Recapture Radio’s Roots with an Updated Regenerative Receiver

Crystal radios used to be the “gateway drug” into hobby electronics. Trouble was, there’s only so much one can hope to accomplish with a wire-wrapped oatmeal carton, a safety-pin, and a razor blade. Adding a few components and exploring the regenerative circuit can prove to be a little more engaging, and that’s where this simple breadboard regen radio comes in.

Sometimes it’s the simple concepts that can capture the imagination, and revisiting the classics is a great way to do it. Basically a reiteration of [Armstrong]’s original 1912 regenerative design, [VonAcht] uses silicon where glass was used, but the principle is the same. A little of the amplified RF signal is fed back into the tuned circuit through an additional coil on the ferrite rod that acts as the receiver’s antenna. Positive feedback amplifies the RF even more, a germanium diode envelope detector demodulates the signal, and the audio is passed to a simple op amp stage for driving a headphone.

Amenable to solderless breadboarding, or even literal breadboard construction using dead bug or Manhattan wiring, the circuit invites experimentation and looks like fun to fiddle with. And getting a handle on analog and RF concepts is always a treat.

[via r/electronics]

Derek Schulte: Path Planning for 3D Printers

[Derek Schulte] designed and sells a consumer 3D printer, and that gives him a lot of insight into what makes them tick. His printer, the New Matter MOD-t, is different from the 3D printer that you’re using now in a few different ways. Most interestingly, it uses closed-loop feedback and DC motors instead of steppers, and it uses a fairly beefy 32-bit ARM processor instead of the glorified Arduino Uno that’s running many printers out there.

The first of these choices meant that [Derek] had to write his own motor control and path planning software, and the second means that he has the processing to back it up. In his talk, he goes into real detail about how they ended up with the path planning system they did, and exactly how it works. If you’ve ever thought hard about how a physical printhead, with momentum, makes the infinitely sharp corners that it’s being told to in the G-code, this talk is for you. (Spoiler: it doesn’t break the laws of physics, and navigating through the curve involves math.)

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A Buck-Boost Converter from the Ground Up

DC to DC conversion has come a long way. What was once took an electromechanical vibrator and transformer has been reduced to a PC board the size of a largish postage stamp that can be had for a couple of bucks on eBay. So why roll your own buck-boost converter for the ground up? Maybe because sometimes the best way to learn is by doing.

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Building a Ball-Balancing Robot


If you want a different kind of feedback systems challenge, ditch the Segway-style robots and build one that can balance on a ball. UFactory is a startup in Shenzhen, and this impressive little guy is a way of showing their skills applied to the classic inverted pendulum. At nearly 18 inches tall and weighing just over six pounds, the robot boasts a number of features beyond an accelerometer and gyroscope: it has both a WiFi module and a camera, and can be controlled via a homemade remote control or a Kinect.

The build uses plastic omni-directional wheels attached to 3 brushed dc motors, which attach to the base of the robot with custom-made aluminum brackets. The UFactory gang constructed the robot’s body out of three acrylic discs, which hold the electronics directly above the wheels. The brain seems to be an STM32 microcontroller that connects up to the motors and to the sensors.

You won’t find the code on their Instructable yet, but according to the comments they have plans to make the entire project open source. If you’re desperate for more details, the UFactory team seems willing to provide source code and other information via email. Make sure you see the video after the break, particularly the end where they demonstrate interference and carrying loads. This isn’t the first ball pendulum we’ve seen; take a trip down memory lane with the BallP ball balancing robot from 2010.

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Causing trouble at RedBull Creation 2013

Skullduggery systems (a first time participant) came up with an extremely ambitious idea for their instrument. It was to be a jug, that would have a changing pitch based on water being pumped in and out. Ultimately, they ran into a few issues that meant that the effect wasn’t quite what they were looking for. They shouldn’t feel too bad, a bunch of teams didn’t succeed in making things the first year they participated.

What their instrument did do, however, I found simply delightful. The jug sounded just like feedback from the sound system. The contest was happening during a big music festival called the NorthSide festival.  There was a stage and a huge crowd most of the time.  They were testing their jug and we noticed that the band on stage (with a full crowd at the time), had stopped playing and was checking all their equipment. The sound guys were running around like crazy. They thought they were getting feedback.

We held off for a while and decided we would wait till sound checks to mess with them. While we wanted to cause trouble, we didn’t want to ruin the show for an entire crowd.  As you can see in the video, the sound is very much like feedback. They would begin to play, then stop to track down this mysterious feedback. We even tricked [Tyler] the announcer that was talking over our local sound system in the Redbull tent (by accident, I assure you).

Mouse and HDD combo show off your data gluttony


So we know you’ve got a lot of porn on your computer, but just how much is a lot? This concept mouse and hard drive combo aims to show you just how much digital junk you have acquired through physical feedback.

The DataBot mouse looks like a typical run of the mill scroll mouse that you might get with a new computer. Inside however, the designers have added a small servo which alters the ease with which the ball moves. The more files you have stuffed into the folder you are moving around, the more the mouse resists, giving you a sense of the physical “weight” of your computer’s contents.

The DataBot hard drive gives you a sense of how full your computer is by growing and shrinking based on space usage. During file transmissions the hard drive blinks its LEDs to indicate how fast or slowly your files are moving. When the inevitable file access error occurs, the LEDs switch to a bright red hue and the drive shakes to indicate there is a problem afoot.

With the price of data storage decreasing by the day, it’s easy to get lost in a glut of information without realizing just how much data you have. This is definitely an interesting way to get a different look at your data consumption.

Check out the videos below to see the pair in action.

[via Dvice]

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Complete the Hack A Day survey, win a shirt

Take our reader survey. Do it. Do it right now.  Do you think we should run more articles on the dietary needs of Llamas? Here is your chance to let us know.  We got a lot of great feedback from [Jason]’s post, and now we’re ready for more. We’ve put together 10 quick questions that will help us get a feeling for what you want. We will be choosing 5 participants at random to give free t-shirts (the basic logo one).

Update: While we wait for our survey slave to get the changes made, please just put something in the fields that are mandatory(questions 7-9). Even if you put “no opinion”, we’ll get good info from the rest of the survey.