[Dirk] shared a fascinating project of his that consists of several different parts coming together in a satisfying whole. It’s all about wanting to do target practice, indoors, using a simple red laser dot instead of any sort of projectile. While it’s possible to practice by flashing a red laser pointer and watching where it lands on a paper target, it’s much more rewarding (and objective) to record the hits in some way. This is what led [Dirk] to create human-powered, battery-free laser guns with software to track and display hits. In the image above, red laser hits on the target are detected and displayed on the screen by the shooter.
There are several parts to this project and, sadly, the details are a bit incomplete and somewhat scattered around, so we’ll go through the elements one at a time. The first is the guns themselves, and the star of the show is his 3D printed cowboy rifle design. The rifle paints the target with a momentary red laser dot when the trigger is pressed, but that’s not all. [Dirk] appears to have embedded a stepper motor into the lever action, so that working the lever cranks the motor as a generator and stores the small amount of power in a capacitor. Upon pulling the trigger, the capacitor is dumped into the laser (and into a piezo buzzer for a bit of an audio cue, apparently) with just enough juice to create a momentary flash. We wish [Dirk] had provided more details about this part of his build. There are a few more images here, but if you’d like to replicate [Dirk]’s work it looks like you’ll be on your own to some extent.
As for the target end of things, blipping a red dot onto a paper target and using one’s own eyeballs can do the job in a bare minimum sort of way, but [Dirk] went one further. He used Python and OpenCV with a camera to watch for the red dot, capture it, then push an image of the target (with a mark where the impact was detected) to a Chromecast-enabled screen near the shooter. This offers much better feedback and allows for easier scoring. The GitHub repository for the shot detector and target caster is here, and while it could be used on its own to detect any old laser pointer, it really sings when combined with the 3D printed cowboy rifle that doesn’t need batteries.
Not using projectiles in target practice does have some benefits: it’s silent, it’s easy to do safely, there is no need for a backstop, there are no consumables or cleaning, and there is no need to change or patch targets once they get too many holes. Watch it all in action in the video embedded below.
Car manufacturers have a problem when it comes to climate change. Among the variety of sources for extra atmospheric CO2 their products are perhaps those most in the public eye, and consequently their marketing departments are resorting to ever more desperate measures to sanctify them with a green aura. Among these are the French marque Peugeot, whose new electric version of their 208 model features in a slick video alongside a futuristic energy-harvesting billboard.
This is no ordinary billboard, nor is it a conventional wind turbine or solar array, instead it harvests ambient noise in one of the busiest parts of Paris, and turns it into electricity to charge the car with an array of piezoelectric energy capture units. This caught our eye here at Hackaday, because it seemed rather too good to be true. Is it a marketing stunt, or could you make a piezo billboard as a practical green energy device? Let’s take a closer look.
[Vadim Panov]’s 3D printed solar harvester is in effect a rechargeable outdoor battery, and the real challenge he faced when designing it was having it handle the outdoors reliably. The good news is that part is solved, and his newest design is now also flexible enough to handle a variety of common and economical components such as different battery connectors, charge controllers, and solar panel sizes. All that’s left is to set it up using the GoPro-style mounting clamp and let it soak up those solar rays.
We saw his first version earlier this year, which uses inventive and low-cost solutions for weatherproofing like coating the 3D print with epoxy (the new version makes this easier and less messy, by the way.) It was a fine design, but only worked with one specific solar panel size and one specific configuration of parts. His newest version makes a few mechanical improvements and accommodates a wide variety of different components and solar panel sizes. The CAD files are all available on the GitHub repository but he’s conveniently provided STL files for about a dozen common sizes.
When it comes to harvesting light, staying indoors offers less power but requires a far less rugged setup. If that interests you, be sure to check out the Tiny Solar Energy Module (TSEM) which can scrape up even indoor light.
Harvesting energy from the human body may sound scary, but fortunately a Matrix-style setup exists only as a cinematic fiction. Instead a typical path lies in external contraptions that use the body’s natural motions to drive a small generator, a bit of flexible piezo material, and so on. A popular target for harvesting the body’s kinetic energy is the knee joint, as this has a comparatively large range of motion and is fairly easy to use.
Thus a team from Hong Kong university opted to pick this part of the human anatomy for their experiment as well. While at first glance their results do not seem particularly impressive, with up to 1.6 mW of power generated, a look at their published results in the Applied Physics Letters journal showed their reasoning behind this setup. While one generator-based setup referenced produces on average 4.8 Watt of power, the device itself weighs 1.6 kg and increases the rate at which the person wearing it burns calories by a significant amount.
The goal for this device was to have a way to generate significant amounts of power without having the user exerting themselves more than usual. This led to them using flexible piezoelectric composites, resulting in a weight of just 307 grams, based upon two M8514-P2 pieces (Smart Materials Corp. manufacturer). Tests with volunteers on a treadmill show that users do not burn more calories than without.
As with all piezo materials, they can flex a bit, but not too much, so a lot of time and effort went into calculating the optimal bend radius in different usage scenarios. While around 1 mW of power is not massive, it is a reliable source of power for individuals who do any amount of walking during the day and doesn’t require any effort beyond strapping the device onto one’s legs.
At first glance, adding solar power to your project might seem easy. Get a photovoltaic panel, point it towards the big ball of burning gas in the sky, and off you go. But in reality, there’s a bit more to it than that. Especially when you’re trying to do something on a small scale. Without a rooftop full of panels pumping out power, you’ve got to take what you can get.
As far as the electronics go, this project is about as straightforward as it gets. The three watt panel is connected up to a simplistic charging circuit, which in turn feeds into a single 18650 cell. You might be wondering why a charge controller is even necessary in such a simple set up. One problem is that the output voltage of the panel is higher than that of the battery. You also need a blocking diode that will prevent the battery from discharging into the cell during the night or in cloudy conditions.
While the electronics might seem elementary to some readers, we think the 3D printed case alone is worth taking a look at. Not only has [Vadim] come up with a design that perfectly encloses the fragile solar panel and associated electronics, but in the video after the break, he also explains how the entire thing can be made waterproof with an epoxy coating. As 3D prints can have a tendency to be porous, this technique is definitely something you should file away mentally if you’ve been thinking of deploying a printed enclosure outdoors.
Jewelry making offers many opportunities for the electronics tinkerer, and on these pages we’ve seen some eye-catching creations using LEDs to great effect. They all have the same limitation though, it’s difficult to power something that tiny without a cumbersome battery. In seeking to solve that problem there have been a variety of inventive solutions tried, but they haven’t matched the approach of [Lloyd Konneker] who has turned the whole premise of most electronic jewelry on its head.
Instead of LEDs, the party trick of his earring is an electric motor that makes it spin, and instead of giving out light it takes it in as solar power. The motor is a pager alert device, the solar cells are repurposed photodiodes, and the power is stored in a capacitor until there is enough to drive the motor, at which point a MOSFET is triggered to do the work. It’s all made possible by a Texas Instruments TPS3839 supply voltage supervisor chip, and it works well enough to turn from time to time in bright sunlight. The prototype uses a conventional PCB, but a better version is in the works with a flexible board.
His write-up should be of interest to anyone with a need to learn about micropower circuits, as it goes into significant detail on their tuning and operation. Last year’s Hackaday Prize had an entire section devoted to energy harvesting which is well worth searching the site for, a typical example was this solar powered microcontroller board.
The Tiny Solar Energy Module (TSEM) by [Jasper Sikken] is not only physically tiny at one-inch square, but it is all about gathering tiny amounts of solar energy — amounts too small to be useful in a conventional sense — and getting meaningful work done, like charging a battery for later use. Elements that make this board easy to integrate into other projects include castellated vias, 1.8 V and 3.3 V regulated outputs that are active when the connected battery has a useful charge, and a low battery warning that informs the user of impending shutdown when the battery runs low. The two surface-mount solar cells included on the tiny board are capable of harvesting even indoor light, but the board also has connection points for using larger external solar cells if needed.