Bringing A Cloud Based Monitor Home

November 14, 2026 by Matt Varian No comments

When setting up to grow plants hydroponically, it’s important to keep an eye on the numbers, temperature, pH, and electrical conductivity, to name a few. To do this, [Joziti] bought a Bluelab Guardian monitor, which worked well but had a fatal flaw: it required an internet connection. To free the Guardian from the cloud, [Joziti] developed an ESPHome connection for the Bluelab Guardian.

As far as hardware projects go, this one is pretty straightforward. It involves replacing the built-in wireless chip with an ESP32-S3. [Joziti] used an Adafruit ESP32-S3 Feather, though other ESP32-S3s should work for this purpose too. Once you’ve opened up the Guardian and removed the factory Wi-Fi board, it’s a simple matter of tapping into the +5V/GND/TX/RX pins with your flashed ESP32-S3. Once the hardware is in place, the ESP32-S3 should be reaching out to your Home Assistant instance with all the data the Guardian used to send to the cloud is now sitting on just your local network.

The great part about this hack is that it opens up even more capabilities for your growing setup. With the data sitting in Home Assistant, you can now control automations using that data. Too cold? Flip on some lights. pH out of bounds? Maybe have it send you a message to check it out. Thanks for sharing this improvement on a product, [Joziti]. It’s always great to see a hack that turns a product you bought into a product you own. Be sure to check out some of our other ESPHome hacks we’ve featured over the years.

A series of ten close up images of two pieces of coral. In the first, on the top left, the coral on the left is bright white while the one on the right is brown with darker brown spots. Text reads: "Week 0." The last image, on the bottom right, shows both pieces of coral as brown with darker brown spots and the text, "Week 9." The intervening images show the white, dead coral, slowly becoming more brown as time progresses.

Spreading Life To Bleached Coral

October 20, 2026 by Navarre Bartz 18 Comments

Coral bleaching is a major problem for ocean ecosystems as the ocean gets warmer. Researchers at Stanford have found a new method for regenerating bleached corals.

Scientists working on coral found that when they had a bleached and healthy example accidentally touching in the lab, the symbionts from the healthy coral that make its food were able to spread to the bleached coral, reviving it in a matter of weeks. Contact was only required for one week, although three days was sufficient in a few cases. The effect only seems to work with corals of the same genet as the healthy corals of other genets just take over the bleached coral antagonistically.

This is particularly exciting, as areas where not all coral has bleached may indicate the presence of symbionts that are more heat tolerant, and being able to spread these symbionts to their neighbors quickly can greatly speed up the process of coral regeneration and save the reef. Coral reefs are some of the most vibrant ecosystems in the ocean, so if you save the coral, you can save many other species as well that rely on them.

If you’d like to explore how the coral is doing near you, perhaps you should try an open ROV or a bionic jellyfish?

Making Photovoltaic Solar Cells With A Microwave

October 19, 2026 by Maya Posch 4 Comments

Although solar panels may seem like a kind of magic, they’re really quite simple devices, in their silicon form featuring nothing but the p-type silicon wafer and an n-type layer doped with e.g. phosphorus. Because of this simplicity it’s quite possible to make your own solar cells at home using only a few basic, off-the-shelf ingredients and a kiln, which in this recent video by [Dr. Semiconductor] uses a microwave kiln and thus justifies the video’s title.

Even the silicon wafer that you start with can be easily purchased online, though you have to be careful that it’s a bare wafer, without existing etchings on it. On this you need to get a phosphorus-rich layer, which is done by creating a delicious mixture of 1 mL of tetraethyl orthosilicate (TEOS), 0.3 mL of 85 wt% phosphoric acid, 5 mL of ethanol and 0.25 mL of distilled water. After low heat boiling this for 30 minutes, it is spincoated onto the cut square of silicon wafer using a spinning platform, like a PC fan.

Next, you shove the coated silicon into the kiln and put it into the microwave to bake at a fairly low power level for half an hour. In the video it took less than 50% power of the microwave to not melt the silicon, so remember that those microwave kilns get pretty hot.

With the delightful smells of freshly baked silicon now teasing your nostrils, you can then take out the doped silicon to sand or etch off the thin layer of glass that’s formed around the new PV cell. On the clear spots you can now put a gallium-indium contact on the p-type Si side and a wad of indium on the newly doped Si-P side, which are now your contacts for the PV cell.

The full recipe along with many of the issues discussed in the video can also be found on the blog article, though the video conclusion notes that many improvements are still possible. The created PV cell in the video reaches an efficiency of about 5%, but this could be improved through changes like the use of a clean-room, adding an anti-reflection coating and improving the contact with the cell.

Continue reading “Making Photovoltaic Solar Cells With A Microwave” →

Counting The PET Bottles Needed To Make 1 Kg Of Printer Filament

October 13, 2026 by Maya Posch 34 Comments

In countries where PET bottles do not get slapped with an additional fee that induces you to return it for recycling and said fee back, the resulting piles of discarded bottles have led many enterprising individuals to consider using them to make their own PETG filament. One big question of course is just how much work it is to create even a single 1 kg spool of PETG, which is a question that [PETCraft] was only too happy to answer in a recent video.

With the channel owner clearly living in a country without a bottle deposit, it’s very easy to see PET bottles strewn about as trash, including multi-liter water bottles. As a very recycling-focused channel, this provides an excellent opportunity to show how they go about recycling these into filament.

The heat-smoothed water bottles, ready for cutting.

The detailed process is covered in previous videos in the channel, but essentially they are first heat-smoothed to make them much easier to cut into thin strips. This is done with a very DIY cutter – also constructed from mostly salvaged and other common parts – before the strips are passed through the heated extruder nozzle of the DIY filament extruder before being wound onto spools.

Ultimately it took thirteen 5 liter bottles, a 10 L, two 8 L and a single 1.5 L bottle to hit the 1 kg target, which is quite an impressive amount of work. The next challenge will be to actually print with it, which will – naturally – be done with a DIY 3D printer made from salvaged parts and an Arduino board.

The good news about recycling bottles like this into filament is that basically all PET bottles will actually be PETG anyway, as the glycol adds the flexibility that’s essential in water bottles so that they do not shatter or rip easily. The real question you have to ask yourself is whether cleaning, cutting and spooling dozens of bottles is worth saving perhaps 10-20 bucks on a commercial spool of 1 kg PETG filament.

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DIY Algae Biodiesel Is Harder Than You Think

October 6, 2026 by Tyler August 54 Comments

There’s one thing [Silent H] wants you to know before you watch his video about making biodiesel, embedded below: he started this project before he’d even heard of the Strait of Hormuz. No, he’s just independent-minded and wanted to try making his own fuel when diesel was– in retrospect– cheap as chips. That’s probably a good thing, because while [Silent] gets his pint of fuel at the end of the video, it’s not from algae; it’s from a backup crop of sunflowers.

As it turns out, he picked what was the perfect algae and the absolute worst algae for making biodiesel from: Chlorella Vulgaris. It’s perfect because it’s easy to grow, and easy to extract from the growth medium, as it sinks when it is ‘ripe’, and has a very high oil content. Of course [Silent] didn’t want to toss algae cakes into a steam powered canoe, he wanted diesel fuel for his vehicle. That’s where the project broke down: Chlorella Vulgaris cells are exceptionally tough, and if you can’t rupture the cell wall, you can’t can’t get out any appreciable oil. A few grams by solvent extraction is all he manages before switching to more tractable feedstock.

That feedstock is sunflowers, which give up their oil through the application of violent pressure. That is to say, he crushes the seeds in an oil press. Oil acquired, he goes on to transesterfy the stuff, extracting glycerine to produce biodiesel– a process ripe for hacking that you’d think we’d cover more often.

We have covered the algae growth side of things before, but that algae seemed to be destined for other uses than fuel.

Continue reading “DIY Algae Biodiesel Is Harder Than You Think” →

Gardening With…OpenSCAD?

October 1, 2026 by Tom Nardi 16 Comments

Unless it’s automated or using some other form of high-tech trickery, a vegetable garden isn’t exactly the sort of thing you’d expect to see on Hackaday. Be that as it may, the bountiful crop of peppers [Mihai Oltean] grew on the side of his house was done the old fashioned way, with nary a transistor in sight. So what’s the catch?

Well, in this case, it’s more about the journey than the end result. The produce sprouting in [Mihai]’s garden may be common enough, but the method in which he designed the garden itself is worth a closer look. To our knowledge, it’s the first time somebody sat down and wrote out all the code to generate a 3D model of a vertical garden in OpenSCAD.

Usually, we see OpenSCAD used to produce design files for 3D printing or occasionally 2D CNC operations. But that’s not what’s happening here. The goal was to simply plan out how all the parts of the system would come together, and [Mihai] felt comfortable tackling it in the code-centric workflow offered by OpenSCAD. We know the feeling well.

Though the code isn’t necessarily being used to produce parts for manufacture, [Mihai] does bring in a bunch of virtual components to stand in for their corporeal counterparts. We’re partial to using a parts library such as NopSCADlib for this kind of thing, but from the looks of the GitHub repo, [Mihai] decided to implement his own versions of the screws, nuts, washers, and sections of metal extrusion used to construct the garden wall.

We recently covered the advantages of “building” a complex multi-part project like a CNC control cabinet virtually in your CAD tool of choice before bending metal on the real thing. This project is a fantastic example of that concept, as it shows that the technique isn’t limited to electronic components.

Dumpster-dived Window A/C Becomes Ground-Source Heat Pump

September 22, 2026 by Tyler August 22 Comments

Heat pumps are great, because they pump heat around, and we often don’t want heat where it is. Need it somewhere else? Pump it! It’s great. It’s also a bit pricey if you’re buying new, but [Craftsman Chris] over on YouTube realized that the window air conditioning unit he found in a dumpster is, in fact, a heat pump. Normally it’s an air-source heat pump, but with a delightful series of hacks, he gets it automated and hooked into a ground loop in his latest YouTube video.

The heat sink is provided by a bunch of PEX tubing [Chris] buried in his back yard. After experimenting with using the water loop for cooling directly, he realized that pumping heat out of his house into the cold ground would go much better with a heat pump. That’s where the window A/C came in. After cleaning and servicing it, it was time to convert it to dump heat into water rather than outside air. To do that, [Chris] welded up a tank made of scrap metal around the existing heat exchanger. It’s designed for air, sure, but water takes its heat just fine. The nice thing about this is that by keeping the internals of the air conditioner mostly stock, he doesn’t let out any of the tasty, tasty CFCs that may be hiding inside.

Connecting this unit to his thermostat is equally hacky– he takes an old Programmable Logic Controller that looks fit to run a small factory, and hooks it to a single linear actuator to poke the A/C unit’s stock power button. Is it elegant? No. Does it work? Yes. Is it a hack? Indubitably!

We’ve seen window units pressed into whole-house A/C service before, but adding the water loop is a great hack. We saw a window A/C used as a ground-source pump before, too, but that was a Canadian project and so sensibly turned the machine around to provide heating for the maple mansion.

Continue reading “Dumpster-dived Window A/C Becomes Ground-Source Heat Pump” →