A white man in a dark t-shirt and glasses stands next to a pegboard. On the pegboard is a cylindrical wooden bird house with a small piece of metal roof attached to the top. A set of heat lamps are suspended above and give the image a reddish-orange glow. 87˚F is in white text in the lower left corner.

Do Metal Roofs Turn A Bird House Into An Oven?

June 27, 2026 by Navarre Bartz 33 Comments

Birdhouses can be a great way to help out nesting birds in your area, but they can be a bit intensive to make. As part of a 500 birdhouse marathon, [Of Human and Nature] decided to test whether a metal roof would be safe or turn the birdhouse into an oven.

Most DIY birdhouses are made of wood to encourage cavity nesting species that would naturally find a hole in a tree to use the house. Unfortunately, an unprotected chunk of wood will deteriorate much faster than a whole tree full of holes might. A metal roof reduces the exposure to the elements, but does it make the box too hot?

[Of Human and Nature] heeded concerns from commenters and actually tested his hypothesis with a simple set of thermocouples, a heat lamp, and an assembled birdhouse. While the metal roof was held at 70˚C for four hours, the inside of the house stayed in the mid 20˚C range thanks to the separation between the roof and the actual box which allows air to flow between the two.

Maybe a metal roof could help you house your homing pigeons as well? If you want to spread the mesh with your birdhouse instead, how about a solar panel roof with a LoRa node?

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Come With Me If You Want To Weed: Autonomous Weedinator Robot Back For 2026

June 19, 2026 by Tyler August 18 Comments

The WEEDINATOR agricultural robot is one of the longer-running projects we’ve featured here on Hackaday. We first featured it way back in 2017 for that year’s Hackaday prize, and after a nearly a decade of work on-and-off it has hit a very important milestone: it is now an effective horticultural instrument, as you can see in the latest demo video below.

There have been some big changes over the years. For one, the scope of the project narrowed considerably with the adoption of a commercial tractor as the base, specifically an Iseki 321 . They picked the Iseki after examining several competitors, and it won out because its hydrostatic drive was best able to handle the very low speeds desired. It looks like they’re now focused on cultivation — that is, tearing out weeds mechanically — rather than the flame weeder they started with. The cultivators are of the claw type, and has three claws powered via the tractor’s hydraulics for control in all three axis: X, Y and Z. Of course the project now leverages modern computer vision toolsets, using a combination of OpenCV and YOLO26n running on a Jetson Nano board. The robotics half of the equation is handled on an STM32 Nucleo.

Aside from being one of our longer-running submissions, we have to call out the team for being one of the very few — perhaps the only — to go to the effort of creating a theme song for their project. If you’ve only got a minute to see the robot run, you might as well look at the second video embedded below and give a listen.

While WEEDINATOR has got the most persistence, they’re not the only ones in the garden robot game. We’ve seen projects using everything from concentrated sunlight to precision-applied herbicides to clear unwanted plants over the years.

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Building An Organic Flow Battery Based On Green Tea

June 17, 2026 by Maya Posch 9 Comments

As simple of a concept flow batteries are, the used chemicals can still be somewhat problematic in the context of a school experiment. To this end [Markus Bindhammer] decided to implement a flow battery version that uses compounds from green tea for its electrolyte, based on a German research paper from 2016.

These organic flow batteries can use gallic acid, pyrogallol as well as the polyphenols in green tea, making them rather safe even in the hands of more careless students. The demonstrated flow battery uses a carbon electrode with activated carbon around it to increase surface area, a platinum wire electrode, and a graphite foil as third electrode.

In the paper a silver electrode is also used, along with the additional electrodes, and a terracotta flower pot as the barrier between the carbon and graphite electrodes, with [Markus] further explaining that there are fortunately cheaper options than what he is using, especially with the flower pot instead of a special ceramic vessel.

The electrolyte solution has epigallocatechin gallate (EGCG) dissolved in it, which here comes in the form of finely ground green tea powder (commonly known as matcha), which so happens to be pretty rich in this substance. In the below graphic by [Markus] you can see the complete set of solutions and other relevant details.

Of course, the performance of this type of flow cell isn’t amazing, with a cell voltage of less than a volt and a few mA of current, but it’s enough to spin a small fan, and to light up a few LEDs. This would be more than enough to demonstrate the reaction and flow cells in general, as long as you don’t mind donating some tasty matcha to science.

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Bike-Powered Shredder Makes Short Work Of 3D Printer Waste

June 16, 2026 by Donald Papp 17 Comments

[Brogan M Pratt] and his students do a lot of 3D printing, and as such found themselves producing a lot of plastic waste. Seeing an opportunity, they built a bike-powered plastic shredder that turns a little human exercise into the power needed to transform waste plastic into small bits. Shredding plastic is a necessary first step for any sort of processing, so getting this part working reliably is as important as it is educational.

Shredding is a necessary first step to processing plastic waste.

Being in the Netherlands, using a bike makes perfect sense. But it turns out there’s a lot more to making a human-powered plastic shredder than simply bolting a sprocket to a shredder, looping the bike chain over it, then climbing on and working up a sweat.

In between the bike and the shredder is a large gear reduction, a fifteen kilogram flywheel, and a heavy-duty frame to anchor everything in the face of so much mass and torque. Add some covers and safety guards and the result is a stationary bike with a hopper for waste, a bin for output, and enough rotational torque and inertia to chew through stubborn bits without stalling.

Now that the shredder works, what’s the plan for all the little plastic shreds? The goal is to turn it back into usable filament which is obviously very useful, but we’ve also seen that compression molding plastic waste can work pretty well, too.

Being an educator, [Brogan] makes it clear that a bike-powered shredder, while pretty cool, is not the only missing link in sustainability. There is currently no easy way to recycle plastic at scale. But the shredder is a critical part of demonstrating the whole process in a hands-on way, and learning why recycling plastic at scale is a genuinely difficult job.

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Desalinating Seawater With Solar And No Brine

June 7, 2026 by Maya Posch 40 Comments

Although desalination is very commonly used these days to convert seawater into fresh water, one of the major disadvantages of current approaches is that commercial desalination plants produce a lot of brine, which has to be dumped somewhere ideally without causing major environmental issues. A new solar-thermal method as demonstrated by [Luheng Tang] et al. was published in Light: Science and Applications, with accompanying PR article.

This method is claimed to require no pre-treatment or leave brine, using special panels that wick water across their surface and then use solar radiation to distill this water. This differs from previous similar methods through a special surface treatment that prevents build-up of salts which would require cleaning or replacement.

The salts and other contaminants that would normally end up in the brine slough off these cells and can then be further processed to recover everything from plain table salt to lithium as well as gold, uranium and other substances of interest that are prevalent in seawater.

So far these self-cleaning cells have been tested with water from a number of oceans with a claimed 74% solar-to-vapor conversion efficiency and nearly 100% salt extraction. As always the challenge will be in scaling this up to industrial levels, but so far it looks promising.

From Scrappy Pallet Wood To Fancy Tea Tray

June 2, 2026 by Maya Posch 16 Comments

Pallets are a wonderful way to package goods and move them around, but especially the wooden ones have a very finite lifespan. This means that many of them are discarded every day, even though there is still good wood on them. Even if it’s not the highest quality wood, you can still use it for some nice wooden items, like the tea tray that [GR Woodworking] recently put together.

The reclaimed wood is the typical fast-growing, soft type, with the suspicion of it being paulownia here. Of course, wooden pallets use a wide variety of wood varieties, so not all reclaimed wood is equally suitable for applications like this, and identifying the type can be a challenge in itself.

In the video it’s shown how the wood is planed to make it smooth and straight, before the joints are created and it is married to the poplar or aspen base plate. Of note is that absolutely no power tools or bulky things like router tables are used here, just basic hand tools that should make this kind of woodworking accessible to people even without that kitted-out woodworking shop.

After assembly it’s finished with Vararhana oil-based stain to give it a darker look and really bring out the grain. Naturally, since it’s a tea tray it has to be commissioned with a proper tea ceremony, which it passes with flying colors.

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On The Wisdom Of Replacing A NiMH Module In A Prius Battery Pack

June 1, 2026 by Maya Posch 81 Comments

Old versus new Prius NiMH module. (Credit: HubNut, YouTube)

It’s possible to get a pretty good deal on used Toyota Prius cars, but as with all hybrid cars that also means a used battery pack and resulting issues. In the case of the Gen 2 Prius that [HubNut] recently acquired it was clear that its battery was effectively toast, with the engine running constantly and the car often giving up due to detected issues with the pack. After getting to an EV-focused garage for repairs, a spare NiMH module was used to replace a problematic module to bring it back to good health, while raising the question of how sensible such a repair is.

Certainly, compared to the average BEV where a much larger battery is generally integrated well into the frame, a Prius makes things very easy, with the compact battery readily accessible and removable from the trunk. It is also a very modular battery, with some elbow grease and bolt-twisting enough to disassemble it.

Even with that it still a high-voltage battery with all the associated risks, and as raised in the comments there’s a big question about putting a new(er) cell into a pack with more worn-out NiMH cells as generally the cells wear out fairly evenly. While this fix can give the pack some more life, the new cell won’t match the internal resistance and other parameters of the pack, leading to issues like voltage drift. Then there’s the issue that if one cell failed, others probably aren’t far behind, so this hack would soon become a regular ritual.

Much like swapping one bad 18650 Li-ion cell in a bigger battery, it’s probably a more sustainable solution to simply replace the entire battery at once, or at least replace all modules or cells to properly refurbish it. For [HubNut] this fix suffices because he suspects that this pack was already assembled from random modules, it’s an important consideration to make if you don’t enjoy ending up stranded during a trip.

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