2025 One Hertz Challenge: An Ancient Transistor Counts The Seconds

July 12, 2025 by Jenny List 3 Comments

If you’ve worked with germanium transistors, you’ll know that many of them have a disappointingly low maximum frequency of operation. This has more to do with some of the popular ones dating from the earliest years of the transistor age than it does to germanium being inherently a low frequency semiconductor, but it’s fair to say you won’t be using an OC71 in a high frequency RF application. It’s clear that [Ken Yap]’s project is taking no chances though, because he’s using a vintage germanium transistor at a very low frequency — 1 Hz, to be exact.

The circuit is a simple enough phase shift oscillator that flashes a white LED, in which a two transistor amplifier feeds back on itself through an RC phase shift network. The germanium part is a CV7001, while the other transistor is more modern but still pretty old these days silicon part, a BC109. The phase shift network has a higher value resistor than you might expect at 1.8 MOhms, because of the low frequency of operation. Power meanwhile comes from a pair of AA cells.

We like this project not least for its use of very period passive components and stripboard to accompany the vintage semiconductor parts. Perhaps it won’t met atomic standards for timing, but that’s hardly the point.

This project is an entry in the 2025 One Hertz Challenge. Why not enter your own second-accurate project?

Limitations, Creativity, And Challenges

June 28, 2025 by Elliot Williams 6 Comments

This week, we announced the winners for the previous Pet Hacks contest and rang in our new contest: The One Hertz Challenge. So that’s got me in a contesty mood, and I thought I’d share a little bit of soap-box philosophizing and inside baseball all at once.

The trick to creating a good contest theme, at least for the creative Hackaday crowd, is putting on the right limitation. Maybe you have to fit the circuit within a square-inch, power it only with a coin cell, or use the antiquated and nearly useless 555 timer IC. (Yes, that was a joke!)

There are two basic reactions when you try to constrain a hacker. Some instantly try to break out of the constraint, and their minds starts to fly in all of the directions that lead out of the box, and oftentimes, something cool comes out of it. The other type accepts the constraint and dives in deep to work within it, meditating deeply on all the possibilities that lie within the 555.

Of course, we try to accommodate both modes, and the jury is still out as to which ends up better in the end. For the Coin Cell challenge, for instance, we had a coin-cell-powered spot welder and car jumpstarter, but we also had some cool circuits that would run nearly forever on a single battery; working against and with the constraints.

Which type of hacker are you? (And while we’re still in the mood, what contest themes would you like to see for 2026?)

Announcing The 2025 Hackaday One Hertz Challenge

June 26, 2025 by Elliot Williams 53 Comments

It’s about time! Or maybe it’s about time’s reciprocal: frequency. Whichever way you see it, Hackaday is pleased to announce, just this very second, the 2025 One Hertz Challenge over on Hackaday.io. If you’ve got a device that does something once per second, we’ve got the contest for you. And don’t delay, because the top three winners will each receive a $150 gift certificate from this contest’s sponsor: DigiKey.

What will you do once per second? And how will you do it? Therein lies the contest! We brainstormed up a few honorable mention categories to get your creative juices flowing.

Timelords: How precisely can you get that heartbeat? This category is for those who prefer to see a lot of zeroes after the decimal point.
Ridiculous: This category is for the least likely thing to do once per second. Accuracy is great, but absurdity is king here. Have Rube Goldberg dreams? Now you get to live them out.
Clockwork: It’s hard to mention time without thinking of timepieces. This category is for the clockmakers among you. If your clock ticks at a rate of one hertz, and you’re willing to show us the mechanism, you’re in.
Could Have Used a 555: We knew you were going to say it anyway, so we made it an honorable mention category. If your One Hertz project gets its timing from the venerable triple-five, it belongs here.

We love contests with silly constraints, because you all tend to rise to the challenge. At the same time, the door is wide open to your creativity. To enter, all you have to do is document your project over on Hackaday.io and pull down the “Contests” tab to One Hertz to enter. New projects are awesome, but if you’ve got an oldie-but-goodie, you can enter it as well. (Heck, maybe use this contest as your inspiration to spruce it up a bit?)

Time waits for no one, and you have until August 19th at 9:00 AM Pacific time to get your entry in. We can’t wait to see what you come up with.

Announcing The 2025 Pet Hacks Winners

June 24, 2025 by Elliot Williams 9 Comments

When you really love your pawed, feathered, or scaled friends, you build projects for them. (Well, anyway, that’s what’s happened to us.) For the 2025 Pet Hacks Challenge, we asked you to share your favorite pet-related hacks, and you all delivered. So without further ado, here are our favorites, as well as the picks-of-the-litter that qualified for three $150 DigiKey gift certificates. Spoiler alert: it was a clean sweep for team cat.

Continue reading “Announcing The 2025 Pet Hacks Winners” →

2025 Pet Hacks Contest: Cat At The Door

June 12, 2025 by Matt Varian 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.

Continue reading “2025 Pet Hacks Contest: Cat At The Door” →

2025 Pet Hacks Contest: Fort Bawks Is Guarded By Object Detection

June 9, 2025 by Tyler August 5 Comments

One of the difficult things about raising chickens is that you aren’t the only thing that finds them tasty. Foxes, raccoons, hawks — if it can eat meat, it probably wants a bite of your flock. [donutsorelse] wanted to protect his flock and to be able to know when predators were about without staying up all night next to the hen-house. What to do but outsource the role of Chicken Guardian to a Raspberry pi?

Object detection is done using a YOLOv8 model trained on images of the various predators local to [donutorelse]. The model is running on a Raspberry Pi and getting images from a standard webcam. Since the webcam has no low-light capability, the system also has a motion-activated light that’s arguably goes a long way towards spooking predators away itself. To help with the spooking, a speaker module plays specific sound files for each detected predator — presumably different sounds might work better at scaring off different predators.

If that doesn’t work, the system phones home to activate a siren inside [donutorelse]’s house, using a Blues Wireless Notecarrier F as a cellular USB modem. The siren is just a dumb unit; activation is handled via a TP-Link smart plug that’s hooked into [donutorelse]’s custom smart home setup. Presumably the siren cues [donutorelse] to take action against the predator assault on the chickens.

Weirdly enough, this isn’t the first time we’ve seen an AI-enabled chicken coop, but it is the first one to make into our ongoing challenge, which incidentally wraps up today.

2025 Pet Hacks Contest: Weigh Your Dog The Easy Way

June 1, 2025 by Jenny List 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.