DIY Newton’s Cradle Uses Parts Designed on a Smart Phone

Injection Molded Parts

As far as physics demonstrations go, the Newton’s Cradle is probably one of the most recognizable. Named after Sir Isaac Newton, the Newton’s Cradle demonstrates the law of conservation of momentum using swinging ball bearings.

[Scorchworks] decided he wanted to build his own Newton’s Cradle. The frame appears to be cut from MDF or particle board and then screwed together. That material is really easy to obtain and also to work with using inexpensive tools. The tricky part was the ball bearings. Most of the time when you see a Newton’s Cradle, the ball bearings have a small hole drilled in the top with an eye hook attached. The string is then attached to the eye hook.

[Scorchworks] decided to do something different. His plan was to make custom injection molded plastic rings that would fit perfectly around the ball bearings. The most interesting thing is that he designed the injection molding plates entirely on his smart phone while at his child’s baseball practice. To do this, [Scorchworks] used his own Android app, ScorchCAD. ScorchCAD is a free clone of OpenSCAD that is designed to run on Android devices. Most of the functionality of OpenSCAD has been implemented in ScorchCAD, though not all functions work yet. You can find a list of all the supported functions on the project’s website or in the Google Play store.

Once the plates were designed within ScorchCAD, [Scorchworks] exported the STL file and then used Meshcam to generate the gcode for his CNC milling machine. Once he had the plates machined, he just placed the ball bearing into the mold and injected the molten plastic around it. The plastic formed a perfectly shaped ring around the bearing with small loops for the string. [Scorchworks] repeated the process several times to get all of the ball bearings finished.

Finally, the bearings were strung up using some fishing line. A Newton’s Cradle is very sensitive to the positioning of the ball bearings. To account for this, [Scorchworks] tied each end of the fishing line to two different screws on top of the cradle. This way, each screw can be tightened or loosened to adjust the position of each ball bearing.

Android Based Wireless ECG

ECG

The title of [Nuclearrambo's] post says it all, “Android based wireless ECG monitoring (Temperature sensor and glucometer included).” Wow! What a project!

The project is built around the HC-06 bluetooth module and the Stellaris LaunchPad from TI, an inexpensive ARM developer kit. Building an ECG is a great way to learn about instrumentation amplifiers, a type of differential amplifier used for its extremely high common mode rejection ratio (CMRR). Please be sure to keep in mind that there are a myriad of safety issues and regulation concerns for medical device, and there is no doubt that an ECG is considered a medical device. Sadly, [Nuclearrambo's] post does not include all of the code and design files you need to build the system, which is understandable considering this is a medical device. That being said, he provides a lot of information about building high-quality ECG instrumentation and the web interface.

It would be great if [Nuclearrambo] could post the Android application code and Stellaris LaunchPad code. Even with these omissions, this post is still worth reading. Designing medical devices requires a lot of know-how, but who knows, maybe your next project can save your life!

Magsafe On An Android, Cats And Dogs Living Together

Mag

We’re thinking most Hackaday readers have at one time or another been tasked with replacing the power connector in a laptop. Anyone who has done so can easily see the genius behind the Apple Magsafe connector. Since the second gen iPhone, there have been rumors Apple will release a cellphone with the Magsafe connector, a great idea, seeing as how cell phones are thrown around even more than laptops. [Tony] got tired of waiting, and had an Android device anyway, so he decided to retrofit a Magsafe power adapter to his Note II.

In the interest of excess, [Tony] is using the absurdly large ZeroLemon 9300mAh battery and case for his device, giving him a lot of room for this hardware mod. A tiny 3D printed adapter fits around a slightly modified Magsafe connector, and with a little bit of super glue and solder, the connector is wired up to the charging port.

Of course the charger isn’t a stock Apple power supply; it’s just another Magsafe plug wired into a 5V wall wart. We’re not going to take a guess at what would happen if [Tony] plugged a stock Apple charger into his modded phone, but the mod works perfectly without the danger of ripping a USB port out of his phone.

Open Source Humanoid Robot Is Awesom-o

awesome-o

Coming from a lab in France is The Poppy Project, an open source humanoid robot that’s at least as cool as ASIMO.

Poppy was designed as an affordable bipedal robot for use in education and art. It’s a small robot at just over 80 cm in height, but it can walk, move its arms, rotate its torso, and interact with bags-of-meat humans with two cameras and an LCD face.

Although Poppy is open source, that doesn’t mean it’s exactly cheap; the current design includes twenty-one Robotis Dynamixels MX-28 robotic actuators, actually servos with magnetic encoders, temperature sensor, and an ARM microcontroller. These actuators sell for about $200, meaning Poppy contains $4000 in motors alone. The estimated cost of the entire robot is €7500-8000, or about $10,000 to $11,000 USD.

Still, there’s an incredible software platform that comes along with Poppy, and being open source any enterprising engineer can take up the project and attempt to bring the costs down. We’d love to take one out for a walk. Just get rid of the hands. That’s too far down the uncanny valley for us. Video below.

 

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NFC Ring Unlocks Your Phone

NFC Ring

This little ring packs the guts of an NFC keyfob, allowing [Joe] to unlock his phone with a touch of his finger.

The NFC Ring was inspired by a Kickstarter project for a similar device. [Joe] backed that project, but then decided to build his own version. He took apart an NFC keyfob and desoldered the coil used for communication and power. Next, he wrapped a new coil around a tube that was matched to his ring size. With this assembly completed, epoxy was used to cast the ring shape.

After cutting the ring to size, and quite a bit of polishing, [Joe] ended up with a geeky piece of jewelry that’s actually functional. To take care of NFC unlocking, he installed NFC LockScreenOff. It uses Xposed, so a rooted Android device is required.

We’ll have to wait to see how [Joe]‘s homemade solution compares to his Kickstarter ring. Until then, you can watch a quick video of unlocking a phone with the ring after the break.

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A Cocktail Shaker With Android And Arduino

drinks

The most rewarding part of any project must be sitting down to see the fruits of your labors set in action for the first time and relaxing with a nice drink. [Tony DiCola] is really showing off his ability to think ahead, because his smart cocktail shaker takes care of the post-build celebration, measuring out drinks with exacting precision.

The build measures out precise amounts of any liquid with the help of a small electronic scale [Tony] picked up from Harbor Freight. Instead of trying to interface with the electronics in the scale, he instead connected a INA125 instrument amplifier to the load cell. An Arduino micro measures the weight on the load cell, and with the known densities of gin, vermouth, and Kahlua, [Tony] can get a very good idea of how much liquid is in the cocktail shaker.

The really neat part of this build is the interface: [Tony] wrote an Android app for his tablet that talks to the Arduino with an Adafruit Bluefruit Bluetooth adapter. The app receives the current weight on the load cell, displays the current amount of liquor in the cocktail shaker, and provides step-by-step instructions for making any cocktail.

It’s a handy little device to keep around the liquor cabinet, and with an absurd amount of pumps and valves could easily become the basis for a very cool cocktail bot.

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An Android Controlled Arduino Drone

Drone

Who among us has not wanted to create their own drone? [Stefan] wrote in to tell us about a project for high school students, where a Styrofoam glider (translated) is converted into an Android (or PC) controlled drone.

[Stefan] tells us that the inspiration for this project comes from 100 years ago, when “steam-engines were THE thing” and children became introduced to modern technology with toy engines. “Today, mechatronic designs are all around us and this is an attempt to build the equivalent of the toy steam engine.” This project showcases how modern tools make it easy for kids to get involved and excited about hardware hacking, electronics, and software.

At the heart of the glider is an Arduino Pro Mini which communicates with either a computer or an Android phone via Bluetooth. It is especially interesting to note that the student’s used Processing to create the Android app, rather than complicating things by using Eclipse and Android Development Tools (ADT). While the more detailed PDF documentation at the end of the project page is in German, all of the Processingand Arduino code needed to build the project is provided. It would be awesome to see more Bluetooth related projects include a simple Android application; after all, many of us carry computers in our pockets these days, so we might as well put them to good use!

Do you have any well documented projects that introduce young and budding engineers to hardware or software hacking? Let us know in the comment section or send us a tip!

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