[Chris Gunawardena] is still holding his breath on Valve and Facebook surprising everyone by open sourcing their top secret VR prototypes. They have some really clever ways to track the exact location and orientation of the big black box they want people to strap to their faces. Until then, though, he decided to take his own stab at the 3D tracking problems they had to solve.
While they used light to perform the localization, he wanted to experiment with using electromagnetic fields to perform the same function. Every phone these days has a magnetometer built in. It’s used to figure out which way is up, but it can also measure the local strength of magnetic fields.
Unfortunately to get really good range on a magnetic field there’s a pesky problem involving inverse square laws. Some 9V batteries in series solved the high current DC voltage source problem and left him with magnetic field powerful enough to be detected almost ten centimeters away by his iPhone’s magnetometer.
As small as this range seems, it ended up being enough for his purposes. Using the existing math and a small iOS app he was able to perform rudimentary localization using EM fields. Pretty cool. He’s not done yet and hopes that a more sensitive magnetometer and a higher voltage power supply with let him achieve greater distances and accuracy in a future iteration.
Learning how magnets and magnetic fields work is one thing, but actually being able to measure and see a magnetic field is another thing entirely! [Stanley’s] latest project uses a magnetometer attached to a robotic arm with 3 degrees of freedom to measure magnetic fields.
Using servos and aluminium mounting hardware purchased from eBay, [Stanley] build a simple robot arm. He then hooked an HMC5883L magnetometer to the robotic arm. [Stanley] used an Atmega32u4 and the LUFA USB library to interface with this sensor since it has a high data rate. For those of you unfamiliar with LUFA, it is a Lightweight USB Framework for AVRs (formerly known as MyUSB). The results were plotted in MATLAB (Octave is free MATLAB alternative), a very powerful mathematical based scripting language. The plots almost perfectly match the field patterns learned in introductory classes on magnetism. Be sure to watching the robot arm take the measurements in the video after the break, it is very cool!
[Stanley] has graciously provided both the AVR code and the MATLAB script for his project at the end of his write-up. It would be very cool to see what other sensors could be used in this fashion! What other natural phenomena would be interesting to map in three dimensions?
Continue reading “Measuring Magnetic Fields with a Robotic Arm”
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.
Continue reading “Robotic eye surgery controlled with magnets”
What would you do if you were driving along the highway and you glanced into a field to see a giant array of fluorescent tubes lit wirelessly from the electromagnetic fields of power lines. Back in 2004, [Richard Box] set up this display after hearing about a friend playing “light saber” with fluorescent tubes under power lines. The tubes can be lit pretty easily by have a variation in voltage between the ends. By sticking one end in the ground and the other up in the air, he’s harnessing the strong magnetic field from the power lines. Though some thought the display was made to bring people’s attention to possible hazards of living near the lines, [Box] states that he did it just because it looked cool.