One thing you can look forward to when arriving at home after a long, arduous day at the office is some peppy theme music when you walk in the door. [Sebastian Sommer] built the system, and shows it off in the video after the break by dancing to James Brown’s I feel good.
The setup uses an Arduino as a microcontroller. It monitors a hall effect sensor on the jamb which detects a passing magnet on the door. We guess this means the system doesn’t know if you’re coming or going but perhaps a future upgrade would add an infrared beam to detect your legs as head out the door. The music itself is played by an SparkFun MP3 shield which has a decoder chip, microSD slot, and audio jack for the powered speakers. [Sebastian] grabbed a copy of [Bill Porter’s] mp3 shield library to get the project up and running quickly.
This is a pretty cool addition if you’re already using an Arduino for a door lock or vice versa. Or maybe you’re not home enough to make this hack worth it, in which case you simply must take this music playing Tesla coil hat along on your commute.
Continue reading “Your theme song greets you at the front door”
Hackaday regular [Mikey Sklar] is no stranger to body modifications. He enjoys tweaking his body in ways that help him with day to day tasks, including a ruler tattoo on his arm and an RFID chip embedded in the web of his hand. Lately, he has been toying around with a less invasive means of getting a better feel for magnetic fields in his surroundings.
Turned on to magnetic rings by a friend, he now wears an epoxy-coated rare earth ring every day, changing the way he interacts with the world. He says that besides the obvious ability to tell when he’s near iron-heavy material, he can also feel cell phone calls, as the speaker draws the ring closer while producing sound.
He says that holding the electric cord of his tea kettle gave him the biggest start, making him feel as if he had been electrocuted, minus the actual shock.
While it’s not the most high-tech hack, [Mikey] is quite happy with the “sixth sense” this reasonably price ring has been able to provide – we just might have to try it out ourselves.
[Andrey Mikhalchuk] built his own magnetic levitation device and you can too… if you have the patience. He’s not using electromagnets, like the Arduino levitator or the floating globe. Instead, a pair of ceramic ring magnets and a few hours are all it takes.
The base of his device is a couple of very large ring magnets that would most often be used in speakers. It’s hard to see them in the image above because there’s an inverted plastic container obscuring them. A second (or third depending on how you’re counting) ring magnet is selected because it is smaller than the circular void in the magnetic base. It’s impossible to simply balance the magnet in the air, but spinning it is a different story. By creating a perfectly balance magnetic top, then spinning it inside the magnetic field of the base, you can leave it floating in mid-air.
Check out the video after the break. It’s a neat effect, but you really do have to have a perfect setup for it to work. [Andrey] mentions that it takes a couple of hours to fine-tune. And if the ambient conditions change slightly, it throws the whole thing off.
Continue reading “Frustrating fun with magnetic levitation”
When working in hard to reach areas, magnetized tools can mean the difference between wrapping things up quickly and spending way too much time blindly grasping for dropped screws. [Damir] wrote in to share a handy little contraption he built which allows him to magnetize and demagnetize his tools as needed.
While rubbing a magnet against the tip of a screwdriver will impart a weak and temporary magnetic field, he felt that a stronger more permanently magnetized tool was far more useful. It is pretty well known that subjecting metal to a direct current magnetic field will magnetize the item, and an alternating magnetic field will demagnetize the same object. [Damir’s] wand will perform either task with the simple flip of a switch.
He salvaged the motor coil from a broken washing machine and mounted it in a project box, along with a single-pole changeover switch. A small diode is used to perform rectification on the AC input, providing the DC current required for magnetizing his tools.
Every once in awhile we find the need for magnetized tools, so we think this would be great to have around the workshop.
Check out a quick video demo of the magnetizing wand after the jump.
Continue reading “Salvaged coil magnetizes tools on demand”
You can get class credit for the coolest things these days. Take for instance, this Automatic Chessboard that [Brian] and [James] built for the final project in one of their classes this spring. We just looked at a robotic chess setup on Monday that used a gripper mounted on a gantry to move the pieces. This one’s a lot more user-friendly and borders on magical. That’s because the moving parts are all located below the board and could be hidden from view if a proper case were built around the edges.
There are two main components to this build. The first is a grid of reed switches that detect the moves made by a human. This works because each piece the human player uses has a weak magnet glued to the bottom which is just strong enough to actuate the reed switch and let the computer sense what move was just made. On the robotic side of things this works like a plotter. Each of the computer’s pieces has a metallic disc glued to the base. What basically amounts to a plotter under the board uses rare-earth magnets to grab the computer’s piece and drag it to the next playing position.
The use of two separate magnetic systems provides some interesting design challenges. You can see the device in action in the video after the break, and a full writeup and source code package is available at the blog linked at the top of this feature. But for your convenience we’ve also mirrored the PDF whitepaper after the break which lays bare all of the juicy details.
Continue reading “Automated chess set does it from below”
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.
Continue reading “Fabric speaker”
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.