Laser Projector Built From An Old Hard Drive

May 12, 2023 by Bryan Cockfield 41 Comments

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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Kerfmeter Measures Laser Cutter Kerf Allowances On The Fly

May 3, 2023 by Dan Maloney 21 Comments

Nothing beats a laser cutter and a sheet of Baltic birch plywood or MDF when it comes to making quick, attractive enclosures. Burning out all the pieces and fitting them together with finger joints is super satisfying — right up until you realize that you didn’t quite get the kerf allowance right, and your pieces don’t fit together very nicely. If only there was a way to automate kerf measurement.

There is, in the form of Kerfmeter. It comes to us by way of the lab of [Patrick Baudisch] at the University of Potsdam, where they’ve come up with a clever way to measure the kerf of a laser cutter right during the cutting session. With the Kerfmeter mounted directly to the laser cutter head, a small test artifact based on an Archimedean spiral is cut into a corner of the workpiece. Pins on a small motor engage with the object and turn it until it jams in its hole; the wider the kerf, the greater the angle. Once the kerf is calculated, the rest of the design can be dilated by the proper amount to achieve a perfect fit. The video below shows it better than words can explain it.

What we like about this is its simplicity — all it involves is a motor and a microcontroller, plus a little software. It seems much faster than using a traditional kerf gauge, not to mention more precise. And while it does use up a little bit of material, the test pattern is really pretty small, all things considered. Seems like a reasonable trade-off to us. Still, if you want to figure out your kerfs the old-fashioned way, we’ve got you covered.

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Better Laser Cuts: Know Your Kerf

April 15, 2023 by Al Williams 19 Comments

The recent crop of laser cutters are nothing short of miraculous. For a few hundred dollars you can get a machine that can easily engrave and — subject to materials — cut well, too. [Nate] has been taking advantage of a laser to make boxes that join together using finger joinery. The problem is, the pieces have to fit exactly to get a good box. While setting dimensions in software is fine, you need to account for how much material the laser removes — something traditional woodworkers and machinists know as kerf.

You can, of course, employ trial and error to get good results. But that’s wasteful and potentially time-consuming. [Nate] built a “tolerance fence” that is quick to cut out and allows accurate measurement of kerf. You can quickly use the tolerance fence to make measurements and increase your chances of nailing your boxes on the first cut.

You have to customize the fence based on the thickness of your material. [Nate] uses Lightburn, which probably has a kerf offset already set by default in your layers. If not, you’ll need to turn it on and set an estimate of your kerf size. Then you are ready to cut the fence pieces and see how they fit together.

If the fit is too loose, you want to raise the kerf setting and try again. If it is too tight, you lower the kerf setting. As [Nate] says, “Lower equals looser.”

The results speak for themselves, as you can see in the treasure chest image [Nate] provided. Well worth the effort to get this parameter right. We do enjoy laser cutting and engraving things. If you are cutting and don’t have air assist, you really need to hack up something.

Laser And Webcam Team Up For Micron-Resolution Flatness Measurements

March 16, 2023 by Dan Maloney 36 Comments

When you want to measure the length, breadth, or depth of an object, there are plenty of instruments for the job. You can start with a tape measure, move up to calipers if you need more precision, or maybe even a micrometer if it’s a really critical dimension. But what if you want to know how flat something is? Is there something other than a straightedge and an eyeball for assessing the flatness of a surface?

As it turns out, there is: a $15 webcam and a cheap laser level will do the job, along with some homebrew software and a little bit of patience. At least that’s what [Bryan Howard] came up with to help him assess the flatness of the gantry he fabricated for a large CNC machine he’s working on.

The gantry arm is built from steel tubing, a commodity product with plenty of dimensional variability. To measure the microscopic hills and valleys over the length of the beam, [Bryan] mounted a lens-less webcam to a block of metal. A cheap laser level is set up to skim over the top of the beam and shine across the camera’s image sensor.

On a laptop, images of the beam are converted into an intensity profile whose peak is located by a Gaussian curve fit. The location of the peak on the sensor is recorded at various points along the surface, leading to a map of the microscopic hills and valleys along the beam.

As seen in the video after the break, [Bryan]’s results from such a quick-and-dirty setup are impressive. Despite some wobblies in the laser beam thanks to its auto-leveling mechanism, he was able to scan the entire length of the beam, which looks like it’s more than a meter long, and measure the flatness with a resolution of a couple of microns. Spoiler alert: the beam needs some work. But now [Bryan] knows just where to scrape and shim the surface and by how much, which is a whole lot better than guessing. Continue reading “Laser And Webcam Team Up For Micron-Resolution Flatness Measurements” →

A Hacker’s Introduction To DIY Light Guide Plates

March 13, 2023 by Sonya Vasquez 38 Comments

Last year, I found myself compelled to make a scaled-down replica of the iconic test chamber signs from the video game Portal. If you’ve played the game, you’ll remember these signs as the illuminated monoliths that postmarked the start of every test chamber. In hyperstylized video game fashion, they were also extremely thin.

https://www.thonky.com/portal-walkthrough/test-chamber-19 — Stay tuned for cake at the end of this article.

True to the original, my replica would need to be both slimmed down and backlit with a uniform, natural white glow. As fate would have it, the crux of this project was finding a way to do just that: to diffuse light coming in from the edges so that it would emit evenly from the front.

What I thought would be quick project ended up being a dive down the rabbit hole that yielded some satisfying results. Today, I’d like to share my findings and introduce you to light guide plates, one of the key building blocks inside of much of today’s backlit screen technology. I’ll dig into the some of the working principles, introduce you to my homebrew approach, and leave you with some inspirational source code to go forth and build your own. Continue reading “A Hacker’s Introduction To DIY Light Guide Plates” →

Laser Scanner Upgraded To Use PCB Motor

February 22, 2023 by Chris Lott 10 Comments

[Rik]’s Hexastorm laser scanner project originally used a discrete polygon mirror controller+motor module from Sharp to spin a prism. But the scanner head was a bit difficult to assemble and had a lot of messy wires. This has all been replaced by a single board featuring a PCB-printed motor, based on the work of [Carl Bugeja]. The results are promising so far — see video below the break.

Since the prism is not attached to anything, currently it will fall off if mounted in the intended vertical orientation. One of [Rik]’s next steps is to improve the mount’s design to constrain the spinning prism. The previous Sharp motor was specified to 21000 RPM, but was only driven to 2400 RPM in [Rik]’s first version. This new PCB motor spins at 2000 RPM in these tests, comparable to his previous experiments ( we’re not sure about the maximum RPM ).

See our original writeup from 2019 to review the goals of this project, and be sure to checkout details and documentation on the Hexastorm project page. To learn more about PCB motors, read our article about [Carl]’s first design and visit his Hackaday.io page. Thanks to [Jonathan Beri] for the tip.

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Drilling Glass With Femtosecond Lasers Just Got Even Better

February 16, 2023 by Lewin Day 48 Comments

Glass! It’s a finicky thing. Strong as hell, yet chip it and glance at it the wrong way, and you’re left with a bunch of sharp rubbish. It’s at once adored for its clarity and smoothness, and decried for how temperamental it can be in the case of shock, whether mechanical, thermal, or otherwise.

If you’ve ever tried to drill glass, you’ll know it’s a tough errand. To do so without cracking it is about as likely as winning the lottery on Mars. Even lasers aren’t great at it. However, a research team from France has developed a new technique that uses femtosecond lasers to drill microscopic holes in glass with a minimum of tapering and no cracking! Brilliant, no?
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