Automatic Antenna Tuner

January 6, 2014 by Eric Evenchick 48 Comments

To get the best power transfer into an antenna, tuning is required. This process uses a load to match the transmission line to the antenna, which controls the standing wave ratio (SWR).

[k3ng] built his own automatic antenna tuner. First, it measures the SWR of the line by using a tandem match coupler. This device allows the forward and reflected signals on the line to be extracted. They are buffered and fed into an Arduino for sampling. Using this data, the device can calculate the SWR. The RF signal is also divided and sampled to measure frequency.

To automate tuning, an Arduino switches a bank of capacitors and inductors in and out of the circuit. By varying the load, it can find the ideal matching for the given antenna and frequency. Once it does, the settings are stored in EEPROM so that they can be recalled later.

After the break, check out a video of the tuner clicking its relays and matching a load.

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Retro Chaser Sign Lights Up Your Life

January 5, 2014 by Adam Fabio 47 Comments

lighted-sign

[Gnsart] builds props often used in the film industry. He’s created an amazing retro Vegas style light chaser sign. The sign was started as a job a few years ago. While [Gnsart] could handle the physical assembly, the cost of a mechanical light chaser pushed the project over budget. The sign project was cancelled back then, but he never forgot it.

Fast forward to a few weeks ago. [Gnsart] happened upon the Arduino community. He realized that with an Arduino Uno and a commonly available relay board, he could finally build the sign. He started with some leftover cedar fence pickets. The pickets were glued up and then cut into an arrow shape. The holes for the lights were then laid out and drilled with a paddle bit. [Gnsart] wanted the wood to look a bit aged, so he created an ebonizing stain. 0000 steel wool, submerged and allowed to rust in vinegar for a few days, created a liquid which was perfect for the task. The solution is brushed on and removed just like stain, resulting in an aged wood. We’ve seen this technique used before with tea, stain, and other materials to achieve the desired effect.

[Gnsart] then built his edging. 22 gauge steel sheet metal was bent to fit the outline in a bending brake. The steel sheet was stapled to the wood, then spot welded to create one continuous piece. Finally, the light sockets were installed and wired up to the Arduino. [Gnsart] first experimented with mechanical relays, and while we love the sound, we’re not sure how long they’d last. He wisely decided to go with solid state relays for the final implementation. The result speaks for itself. LEDs are great – but there is just something about the warm glow of low-wattage incandescent lights.

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Roving Hexapod Poops Out 3D Prints

December 30, 2013 by Adam Fabio 21 Comments

[Jia Wu, Mary Sek, and Jeff Maeshiro], students at the California College of the Arts (CCA) in San Francisco, took on the task of developing a walking 3D printer. The result is Geoweaver, a hexapod robot with a glue gun extruder system. Hackaday has seen walking CNC machines before, but not a 3D printer. Geoweaver uses two servos on each of its six legs to traverse the land. The team was able to program several gaits into the robot, allowing it to traverse uneven terrain. Walking is hard enough on its own, but Geoweaver also uses a glue gun based extruder to make 3D prints. The extruder head uses two servos to swing in a hemispherical arc. The arc is mapped in software to a flat ~~plain~~ plane, allowing the robot to drop a dollop of glue exactly where it is programmed to. Geoweaver doesn’t include much in the way of on board processing – an Arduino Uno is used to drive the 15 servos. Those servos coupled with a glue gun style heater pull quite a bit of power, which has earned Geoweaver nicknames such as Servo Killer, Eater of Shields, Melter of Wires, and Destroyer of Regulators.

Geoweaver’s prints may not be much to look at yet, however the important thing to remember is that one of the future visions for this robot is to print on a planetary scale. Geoweaver currently uses reacTIVision to provide computer control via an “eye in the sky”. ReacTIVision tracks a fiducial marker on the robot, and applies it to a topographical map of the terrain. This allows Geoweaver to change its height and print parameters depending on the flatness of the ground it is printing on. On a scaled up Geoweaver, reacTIVision would be replaced by GPS or a similar satellite based navigation system. Most of the software used in Geoweaver is opensource, including Grasshopper and Firefly, written by the team’s professor, [Jason Kelly Johnson]. The exception is Rhino 5. We would love to see an option for a free or open source alternative to laying out ~$1000 USD in software for our own Geoweaver.

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Hackaday Links: December 29, 2013

December 29, 2013 by Mike Szczys 6 Comments

There are a ton of cheap RF transceiver boards available. [Martin] recently took a look at several of the most common ones and reports back on what you want to look for when acquiring wireless hardware for your projects.

Ikea picture frame plus old laptop equals a roll-your-own digital picture frame which [Victor] built. It runs Ubuntu and is more powerful and extensible than anything you could purchase outright.

Our friend [HowToLou] sure loves the FlowRider. So much so that he’s trying to figure out how to make them less expensive to operate. He put together an example of how he thinks a standing wave can be created that follows the rider as they move along the surfing area.

[Garrett] released an Arduino library that offers threading, debugging, and error handling. The usertools package can be downloaded from his Github repository.

There’s only one way to gauge your Christmas cheer — hook yourself up to the XMeter built by [Geoff]. He’s the same guy who built a breathalyzer a couple of years back. It flashes images of holiday activities on a television while measuring galvanic response using a couple of DIY probes.

And finally, play around with a virtual x86 system. [Fabian Hemmer] wrote the incredibly full-featured virtual machine in JavaScript. You can get your hands on the code via his GitHub repo. [Thanks Martin]

The Magnetophone

December 28, 2013 by Eric Evenchick 6 Comments

The Magnetophone is the latest electro-acoustic instrument from [Aaron Sherwood]. This tower contains 14 strings, and 14 hand-wound electromagnets. By energizing each electromagnet with a square wave, the strings can be vibrated to create music.

The brains of the device consist of an Arduino Mega attached to the top of the tower. The microcontroller has 6 timers, which allows for 6 notes to play at the same time. An open source tone library was used to generate square waves at the correct frequencies. These square waves are amplified by LM386 based circuits, which provide enough power to the coil to oscillate the string. By using square waves at specific frequencies, overtones of strings can be created.

This isn’t the first time we’ve seen [Aaron] combine strings and electronics. His Glockentar used solenoids to strike strings. However, this project provides new possibilities by allowing the rate of oscillation to be controlled precisely. You can see the instrument in action after the break.

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Quick Candy Sorting Machine

December 21, 2013 by Phillip Ryals 32 Comments

OCD. Sometimes things just get to you, like those pesky bags of randomly assorted candies. [Torsten] decided to build a sorting machine capable of sorting Skittles or M&Ms into separate cups by color at around 80 pieces per minute. It’s a great implementation, using an Arduino Duo. He based the code on the principles of a finite-state machine, in order to make it as quick as possible.

It works as you would expect: When a candy piece is loaded, the color is determined using an RGB sensor. A 360-degree servo is used to move the chute to the proper position, and interestingly, the system preemptively releases the candy before the chute is in position in order to maximize the speed. If you watch closely, you can see this behavior in the video (embedded after the break).

[Torsten] includes a complete bill of materials, if you’d like to try it for yourself. He also included a list of possible improvements.

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3D Scanner Using A Sharp Infrared Sensor

December 21, 2013 by Phillip Ryals 13 Comments

[Fernando] sent in a tip about a pet project he’s been working on. It’s an interesting take on a 3D scanner. He used a stepper motor to rotate the object being scanned, and an Arduino for control, but the real novelty is the way he used the sensor. [Fernando] mounted a Sharp GP2D120X on vertical surface, and used a second stepper motor to raise the sensor during the scan. As you can see in the videos (embedded after the break), this results in the scan being put together in an ascending spiral.

The Sharp sensor is cheap and decent, but you’re obviously not going to get amazing accuracy. Still, using the average of several measurements, he ends up with a decent result. Happily, [Fernando] has released the code, and it should be easy enough to repurpose it with a more accurate sensor. It would be interesting to see a laser-based sensor paired with this code.

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