Gigabit Ethernet Through The Air

March 10, 2016 by Elliot Williams 70 Comments

There are a couple of really great things about transmitting data using light as the carrier. It can be focused so that it doesn’t spill all over the neighborhood like radio signals do — giving it both some security against eavesdropping and preventing one signal from stepping on another’s toes. And while you can modulate radio signals up nearly to the carrier frequency, the few gigahertz we normally use for radio just won’t cut it for really high bit rates. Light gets you terahertz.

The Koruza project is an open-source, “inexpensive” system that aims to transmit 1 Gb/sec over distances around 100 meters, using modulated infrared light. The intended use-case is urban building-to-building communication at speeds that would otherwise require laying fiber-optic cables. Indeed, the system piggy-backs on existing fiber-optic equipment to get the job done, but the hard part is aligning the units to get maximum signal from point A to point B.

Koruza does this by including motorized lenses on the 3D-printed chassis. You make a rough alignment with a visible green laser, and then fine-tune the IR beams from a web console where you get immediate feedback on how the received signal strength is changing. Both Koruza boxes have a Raspberry Pi inside and use normal networking for calibration and signal-strength statistics. It’s a really neat system, and it’s fully DIY’able except for the commodity fiber-optic bits.

We’ve always had a soft-spot in our heart for transmitting data over light beams. The Ronja project has been doing so since 2001, and over longer distances, with completely DIY hardware, if at a slower bitrate. And now that Li-Fi seems to be getting traction, we might see an unfocused equivalent running inside our homes.

Thanks [Pavel] for the tip!

Etching PCBs With A 3D Printer

March 3, 2016 by Brian Benchoff 58 Comments

With the coming of very cheap blue laser diodes, PCB fabrication has become increasingly interesting. Instead of making a photoresist, placing it over a piece of pre-sensitized copper clad board, and putting the whole assemblage under a blacklight, it’s possible to put a photomask on a board with a tiny bit of very blue light. All you need is a CNC machine. A 3D printer can be a very precise CNC machine, and when you combine these two ideas together, you can make printed circuit boards with an Ultimaker.

[Geggo] had the idea of attaching a blue laser diode to his Ultimaker to burn a few traces into presensitized copper board. With a 3D printed adapter, he was able to mount the diode and associated electronics right on the extruder body. With a small ring to tighten up the aperture, [geggo] was able to put a 50 micrometer wide dot of light on a piece of copper. The laser is powered directly from the PWM fan output on the printer controller board, allowing this entire mish-mash of cheap electronics to be controlled via G-code.

A few experiments were necessary to determine the correct speeds and power settings, with the best results being 1000 mm per minute at 40 mA. The finished board looks fantastic, and a few minutes after [geggo] was done etching a board, he started using his 3D printer as a printer. It’s a result that is so good, so easy to accomplish, and requires so little effort it makes us wonder why we don’t see more of this.

VHS-Tape-Plasma Mirror Drives Tiny Particle Accelerator

February 9, 2016 by Elliot Williams 28 Comments

When you think of a particle accelerator, you’re probably thinking of tens of kilometers of tube buried underground, at high vacuum, that uses precisely timed electromagnetic fields to push charged particles like electrons up to amazing speeds (and energies). However, it’s also possible to accelerate electrons in other ways, and lasers are a good bet. Although a laser-based particle accelerator can push electrons very effectively for a few centimeters, they top out at a relatively low maximum “speed” of a couple billion electron-volts, as opposed to the trillions of eV that you can get out of a really big traditional accelerator.

If only you could repeat the laser trick again, “hitting” the already-moving electrons from behind with another beam, you could boost them up to even higher energies. Doing so would take something like a one-way mirror that lets the electrons pass through, but that you could then bounce a laser beam off of. In a fantastic mixture of science and mother-of-invention-style hacking, these scientists from Lawrence Berkeley National Labs use plain-old VHS tape to make plasma mirrors to do just that. Why VHS tape? Because it’s cheap, flexible, and easy to move through the apparatus at high speeds.

The device works like this: a first laser beam passes through a jet of ionized gas and pulls some electrons with it. These electrons are then focused into a beam and pass through some (moving) VHS tape. The electrons punch a hole through the tape. In their wake they leave a hot plasma of mid-90s TV shows you never got around to watching. The second laser beam is then bounced off this plasma mirror and further accelerates the electron beam from behind. In principle, you could repeat this second stage enough times to build up the energy you needed, but for now the crew is working to characterize their single-stage beam. Getting the timing right on the second-stage beam is, naturally, non-trivial.

Anyone who has spent some time in a science lab knows that there are millions of these tiny get-it-done-quick hacks behind the scenes, but it’s nice to see one take center stage as well. If you’ve got stories of great lab hacks that you’d like to see us cover, post up in the comments!

Thanks [Bruce] for the tip, via Science Daily.

Hackaday Links: December 27th, 2015

December 27, 2015 by Brian Benchoff 20 Comments

PCBs can be art – we’ve known this for a while, but we’re still constantly impressed with what people can do with layers of copper, fiberglass, soldermask, and silkscreen. [Sandy Noble] is taking this idea one step further. He took C64, Spectrum, and Sinclair PCBs and turned them into art. The results are incredible. These PCBs were reverse engineered, traced, and eventually turned into massive screen prints. They look awesome, and they’re available on Etsy.

$100k to bring down drones. That’s the tagline of the MITRE Challenge, although it’s really being sold as, “safe interdiction of small UAS that pose a safety or security threat in urban areas”. You can buy a slingshot for $20…

[styropyro] mas made a name for himself on Youtube for playing with very dangerous lasers and not burning his parent’s house down. Star Wars is out, and that means it’s time to build a handheld 7W laser. It’s powered by two 18650 cells, and is responsible for more than a few scorch marks on the walls of [styropyro]’s garage.

Everybody is trying to figure out how to put Ethernet and a USB hub on the Pi Zero. This means a lot of people will be launching crowdfunding campaigns for Pi Zero add-on boards that add Ethernet and USB. The first one we’ve seen is the Cube Infinity. Here’s the thing, though: they’re using through-hole parts for their board, which means this won’t connect directly to the D+ and D- USB signals on the Pi Zero. They do have a power/battery board that may be a little more useful, but I can’t figure out how they’re doing the USB.

[Keith O] found a fascinating video on YouTube and sent it into the tips line. It’s a machine that uses a water jet on pastries. These cakes start out frozen, and come out with puzzle piece and hexagon-shaped slices. Even the solution for moving cakes around is ingenious; it uses a circular platform that rotates and translates by two toothed belts. Who would have thought the latest advancements in cutting cakes and pies would be so fascinating?

It’s time to start a tradition. In the last links post of last year, we took a look at the number of views from North Korea in 2014. Fifty-four views, and we deeply appreciate all our readers in Best Korea. This year? For 2015, we’ve logged a total of thirty-six views from the Democratic People’s Republic of Korea. That’s a precipitous drop that deserves an investigation. Pyongyang meetup anyone?

Raspberry Pi Laser Beam Profiler

December 21, 2015 by Rud Merriam 3 Comments

[Anthony] at UCLA needed to verify the shape of a laser beam. Commercial units for this, as you would expect, are expensive. But a Raspberry Pi with a Pi Noir camera easily handles the task. Not only is the use of the Pi cool but so is the task – they are using lasers to cool molecules to study quantum effects. The Pi camera without the IR filter captures a wide bandwidth making it suitable for use with non-visible lasers. [Anthony] captures the beam along two axes and plots both curves on the LCD touchscreen. That data, based on the pictures, is also available on a host PC. All this in a super compact package with a 7″ touch screen display.

7" Raspberry Pi Touch Display showing laser beam

2D crystal of Yb ions.

One reason I find this fascinating is I did something similar 1977 at the University of Rochester Laboratory for Laser Energetics. My project was measuring the energy cross-section of a laser beam. The research goal of the Laboratory was the study of inertial confinement laser fusion. While [Anthony] uses an entire camera my project was limited to a 1 dimensional array of charge coupled devices (CCD). The output went to a Tektronix storage terminal and was printed on thermal paper for reference. He uses Python running on the target system. My work used a Z80 development system the size of a tower PC to write my program in assembly language which was then executed on a single board computer. We’ve come a long way. My code is long gone but you can get [Anthony’s] on GitHub.

Raspberry Pi Communication Via LASER

December 12, 2015 by Al Williams 28 Comments

[Nick Touran] wanted to make two Raspberry Pi’s communicate wirelessly. There are lots of options, but [Nick] used a LASER and a photoresistor, along with Morse code. If you don’t find Morse code fancy enough, you could always refer to it as OOK (on/off keying). The circuit uses a common LASER module and an ordinary photoresistor that varies in resistance based on light. A resistor forms a voltage divider with the photoresistor and an external A/D reads the resulting voltage.

The circuit works, but we couldn’t help but notice a few items. Not all photoresistors are as sensitive to the same light wavelengths, so for the maximum range you’d want to pick a particular photoresistor. While the analog to digital converter is certainly workable, we couldn’t help but wonder if you couldn’t set up the divider to use the inherent threshold of the Raspberry Pi’s input pins for a simpler circuit. Of course, if you used the same technique with an Arduino, you could use the built-in A/D converter, and the A/D converter is probably easier to get working.

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Graphene Super Caps: Coming Soon?

December 10, 2015 by Al Williams 29 Comments

If you read Hackaday regularly, you’ve probably heard that you can use a LASER to create graphene. There’s been a bit of research on how to make practical graphene supercapacitors using the technique (known as LIG or LASER-induced graphene). Researchers at Rice University have been working on this, and apparently they’ve had significant success inducing graphene capacitors on a Kapton substrate. The team has published a paper in Advanced Materials (which is behind a paywall) about their work.

In particular, Rice claims that they have easily produced supercapacitors with an energy density of 3.2 mW/cubic centimeter (that’s what the University’s website reports; they probably mean mW-hours/cubic centimeter) with capacitances near one millifarad per square centimeter. A key benefit of the construction method is that the capacitors continued to work after researchers bent them 10,000 times. A flexible capacitor is useful in wearable devices that would often flex, or in a device like a cell phone that could bend in your back pocket as you sit.

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