The curved section of each PVC piece goes toward the chain, leaving the edges toward the ground for great traction. The tree wheels which support the middle of the tread each have a hinge and spring to absorb the shock of running full speed into concrete sidewalk corners like we see in the video after the break.

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Pikachu is coming for you (especially on carpet)

If you look closely, you’ll see that Pikachu isn’t sporting a pair of funky throwing stars, but is actually suspended between there. Our furry friend is just putting a happy face on this carpet roving robot called the Carpet Monkey V5. It’s been in the works for years, and this is just one more stop in the prototyping process as the development of version 6 is already under way.

The project is a testament to what can be accomplished using all of the design tools at your disposal. The motive mechanism was conceived as a cross between the qualities of legs and the ease of using wheels. Each of the appendages are covered with strategically placed points meant to grab onto carpet, and allow the ‘wheel’ to grip objects as the machine vaults over them. You can see that each has a spring mechanism to further facilitate gripping with each turn of the axle. This seems to go far beyond what usually comes out of hobby robotics, and we think that’s a great thing!

After the break there’s a video showing how all the parts of these grippers are assembled. See the bot cruising around the room at about 3 minutes in.

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