2025 Pet Hacks Contest: Cat At The Door

Note: This article is an original, publish-ready synthesis based on real 2025 maker-project details, reputable pet-care guidance, and practical cat-owner experience. No source-code artifacts or citation placeholders are included.

Every cat owner knows the sound: one tiny paw at the door, one offended meow, and then the long, theatrical silence of a creature wondering why its staff has failed so completely. The 2025 Pet Hacks Contest: Cat At The Door project turns that everyday feline drama into a clever DIY technology story. Instead of relying on superhuman hearing, scratched paint, or a cat’s ability to guilt-trip through solid wood, the project uses sensors and wireless communication to notify a human when the cat is waiting outside.

CAT AT THE DOOR, created by Andrea Favero, became one of the standout winners of Hackaday’s 2025 Pet Hacks Challenge. It is open-source, practical, funny in the best maker-culture way, and just over-engineered enough to make engineers smile. The idea is simple: detect when a known cat is at the door, identify which cat it is, and send a notification to a portable device so the human can perform the ancient ritual known as “opening the door.”

But behind that simple goal sits a thoughtful mix of mmWave radar, BLE tags, LoRa communication, an ESP32-based controller, 3D-printed enclosures, e-paper display alerts, and a buzzer. In other words, this is not just a cat doorbell. It is a tiny smart-home system built for a very demanding client with whiskers.

What Is the 2025 Pet Hacks Contest?

The 2025 Pet Hacks Challenge invited makers to build creative, useful, and occasionally delightfully ridiculous projects inspired by pets. The entries ranged from smart feeders and cat bowl monitors to pet activity trackers, fountains, dog doors, and cat-focused safety systems. The contest celebrated a charming truth: people will absolutely solder wires, write code, print plastic parts, and debug wireless connections if it means making life better for their animals.

CAT AT THE DOOR stood out because it solved a common real-world problem without pretending cats are predictable. Many cats do not politely ring a bell. Some scratch. Some sit silently. Some meow once and then act personally betrayed when nobody appears in three seconds. For households where a cat has supervised outdoor access, a garden, a patio, or a building rule that prevents installing a cat flap, a notification system can be genuinely helpful.

How CAT AT THE DOOR Works

The project is built around two main devices: a stationary unit and a portable unit. The stationary unit sits indoors near the door or window where the cat usually returns. The portable unit stays with the owner and provides an alert when the system recognizes that a known cat is waiting outside.

Step 1: Radar Detects Movement Near the Door

The system uses a 24GHz mmWave radar module to notice movement or presence near the doorway. This is a smart choice because radar can work in low light, through certain non-metal materials, and in conditions where a camera might struggle. A camera can be powerful, but it introduces privacy concerns, lighting problems, training complexity, and more processing overhead. A simple motion sensor, such as PIR, may be affected by sunlight, temperature shifts, and the cat’s exact position.

Radar is not magic, of course. The project documentation notes that placement and tuning matter. If the radar is too sensitive, it may detect rain, movement in the wrong area, or other environmental noise. If it is too narrow or poorly aimed, it may miss a cat approaching from an odd angle. Anyone who has lived with cats knows they rarely choose the sensible path when a dramatic side entrance is available.

Step 2: BLE Tags Identify the Cat

Detecting “something” at the door is not enough. It could be your cat, a neighbor’s cat, a curious squirrel, or a delivery driver who is about to become deeply confused by a cat buzzer system. CAT AT THE DOOR solves this by using Bluetooth Low Energy tags attached to the cats’ collars. When the radar sees movement, the ESP32-based unit scans for registered BLE tags. If the tag matches a known cat, the system knows who is waiting.

This is one of the most practical parts of the design. Microchips are excellent for permanent identification, but pet microchips are not GPS trackers and are not designed for long-range real-time detection. They are passive identification devices that typically require close scanning. BLE tags, by contrast, can broadcast a signal that a nearby device can detect. The project uses this difference wisely: microchips remain important for lost-pet recovery, while BLE tags help with local door detection.

Step 3: LoRa Sends the Alert Through the House

Once the stationary device recognizes the cat, it sends a wireless message to the portable unit using LoRa. LoRa is useful for long-range, low-power communication, especially where Wi-Fi may be unreliable through walls, floors, or garden-facing structures. In a typical home, this means the owner does not need to stand near the door listening for a tiny royal summons.

The project also includes a clever LoRa power negotiation system. The devices can adjust transmission power based on signal strength, helping maintain a reliable connection while conserving battery. That detail may sound nerdy, but it matters. Battery-powered projects live or die by power management, and a portable notifier that dies quietly in a drawer is just a very small paperweight.

Step 4: The Portable Unit Notifies the Human

The portable device uses an e-paper display and a buzzer. The e-paper screen is a great fit because it consumes very little power when static and remains readable without needing a bright backlight. The buzzer adds the “hey, servant, your cat awaits” energy. Together, they make the alert both visible and audible.

Importantly, the project does not automatically open the door. It notifies the human. That distinction matters for safety. Automatic doors can introduce risks: tails, paws, unfamiliar animals, weather, and security concerns. CAT AT THE DOOR keeps the human in the loop, which is often the best design decision when animals and moving hardware are involved.

Why This Pet Hack Feels So Useful

The magic of this project is not that it uses advanced components. The magic is that it starts with a familiar pet-owner frustration and builds only what is needed. Many smart-home gadgets fail because they begin with technology and go hunting for a problem. CAT AT THE DOOR begins with a problem: “My cat is outside, and I do not always know it.” Then it chooses technology that fits.

For example, a camera-based system might identify the cat visually, but it could fail at night, require training data, and create privacy questions. A simple pressure mat might work in one location but fail if the cat sits three inches away, because cats consider precision beneath them. A bell requires training, and some cats will either refuse to use it or use it at 3:14 a.m. for entertainment. The radar-plus-BLE approach balances detection and identification without turning the door into a full surveillance studio.

Pet Safety: Smart Tech Should Support Good Care

Any article about a cat waiting outside should also talk about safety. Outdoor access can expose cats to traffic, predators, parasites, extreme weather, fights with other animals, infectious disease, and the general chaos of the world beyond the couch. Many veterinary and animal-welfare organizations recommend keeping cats indoors or offering controlled outdoor access, such as leash walks, enclosed patios, or catios.

That does not mean every household has the same setup. Some cats live in places where supervised garden time is common. Some homes have enclosed yards. Some cats are former outdoor cats who need a gradual transition. The responsible approach is to reduce risk wherever possible: keep vaccinations current, use parasite prevention recommended by a veterinarian, consider microchipping, update contact information, and use a properly fitted breakaway collar if a collar is part of the setup.

CAT AT THE DOOR fits best as a notification aid, not as permission to let a cat roam freely without thought. It can help an owner respond quickly when a cat returns, especially in bad weather or colder months. It can reduce scratching and missed meows. It can also make supervised outdoor routines smoother. But the best pet hack is always the one that respects the animal’s safety first.

Design Lessons From CAT AT THE DOOR

1. Build for the Animal’s Real Behavior

Cats do not read manuals. They do not care that you spent six hours tuning a sensor. A good pet-tech project has to work around real behavior, not fantasy behavior. CAT AT THE DOOR does this well by detecting presence rather than requiring the cat to push a button, step on a platform, or perform a tiny TED Talk at the threshold.

2. Keep the Human in Control

Instead of creating an automatic door opener, the project sends a clear alert. This is a sensible compromise. The owner still decides when to open the door and can check whether the cat is wet, muddy, carrying prey, or followed by an uninvited guest. In pet tech, automation is helpful only when it does not remove necessary judgment.

3. Use the Right Sensor for the Job

The project considered the limitations of other options. Cameras need light and image processing. Passive infrared sensors can be tricky outdoors. Microchips are not suited for this detection range. BLE alone may not reliably prove a cat is physically waiting at the door. Combining radar with BLE creates a more reliable trigger: radar says “something is here,” and BLE says “it is one of our cats.”

4. Documentation Makes a Project More Valuable

One reason CAT AT THE DOOR attracted attention is its documentation. A project that includes code, 3D print files, build instructions, hardware notes, and troubleshooting tips is more than a personal invention. It becomes a learning resource. Makers can borrow the radar tuning approach, the LoRa strategy, the enclosure design, or the general architecture for other pet and smart-home projects.

Could the Average Cat Owner Build It?

Maybe, but this is not a five-minute craft involving cardboard and optimism. CAT AT THE DOOR requires intermediate DIY skills. Builders should expect firmware flashing, soldering, configuration files, BLE scanning, radar tuning, 3D printing or access to printed parts, and general patience. If you have used ESP32 boards, MicroPython, or small electronics before, the project is approachable. If your last tool-related achievement was assembling a cat tree while losing only two screws, you may want help from a maker friend.

That said, the idea can inspire simpler versions. A beginner might start with a basic wireless doorbell triggered by a cat-accessible button. Another person might use a camera notification system pointed only at a private backyard. Someone else might create an indoor “cat wants out” button, which is brave, because some cats will immediately weaponize it. CAT AT THE DOOR is the polished maker version, but the underlying goal can be adapted to different homes and skill levels.

What Makes This Project SEO-Worthy and Reader-Friendly?

From a content perspective, 2025 Pet Hacks Contest: Cat At The Door has excellent search potential because it connects multiple interests: DIY pet hacks, smart home projects, cat door solutions, LoRa pet technology, BLE tags for cats, ESP32 builds, and safe outdoor cat management. Readers may arrive because they love cats, because they build electronics, or because their own cat has been treating the back door like a complaint department.

The article also has a natural emotional hook. Almost every cat owner has experienced the “cat at the door” situation. The technology is interesting, but the relatable problem makes it memorable. That balance is ideal for SEO: useful information, clear structure, related keywords, and a story people actually want to read.

Practical Tips for Cat Owners Inspired by This Project

• Use identification wisely: A microchip is still one of the best permanent identification tools, but it is not a live tracker.
• Choose breakaway collars: If your cat wears a collar, use a safety-release design to reduce snagging risk.
• Offer safe outdoor enrichment: A catio, enclosed porch, supervised garden time, or leash training can provide stimulation with less risk.
• Reduce door stress: If your cat scratches or meows at doors, add indoor enrichment, vertical space, puzzle feeders, and predictable routines.
• Do not over-automate: A notification system is safer than a fully automatic door in many homes.
• Test in real conditions: Rain, darkness, sunlight, walls, and cat stubbornness can all affect a pet-tech build.

Experience-Based Notes: Living With a “Cat at the Door” Problem

The funniest thing about the CAT AT THE DOOR project is that it solves a problem cat owners instantly understand. A cat does not simply arrive at a door. A cat stages an event. Some cats announce themselves with a dramatic yowl that sounds like they have returned from sea. Others tap once, sit perfectly still, and then blame you for missing the signal. Some cats scratch the door with the steady rhythm of a tiny debt collector. The human, meanwhile, is upstairs, in a meeting, cooking dinner, or wearing headphones, completely unaware that a furry supervisor is waiting outside and filing a mental complaint.

In real life, a door-notification system can change the household rhythm. Instead of checking the door every few minutes, the owner gets a direct alert. That means less anxiety, fewer scratches, and fewer moments of suddenly wondering, “Wait, is the cat still outside?” For families with more than one cat, individual identification is especially helpful. One cat may be allowed in the garden for ten minutes, while another may need to stay indoors because of age, medication, diet, or personality. BLE-based identification makes the alert more meaningful than a generic motion notification.

There is also a comfort factor. On cold, wet, or windy days, a fast alert can help the owner bring the cat in sooner. During evening hours, it may prevent a cat from waiting quietly in low visibility. The system does not replace supervision, but it adds a helpful safety net. Think of it as a polite digital butler who says, “Excuse me, Macchia is at the door,” instead of forcing the cat to escalate to window boxing.

Of course, any experience-based setup needs a training periodfor the human, not just the cat. The owner has to learn where the cat usually stands, how the radar responds to weather, how far the BLE tag reads, and whether the buzzer is loud enough without becoming a household villain. The first few days of testing may include false alerts. Rain may look suspicious. A neighbor’s cat may trigger motion but fail identification. A known cat may approach from the side and miss the detection zone. This is normal. Pet technology works best when tuned around the actual animal, not around the diagram in your head.

The best practical experience tip is to keep the system simple from the cat’s point of view. Do not make the cat wear a huge tag, approach a strange object, or stand in one exact square like a furry airport passenger at security. The more invisible the system feels, the better. The project’s inside-mounted stationary unit is smart for that reason. The cat simply comes to the door. The technology does the noticing. The human does the opening. The cat accepts the service without tipping.

Another useful lesson is that pet hacks should solve one clear problem first. It is tempting to add a camera, cloud dashboard, phone app, automatic feeder integration, facial recognition, weather data, and maybe a tiny theme song. But the core job is simple: tell me when my cat is at the door. CAT AT THE DOOR succeeds because it stays focused. It can be expanded, but it does not need to become a spaceship to be useful.

For cat owners, the emotional payoff is real. A project like this says, “I understand my pet’s routine, and I built something to make it safer and easier.” That is the heart of good pet technology. It is not about replacing attention. It is about making attention arrive at the right moment. And if the cat still looks offended when you open the door, congratulations: the system is working, and the cat is still a cat.

Conclusion

2025 Pet Hacks Contest: Cat At The Door is a charming example of how maker culture can turn a small daily annoyance into a smart, practical, and surprisingly educational project. It blends radar sensing, BLE identification, LoRa communication, low-power display design, and 3D-printed hardware into one very specific mission: notify the human when the cat wants in.

The project is not just a gadget; it is a reminder that the best DIY pet hacks begin with observation. What does the animal actually do? What does the owner actually need? What can technology improve without making the situation less safe? CAT AT THE DOOR answers those questions with a design that is clever, documented, and wonderfully cat-aware.

Whether you build the full system, borrow one idea from it, or simply admire the lengths humans will go to for their pets, this project deserves its spotlight. After all, cats have trained humans for thousands of years. In 2025, humans finally added LoRa.