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Cat at the door

2025 Pet Hacks Contest: Cat At The Door

June 12, 2025 by 14 Comments

This Pet Hacks Contest entry from [Andrea] opens the door to a great collaboration of sensors to solve a problem. The Cat At The Door project’s name is a bit of a giveaway to its purpose, but this project has something for everyone, from radar to e-ink, LoRa to 3D printing. He wanted a sensor to watch the door his cats frequent and when one of his cats were detected have an alert sent to where he is in the house

There are several ways you can detect a cat, in this project [Andrea] went with mmWave radar, and this is ideal for sensing a cat as it allows the sensor to sit protected inside, it works day or night, and it doesn’t stop working should the cat stand still. In his project log he has a chapter going into what he did to dial in the settings on the LD2410C radar board.

How do you know if you’re detecting your cat, some other cat, a large squirrel, or a small child? It helps if you first give your cats a MAC address, in the form of a BLE tag. Once the radar detects presence of a suspected cat, the ESP32-S3 starts looking over Bluetooth, and if a known tag is found it will identify which cat or cats are outside waiting.

Once the known cat has been identified, it’s time to notify [Andrea] that his cat is waiting for his door opening abilities. To do this he selected an ESP32 board that includes a SX1262 LoRa module for communicating with the portable notification device. This battery powered device has a low power e-paper display showing you which cat, as well as an audio buzzer to help alert you.

To read more details about this project head over to the GitHub page to check out all the details. Including a very impressive 80 page step-by-step guide showing you step by step how to make your own. Also, be sure to check out the other entries into the 2025 Pet Hacks Contest.

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Piano Doorbell Adds Music To Your Home

June 8, 2025 by 16 Comments

Regular ding-dong doorbells are fun and all, but it can be nice to put something a little more special by your front door. To that end, [Arpan Mondal] built this neat little piano doorbell to make visiting his home just a touch more fun.

The heart of the build is an ESP32 microcontroller. It’s responsible for reading the state of five 3D printed piano keys: three white, two black. It’s nowhere near a full octave, but for a doorbell, it’s enough. When a key is pressed, the ESP32 plays a short audio sample embedded within the program code itself. This is done with the help of a PAM8403 audio amplifier module, which jacks up the output to drive the doorbell speaker loud enough to be heard throughout the home. It’s not exactly studio quality audio, but for a doorbell, it sounds pretty solid.

If you’re looking for a fun and easy build to make your home just a little bit more whimsical, it’s hard to beat something like this. Your musical friends will love it—they might even develop an intro riff of their very own. We’ve featured some other fun doorbell builds before, too—the best of which are the Halloween projects.
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Adding Assistive Technology To A Doorbell

June 4, 2025 by 4 Comments

The advent of affordable computing over the last few decades has certainly been a boon for many people with disabilities, making it easier to access things like text-to-speech technology, automation, or mobility devices, and even going as far as making it easier to work in general by making remote work possible. Some things still lag behind, though, like user interfaces that don’t take the colorblind into account, or appliances that only use an audio cue to signal to their users. This doorbell, for example, is one such device and [ydiaeresis] is adding features to it to help their mother with some hearing issues.

The first thing up for this off-the-shelf remote doorbell is a “brain transplant” since the built-in microcontroller couldn’t be identified. There are only a few signals on this board though so an ATtiny412 made for a suitable replacement. A logic analyzer was able to decode the signals being fed to the original microcontroller, and with that the push of the doorbell can be programmed to do whatever one likes, including integrating it with home automation systems or other assistive technology. In [ydiaeresis]’s case there’s an existing LED lighting system that illuminates whenever the phone rings.

Although it would be nice if these inexpensive electronics came with the adaptive features everyone might need from them, it’s often not too hard to add it in as was the case with this set of digital calipers. To go even further, some other common technology can be used to help those with disabilities like this hoverboard modified to help those with mobility issues.

Thanks to [buttim] for the tip!

2025 Pet Hacks Contest: Weigh Your Dog The Easy Way

June 1, 2025 by 4 Comments

If you need to weigh your pet, you’ll soon find that getting an animal to stand on a weighing machine to order is very difficult indeed. If the critter in question is a cat or a small dog you can weigh yourself both holding them and not holding them, and compute the difference. But in the case of a full size Bernese mountain dog, the hound is simply too big for that. Lateral thinking is required, and that’s how [Saren Tasciyan] came up with the idea of making a dog bed that’s also a weighing machine. When the mutt settles down, the weight can be read with ease. The bed itself is a relatively straightforward wooden frame, with load cells placed above rubber feet. The load cells in turn talk to an ESP8266 which has an LCD display to deliver the verdict. Dog weighed, without the drama.

This project is of course part of the Hackaday 2025 Pet Hacks contest, an arena in which any of the cool hacks you’ve made to enhance you and your pet’s life together can have an airing. Meanwhile this isn’t the first time this particular pooch has had a starring role; he’s sported a rather fetching barrel in a previous post.

2025 Hackaday Pet Hacks Contest
Rusty bathtub outdoors on equally rusty car springs

Hot Rod Backyard Bath On Steel Spring Legs

May 31, 2025 by 16 Comments

In a fusion of scrapyard elegance and Aussie ingenuity, [Mark Makies] has given a piece of old steel a steamy second life with his ‘CastAway Tub’. Call it a bush mechanic’s fever dream turned functional sculpture, starring two vintage LandCruiser leaf springs, and a rust-hugged cast iron tub dug up after 20 years in hiding. And put your welding goggles on, because this one is equal parts brute force and artisan flair.

What makes this hack so bold is, first of all, the reuse of unforgiving spring steel. Leaf springs, notoriously temperamental to weld, are tamed here with oxy-LPG preheating, avoiding thermal shock like a pro. The tub sits proudly atop a custom-welded frame shaped from dismantled spring packs, with each leaf ground, clamped, torched, and welded into a steampunk sled base. The whole thing looks like it might outrun a dune buggy – and possibly bathe you while it’s at it. It’s a masterclass in metalwork with zero CAD, all intuition, and a grinder that’s seen things.

Inspired? For those with a secret love for hot water and hot steel, this build is a blueprint for turning bush junk into backyard art. Read up on the full build at Instructables.

2025 Pet Hacks Contest: Keep The Prey At Bay With The Cat Valve

May 30, 2025 by 11 Comments

Some cats are what you might call indoor cats, happy to stretch out in the lap of indoor luxury and never bother themselves with the inclement outdoors again. Others however are fully in touch with their Inner Cat, and venture forth frequently in search of whatever prey they can find.

[Rkramer] has a cat of this nature,sadly one with a propensity for returning with live prey. To avoid this problem a solution is called for, and it comes in the shape of the Cat Valve, an automated cat door which enforces a buffer zone in their cellar to prevent unwanted gifts.

It’s a simple enough idea, when an IR sensor connected to a Raspberry Pi 4 detects the cat heading out into the world through the exterior cat flap, the computer fires up a motor connected to a lead screw which closes the flap between buffer zone and house. The cat then has the safety of the buffer zone, but can’t bring the prey fully inside.

If you’re a cat lover you’ll forgive them anything, but we have to admit to being on [Rkramer]’s side with this one. A useful way to keep the prey at bay is something we could have used a few times in the past, too. This project is part of the 2025 Pet Hacks contest. Done something similar for your cat? Why not make it an entry!

2025 Hackaday Pet Hacks Contest

2025 Pet Hacks Challenge : Poopopticon Is All Up In Kitty’s Business

May 29, 2025 by 6 Comments

After seeing this project, we can say that [James] must be a top-tier roommate. He has two flatmates– one human, one feline, and the feline flatmate’s litterbox was located in a bathroom close to the other human’s room. The odors were bothersome. A bad roommate might simply say that wasn’t their problem, but not [James].

Instead, he proclaimed “I shall build a poopopticon to alert me so I may clean the litterbox immediately, before smells can even begin to occur, thus preserving domestic harmony!”* We should all aspire to be more like [James].

It was, admittedly, a fairly simple project. Rather than dive into feline facial recognition, since it only has to detect a single cat, [James] used a simple IR sensor out of his parts bin, the sort you see on line-following robots. The microcontroller, an ESP8266, also came from his parts bin, making this project eligible for the ‘lowest budget’ award, if the contest had one.

The ESP8266 is set to send a message to a waiting webhook. In this case it is linked to a previous project, a smart ‘ring light’ [James] uses to monitor his Twitch chats. He’s also considered hooking it up to his lazy-esp32-banner for a big scrolling ‘change the litterbox!’ message. Since it’s just a webhook, the sky is the limit. Either way, the signal gets to its recipient and the litter gets changed before it smells, ensuring domestic bliss at [James]’ flat. If only all our roommates had been more like [James], we’d be much less misanthropic today.

2025 Hackaday Pet Hacks Contest
  • He did not, in fact, say that.