The theory behind speaker operation is pretty simple. There’s a coil that is attached to some type of diaphragm and a permanent magnet. When electrical signals pass through the coil a magnetic field is generated, and that field’s interaction with the permanent magnet causes the diaphragm to vibrate and create sound. But we’ve always assumed that the vibrating material must be stretched tight for this to work. [Hannah Perner-Wilson] proved us wrong by making this speaker out of fabric. It uses conductive tape as the coil on a heavy piece of canvas. The permanent magnet is resting on a table and for the demonstration the fabric is just laid on top.
Check out the video after the break to hear the sounds generated by this device as well as a design that uses conductive thread instead of tape. This gets us wondering if what we’re hearing is the result of the magnet vibrating against the tabletop? Let us know your thoughts, and if you’ve got any information about the paper-backed circuit (seen at 0:04 into the video) driving the speakers we’d love to hear about that too.
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This collection of gauss weapons use rare earth magnets to accelerate projectiles to damaging speeds. They work using the same concepts as a coil gun, but instead of just one projectile travelling along a length of guide track, there are many projectiles that work in a chain reaction. A series of magnets are placed at equal distances along the track. Each has a couple of large ball bearings on the muzzle side of the magnet. The first ball bearing is fired using mechanical force – like a spring mechanism – and accelerates as it approaches the magnet due to the attractive force of that magnetic field. When it impacts the magnet it sends one of the ball bearings on the opposite side down the track where it will accelerate when it nears the next magnet in the chain. The weapon above achieves a final projectile speed of about 68 miles per hour, breaking six fluorescent tubes in a row on at the right side of the apparatus.
Still prefer rail guns that use electromagnets? Check out this gauss pistol kit that is about as powerful as a BB gun.
Above you see a solenoid being used as a digital scale. The magnetic field from the coil in the base levitates the platform above, where a load to be measured is place. This floating platform has a permanent magnet in it, hovering above a hall effect sensor in the base. As the distance between that magnet and the sensor changes, the measurable magnetic field changes as well. The hall effect sensor is linear so the measured value can easily be correlated with a weight. In the video after the break [Vsergeev] demonstrates the device using test weights to show off its 0.5 gram resolution. He thinks that with a few hardware improvements he could easily achieve 0.1g accuracy.
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This hack’s old as dirt to be sure, but new to us and a great accomplishment. The plane above, which is meant to fly without an operator, has been given RC control thanks to parts from that little car. The transmitter and receiver pair are the obvious transplant, but how do you add steering to a $7 plane that wasn’t manufactured to have that feature? The tail was cut and reconnected with mylar hinges to turn it into a rudder. A rare earth magnet and a coil are also thrown into the mix to provide movement. Basically this is a simple solenoid where the coil pushes against the magnet when energized, actuating the rudder. This in combination with an upgraded motor allows for both speed control and yaw. It doesn’t look like you can control roll and pitch but what more can you really expect?
This would be a nice first step on that path to building an epic flying camera rig.
It has been recently discovered that all of the snap decisions that your brain makes on which hand to use to do simple tasks, such as picking up an object from a table, can now be automatically decided for you. This is done using magnetic stimulation that is applied using transcranial magnetic stimulation or TMS. This TMS will affect the brains ability to process motor movements and reduces the chances that the right hand will be chosen over the left. This major discovery was found by PNAS (Proceedings of the National Academy of Sciences of the United States of America) who hopes to use this later on for rehabilitating stroke victims, making them using the limbs that may suffer from the event. Here is to hoping that an in home product will be released in the future so children can become ambidextrous in everything they do. It seems like that is a way off but it does seem more natural than most hacks to your body.
If you’re in need of eye surgery you might just find yourself strapped into this contraption. It’s a magnetic field generator used to manipulate a tiny, untethered probe. It’s called OctoMag and the idea is that a robot less than half a millimeter in size is injected into your vascular system and, through the use of those coils, it busts up blood clots in the small passages inside of the eye.
Once you’ve seen the clip after the break we’re sure you’ll agree that this is amazing technology. Nonetheless it makes us cringe to think of the procedure done on a living organism but we’re sure that fear will subside given time. For now this seems more like a treatment from A Clockwork Orange.
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[Alexy Sha] has done this fantastic hack, where he modified a magnetic floating globe to be motorized and spin on a tilted axis. The original globe was simply levitating via a magnet mounted inside. Though you could spin it by hand, it wasn’t motorized, and actually floated completely vertically instead of being tilted.
[Alexy] wanted to take this idea further and make it automatically spin on a rotated axes. He built a rotation assembly that was basically a motor, hung off-center, attached at the center of the globe. He had to power it via a coil hidden in the base unit, so that it could remain light enough to float. He did a fantastic job and the final product seems like it is the true way it should have been sold.
Check out a video of it in action after the break. We actually like the spinning ring, when he’s testing it, just as much as the final spinning globe.
Continue reading “Floating globe, hacked to rotate”