Taking a picture with a single photoresistor is a brain-breaking idea. But go deeper and imagine taking that same picture with the same photoresistor, but without even facing the object. [Jon Bumstead] did exactly that with compressed sensing and a projector. Incredibly, the resulting image is from the perspective of the projector, not the “camera”.

This camera setup is very similar to one we’ve seen before, but far more capable. The only required electronics are a small projector and a single photodiode. The secret sauce in this particular design lies in the pattern projected and the algorithm to parse the data.

Video is projected onto the target in the form of sinusoidal waves. As these waves change and move their way across the object, the sensor picks up whatever intensity value is reflected. Putting all this data together allows us to create a measured Fourier transform. Use the inverse Fourier transform, and BOOM, you got yourself an image. Better yet, you can even take a picture indirectly. Anything becomes a mirror — even paper — when all you rely on is the average relative intensity of light. If you want to take pictures like this on your own, check out [Jon]’s Instructable.

The science behind this technique is similar to the math that powers CT scanners and VAM 3D printing.

Thanks, [MrSVCD], for the tip!

QR codes are something that we all take for granted in this day and age. There are even a million apps to create your own QR codes, but what if you want to make a barcode? How about making a specific kind of barcode that follows UPC-E, CODE 39, or even the infamous… CODABAR? Well, it might be more difficult to find a single app that can handle all those different standards. Using “yet-another-web-app”, Barcode Tool – Generator & Scanner, you can rid these worries, created by [Ricardo de Azambuja].

When going to [Ricardo]’s simple application, you will find a straightforward interface that allows you to make far more different strips and square patterns than you’ve ever imagined. Of course, starting with the common QR code, you can create custom overlaid codes like many other QR generators. More uniquely, there are options for any barcode under the sun to help organize your hacker workspace. If you don’t want to download an app to scan the codes, you can even use the included scanner function.

If you want to use the web app, you can find it here! In-depth solutions to rather simple problems are something we strive to provide here at Hackaday, and this project is no exception. However, if you want something more physical, check out this specialized outdoor city cooking station.

Learning new instruments is never a simple task on your own; nothing can beat the instant feedback of a teacher. In our new age of AI, why not have an AI companion complain when you’re off note? This is exactly what [Ada López] put together with their AI-Powered Piano Trainer.

The basics of the piano rely on rather simple boolean actions, either you press a key or not. Obviously, this sets up the piano for many fun projects, such as creative doorbells or helpful AI models. [Ada López] started their AI model with a custom dataset with images of playing specific notes on the piano. These images then get fed into Roboflow and trained using the YOLOv8 model.

Using the piano training has the model run on a laptop and only has a Raspberry Pi for video, and gives instant feedback to the pianist due to the demands of the model. Placing the Pi and an LCD screen for feedback into a simple enclosure allows the easy viewing of how good an AI model thinks you play piano. [Ada López] demos their device by playing Twinkle Twinkle Little Star but there is no reason why other songs couldn’t be added!

While there are simpler piano trainers out there relying on audio cues, this project presents a great opportunity for a fun project for anyone else wanting to take up the baton. If you want to get a little more from having to do less in the physical space, then this invisible piano is perfect for you!

Look out of a window, ask yourself the question, “Has a nuke gone off?”. Maybe, maybe not, and all of us here at Hackaday need to know the answer to these important questions! Introducing the hasanukegoneoff.com Indicator from [bigcrimping] to answer our cries.

An ESP32 running a MicroPython script handles the critical checks from hasanukegoneoff.com for any notification of nuclear mayhem. This will either power the INS-1 neon bulb, indicating “no” or “yes” in the unfortunate case of a blast. Of course, there is also the button required for testing the notification lights; no chance of failure can be left. All of this is fitted onto a custom dual-sided PCB and placed inside a custom 3D-printed enclosure.

Hasanukegoneoff.com’s detection system, covered before here, relies on an HSN-1000L Nuclear Event Detector to check for neutrons coming from the blast zone. [bigcrimping] also provides the project plans for your own blast detector to answer the critical question of “has a nuke gone off” from anywhere other than the website’s Chippenham, England location.

This entire project is open sourced, so keep sure to check out [bigcrimping]’s GitHub for both portions of this project on the detector and receiver. While this project provides some needed dark humor, nukes are still scary and especially so when disarming them with nothing but a hacksaw and testing equipment.

Thanks to [Daniel Gooch] for the tip.

XR may not have crashed into our lives as much as some tech billionaires have wished, but that doesn’t stop the appeal of a full display that takes up no physical space. At that point, why not get rid of the computer that takes up living space as well? That is what [Michael] tries to do with Bento, the form factor of an Apple Magic keyboard and the power of a Steam Deck. 

Steam Deck modding is a great project to get started on but we don’t see too many VR or XR uses of the mobile pc. While the VR gaming potential is limited by lackluster power, general productivity is a perfect use case. All that productivity power can be found in a 3D printed case with a battery, allowing for some mobile use. A magic keyboard sits on top of the case, so the entire package takes up less space than the average mechanical keyboard. However, we could always support the addition of a mechanical key version. There’s plenty of spare room in this current design, just look at the storage area!

[Michael] believes that this use of XR fulfills a more true course for “spatial computing” than Apple’s Vision Pro. Of course, this design is not restricted to only XR use; the Steam Deck is capable of running on any normal monitor you would like. Regardless, we need to see the model files to verify for ourselves! [Michael] claims these resources will be available soon, and trust us that we will be waiting!

Minimalist builds are far from unheard of here on Hackaday. After all, less room taken up by random cables or clutter means more room for projects. This is a lesson clearly followed by similar projects such as this completely wireless-powered desktop!

With the newer generation of quick and reliable 3D printers, we find ourselves with the old collecting dust and cobwebs. You might pull it out for an emergency print, that is if it still works… In the scenario of an eternally resting printer (or ones not worth reviving), trying to give new life to the functional parts is a great idea. This is exactly what [MarkMakies] did with a simple RC rover design from an old Makerbot Replicator clone. 

Using a stepper motor to directly drive each wheel, this rover proves its ability to handle a variety of terrain types. Stepper motors are far from the most common way to drive an RC vehicle, but they can certainly give enough power. Controlling these motors is done from a custom protoboard, allowing the use of RC control. Securing all these parts together only requires a couple of 3D printed parts and the rods used to print them. Throw in a drill battery for power, and you can take it nearly anywhere! 

With the vehicle together [MarkMakies] tested to a rocketing 0.6 m/s fully loaded 4WD. Of course, less weight proves more exciting. While [Mark] recognizes some inherent issues with a stepper-driven all-terrain vehicle, we could see some clever uses for the drive system.

Broken down 3D printers are a dime a dozen, so you should try making something similar by checking out [Mark]’s design files! 3D printers are machines of fine-controlled movement so it’s no surprise to find reuse in these projects is fairly common. Just like this nifty DIY camera slider!

We all love combat robotics for its creative problem solving; trying to fit drivetrains and weapon systems in a small and light package is never as simple as it appears to be. When you get to the real lightweights… throw everything you know out the window! [Shoverobotics] saw this as a barrier for getting into the 150g weight class, so he created the combat robotics platform named Project SVRN.

You want 4-wheel drive? It’s got it! Wedge or a Grabber? Of course! Anything else you can imagine? Feel free to add and modify the platform to your heart’s content! Controlled by a Malenki Nano, a receiver and motor controller combo board, the SVRN platform allows anyone to get into fairyweight fights with almost no experience.

With 4 N10 motors giving quick control, the platform acts as an excellent platform for various bot designs. Though the electronics and structure are rather simple, the most important and impressive part of Project SVRN is the detailed documentation for every part of building the bot. You can find and follow the documentation yourself from [Shoverobotics]’s Printables page here!

If you already know every type of coil found in your old Grav-Synthesized Vex-Flux from your Whatsamacallit this might not be needed for you, but many people trying to get into making need a ramp to shoot for the stars. For those needing more technical know-how in combat robotics, check out Kitten Mittens, a bot that uses its weapon for locomotion!

Do you ever get tired of stressing your neck looking for planes in the sky? Worry not! Here is a neat and cheap Arduino/Ras Pi project to keep your neck sore free! [BANK ANGLE] presents a wonderfully simple plane tracking system using an affordable camera and basic microcontrollers.

The bulk of the system relies on a cheap rotating security camera that gets dissected to reveal its internals. Here stepper control wires can be found and connected to the control boards required to allow an Arduino nano to tell the motors when and where to spin. Of course, the camera system doesn’t just look everywhere until it finds a plane, a Raspberry Pi takes in data from local ADS-B data to know where a nearby plane is.

After that, all that’s left is a nifty overlay to make the professional look. Combining all these creates a surprisingly capable system that gives information on the aircraft’s azimuth, elevation, and distance.

If you want to try your hand at making your own version of [BLANK ANGLE]’s tracker, check out his GitHub page. Of course, tracking planes gets boring after a while so why not try tracking something higher with this open-source star tracker?

Thank you Israel Brunini for the tip.

DIY mechatronics always has some unique challenges when relying on simple tools. 3D printing enables some great abilities but high precision gearboxes are still a difficult problem for many. Answering this problem, [Sergei Mishin] has developed a very interesting gearbox solution based on a research paper looking into simple rollers instead of traditional gears. The unique attributes of the design come from the ability to have a compact angled gearbox similar to a bevel gearbox.

Multiple rollers rest on a simple shaft allowing each roller to have independent rotation. This is important because having a circular crown gear for angled transmission creates different rotation speeds. In [Sergei]’s testing, he found that his example gearbox could withstand 9 Nm with the actual adapter breaking before the gearbox showing decent strength.

Of course, how does this differ from a normal bevel gear setup or other 3D printed gearboxes? While 3D printed gears have great flexibility in their simplicity to make, having plastic on plastic is generally very difficult to get precise and long lasting. [Sergei]’s design allows for a highly complex crown gear to take advantage of 3D printing while allowing for simple rollers for improved strength and precision.

While claims of “zero backlash” may be a bit far-fetched, this design still shows great potential in helping make some cool projects. Unique gearboxes are somewhat common here at Hackaday such as this wobbly pericyclic gearbox, but they almost always have a fun spin!

Thanks to [M] for the tip!

Don’t you hate it when making your DIY X-ray machine you make an uncomfortable amount of ozone gas? No? Well [Hyperspace Pirate] did, which made him come up with an interesting idea. While creating a high voltage supply for his very own X-ray machine, the high voltage corona discharge produced a very large amount of ozone. However, normally ozone is produced using lower voltage, smaller gaps, and large surface areas. Naturally, this led [Hyperspace Pirate] to investigate if a higher voltage method is effective at producing ozone.

Using a custom 150kV converter, [Hyperspace Pirate] was able to test the large gap method compared to the lower voltage method (dielectric barrier discharge). An ammonia reaction with the ozone allowed our space buccaneer to test which method was able to produce more ozone, as well as some variations of the designs.

Large 150kV gaps proved slightly effective but with no large gains, at least not compared to the dielectric barrier method. Of which, glass as the dielectric leads straight to holes, and HTPE gets cooked, but in the end, he was able to produce a somewhat sizable amount of ammonium nitrate. The best design included two test tubes filled with baking soda and their respective electrodes. Of course, this comes with the addition of a very effective ozone generator.

While this project is very thorough, [Hyperspace Pirate] himself admits the extreme dangers of high ozone levels, even getting close enough to LD50 levels for worry throughout out his room. This goes for when playing with high voltage in general kids! At the end of the day even with potential asthma risk, this is a pretty neat project that should probably be left to [Hyperspace Pirate]. If you want to check out other projects from a distance you should look over to this 20kW microwave to cook even the most rushed meals!

Thanks to [Mahdi Naghavi] for the Tip!

A common ratchet from your garage may work wonders for tightening hard to reach bolts on whatever everyday projects around the house. However, those over at [Chronova Engineering] had a particularly unusual project where a special ratchet mechanism needed to be developed. And developed it was, an absolutely beautiful machining job is done to create a ratcheting actuator for tendon pulling. Yes, this mechanical steampunk-esk ratchet is meant for yanking on the fleshy strings found in all of us.

The unique mechanism is necessary because of the requirement for bidirectional actuation for bio-mechanics research. Tendons are meant to be pulled and released to measure the movement of the fingers or toes. This is then compared with the distance pulled from the actuator. Hopefully, this method of actuation measurement may help doctors and surgeons treat people with impairments, though in this particular case the “patient” is a chicken’s foot.

Manufacturing the mechanism itself consisted of a multitude of watch lathe operations and pantographed patterns. A mixture of custom and commercial screws are used in combination with a peg gear, cams, and a high performance servo to complete the complex ratchet. With simple control from an Arduino, the system completes its use case very effectively.

In all the actuator is an incredible piece of machining ability with one of the least expected use cases. The original public listed video chose to not show the chicken foot itself due to fear of the YouTube overlords.

If you wish to see the actuator in proper action check out the uncensored and unlisted video here.

Thanks to [DjBiohazard] on our Discord server tips-line!

RepRap was the origin of pushing hobby 3D printing boundaries, and here we see a RepRap scaled down to the smallest detail. [Vik Olliver] over at the RepRap blog has been working on getting a printer working printing down to the level of micron accuracy.

The printer is constructed using 3D printed flexures similar to the OpenFlexure microscope. Two flexures create the XYZ movement required for the tiny movements needed for micron level printing. While still in the stages of printing simple objects, the microscopic scale of printing is incredible.

[Vik] managed to print a triangular pattern in resin at a total size of 300 µm. For comparison SLA 3D printers struggle at many times that scale. Other interesting possibilities from this technology could be printing small scale circuits from conductive resins, though this might require some customization in the resin department.

In addition to printing with resin, µRepRap can be seen making designs in marker ink such as our own Jolly Wrencher! At only 1.5 mm the detail is impressive especially when considering the nature of scratching away ink.

If you want to make your own µRepRap head over to [Vik Olliver]’s GitHub. The µRepRap project has been a long going project. From the time it started the design has changed quite a bit. Check out an older version of the µRepRap project based around OpenFlexure!