Inside An EBay Marking Laser

June 11, 2022 by Dan Maloney 13 Comments

When it comes to trolling eBay for cool stuff, some people have all the luck. Whereas all we ever seem to come across is counterfeit chips and obviously broken gear listed as, “good condition, powers on”, [Les Wright] actually managed to get more than he bargained for with one of his recent eBay purchases.

In his video teardown and tour of an industrial marking laser, [Les] suggests that he was really just in it for the optics — which is not a surprise, given his interest in optics in general and lasers in particular. The 20-W CO₂ laser once etched barcodes and the like into products on assembly lines, but with a 2009 date code of its own, it was a safe bet that it was pitched due to a burned-out laser tube. But there were still high-quality IR optics and a precision X-Y galvanometer assembly to be harvested, so [Les] pressed on.

The laser itself ended up being built around a Synrad RF-stimulated CO₂ tube. By a happy accident, [Les] found that the laser actually still works, at least most of the time. There appears to be an intermittent problem with the RF driver, but the laser works long enough to release the magic smoke from anything combustible that gets in its way. The galvos work too — [Les] was able to drive them with a Teensy and a couple of open-source libraries.

Galvos, lenses worth more than $800, and a working laser tube — not a bad haul. We’ll be following along to see what [Les] makes of this booty. Continue reading “Inside An EBay Marking Laser” →

Bug Eliminator Zaps With A Laser

June 6, 2022 by Bryan Cockfield 26 Comments

Mosquitoes tend to be seen as an almost universal negative, at least in the lives of humans. While they serve as a food source for plenty of other animals and may even pollinate some plants, they also carry diseases like malaria and Zika, not to mention the itchy bites. Various mosquito deterrents have been invented over the years to solve some of these problems, but one of the more interesting ones is this project by [Ildaron] which attempts to build a mosquito-tracking laser.

The device uses a neural learning algorithm to identify mosquitoes flying nearby. Once a mosquito is detected, a laser is aimed at it and activated in order to “thermally neutralize” the pest. The control system as well as the neural network and machine learning are hosted on a Raspberry Pi and Jetson Nano which give it plenty of computing power. The only major downside with this specific project is that the high-powered laser can be harmful to humans as well.

Ideally, a market for devices like these would bring the price down, perhaps even through the use of something like an ASIC specifically developed for these mosquito-targeting machines. In the meantime, [Ildaron] has made this project available for replication on his GitHub page. We have also seen similar builds before which are effective against non-flying insects, so it seems like only a matter of time before there is more widespread adoption — either that or Judgement day!

Continue reading “Bug Eliminator Zaps With A Laser” →

A frosted glass disk with geometrical markers

Using A Laser Cutter To Replicate An Optical Comparator Screen

May 30, 2022 by Robin Kearey 13 Comments

Precision instruments often contain specialized components that are essential to their function, but nearly impossible to replace if they fail. [Andre] had just such a problem with an optical comparator, which is an instrument typically used in machine shops to help check the tolerances of a finished part. It does this by projecting a magnified picture of an object onto a glass screen with markings showing angles and distances.

In the old comparator [Andre] bought on eBay, the markings on the glass had faded to such a degree that the instrument was almost unusable. So he contacted [James] over at Clough42, who was able to create a near-perfect replacement screen by using a laser cutter, as shown in the video embedded below.

The first step was to replicate the screen’s markings in a CAD program. [James] explains the process in Fusion 360, demonstrating how you can generate all the different scales nearly automatically through the proper use of constraints, variables and patterns. He then transferred the drawing to Lightburn, which drives the laser cutter and etches the markings into a sheet of glass covered with CerMark, a marking solution that turns a deep black when heated by a laser.

After etching, the final step was to apply frosting to the glass to turn it into a projection screen. While there are several ways to achieve this, [James] went for a simple spray-based method that gave surprisingly good results. It took a few experiments to find out that etching the markings on the back of the glass and applying the frosting on that side as well gave the best combination of sharpness and durability.

[James]’s project shows that even delicate instruments with custom glass components can be repaired, if you just have the right tools. A similar strategy might also work for creating custom scales for analog meters, or even old radio dials. If you’re not familiar with laser cutters, have a look at our experiments with an Ortur model. Thanks for the tip, [poiuyt]!

Continue reading “Using A Laser Cutter To Replicate An Optical Comparator Screen” →

Laser-Engraving Hairlines: When A Line Isn’t A Line

May 29, 2022 by Donald Papp 8 Comments

When is a line not a line? When it’s a series of tiny dots, of course!

The line is actually tiny, laser-etched craters, 0.25 mm center-to-center.

That’s the technique [Ed Nisley] used to create a super-fine, colored hairline in a piece of clear plastic — all part of his project to re-create a classic Tektronix analog calculator from the 1960s, but more on that in a moment.

[Ed] tried a variety of methods and techniques, including laser engraving a solid line, and milling a line with an extremely tiny v-tool. Results were serviceable, but what really did the trick was a series of tiny laser-etched craters filled in with a red marker. That resulted in what appears — to the naked eye — as an extremely fine hairline. But when magnified, as shown here, one can see it is really a series of small craters. The color comes from coloring in the line with a red marker, then wiping the excess off with some alcohol. The remaining pigment sitting in the craters gives just the right amount of color.

This is all part of [Ed]’s efforts to re-create the Tektronix Circuit Computer, a circular slide rule capable of calculating all kinds of useful electrical engineering-related things. And if you find yourself looking to design and build your own circular slide rule from scratch? We have you covered.

Adjustable Workholding For Honeycomb Tables, With A Bit Of DIY

May 29, 2022 by Donald Papp 6 Comments

Honeycomb tables are often found on laser cutters, where they provide a way for work material to be laid flat while not interfering with things like airflow. This leads to a cleaner laser cut and a nicer finish, but if one’s work depends on precise positioning and placement, they leave something to be desired because there’s no good way to attach rails, jigs, or anything of the sort in an easy and stable fashion.

The solution [Ed] found for this was to make himself some adjustable offset stops designed to fit into his laser cutter’s honeycomb table. Each consists of a laser-cut disc of wood, which is screwed off-center into an acetal “plug” sized to fit into the vertical gaps in the honeycomb table. This allows each disc to be rotated to fine-tune positioning. With the help of some T-shaped pegs that are also sized to fit into the honeycomb table, [Ed] has all he needs to fix something like a workpiece or jig into a particular and repeatable position.

The whole thing depends on a friction fit, so the sizing of the plug needs to match a particular honeycomb table’s construction. We think this makes it a good match for 3D printing, as one can measure and print plugs (perhaps employing the Goldilocks approach) that fit with just the right amount of snug.

Honeycomb tables are fantastic for laser cutting, but if you find yourself in a pinch for a replacement, an old radiator can make a pretty decent stand-in.

The laser driver's internals, showing the custom PCB, the PSU, connectors and the interlocks.

Laser Driver Design Keeps Safety First

May 29, 2022 by Arya Voronova 20 Comments

[Les] from [Les’ Lab] has designed a driver for laser diodes up to 10 watts, and decided to show us how it operates, tells us what we should keep in mind when designing such a driver, and talks about laser safety in general. This design is an adjustable current regulator based on the LM350A, able to provide up to 10 watts of power at about 2 volts – which is what his diode needs. Such obscure requirements aren’t easily fulfilled by commonly available PSUs, which is why a custom design was called for.

He tells us how he approached improving stability of the current regulation circuit, the PCB design requirements, and planning user interface for such a driver. However, that’s just part of the battle – regulating the current properly is important, but reducing the potential for accidental injuries even more so. Thus, he talks extensively about designing the driver circuit with safety in mind – using various kinds of interlocks, like a latching relay circuit to prevent it from powering up as soon as power is applied.

Continue reading “Laser Driver Design Keeps Safety First” →

Building Petahertz Logic With Lasers And Graphene

May 17, 2022 by Al Williams 19 Comments

There was a time when we thought a 50 MHz 486 was something to get excited about. In comparison, the computer this post was written on clocks in at about 3.8 GHz, which these days, isn’t an especially fast machine. But researchers at the University of Rochester and the Friedrich-Alexander-Universität Erlangen-Nürnberg want to blow the doors off even the fastest modern CPUs. By using precise lasers and graphene, they are developing logic that can operate at nearly 1 petahertz (that’s 1,000,000 GHz).

These logic gates use a pair of very short-burst lasers to excite electrical current in graphene and gold junctions. Illuminating the junctions very briefly creates charge carriers formed by electrons excited by the laser. These carriers continue to move after the laser pulse is gone. However, there are also virtual charge carriers that appear during the pulse and then disappear after. Together, these carriers induce a current in the graphene. More importantly, altering the laser allows you to control the direction and relative composition of the carriers. That is, they can create a current of one type or the other or a combination of both.

This is the key to creating logic gates. By controlling the real and virtual currents they can be made to add together or cancel each other out. You can imagine that two inputs that cancel each other out would be a sort of NAND gate. Signals that add could be an OR or AND gate depending on the output threshold.

[Ignacio Franco], the lead researcher, started working on this problem in 2007 when he started thinking about generating electrical currents with lasers. It would be 2013 before experiments bore out his plan and now it appears that the technique can be used to make super fast logic gates.

We often pretend our logic circuits don’t have any propagation delays even though they do. If you could measure it in femtoseconds, maybe that’s finally practical. Then again, sometimes delays are useful. You have to wonder how much the scope will cost that can work on this stuff.