Electro-Optical Control Of Lasers With A Licorice Twist

You’ve got to hand it to [Les Wright]; he really knows how to dig into optical arcana and present topics in an interesting way. Case in point: an electro-optical control cell that’s powered by ouzo.

OK, the bit about the Greek aperitif may be stretching things a bit, but the Kerr Cell that [Les] builds in the video below does depend on anethole, the essential component of aniseed extract, which lends its aromatic flavor to everything from licorice to Galliano and ouzo. As [Les] explains, the Kerr effect uses a high-voltage field to rapidly switch light passing through a medium on and off. The most common medium in Kerr cells is nitrobenzene, a “distressingly powerful organic solvent” with such fun side effects as toxicity, flammability, and carcinogenicity.

Luckily, [Les] found a suitable substitute in the form of anethole — a purified sample, not just an ouzo nip. The solution went into a plain glass cuvette equipped with a pair of aluminum electrodes, which got connected to one of the high-voltage supplies we’ve seen him build before for his nitrogen laser. A pair of polarizing filters go on either end of the cuvette, and are adjusted to blank out the light passing through it. Applying 45 kilovolts across the cell instantly turns the light back on. Watch it in action in the video below.

There’s a lot of room left for experimentation on this one, including purification of the anethole for potentially better results. We’d also be curious if plain ouzo would show some degree of Kerr effect. For science, of course.

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Review: WAINLUX K8, A Diode Laser That’s Ready To Work

Rarely a week goes by that some company doesn’t offer to send us their latest and greatest laser. You know the type — couple of aluminum extrusions, Class 4 diode flopping around in the breeze, and no enclosure to speak of unless you count the cardboard box they shipped it in. In other words, an accident waiting to happen. Such gracious invitations get sent to the trash without a second thought.

Now don’t get me wrong, I have no doubt that the average Hackaday reader would be able to render such a contraption (relatively) safe for use around the shop. Build a box around it, bolt on a powerful enough fan to suck the smoke out through the window, and you’ve turned a liability into a legitimate tool. But the fact remains that we simply can’t put our stamp on something that is designed with such a blatant disregard for basic safety principles.

The earlier WAINLUX JL4 — lucky rabbit foot not included.

That being the case, a recent email from WAINLUX nearly met the same fate as all those other invitations. But even at a glance it was clear that this new machine they wanted to send out, the K8, was very different from others we’d seen. Different even from what the company themselves have put out to this point. This model was fully enclosed, had a built-in ventilation fan, an optional air filter “sidecar”, and yes, it would even turn off the laser if you opened the door while it was in operation. After reading through the promotional material they sent over, I had to admit, I was intrigued.

It seemed like I wasn’t the only one either; it was only a matter of days before the Kickstarter for the WAINLUX K8 rocketed to six figures. At the time of this writing, the total raised stands at just under $230,000 USD. There’s clearly a demand for this sort of desktop laser, the simplicity of using a diode over a laser tube is already appealing, but one that you could actually use in a home with kids or pets would be a game changer for many people.

But would the reality live up to the hype? I’ve spent the last couple of weeks putting a pre-production WAINLUX K8 through its paces, so let’s take a look and see if WAINLUX has a winner on their hands.

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Laser Engraver Uses All Of The DVD Drive

For the last ten to fifteen years, optical drives have been fading out of existence. There’s little reason to have them around anymore unless you are serious about archiving data or unconvinced that streaming platforms will always be around. While there are some niche uses for them still, we’re seeing more and more get repurposed for parts and other projects like this tabletop laser engraver.

The build starts with a couple optical drives, both of which are dismantled. One of the shells is saved to use as a base for the engraver, and two support structures are made out of particle board and acrylic to hold the laser and the Y axis mechanism. Both axes are made from the carriages of the disassembled hard drives, with the X axis set into the base to move the work piece. A high-output laser module is fitted to the Y axis with a heat sink, and an Arduino and a pair of A4988 motor controllers are added to the mix to turn incoming G-code into two-dimensional movement.

We’ve actually seen a commercial laser engraver built around the same concept, but the DIY approach is certainly appealing if you’ve got some optical drives collecting dust. Otherwise you could use them to build a scanning laser microscope.

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DIY Laser For Ablating Metal

For those who wish to go beyond through-hole construction on perfboard for their circuit boards, a printed circuit board is usually the next step up. Allowing for things like surface-mount components, multi-layer boards, and a wider array of parts, they are much more versatile but do have a slight downside in that they are a little bit harder to make. There are lots of methods for producing them at home or makerspace, though, and although we’ve seen plenty of methods for their production like toner transfer, photoresist, and CNC milling, it’s also possible to make them using laser ablation, although you do need a special laser to get this job done.

The problem with cutting copper is that it reflects infra-red, so a higher-wavelength blue green laser is used instead. And because you want to ablate the copper, but not melt the surrounding areas or cut straight through the board, extremely short, high-power pulses are the way to go. Here, the [Munich Fab Lab] is using 9 kW pulses of around 30 microseconds each.  With these specifications the copper is ablated from the surface of the board allowing for fine details in the range of about 20 µm, which is fine enough for just about any circuit board. The design of the laser head itself is worth a look.

Aside from the laser, the rest is standard CNC machine fodder, but with an emphasis on safety that’s appropriate for a tool in a shared workspace, and the whole project is published under an open license and offers an affordable solution for larger-scale PCB production with extremely fine resolution and without the need for any amounts of chemicals for the more common PCB production methods. There is a lot more information available on the project’s webpage and its GitHub page as well.

Of course, there are other methods of producing PCBs by laser if you happen to have a 20 W fiber laser just kicking around.

Linear Power Supply’s Current Limiter Is A Lesson In Simplicity

Here at Hackaday we really like to feature projects that push the limits of what’s possible, or ones that feature some new and exciting technology that nobody has ever seen before. So what’s so exciting about this single-voltage linear power supply? Honestly, nothing — until you start looking at its thermally compensated current limiting circuit.

This one is by [DiodeGoneWild], who you’ve really got to hand it to in terms of both the empirical effort he went through to optimize the circuit, as well as the quality of his explanation. The basic circuit is dead simple: a transformer, a full-wave rectifier, an LD1085 adjustable regulator — a low-dropout version of the venerable LM317 — and associated filter caps and trimmer pot to adjust the output between 2.2 and 5.5 volts.

The current limiting circuit, though, is where things get interesting. Rather than use an op-amp, [DiodeGoneWild] chose a simple discrete transistor current-sense circuit. To make it less susceptible to thermal drift, he experimented with multiple configurations of resistors and Schottky diodes over a wide range of temperatures, from deep-freeze cold to hair-dryer-in-a-box hot. His data table and the resulting graph of current versus temperature are works of art, and they allowed him to make sensible component selections for a fixed 250-mA current limit with a reasonably flat thermal response.

As for construction, it’s all classic [DiodeGoneWild], including a PCB with traces ground out with a Dremel and a recycled heat sink. He also dropped a couple of interesting build techniques, like adding leads to turn SMD tantalum caps into through-hole components. The video below shows all the build details along with the exhaustive breadboard testing.

From taking on a potentially risky magnetron teardown to harvesting lasers from headlights, there’s always something to learn from a [DiodeGoneWild] video.

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Modern CO2 Laser Reviewed

If you’ve got a laser cutter, it is highly probable that it uses a laser diode. But more expensive machines use a carbon dioxide laser tube along with mirrors. There was a time when these lasers came in two flavors: very expensive and amazing or moderately expensive and cheaply made. However, we are seeing that even the moderately expensive machines are now becoming quite advanced. [Chad] reviews a 55-watt xTool P2. At around $5,000, it is still a little spendy for a home shop, but it does have pretty amazing features. We can only hope some less expensive diode lasers will adopt some of these features.

[Chad’s] video that you can see below attempts to recreate some of the amazing things xTool did on their product introduction live stream. He was able to recreate most, but not all of the results. In some cases, he was also able to do better.

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Laser Projector Built From An Old Hard Drive

Spinning hard drives are being phased out of most consumer-grade computers in favor of faster technology like solid-state drives and their various interfaces. But there’s still millions of them in circulation that will eventually get pulled from service — so what do we do with them? If you’ve got one that would otherwise be going in the garbage, they can be turned into some other interesting devices like this laser text projector.

Even the slowest drives spin at around 5000 RPM, which is perfect for this type of application. The device works by mounting twelve mirrors, each at a slightly different angle, on a drum which is spun by the drive’s motor. Bouncing a laser off of the spinning drum results in a projection of twelve horizontal lines. By rapidly switching the laser on and off depending on which mirror it’s pointing at, the length of each line can be controlled.

Thanks to persistence of vision, that allows you to show text on the surface that the laser is projected on. At speeds this high, it took [Ben] of Ben Makes Everything quite a few iterations to get it to a usable space. From sensors that were too slow to lasers not bright enough to 3D prints that were not accurate enough, he goes through the design of his build and the process in excellent detail.

After solving all of the problems including building his own constant-current laser power supply, and burning up a few laser diodes in the process, [Ben] has a laser projector capable of displaying readable text at a great distance which is also portable, running on a 12 V power supply. There are some possible areas of improvement that he notes as well, such as an unbalanced 3D printed part causing a bit of a wobble and the Arduino controller not being fast enough for more text. But it’s an impressive project nonetheless, similar to a two-mirror version we saw some time ago but with the ability to display text as well.

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