Fishing For Radio Signals With The Moxon Antenna

July 23, 2014 by Adam Fabio 4 Comments

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[Bill Meara] has finished his latest project, a Moxon antenna for HF on 17 meters. [Bill] is well-known here on Hackaday. When not building awesome radios, he can be found ranting about ham radio. His new antenna turned out to be a true hack. He even used a hacksaw to build it!

The Moxon antenna is named for the late [Les Moxon, G6XN] who first described it in “Two-Element Driven Arrays”, a QST magazine article published in July of 1952. [Bill] built his Moxon loosely based on [Jim/AE6AC’s] excellent instructions. The design is incredibly simple – a two element directional antenna using crappie fishing poles as spreaders. That’s crappie as in the fish, not the quality of the pole. Crappie poles are typically made up of telescoping sections of graphite or fiberglass in common lengths of 14, 16, and 20 feet. The poles can be bought for under $20 at sporting goods stores. [Bill] used 16 foot poles purchased from Amazon.

The antenna is created by connecting all four poles at their bases in an X shape. The wire elements are stretched across the ends of the poles. The entire antenna bends up as the stiff poles hold the driven and reflector elements in tension. [Bill] used some scrap wood and U-bolts to attach the fishing poles, and bungee cord ends at the tips. Since the antenna is directional, [Bill] added a TV antenna rotor to spin the beam around. The antenna is so light that one could get by with a couple of cords and the “Armstrong method” of antenna rotation.

Once up on the roof, [Bill] found his antenna really performed. He was easily able to cross the Atlantic from his Northern Virginia home to France, Belgium, and Latvia. The mostly horizontal antenna makes it a bit more unobtrusive than other directional designs. [Bill] mentions that his neighbors haven’t revolted yet, so he’s continuing to enjoy the fruits of his antenna labors.

POV Display Does It On The Cheap

July 23, 2014 by Adam Fabio 15 Comments

[Sholto] hacked together this ultra low-budget spinning display. He calls it a zoetrope, but we think it’s actually an LED based Persistence Of Vision (POV) affair. We’ve seen plenty of POV devices in the past, but this one proves that a hack doesn’t have to be expensive or pretty to work!

The major parts of the POV display were things that [Sholto] had lying around. A couple of candy tins, a simple brushed hobby motor, an Arduino Pro Mini, 7 green LEDs, and an old hall effect sensor were all that were required. Fancy displays might use commercial slip rings to transfer power, but [Sholto] made it work on the cheap!

The two tins provide a base for the display and the negative supply for the Arduino. The tins are soldered together and insulated from the motor, which is hot glued into the lower tin. A paper clip contacts the inside of the lid, making the entire assembly a slip ring for the negative side of the Arduino’s power supply. Some copper braid rubbing on the motor’s metal case forms the positive side.

[Sholto] chose his resistors to slightly overdrive his green LEDs. This makes the display appear brighter in POV use. During normal operation, the LEDs won’t be driven long enough to cause damage. If the software locks up with LEDs on though, all bets are off!

[Sholto] includes software for a pretty darn cool looking “saw wave” demo, and a simple numeric display. With a bit more work this could make a pretty cool POV clock, at least for as long as the motor brushes hold up!

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Raspberry Pi Turns A Novelty Radio Into A Real Computer

July 15, 2014 by Adam Fabio 32 Comments

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[Strider19] remembers the 90’s, and a great little novelty radio he had back then. Shaped like a computer, the radio was a typical AM/FM affair, with the monitor serving as a speaker. His original radio was long gone, but [Strider19] was able to find a replacement on everyone’s favorite auction site. With the replacement radio in hand, he set his plan in motion: Turning it into an epic Raspberry Pi Case.

The Raspberry Pi fit great, but [Strider19’s] 3.5″ composite monitor didn’t quite make it. Following in [Ben Heck’s] footsteps, [Strider19] cut the LCD’s control PCB down to fit the case. A piece of clear polycarbonate protects the fragile LCD from poking fingers. The monitor’s button board, two USB ports, and an external composite input mounted nicely inside the former battery compartment at the rear of the CRT. There’s even enough room back there to hide a USB WiFi adapter.

The Raspi itself fit perfectly into the base of the radio, along with a DC to DC converter, USB hub, real-time clock module, and a whole bunch of wires used to extend the connectors.

The final result is awesome! Thanks to a request on [Strider19’s] Reddit thread, we have pictures of Doom running on a (former) radio. Even Windows 3.1 runs under DosBox, though it took a bit of tweaking to get the display settings just right. Now [Strider19] just needs to figure out how to turn that tiny keyboard into a working model. We think some old school cell phone keyboard hacking may be in order!

Independent Wheel Drive R/C Car

July 12, 2014 by Adam Fabio 30 Comments

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The picture above looks like a standard four-wheel drive (4WD) touring car. As one looks closer, a few strange things start to pop out. Where’s the motor? 4 electronic speed controls? What’s going on here? [HammerFET] has created this independent drive R/C car (YouTube link) as a research platform for his control system. The car started off life as a standard Schumacher Mi5 1/10th scale Touring Car. [HammerFET] removed the entire drive system. The motor, differentials, belt drive, and ESC all made for quite a pile of discarded hardware.

He replaced the drive system with 4 Turnigy brushless outrunner motors, installed at the chassis center line. To fit everything together, he had to 3D print new drive cups from stainless steel. The Mi5’s CVD drive shafts had to be cut down, and new carbon fiber suspension towers had to be designed and cut.

The real magic lies in [HammerFET’s] custom control board. He’s using an STM32F4 ARM processor and an InvenSense MPU-6050 IMU which drone pilots have come to know and love. Hall effect sensors mounted above each motor keep track of the wheel speed, much like an ABS ring on a full-scale car.

[HammerFET’s] software is created with MATLAB and SimuLink. He uses SimuLink’s embedded coder plugin to export his model to C, which runs directly on his board. Expensive software packages for sure, but they do make testing control algorithms much simpler. [HammerFET’s] code is available on Github.

Since everything is controlled by software, changing the car’s drive system is as simple as tweaking a few values in the code. Front and rear power offset is easily changed. Going from a locked spool to an open differential is as simple as changing a value from 0 to 1. Pushing the differential value past 1 literally overdrives the differential. In a turn, the outer wheel will be driven faster than it would be on a mechanical differential, while the inner wheel is slowed down. Fans of drifting will love this setting!

[HammerFET] is still working on his software, he hopes to implement electronic torque vectoring. Interested? Check out the conversation over on his Reddit thread.

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The Hacklet #7 – MIDI

July 11, 2014 by Adam Fabio 14 Comments

This week’s Hacklet is all about Hackaday.io projects which use MIDI, or Musical Instrument Digital Interface for the uninitiated. MIDI was designed from the ground up as an open communications standard for musical instruments. Nearly every major instrument company participated in the design of the standard. MIDI was first demonstrated in January of 1983, with the communications standard document following in August. Hackers, makers, and musicians immediately ran with it, using MIDI to do things the designers never dreamed of.

[Robert’s] 9×9 Pixel Muon Detector/Hodoscope is a great example of this. [Robert] is using 18 Geiger Muller Tubes to detect cosmic particles, specifically muons. The tubes are stacked in two rows which allows him to use coincidence detection. Rather than just plot some graphs or calculate impact probabilities, [Robert] hacked a Korg Nanokey 2 MIDI controller to output MIDI over USB messages corresponding to the detected muons. Check out his video to see a sample of the music of the universe!

Next up is [Michele’s] DIY MPC style MIDI controller. [Michele] needed a simple low-cost drum controller that wouldn’t wake his neighbors. He loved Akai MPC controllers, so he rolled his own. [Michele] investigated force sensitive resistors but found they were very expensive. At a cost of $8 USD each, his resistors alone would be nearly the cost of a low-end MPC! [Michele] created his own sensitive pads using a sandwich of copper tape and 3M Velostat conductive sheets. An HCF4067 routes all the analog lines to a single pin of Teensy 3.0, which then converts the analog resistor outputs to MIDI messages.

[Johan] loves his analog synths, and wanted them to be able to talk MIDI too. He built MIDI2VC, a circuit which converts MIDI to 1V/Octave (similar to CV/Gate). 1V/Octave is an analog control system used in some early synthesizers, as well as many modern analog creations. Pitches are assigned voltages, and as the name implies, each octave is 1 volt. A4 on the keyboard is represented by 4 volts, while A5 is 5 volts. [Johan] used a Microchip PIC16LF1823 to receive and convert the MIDI signals. The PIC outputs I2C data to an MCP4725 DAC which drives the analog side of the house.

Long before DMX512 came on the scene, hackers were controlling lights via MIDI. [Artis] continues this with El Dance, a wireless system for controlling electroluminescent wire worn by dancers. Similar in function to [Akiba’s] EL wire system, [Artis] took a lower cost route and used the venerable NRF24L01 radio module. He added an antenna which gives the modules a range of about 30 meters. The computer running the dance routine’s music sees the transmitter side of the link as a MIDI instrument. Standard note on and off commands activate the EL wire strings.

Our final hack comes from [Jen] who built a MIDI Vibrator Inductor Synth. [Jen] performs in an experimental music band called My Wife, with instruments as varied as violins and sewing machines. [Jen] must be a fan of Van Halen’s Poundcake as she’s using a similar technique, with a MIDI twist. An Arduino converts MIDI notes to analog values, which are sent to a motor controller board. The motor controller uses PWM to drive a vibrator motor at the frequency of the note being played. Like all DC motors, the vibrator puts out a ton of electromagnetic noise, which is easily picked up by [Jen’s] electric bass.

That’s it for this week’s Hacklet! Tune in next week for more projects from Hackday.io!

[Tom Sachs] Builds His Own Space Program

July 10, 2014 by Adam Fabio 15 Comments

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Born in the mid 60’s, [Tom Sachs] has always been fascinated with space, especially the Apollo program. Just like every kid of his generation, [Tom] imagined himself in Neil Armstrong’s and Buzz Aldrin’s boots, gazing over the lunar surface. He never gave up that dream, and years later as a successful modern artist, he built his own space program.

[Tom Sachs] is a master of bricolage . Taken from the French word for tinkering, Wikipedia defines bricolage as “… the construction or creation of a work from a diverse range of things that happen to be available, or a work created by such a process.” The term could also describe the junkbox procurement methods we use on many of our own projects.

sachs-lunar-lander Both [Tom’s] 2007 lunar program and his 2012 Mars program featured his astonishing lunar lander. Built from plywood, found items, and junk, the lander literally made us do a double take the first time we saw it. The attention to detail is incredible. At first glance one could mistake this for a simulator built by NASA themselves. After a few seconds the custom touches start to jump out, such as a “Thank You” garbage door from a fast food restaurant, or a bar stocked with tequila and vodka. The lander’s tools are not just for show either, as the gallery opens with a simulated space mission, which could best be described as a mix of art, improv, and an epic game of make-believe for adults.

[Tom’s] installations also include mission control, which in his Mars piece consisted of a dizzying array of screens, controls and an 80’s boombox. Dressed in the white shirt, thin tie, and horn rimmed glasses we’ve come to associate with NASA engineers of the 60’s, this is where [Tom] works. He truly is the engineer of this mission.

Editor’s Note [Tom] and the entire hacker community at large have a chance to go to space by entering The Hackaday Prize!

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Light Pen Draws On LED Matrix

July 9, 2014 by Adam Fabio 34 Comments

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Who needs a 1920×1080 OLED display when you can have an 8×8 matrix of LED goodness? That’s the question [Kathy] asked when she built this LED matrix light pen project. It looks simple enough – a 64-LED matrix illuminates as the pen draws shapes. But how does the circuit know which LED is under the pen? Good old fashioned matrix scanning is the answer. Only one LED is lit up at any time.

[Kathy] used a pair of 74LS138 3-to-8 line decoders to scan the matrix. The active low outputs on the ‘138 would be perfect for a common cathode matrix. Of course [Kathy] only had a common anode matrix, so 8 PNP transistors were pressed into service as inverters.

The pen itself is a phototransistor. [Kathy] originally tried a CdS photoresistor, but found it was a bit too slow for matrix scanning. An LM358 op-amp is used to get the signal up to a reasonable level for an Arduino Uno to detect.

The result is impressive for such a simple design. We’d love to see someone use this platform as the start of an epic snake game.