Go Wireless with This DIY Laser Ethernet Link

Most of us have Ethernet in our homes today. The real backbones of the Internet though, use no wires at all. Optical fibers carry pulses of light across the land, under the sea, and if you’re lucky, right to your door. [Sven Brauch] decided to create an optical link. He didn’t have any fiber handy, but air will carry laser pulses over short distances quite nicely. The idea of this project is to directly convert ethernet signals to light pulses. For simplicity’s sake, [Sven] limited the bandwidth to one channel, full-duplex, at 10 Megabits per second (Mbps).

The transmit side of the circuit is rather simple. An op-amp circuit acts as a constant current source, biasing the laser diode. The transmit signal from an Ethernet cable is then added in as modulation. This ensures the laser glows brightly for a 1 bit but never shuts completely off for a 0 bit.

The receive side of the circuit starts with a photodiode. The diode is biased up around 35 V, and a transimpedance amplifier (a current to voltage converter) is used to determine if the diode is seeing a 1 or a 0 from the laser. A bit more signal conditioning ensures the output will be a proper differential Ethernet signal.

[Sven] built two identical boards – each with a transmitter and receiver. He tested the circuit by pointing it at a mirror. His Linux box immediately established a link and was reported that there was a duplicate IP address on the network. This was exactly what [Sven] expected. The computer was confused by its own reflection – but the laser and photodiode circuits were working.

Finally, [Sven] connected his PC and a Raspberry Pi to the two circuits. After carefully aligning the lasers on a wooden board, the two machines established a link. Success! (But be aware that a longer distances, more sophisticated alignment mechanisms may be in order.)

Want to know more about fiber and networking? Check out this article about wiring up an older city. You can also use an optical link to control your CNC.

Photochromic Eggs: Not for Breakfast

Photochromic paint is pretty nifty – under exposure to light of the right wavelength, it’ll change colour. This gives it all kinds of applications for temporary displays.  [Jiri Zemanek] decided to apply photochromic paint to an egg, utilising it to create stroboscopic patterns with the help of a laser.

Patterns for the egg are generated in MATLAB. A Discovery STM32 board acts as a controller, looking after the laser scanner and a stepper motor which rotates the egg. A phototransistor is used to sync the position of the laser and the egg as it rotates.

The photochromic paint used in this project is activated by UV light. To energize the paint, [Jiri] harvested a violet laser from a Blu-ray player, fitting it to a scanning assembly from a laser printer. Instead of scanning the laser across an imaging drum, it is instead scanned vertically on a rotating egg. Patterns can then be drawn on the egg, which fade over time as the paint gives up its stored energy.

[Jiri] exploits this by writing a variety of patterns onto the egg, which then animate in a manner similar to a zoetrope – when visualised under strobing light, the patterns appear to move. There are also a few holiday messages shown for Easter, making the egg all the more appropriate as a billboard.

If you like the idea of drawing on eggs but are put off by their non-uniform geometry, check out the Egg-bot. Video below the break.

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Sudo Make Me a Sandwich

How do you like your Ham and Cheese sandwich? If you answered “I prefer it beefy”, look no further than [William Osman]’s Vin Diesel Ham and Cheese Sandwich! [Osman]’s blog tagline is “There’s science to do” but he is the first to admit this is science gone too far. When one of his followers, [Restroom Sounds], commented “Please sculpt a bust of [Vin Diesel] using laser cut cross-sections of laser sliced ham”, he just had to do it.

His friend [CameraManJohn] modeled the bust using Maya and [Osman] has provided links to download the files in case there’s the remote possibility that someone else wants to try this out. They picked the cheapest packs of sliced ham they could get from the supermarket — so technically, they did not actually laser slice the ham. For help with generating the slice outlines, they found the Slicer app for Autodesk’s Fusion 360 which did exactly what needed to be done. The app converts the 3D model into individual cross sections, similar to an MRI. It helps to measure the thickness of various samples of your raw material so that the Slicer output is not too stretched (or squished). The result is a set of numbered 2D drawings that can be sent to your laser cutter.

The rest of the video scores pretty high on the gross-o-meter, as [Osman] goes about laser cutting slices of ham (and a few slices of cheese), tasting laser cut ham (for Science, of course), and trying to prevent his computer from getting messed up. In the end, the sandwich actually turns out looking quite nice, although we will not comment on its taste. A pair of googly eyes adds character to the bust.

One problem is that the Slicer app does not optimise its results for efficient packing. with the smallest part occupying the same bounding box as the largest. This leads to a lot of wasted pieces of ham slices to be thrown away. [Bill] is still wondering what to do with his awesome sandwich, so if you have suggestions, chime in with your comments after you’ve seen the video linked below. If you know [Vin Diesel], let him know.

This isn’t [Osman]’s first adventure with crazy food hacks — here are a few tasty examples: a Toast-Bot that Butters For You (sometimes), a Laser-Cut Gingerbread Trailer Home, and a Pumpkin-Skinned BattleBot.

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MRRF 17: Laser Resin Printers

The Midwest RepRap Festival is the best 3D printer con on the planet. In the middle of Indiana, you’ll find the latest advances for CNC hot glue guns and the processes that make squirting filament machines better, more accurate, and more efficient. There’s more to 3D printing than just filament-based machines, though, and for the last few MRRFs we’ve been taking a look at resin-based machines.

While most of the current crop of resin printers use either DLP projectors or LCDs and a big, bright backlight [Mark Peng]’s Moai printer uses a 150 mW laser diode and galvos. This is somewhat rare in the world of desktop 3D printers, thanks in no small part to the ugliness between Formlabs and 3D Systems. Still, it’s a printer that looks fantastic and produces prints that are far beyond what’s possible with a filament-based machine.

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Burn Music On To Anything!

If at first you don’t succeed, try, try, and try again. This is especially true when your efforts involve a salvaged record player, a laser cutter, and He-Man. Taking that advice to heart, maniac maker extraordinaire [William Osman] managed to literally burn music onto a CD.

Considering the viability of laser-cut records is dubious — especially when jerry-built — it took a couple frustrating tests to finally see results, all the while risking his laser’s lens. Eventually, [Osman]’s perseverance paid off. The lens is loosely held by a piece of delrin, which is itself touching a speaker blaring music. The vibrations of the speaker cause the lens to oscillate the focal point of the laser into a wavelength that is able to be played on a record player. You don’t get much of the high-end on the audio and the static almost drowns out the music, but it is most definitely a really shoddy record of a song!

Vinyl aficionados are certainly pulling their hair out at this point. For the rest of us, if you read [Jenny’s] primer on record players you’ll recognize that a preamplifier (the ‘phono’ input on your amp) is what’s missing from this setup and would surely yield more audible results.

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Light Replaces Electrons for Giant Vector-Graphics Asteroids Game

For all its simplicity, the arcade classic Asteroids was engaging in the extreme, with the ping of the laser, the rumble of the rocket, the crash of crumbling space rocks, and that crazy warble when the damn flying saucers made an appearance. Atari estimates that the game has earned operators in excess of $500 million since it was released in 1979. That’s two billion quarters, and we’ll guess a fair percentage of those coins came from the pockets of Hackaday’s readers and staff alike.

One iconic part of Asteroids was the vector display. Each item on the field was drawn as a unit by the CRT’s electron beam dancing across the phosphor rather than raster-scanned like TV was at the time. The simple graphics were actually pretty hard to create, and with that in mind, [standupmaths] decided to take a close look at the vector display of Asteroids and try to recreate it using a laser.

To be fair, [Seb Lee-Delisle] does all the heavy lifting here, with [standupmaths] providing context on the history and mathematics of the original vector display. [Seb] is a digital artist by trade, and has at the ready a 4-watt RGB laser projector for light shows and displays. Using the laser as a replacement for the CRT’s electron beam, [Seb] was able to code a reasonably playable vector-graphic version of Asteroids on a large projections screen. Even the audio is faithful to the original. The real treat comes when the laser is slowed and a little smoke added to show us how each item is traced out in order.

All [Seb]’s code is posted on GitHub, so if you have a laser projector handy, by all means go for it. Or just whip up a custom vector display for your own tabletop version of Asteroids.

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Toast-Bot Butters For You (Sometimes)

Sometimes — despite impracticality, safety, failure, and general good sense — one has an urge to see a project through for the sake of it. When you’re sick of buttering your toast every morning, you might take a leaf out of Rick Sandc– ahem, [William Osman]’s book and build a toast-bot to take care of the task for you.

[Osman] — opting for nail the overkill quotient — is using a reciprocating saw motor to hold the butter while the toast moves underneath the apparatus on a platform controlled by a linear stepper motor. The frame and mounts for Toast-Bot were cut out of wood on his home-built laser cutter — affectionately named Retina Smelter 9000′ — and assembled after some frustration and application of zip-ties. The final result DOES butter toast, but — well — see for yourself.

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