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Lost PLA Casting With a Little Help From Your Microwave

lost-pla

[Julia and Mason] have been perfecting their microwave-based lost PLA casting technique over at Hackaday.io. As the name implies, lost PLA is similar to lost wax casting techniques. We’ve covered lost PLA before, but it always involved forges. [Julia and Mason] have moved the entire process over to a pair of microwaves.

Building on the work of the FOSScar project, the pair needed a way to burn the PLA out of a mold with a microwave. The trick is to use a susceptor. Susceptors convert the microwave’s RF energy into thermal energy exactly where it is needed. If you’ve ever nuked a hot pocket, the crisping sleeve is lined with susceptor material. After trying several materials, [Julia and Mason] settled on a mixture of silicon carbide, sugar, water, and alcohol for their susceptor.

The actual technique is pretty simple. A part printed in PLA is coated with susceptor. The part is then placed in a mold made of plaster of paris and perlite. The entire mold is cooked in an unmodified household microwave to burn out the PLA.

A second microwave with a top emitter is used to melt down aluminum, which is then poured into the prepared mold. When the metal cools, the mold is broken away to reveal a part ready to be machined.

We think this is a heck of a lot of work for a single part. Sometimes you really need a metal piece, though. Until metal 3D printing becomes cheap enough for everyone to do at home, this will work pretty well.

The ChipWhisperer At Defcon

We’ve seen [Colin]‘s entry to The Hackaday Prize before. After seeing his lightning talk at Defcon, we had to get an interview with him going over the intricacies of this very impressive piece of hardware.

The ChipWhisperer is a security and research platform for embedded devices that exploits the fact that all security measures must run on real hardware. If you glitch a clock when a microcontroller is processing an instruction, there’s a good probability something will go wrong. If you’re very good at what you do, you can simply route around the code that makes up the important bits of a security system. Power analysis is another trick up the ChipWhisperer’s sleeve, analyzing the power consumption of a microcontroller when it’s running a bit of code to glean a little information on the keys required to access the system. It’s black magic and dark arts, but it does work, and it’s a real threat to embedded security that hasn’t had an open source toolset before now.

Before our interview, [Colin] did a few short and sweet demos of the ChipWhisperer. They were extraordinarily simple demos; glitching the clock when a microcontroller was iterating through nested loops resulted in what can only be described as ‘counter weirdness’. More advanced applications of the ChipWhisperer can supposedly break perfectly implemented security, something we’re sure [Colin] is saving for a followup video.

You can check out [Colin]‘s 2-minute video for his Hackaday Prize entry below.

[Read more...]

Hands Free Recording – Looks Silly but is Super Effective

Video goggles

While most hackers probably like to claim they’re good at everything, no one is good at filming one-handed. Setting up a tripod and adjusting it every shot can be tedious — wouldn’t it be great if you could just film what you see?

That’s what inspired [Hans de Bruin] to make these camera goggles. He’s using those big old school safety glasses that you can remove the glass lenses from. From there he traced the outline and 3D printed an adapter that would fit snugly in the glasses while holding up a video camera — He’s using a Chinese version of the GoPro called the SJ4000, but it should fit a real one too.

But wait, you’ll get a headache staring into one pixeley LCD screen! [Hans] also added a biconvex optical lens between his eye and the camera – it’s the same kind used in Google’s Cardboard VR kit.

Sound like a tool you could use? Head on over to Thingiverse to grab the files and print it out!

Steam Gauge Keeps Track of Your Internet Usage

Pressure Gauge Used to Monitor Internet Usage

There’s a certain appeal to analog gauges in a vastly digital world. [Ed Konowal] is a Network Operations Supervisor for a school district in Florida — part of his job is to ensure a stable and fast internet connection, so he decided to make an internet usage gauge for his office.

What we really like about this hack is the fact that [Ed] had no idea how to do it. It’s a simple enough idea, right? Google was his friend and Ed started learning about all kinds of things. Raspberry Pi’s and Arduinos, wireless receiver/transmitters, servos and steppers, Python…

After quite a bit of trial and error, [Ed] eventually settled on a wired design which uses a Raspberry Pi running a Python program to poll the internet bandwidth, which in turn calculates the servo position for the dial and sends that number to the Arduino to move it into position. This repeats every 10 seconds. Pretty cool!

Kind of reminds us of this project to make custom gauges using a stepper motor breakout board!

[Thank Justin!]

Faucet Add-On Attempts to Save Water by Changing Colors

FU8WVVBHW6T8E8I.LARGE

This augmented water device was rapidly developed during an H2O hackathon in Lausanne, Switzerland. It was built by a software engineer code-named [tamberg]. His creation contained an Arduino Uno, a strip of NeoPixels, a liquid flow sensor, and a tiny lithium-ion battery attached to a cut medical tube that was re-purposed for monitoring water use.

From the looks of it, this project addressed a specific problem and went on to solve it. The initial prototype showed a quick and dirty way to monitor precious water that is literally being flushed down the drain.

To see how the device was made, click the first link posted above for a set of Instructables. Code for the device can be found on [tamberg]‘s bitbucket account. A demo video of the device being tested on a sink can be seen after the break.

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A MIPI DSI Display Shield/HDMI Adapter

MIPI DSI shield

[Tomasz] tipped us about the well documented MIPI DSI Display Shield / HDMI Adapter he put on hackaday.io. The Display Serial Interface (DSI) is a high speed packet-based interface for delivering video data to recent LCD/OLED displays. It uses several differential data lanes which frequencies may reach 1 GHz depending on the resolution and frame rate required.

The board explained in the above diagram therefore allows any HDMI content to be played on the DSI-enabled scrap displays you may have lying around. It includes a 32MB DDR memory which serves as a frame buffer, so your “slow” Arduino platform may have enough time to upload the picture you want to display.

The CP2103 does the USB to UART conversion, allowing your computer to configure the display adapter internal settings. The platform is based around the XC6SLX9 Spartan-6 FPGA and all the source code may be downloaded from the official GitHub repository, along with the schematics and gerbers. After the break we’ve embedded a demonstration video in which a Raspi drives an iPhone 4 LCD.

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Retrotechtacular: Forces Acting On An Airfoil

floating film title We’ve probably all experimented with a very clear demonstration of the basic principles of lift: if you’re riding in a car and you put your flattened hand out the window at different angles, your hand will rise and fall like an airplane’s wing, or airfoil. This week’s Retrotechtacular explains exactly how flight is possible through the principles of lift and drag. It’s an Army training documentary from 1941 titled “Aerodynamics: Forces Acting on an Air Foil“.

What is an airfoil? Contextually speaking, it’s the shape of an airplane’s wing. In the face of pressure differences acting upon their surfaces, airfoils produce a useful aerodynamic reaction, such as the lift that makes flight possible. As the film explains, the ideas of lift and drag are measured against the yardstick of relative wind. The force of this wind on the airfoil changes according to the acute angle formed between the airfoil and the direction of the air flow acting upon it. As you may already know, lift is measured at right angles to the relative wind, and drag occurs parallel to it. Lift is opposed by the weight of the foil, and drag by tension.

wind tunnel testing

Airfoils come in several types of thicknesses and curvatures, and the film shows how a chord is derived from each shape. These chords are used to measure and describe the angle of attack in relation to the relative wind.

The forces that act upon an airfoil are measured in wind tunnels which provide straight and predictable airflow. A model airplane is supported by wires that lead to scales. These scales measure drag as well as front and rear lift.

In experimenting with angles of attack, lift and drag increase toward what is known as the stalling angle. After this point, lift decreases abruptly, and drag takes over. Lift and drag are proportional to the area of the wing, the relative wind velocity squared, and the air density. When a plane is in the air, drag is a retarding force that equals the thrust of the craft, or the propelling force.

monometer tubesAirfoil models are also unit tested in wind tunnels. They are built with small tubes running along many points of the foil that sit just under the surface. The tubes leave the model at a single point and are connected to a bank of manometer tubes. These tubes compare the pressures acting on the airfoil model to the reference point of atmospheric pressure. The different liquid levels in the manometer tubes give clear proof of the pressure values along the airfoil. These levels are photographed and mapped to a pressure curve. Now, a diagram can be made to show the positive and negative pressures relative to the angle of attack.

In closing, we are shown the effects of a dive on lift as an aircraft approaches and reaches terminal velocity, and that lift is attained again by pulling slowly out of the dive. Remember that the next time you fly your hand-plane out the window.

[Read more...]

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