ShakeIt – An Interactive Light Game

June 3, 2015 by 7 Comments

Learning becomes interesting when you make it fun, interactive and entertaining. [Arkadi] built ShakeIt – an interactive game for the Mini MakerFaire in Jerusalem to demonstrate to kids and grownups how light colors are mixed. It is a follow up to his earlier project – Smart juggling balls which we featured earlier.

The juggling balls consist of a 6 dof sensor (MPU 6050), a micro controller, transmitter (NRF24L01+), some addressable RGB LED’s and a LiPo battery. An external magnet activates a reed switch inside the balls and triggers them in to action. The ShakeIt light fixture consists of an Arduino Nano clone, NRF24L01+ with SMA Antenna, buck converter, 74 addressable RGB LED’s, and a bluetooth module. The bluetooth module connects to a smartphone app.

[Arkadi] starts out by handing three juggling balls, each with a predefined color (Red, Green, Blue). When the ball is shaken, the light inside the ball becomes stronger. The ShakeIt light fixture is used as a mixer. It communicates with the balls and receives the value of how strong the light inside each of the smart balls is, mixing them up, and generating the mixed color.

The fun starts when the interactive game mode is enabled. Instead of just mixing the light, the Light fixture generates patterns based on how strong the balls are shaken. At first the light fixture shows all three colors filling up the central ball. The three contenders then fight out to get their color to fill up the sphere completely until only one color remains and the winner is declared.

The kids might be learning some color theory here, but it seems the adults are having a “ball” playing the crazy game. If you’d like to build your own shoulder dislocating ShakeIt game, head over to [Arkadi]’s github repository for the ShakeIt and the Juggling Balls. Check the video below to see the adults having fun.

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Some Snap-Fits For Thought

June 3, 2015 by 15 Comments

While laser cutters, desktop mills, and 3D printers might be wonderful tools for rapid prototyping, it’s best to have a strong understanding on a few techniques to really “digitize” those sheets of Delrin and rolls of PLA into something meaningful. In a nutshell, we need to know how to cut-or-squirt parts that fit together.

[Yoav] has a few tips for HDPE. The first technique is a clip-on, clip-off feature meant for repeated use. The second joins two parts with a joint that can’t be removed except by removing a dowel pin, or other press-fit shaft that holds them together. The last technique is similar to the first, except it embeds the deforming geometry directly into the mating surfaces.

If you’re interested in some detailed design guides and a few equations, have a look at the Bayer Guide and DuPont Design Guide; both provide a detailed set of geometric techniques and information about their associated stresses and deflections.

Finally, if you’re looking for a triumph of snap-fit design, have a look at [Jonathan Ward’s] MTM Snap–a snap-fit desktop milling machine and the direct predecessor to the modern-day Othermill.

Thanks for the tip, [uminded]!

Hackaday Prize Entry: Welding Plastic Filament

June 2, 2015 by 13 Comments

There are a lot of neat toys and accessories that rely on 3D printing filament. The 3Doodler is a 3D printing pen, or pretty much an extruder in a battery-powered portable package. You can make your own filament with a Filastruder, and of course 3D printers themselves use up a lot of filament. [Bodet]’s project for this year’s Hackaday Prize gives those tiny scraps of leftover filament a new life by welding filament together.

The EasyWelder [Bodet] is designing looks a little bit like a tiny hair straightener; it has a temperature control, a power switch, and two tips that grip 1.7 or 3mm diameter filament and weld them together. It works with ABS, PLA, HIPS, Nylon, NinjaFlex, and just about every other filament you can throw at a printer. By welding a few different colors of filament together, you can create objects with different colors or mechanical properties. It’s not as good as dual extrusion, but it does make good use of those tiny bits of filament left on a mostly used spool.

Since the EasyWelder can weld NinjaFlex and other flexible filaments, it’s also possible to weld NinjaFlex to itself. What does that mean? Custom sized O-rings, of course. You can see a video of that below.

The 2015 Hackaday Prize is sponsored by:

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IoT Enabled Thomas The Tank Engine

June 2, 2015 by 6 Comments

This month the popular “Thomas the Tank Engine” toy celebrated its 70 anniversary. As a fun project, [tinkermax] wanted to bring this traditional toy into the age of IoT, while preserving its physical appearance and simple charm.

He used a model called the “Diesel” which seemed big enough to house the electronics, but proved otherwise once he inspected the innards. He needed to fit in an ESP8266 module, an accelerometer breakout, some discrete parts, a nifty analog multiplexer, and a 14500 3.7V LiPo. Once done, he was able to control its speed remotely over WiFi, with an auto “throttle-boost” that kicks in when the accelerometer senses that the train is going uphill, and has remote monitoring of battery state, engine load, inclination and track vibration – all in real-time using MQTT over WiFi. It’s quite a demonstration of the power of these super-cheap WiFi modules that are powering the current wave of IoT innovation.

The train motor works off a single 1.5V battery, so [tinkermax] tried a couple of boost converters to get the ESP-12 to work. But the modules were a tad bigger, and couldn’t provide the high peak current needed by the ESP-12. So he used a 14500 3.7V LiPo battery instead. A series diode drops the LiPo voltage to a circuit friendly 2.9V ~ 3.6V range. The ADXL345 accelerometer is used to measure “pitch” to detect going up and down a hill, “roll” to check for tilt or tip over and vibration to identify track defects. It communicates with the ESP-12 using a special Lite-SPI library that he wrote.

Two analog measurements are performed. One uses a resistor in series with the PWM driven motor to measure its current, with a low pass filter to smooth out PWM noise. The other is a resistor divider network used to monitor battery voltage. But the ESP-12 has just one ADC channel. Instead of adding another ADC module, [tinkermax] used a neat device – the FSA3157 – which allows two analog inputs to be channeled to a single output much like a SPDT switch. One PWM output is used to control motor speed and a second one to pulse a LED.

The sensor data is streamed 5 times a second over the MQTT protocol to a Raspberry Pi based MQTT broker. Finally, a JavaScript webpage receives the MQTT messages and plots the data graphically. One upgrade he would like to implement is speed measurement, to allow constant speed drive. If you have any ideas on how to extract that information from an accelerometer, chip in with your comments below. Check out his build log in the short video below. And if you’d like to see how all of this can be used in the real world, check this other video where [tinkermax]’s colleague gives a run down about a commercial enterprise IoT cloud platform hooked up to Thomas the Tank Engine.

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Solving Rubik’s Cube With An FPGA

June 2, 2015 by 17 Comments

For their final project for ECE 5760 at Cornell, [Alex], [Sungjoon], and [Rameez] are solving Rubik’s Cubes. They’re doing it with an FPGA, with homebrew robot arms to twist and turn a rainbow cube into the correct position.

First, the mechanical portion of the build. The team are using a system of three robot arms positioned on the left, right, and back faces of the cube relative to a camera. When a cube is placed in the jaws of this robot, the NTSC camera data is fed into an FPGA, where a Nios II soft core handles the actual detection of the cube faces, the solver algorithm, and the controller to send servo commands to the robot arms.

The algorithm used for solving the cube is CFOP – solve the white cross, the white corners, the middle layer, the top face, and finally the entire cube. In practice, the robot ended up taking between 60-70 moves. This is not the most efficient algorithm; the Thistethwaite algorithm only requires 52 moves. There’s a reason for this apparent inefficiency – the Thistlethwaite algorithm requires large look-up tables.

Once the cube is scanned and the correct moves are computed, the soft core in sends commands out through the FPGA’s GPIO pins. Each cube can be solved in under three minutes after it has been scanned, but the team ran into problems with scanning accuracy. It’s a problem that can be fixed with the right lighting setup and better aberrant cubie detection, and a great final project using FPGAs.

Video demo below.

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Fail Of The Week: The Deadliest Multimeter

June 2, 2015 by 144 Comments

Need a good multimeter? The Fluke 17B is an excellent basic meter that will last your entire career. It’s also $100 USD. Need something cheaper? Allow me to introduce the AIMOmeter MS8217. On the outside, it’s a direct copy of the Fluke 17b, right down to the screen printing but understandably lacking the yellow enclosure. $30 USD will get you an exact copy of a Fluke 17B, it would seem. Right? Not a chance. [electronupdate] did a teardown of the AIMOmeter, and while this meter looks like a Fluke on the outside, it’s probably going to kill somebody.

The teardown begins with a look at the ratings on the back of this off-brand meter. It does have two fuses, but the engraving on the back strangely claims ‘Wrrebt insurance limit’. If anyone has any idea what a ‘wrrebt’ is, please leave a note in the comments. The only references to this word in Google are mis-OCRed blackletter type in a book from the early 1800s.

Opening up the meter reveals – surprisingly – two real fuses in the meter. There were no markings on the bigger fuse, which could be a problem for verifying if the fuse is of the proper value. That’s not really a problem, though: the fuse isn’t even between ground and the amp probe socket. Yes, this fuse is completely useless, and testing the resistance with the fuse out of the circuit confirms this.

After putting the meter back together, [electron] tests the accuracy of the meter. With a 1 mA current source, the mA setting seems to work, but when testing the larger Amp range of this meter, the results display in milliVolts. Don’t worry, there’s an easy fix for that: just press the dial down just right and the correct setting will be displayed. Wow.

You get what you pay for, and if you only ever use an AIMOmeter for measuring Arduinos and batteries, you might – might – be alright. This is not the kind of meter you want to measure line voltage, motors, or anything else with, though.

Retrotechtacular: Cover Your CONUS With OTH-B Radar

June 2, 2015 by 13 Comments

If you’re a ham, you already know that the ionosphere is a great backboard for bouncing HF signals around the globe.  It’s also useful for over-the-horizon backscatter (OTH-B (PDF)) radar applications, which the United States Air Force’s Rome Laboratory experimented with during the Cold War.

During the trial program, transmit and receive sites were set up ninety miles apart inside the great state of Maine. The 1/2 mile-long transmit antenna was made up of four arrays of twelve dipole elements and operated at 1MW. An antenna back screen and ground screen further expanded the signal’s range. Transmission was most often controlled by computers within the transmit building, but it could also be manually powered and adjusted.

The receive site had 50-ft. antenna elements stretching 3900 feet, and a gigantic ground screen covering nearly eight acres. Signals transmitted from the dipole array at the transmit site bounced off of the ionosphere and down to the receive site. Because of step-scanning, the system was capable of covering a 180° arc. OTH-B radar systems across the continental United States were relegated to storage at the end of the Cold War, but could be brought back into service given enough time and money.

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