Tricking An Air Conditioner Into Cooling

August 31, 2026 by Bryan Cockfield 3 Comments

Modern heat pumps, of which air conditioners are a subset, seem like simple machines in theory. They just move heat from one place to another. But in order to operate efficiently, they need specific temperatures and humidities on either side of the pump or they can behave in non-ideal ways. [GreatScott!] noticed this when his air conditioner worked well during a heatwave, but started acting anemic once the outside air temperature cooled down. At once point it was barely able to bring his indoor house temperature below the temperature outside, and he went on a deep dive to investigate why this would be and then found a way trick his air conditioner into working outside its designed temperature range.

Many things can cause this behavior, and some of them are indicative of malfunctions like low refrigerant levels or problems with the compressor or control circuitry. But [GreatScott!]’s unit is pretty new so it was unlikely to be something like that. To investigate, he built a circuit with a small heater which is paired to the outdoor heat exchanger’s temperature probe, tricking the control circuitry into working in a different mode. With a few temperature sensors inside and outside, this was enough to kick the air conditioner into high gear and start outputting cold air again.

While noting that we aren’t HVAC experts, there are a few things that could cause this. One of which is high indoor humidity which might be likely for Germany in the summer, or the outdoor condenser needing a certain temperature or pressure range to operate efficiently. Whatever the case, [GreatScott!] decided to remove his creation to keep from inadvertently damaging his air conditioner. It is possible, however, to use a bit of machine learning to find out more about why one’s HVAC system isn’t behaving as well as it should.

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Brown wrapped chrome handlebars leaning against a light grey wall. Near the stem, a series of four small pins protrude from the bars to indicate a full battery charge of 100%.

Sleeper E-bike Has Solenoid Display

August 22, 2026 by Navarre Bartz 21 Comments

[GRMNT] decided to bring his grandpa’s beautiful road bike into the future by making a sleeper e-bike conversion.

Going into the project, [GRMNT] didn’t really know what he was working with, but it turned out grandpa had good taste and was rocking a Bianchi. No stovepipe bike boom stuff here, only high quality Tange steel. After cleaning off the years of grime, it was time to rebuild a second-hand Bafang mid-drive electric motor for the electric boost for the ride.

We really like the custom solenoid-powered display that [GRMNT] built into the handlebars for an excellent electromechanical readout of the battery charge. Coupled with the hand-built battery pack inside a leather case and hidden motor actuation button, this build looks slick without screaming e-bike.

We’ve covered some other conversions in the past including this one using an electric skateboard motor or this plug-and-play kit. If you’d rather power things with your bike, you’ll like this hack that can make everything bike powered.

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High-Density Parchment Paper Papertronics With Laser-Carved Hydrophilic Channels

August 8, 2026 by Maya Posch 6 Comments

Paper as a substrate for electronic circuits is not very common, but promising for flexible circuits with low cost and easy recyclability. That said, paper is not an easy material to work with when printing traces, as the cellulose material is both absorbent and irregular, limiting the resolution and accuracy of so-called papertronics. Even when using higher-quality paper with wax-based masks this resulted in poor resolution issues, so [Zahra Rafiee] et al. opted to approach the problem from the other direction, by using hydrophobic parchment paper as the base combined with a laser.

The nice thing about the inks used with papertronics that they aren’t just traces, but can also be functional elements like resistors, which is also demonstrated in the paper. The channels for the inks are created using a 50 Watt CO₂ laser, which etches away the silicone coating on the parchment paper. The achieved resolution in the article is around 250 µm for line widths and 300 µm line spacing, which is much better than that for wax-based alternatives.

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Use Your Head While Trimming Trees

July 29, 2026 by Bryan Cockfield 42 Comments

[Attoparsec] occasionally rides a bicycle for transportation, but with the major downside of doing this in North America, a place where bicycle infrastructure is generally neglected. From snow removal, maintenance, separation from cars, or even existing in the first place, the places bicyclists use are generally last to be cared for. One of these deficiencies is landscaping maintenance, with plant growth routinely extending into travel ways. Rather than continue to get hit in the face by tree branches, [Attoparsec] took matters into his own hands, or in this case, head.

Since he’s riding down the bike path anyway, the original thought was to add a trimmer to the front of the bicycle. This has a notable downside of being dangerous to others, so instead he added a string trimmer to his helmet. The electric trimmer was scavenged from an old handheld landscaping tool, with a 3D printed mount designed in CAD to cleanly mount to his bicycle helmet. It’s wired to a control on the handlebar, so when a branch is coming up it can be activated by hand and then pruned without much thought other than properly aiming one’s head.

By most measures this eccentric contraption seems to work quite well. There’s not enough torque to affect the rider’s head in any negative way, the strings are long enough to reach far enough to trim the leaves and branches before they can impact the rider’s face, and it’s safe for other users of the bike path. [Attoparsec] calls this “guerrilla urban landscaping”, a bit different from other forms of guerrilla gardening we have seen before.

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An image of a brown, red, and black mosquito on light human skin

Keeping Mosquitoes Away With Catnip-Based Repellent

July 24, 2026 by Navarre Bartz 32 Comments

Despite their small size, mosquitoes are one of the deadliest creatures on Earth, and keeping them away from you is one of the best ways to stay safe. DEET has been the mainstay of insect repellents for decades, but what if there was a repellent you could grow yourself?

Researchers at Cardiff University found that the essential oil from catnip plants (Nepeta cataria) could be as effective as DEET at repelling mosquitoes when applied as a 6% lotion. The oil has been shown to be effective against many species of mosquitoes, ticks, and mites in previous research. You can look at the paper for details, but the catnip oil was obtained through steam distillation followed by some processing with hexane. The essential oil was then mixed with “water, glycerin, emulsifying wax, cetyl alcohol, cetyl stearyl alcohol, shea butter, glycerol monostearate, olive oil, coconut oil, sunflower oil, methyl paraben, propyl paraben and silicone oil.” We suspect that list will look familiar to anyone who’s read an ingredient label of most any store bought lotion, unless it was paraben free.

The Guardian’s coverage quotes one of the researchers, [Dr. Simon Scofield]: “We did not conduct any experiments to see if it is attractive to cats, but given that the active ingredient [nepetalactone] has well-known cat-attractive properties, I would expect they would quite like it,” he said. Depending on how your cats react, you may want to consider applying the lotion shortly before departing home.

If you want some more options in your mosquito defense, how about becoming a bug zapper, using drones and sonar, or genetically modifying mosquitoes to curb their numbers.

Recycling Laptops And IMacs Makes PC Building Fun And Affordable Again

July 19, 2026 by Tyler August 55 Comments

Building a PC used to be a fun adventure — what’s the latest, what’s the greatest, what can I afford? Well, that last question seems to have taken over and sucked all the fun out for a lot of people. [Matt] from [DIY Perks] on YouTube has hit upon a solution that’s brought back the fun, at least for him: recycling! The video is embedded below, and he runs a forum whose thread has more details.

Long story short, though, he’s flagging recycled laptop components as both good value for money and a fun rabbit hole to go down researching parts. The best part, of course, is that you can get a mobo with 32GB of RAM soldered on, and embedded RTX graphics, and a decent processor for about what you’d pay for that RAM on sticks these days. The big hack is getting the dang thing started: he needed to make a single-pin ribbon cable after identifying which pin on the keyboard membrane hit the power button. If you can score a laptop that does not power on from the keyboard, you’ll have an easier time in that regard.

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An Interactive Tomato Farm Overseen By AI

July 7, 2026 by Ian Bos 14 Comments

Oh, the farming lifestyle…living off the land, fending for yourself. But who’s got time for all that? For the modern hacker, the best option in the garden space may be this over-engineered automated AI tomato farm created by [Gerd Nicolay]. You can even interact with it right now through the magic of the Internet.

[Gerd] started off with your run-of-the-mill pot and plant, choosing the humble tomato to keep the system simple. Then things started to escalate, with the addition of automatic lighting, watering, and data logging environmental parameters like humidity. Now we’re getting somewhere, but there’s more that can be added. How about an entire AI council to monitor and decide the fate of each individual tomato while recording an entire storyline to go alongside the growing cycle?

That’s right, four different models collaborate to ensure only the utmost quality of care for these tomatoes based on camera feeds, humidity, and various other environmental factors being recorded constantly. Is this a little overkill? Maybe for those who have even a modest sense of gardening knowledge — but who can bash the mountain of documentation and data collection on these wonderful little plants?

Perhaps the best part: you can recommend actions for the AI counsel to take from the comfort of your own web browser. While the TomatoFarm might be slightly unnecessary for the average farmer, if you want to try a more reasonable monitoring system, we have you covered too!