Year: 2014

Public Transportation Display

March 4, 2014 by 17 Comments

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[Adrian] and [Obelix] wanted to have an easy way to know when to expect the public transportation, so they hacked an LED dot matrix display to show arrival times for stops near their dorm.

They found the display on Ebay with a defective controller which they replaced with an ATmega328p. They connected the display to the internet by adding a small TP-Link MR3020 router and connecting it to the ATmega328p via a serial line. Their local transportation office’s web page is polled to gather wait times for the stops of interest. All rendering of the final image to display to the dot matrix display is done on their PC, which then gets pushed through to the MR3020, which in turn pushes it out to the ATmega328p for final display.

[Adrian] and [Obelix] warn about setting proper watchdog timers on the display driver to make sure bugs in the controller don’t fry the dot matrix elements. Their ATmega328p dot matrix driver code can be found on [Adrian]’s GitHub page.

Check out a video of the display in action after the jump.

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Retrotechtacular: Lighting The Way For Talkie Pictures With Optical Sound Recording

March 4, 2014 by 13 Comments

This week’s Retrotechtacular is a 1943 Encyclopædia Britannica film focusing on optical sound reproduction for motion pictures. Both the sound and the images are recorded on film, which is only affected by light. Therefore, the sound waves must be converted to changes in light.

This is done the way you might expect: the sound waves hit a microphone and the changes in current are amplified and used to control the intensity of light falling on the film. Three types of soundtracks are described and wonderfully demonstrated at the end of the film.

All three types are made from a series of thin bars of light, and the corresponding current value is represented by changes in either their length or their width. In the Unilateral Variable Area recording, the bars extend from the right side of the sound track. Bilateral Variable Area recorded bars emanate uniformly toward the edges from the center. In Variable Density recording, all of the bars extend from the left to right extremes, but their thickness varies.

Variable Density recording is done with a light valve, which contains a pair of delicate metallic ribbons in a magnetic field that move like shutters when the sound current flows through them. The light coming through to the film is varied by the slot created in the space between the ribbons. The light patterns are changed back to sound through a photoelectric cell, which converts the variations in light back to changing current. These changes are amplified and run through a loudspeaker. Be sure to watch to the end to catch a demonstration of the recording methods, set to what we’re pretty sure is Camille Saint-Saëns’ Danse Macabre.

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Woodhouse Controls Your House, Avoids Danger Zone

March 4, 2014 by 21 Comments

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[Pat] may not be the world’s most dangerous secret agent, but he does have Woodhouse taking care of his home. [Pat] has been upgrading his sonic screwdriver home automation system these past few months. Waking up to a chilly room led him to start hacking a thermostat interface. [Pat] found that his furnace only needed one 24VAC wire to be shorted to a common during a call for heat. [Pat] was lucky in that his thermostat was low voltage. While researching a thermostat hack, we made the painful discovery that our thermostat is 120VAC, so watch for that if you try this one at home.

[Pat] connected his thermostat leads to a relay controlled by a Raspberry Pi. The Pi would read a temperature sensor and set the relay accordingly. That was fine for a quick hack, but opening an SSH window to change the temperature isn’t the most convenient thing in the world. Enter an old Asus Transformer Prime tablet. [Pat] coded up an Android Holo style interface using AJAX along with HTML/CSS/jQuery and PHP. OpenMic+ constantly listens for voice commands, and fires them off to Tasker tasks as needed. He calls the results Woodhouse, and the interface is very slick. The tablet controls and graphs temperature, [Pat’s] media center, and his lights. Woodhouse is even [Pat’s] right hand man when getting ready for those intimate moments. We can’t wait to see what [Pat] comes up with next.

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TDOA (Time Difference Of Arrival) Directional Antenna

March 4, 2014 by 34 Comments

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We have posted articles in the past on directional antennas such as Yagi antennas used for transmitter hunting otherwise known as fox hunting. Those types of antennas and reception suffer from one major drawback, which is as you get close to the transmitter the S meter will go full scale. At which time the transmitted signal appears to be coming from all directions. To correct for this problem you need to use clever signal attenuators or change to a poor receiving antenna as well as tuning off frequency effectively making your receiver hard of hearing so that only the direct path to the transmitter is loudest.

There is another popular type of antenna that you can build yourself called a TDOA which stands for Time Difference of Arrival. [Byon Garrabrant N6BG]  shared a short video tutorial on the functionality of his home built TDOA antenna. Effectively this is an active antenna that uses a 555 chip or, in [Byon’s] case, a PIC chip to quickly shift between two receiving dipole antennas at either end of a shortened yardstick. In his explanation you learn that as the antenna ends move closer or farther from the source a 640 Hz generated audio tone will go from loud to very soft as the antennas become equal distance from the source. This type of directional reception is not affected by signal strength. This means you can be very close to a powerful transmitter and it will still function as a good directional antenna.

The current circuit diagram, BOM and source code are all available on [Byon’s] TDOA page.

The reason [Byon] used a programmable PIC instead of the 555 for his design is because he wants to add a few more modifications such as feeding back the audio output to the PIC in order to programmatically turn on a left or right LED indicating the direction of the transmitter. Furthermore, he plans on adding a third antenna in a triangular configuration to programmatically control a circle of 6 LEDs indicating the exact direction of the signal. When he finishes the final modifications he can drive around with the antenna array on his vehicle and the circle of LEDs inside indicating the exact direction to navigate.

We look forward to seeing the rest of the development which might even become a kit someday. You can watch [Byon’s] TDOA video after the break.

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RFID Jacket Flashes The Crowd At Make Fashion 2014

March 4, 2014 by 5 Comments

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The [RADLab team] has created an eye-opening RFID jacket for Make Fashion 2014. For this project, [Dan Damron, Chris Zaal, and Ben Reed] of RADLab teamed up with designer [Laura Dempsey] to create a jacket which responded both to a dancer on the runway and the audience itself. RADLab stands for Radio Frequency Identification Application Development Lab, so you can probably guess that RFID was their weapon of choice for interaction. We’ve got a bit of RFID experience here at Hackaday, having recently used it at The Gathering in LA. The [RADLab team] didn’t skimp on processing power for this jacket. A BeagleBone Black running Debian controls the show. The BeagleBone receives data from a Thingmagic M6e 4 port UHF RFID Reader. The M6e is connected to 4 directional antennas. The BeagleBone responds differently depending on which RFID card is read, and which antenna reads it. With the data processed, the BeagleBone then issues commands to a teensy 3.0, which controls  WS2811 “Neopixel” addressable RGB LEDs sewn into the jacket.

During the fashion show, the jacket wearer danced with a second model who had RFID tags sewn into his t-shirt. The LED clusters on the front, back and sleeves of the jacket would light up, and change color and flash frequency based upon which tag and antenna got a read. Once the performance was over, the audience was encouraged to pick up tags and interact with the jacket themselves. The software was still very much beta, so the [RADLab team] monitored everything via WiFi and restarted the software when necessary.

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Coolant Hose Grippers Keep Your Components In Place

March 3, 2014 by 26 Comments

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Whether you have shaky hands when working on tiny components, or just need more control and flexibility, we think this “third hand” gripper using coolant hose is an ingenious solution compared to the little metal ones you can buy.

Not surprisingly this isn’t an original idea. In fact, Sparkfun actually sells it as a kit. That being said… it’s rather expensive — especially when you can build [Frank Zhao’s] version for less than $15.

He’s using a cutting board, three machinery style coolant hoses, and a handful of fasteners from the hardware store. You can use the accessories from a regular metal third hand, but [Frank] also shows us how to recreate them using a few washers, some steel strapping, and a wing nut and bolt.

[Mr. Zhao] is no stranger to Hack a Day either — we’d almost call him an inadvertent contributor we’ve shared so many of his hacks! Just take a look at his tiny USB business card, his awesome LED pocket watch, a detailed reflow oven build, or even his IR based augmented reality setup.

[Thanks Keith!]

Forget Stopping Bullets – Vest Warms You While Stopping Taser

March 3, 2014 by 40 Comments

[Bruce Wayne] [Shenzhen] wanted a garment that would protect him from a jolt, while keeping him toasty in the cold weather. Well that’s not it at all, these are merely two of his projects using the same material in different ways.

We’re going to start with the infrared image on the right. This is a vest with chest and back pieces made of carbon tape totaling two meters of the material swirled on each side. Hook it to a power source and the carbon tape warms the wearer. Portability is something of an issue as each “element” takes 36 W of power (3A at 12V). Click through for advice on how to interface the tape with the power source.

Onto the main event… avoiding electrical shock when you get all up in the grill of that mall cop you’re hated for years. [Shenzhen’s] jacket is really just an ordinary long-sleeved coat. But he separated the lining at the bottom seam and used fusible material to hold the carbon tape in place. The carbon tape provides a better conductor than your skin, preventing the shock from stunning you as it was intended. This really is the thing of superheroes, or former editors who should have known better.