Accelerometer Poi


Even if you’ve never attended a rave, you have probably seen one portrayed on film or television. Those glowing spheres-on-a-string being swung around are called poi, and [Matt Keeter] has designed a pair with an accelerometer upgrade. Poi have a long history and were originally made from plants, but contemporary examples usually feature some kind of light, whether it’s fire, LEDs, or even glowsticks tied to shoelaces.

This build required double-sided PCBs and [Matt] had to custom make the protective covering that slips over the board. The poi are powered by 2 AA batteries fed into a 5V boost regulator. But wait, no microcontroller and no PWM? Actually, we think it’s quite clever that [Matt] took the output from the accelerometer and fed into an inverting amplifier. This keeps the voltage constant while allowing the accelerometer to vary the current. Had he used PWM, the fast motion of the swinging poi would instead produce a blinking effect.

An additional trimmer potentiometer accounts for variability in the accelerometers’ output by adjusting the default brightness. If the recent recap of Burning Man has you excitedly planning to attend next summer, you’d probably find plenty of opportunities to use these in the desert.

24-hour hackathon produces respectable accelerometer labyrinth


We’re not sure if this was some type of corporate team building, but if it was sign us up for the next one. [Filipp], [Saluka], and [Michael] participated in a recent 24-hour hackathon hosted by Microsoft. They whipped up this labyrinth game controlled by a Nexus 4 Android phone.

This thing looks so well crafted we’re shocked that it’s a 24-hour build. Just putting together the walls of a maze that size takes some time. They then mounted it in a gimbaled frame which tilts the using servos. Check out the demo video below to get a look at the underpinnings. There are several elastic bands connecting the base to the maze. These act as shock absorbers to help keep the movement smooth and to prevent any oscillations from the frame flexing. For us this is an important design element that we’ll keep in mind (just in case we need to win another competition by designing a labyrinth).

An Arduino controls the servos, using Bluetooth to communicate with the phone. The team mentions some filtering used to help make the user experience more natural but we didn’t see many details on this aspect of the hack.

Continue reading “24-hour hackathon produces respectable accelerometer labyrinth”

Motorized skateboard controlled by hand gestures


This rough-looking contraption is a hand gesture controlled skateboard which [Aditya] built using parts on hand. So far the sensor for hand gestures is connected by a control wire, but he hopes to transition to an RF unit at some point in the future.

Having access to a couple of high torque brushless motors is what turned him onto the project. He hit up a couple of Mechanical Engineer friends of his to help assemble the chassis and then started on the electronics side of things. A breakout board for an ATmega16 is mounted on the corner of the deck. It monitors an accelerometer which acts as steering as well as throttle. The accelerometer had been abused in a previous project so he had to add an extra switch to bolster his available inputs. We were glad to hear that he also included a kill switch, since putting the control of those motors in the hands of a damaged accelerometer is a bit sketchy.

We remember seeing a similar trike design a few years back. That one powered a single rear wheel while this one powers two wheels and uses a caster for the third.

Prosthetic spines become musical instruments


[Joseph] and [Ian] have been working on a project that turns physical objects into bendable, snake-like controllers

This build is the culmination of an earlier project that digitally modeled a flexible object with accelerometers, gyroscopes, and IMUs. When we first saw this build, we wondered what it could actually be used for, but it seems [Joseph] and [Ian] came up with a pretty cool use for it: turning prosthetic spines and ribs into musical instruments.

These flexible devices are loaded up with sensors along their joints and are connected to a microcontroller with a Zigbee radio transceiver. The positioning data from these devices is transmitted to a computer where it’s turned into audio, effectively turning a dancer into a musical instrument.

For an art piece, it’s pretty cool, but as a new means of interacting with a computer, we’re thinking this might be a game changer. Imagine a gauntlet loaded up with IMUs being turned into a waldo, or precisely controlling virtual objects naturally with your hand.

DIY Airbag, explosions included


Your car’s airbag is one of the major engineering accomplishments of the auto industry. In an accident, a whole host of processes must take place in sequence to keep your face from slamming into the steering wheel, and  everything must happen in just a fraction of a second. [Steve] over at Make thought it would be a cool idea to discover what actually goes in to saving a life with an airbag and decided to build his own.

The electronics of the build consisted of an accelerometer and an Arduino. A lot of research, development, and experimentation has gone into the algorithms that trigger airbags, but [Steve] decided to keep things simple: when a sudden acceleration is detected, set off a small charge of black powder.

The airbag itself is ripstop nylon reinforced with canvas, contained in a small wooded box fitted with hinged doors. All these components are put on wheeled aluminum test rig, manned with a honeydew melon crash test dummy, and pulled into a short wall at a few miles per hour.

Despite [Steve] not putting hundreds of thousands of man hours into the development of his airbag – unlike the ones you’ll find in your steering column – his device actually worked pretty well. While not a complete success, he did manage to come up with something that both looks and acts like the familiar device that has saved countless lives.

Rocketduino, for high-G, high altitude logging


Although the thrill of launching rockets is usually found in their safe decent back to Earth, eventually you’re going to want some data from your flight. Everything from barometric pressure, GPS logging, and acceleration data is a useful thing to have, especially if you’re trying to perfect your craft. [zortness] over on reddit created a data logging board created especially for amateur rocketry, a fabulous piece of work that stands up to the rigors of going very fast and very high.

The design of the board is a shield for the Arduino Mega and Due, and comes with enough sensors for over-analyzing any rocket flight. The GPS logs location and altitude at 66Hz, two accelerometers measure up to 55 G. Barometric, temperature, and compass sensors tell the ground station all the data they would need to know over a ZigBee 900MHz radio link.

Because this is an Arduino, setting up flight events such as deploying the main and drogue chutes are as easy as uploading a bit of code. [zortness] built this for a 4″ diameter rocket, but he says it might fit in a 3″ rocket. We just can’t wait to see some videos of it in action.

Rate Gyroscope circuitry explained


Hackaday alum [Adam Munich] shot a tutorial video on using a rate gyroscope.

Here he’s showing off the really fancy piece of ancient (technologically speaking) hardware. It would have set you back about fifteen grand in the 1960’s (inflation adjusted) but can be had these days for around $30. What a deal! These are not small, or power efficient when compared to the components that go into smart phones or gaming controllers, but they’re a heck of a lot more accurate than the ubiquitous modern parts. That’s because a rate gyroscope — which is the gold cylinder on the left — actually incorporates a spinning motor and a way to monitor how it is affected by changes in gravity. The driver/interface circuitry for this gets hairy relatively fast, but [Adam] does a solid job of breaking down the concept into smaller parts that are easy to manage.

Wondering what is different about this compared to a MEMS accelerometer? We know they’re really not the same thing at all, but wanted a chance to mention [The Engineer Guy’s] video on how those parts are made.

Continue reading “Rate Gyroscope circuitry explained”