2025 One Hertz Challenge: Valvano Clock Makes The Seconds Count

July 14, 2025 by Tyler August 3 Comments

A man named [Jim Valvano] once said “There are 86,400 seconds in a day. It’s up to you to decide what to do with them.” — while we couldn’t tell you who [Jim Valvano] was without a google search*, his math checks out. The quote was sufficiently inspirational to inspire [danjovic] to create a clock count those seconds precisely.

It’s a simple project, both conceptually and electrically. All it does is keep time and count the seconds in the day– a button press switches between counting down, counting up, and HH:MM:SS. In every mode, though, the number displayed will change at one Hertz, which we appreciate as being in the spirit of the challenge. There are only four components: an Arduino Nano, a DS3231 RTC module, a SSD1306 128×64 OLED module, and a momentary pushbutton. At the moment it appears this project is only on breadboard, which is a shame– we think it deserves to have a fancy enclosure and pride of place on the wall. Wouldn’t you be more productive if you could watch those 86,400 seconds ticking away in real time? We think it would be motivating.

Perhaps it will motivate you to create something for our One Hertz Challenge. Plenty of seconds to go until the deadline on August 19th, after all. If you’d rather while away the time reading, you can check out some of [danjovic]’s other projects, like this Cistertian-inspired clock, or this equally-inscruitable timekeeper that uses binary-coded octal.

*Following a google search, he was an American college basketball coach in the mid-20th century.

Building An IR Thermometer That Fits On Your Keychain

July 5, 2024 by Tom Nardi 11 Comments

Non-contact infrared (IR) thermometers used to be something of an exotic tool, but thanks at least in part due to the COVID-19 pandemic, they’re now the sort of thing you see hanging up near the grocery store checkout as a cheap impulse buy. Demand pushed up production, and the economies of scale did the test. Now the devices, and the sensors within them, are cheap enough for us hackers to play with.

The end result is that we now have projects like this ultra compact IR thermometer from [gokux]. With just a handful of components, some code to glue it all together, and a 3D printed enclosure to wrap it all up, you’ve got a legitimately useful tool that’s small enough to replace that lucky rabbit’s foot you’ve got on your keys.

If this project looks familiar, it’s because the whole thing is closely related to the LiDAR rangefinder [gokux] put together last month. It shares the same Seeed Studio XIAO ESP32-C3 microcontroller, 0.49 inch OLED display, and tiny 40 mAh LiPo battery. The only thing that’s really changed, aside from the adjustments necessary to the 3D printed enclosure, is that the LiDAR sensor was replaced with a MLX90614 IR temperature sensor.

[gokux] has put together some great documentation for this build, making it easy for others to recreate and remix on their own. Assembly is particularly straightforward thanks to the fact that both the display and temperature sensor communicate with the ESP32 over I2C, allowing them to be wired daisy chain style — there’s no need for even a scrap of perfboard inside the case, let alone a custom board.

Displays We Love Hacking: SPI And I2C

December 21, 2023 by Arya Voronova 18 Comments

I’ve talked about HD44780 displays before – they’ve been a mainstay of microcontroller projects for literal decades. In the modern hobbyist world, there’s an elephant in the room – the sheer variety of I2C and SPI displays you can buy. They’re all so different, some are LCD and some are OLED, some have a touchscreen layer and some don’t, some come on breakouts and some are a bare panel. No matter which one you pick, there are things you deserve to know.

These displays are exceptionally microcontroller-friendly, they require hardly any GPIOs, or none extra if you already use I2C. They’re also unbelievably cheap, and so tiny that you can comfortably add one even if you’re hurting for space. Sure, they require more RAM and a more sophisticated software library than HD44780, but with modern microcontrollers, this is no problem at all. As a result, you will see them in almost every project under the sun.

What do you need for those? What are the requirements to operate one? What kind of tricks can you use with them? Let’s go through the main aspects.

Continue reading “Displays We Love Hacking: SPI And I2C” →

A mechanical keyboard with a haptic knob and E-ink display

Smart Modular Keyboard Sports An E-ink Display And A Haptic Feedback Knob

July 28, 2022 by Robin Kearey 19 Comments

While most people may think that a keyboard is just a board with keys, those who read Hackaday will no doubt know that there’s an infinite variety of beautiful designs to suit any use case. [Peng Zhihui] is the latest to impress us with an excellent custom keyboard that packs several unusual features (video in Chinese, with English subtitles, embedded below). What started out as a simple lockdown project turned into what [Zhihui] imagines to be the ultimate keyboard for his daily tasks. At first glance it might look like just another custom keyboard with mechanical switches, but when you look inside you’ll find it full of clever design tricks and neat features.

When he started on the design of the main key area, [Zhihui] could have used any of the open-source keyboard frameworks. Instead, he decided to do everything himself in order to obtain maximum performance and configurability. This went all the way down to the readout circuitry: rather than wiring the switches in a matrix, as most keyboards do, he used a set of shift registers. This enables the main ARM controller to read out every key separately, eliminating ghosting and allowing any number of keys to be pressed simultaneously. The shift registers are driven by a 4 MHz SPI clock, which means that a full scan of all keys takes just 40 microseconds.

That is brilliant, but what makes this project really interesting is an extension module on the left side of the keyboard that turns it into what [Zhihui] calls a “smart keyboard”. The bottom part of this module has an E-ink display that can show a variety of useful information: current memory usage, email notifications or simply the weather forecast.

Next to the big E-ink screen is a tiny OLED display that works in tandem with a haptic feedback knob. Based on a brushless DC motor, this knob can be configured in various ways to perform several different tasks. It can be set to friction-less spinning mode, which is useful for quickly scrolling through long documents. It can become a multi-level switch to enable or disable features, or a volume knob with virtual end stops. There’s even an option to use it as a physical indicator for things like the current CPU usage.

The keyboard also houses a USB hub to attach other gadgets, as well as a lithium battery to power the haptic knob, since it uses more power than a standard USB 2.0 port can deliver. There’s even a little capacitive touch strip below the space bar, which allows you to use one of your thumbs to switch between different tabs or to use quick copy/paste functions.

If all of this sounds like your idea of a perfect keyboard, then you’ll be pleased to hear that [Zhihui] plans to open-source all hardware and software designs once he’s cleaned up his code. Until that time, you may want to read up on the working principle of a haptic smart knob, or find out what’s the most efficient way to read out a certain number of buttons with a microcontroller.

Continue reading “Smart Modular Keyboard Sports An E-ink Display And A Haptic Feedback Knob” →

OLED Display Kicks Knob Up Several Accurate Notches

April 19, 2022 by Tom Nardi 9 Comments

As far as input devices go, the potentiometer is pretty straightforward: turn it left, turn it right, and you’ve pretty much seen all there is to see. For many applications that’s all you need, but we can certainly improve on the experience with modern technology. Enter this promising project from [upir] that pairs a common potentiometer with a cheap OLED display to make for a considerably more engaging user experience.

To save time, the code is fine tuned in a simulator.

The basic idea is to mount the display over the potentiometer knob so you can show useful information such a label that shows what it does, and a readout of the currently detected value. But you’ll likely want to show where the knob is currently set within the range of possible values as well, and that’s where things get interesting.

In the video after the break, [upir] spends a considerable amount of time explaining the math behind details like the scrolling tick marks. The nearly 45 minute long video wraps up with some optimization, as getting the display to move along with the knob in real-time on an Arduino UNO took a bit of extra effort. The final result looks great, and promises to be a relatively cheap way to add an elegant and functional bit of flair to an otherwise basic knob.

With the code and this extensive demonstration of how it all works, adding a similar capability to your next knob-equipped gadget shouldn’t be too much of a challenge. Perhaps it could even be combined with the OLED VU meters we’ve covered previously. Be sure to let us know if you end up using this technique, as we’d love to see it in action.

Continue reading “OLED Display Kicks Knob Up Several Accurate Notches” →

An 128x64 OLED display with a weird image on it, showing a mouse cursor, date and time in the bottom right corner, and a whole lot of presumably dithered dots

Making Your Own Technically-HDMI OLED Monitor

April 1, 2022 by Arya Voronova 17 Comments

One day, [mitxela] got bored and decided to build his own HDMI monitor – the unconventional way. HDMI has a few high-speed differential pairs, but it also has an I2C interface used for detecting the monitor’s resolution and issuing commands like brightness control. In fact, I2C is the backbone for a lot of side channels like these – it’s also one of our preferred interfaces for connecting to cool sensors, and in this case, an OLED display!

[mitxela] describes his journey from start to end, with all the pitfalls and detours. Going through the pinout with a broken hence sacrificial HDMI cable in hand, he figured out how to probe the I2C lines with Linux command-line tools and used those to verify that the display was recognized on the HDMI-exposed I2C bus. Then, he turned to Python and wrote a short library for the display using the smbus bindings – and, after stumbling upon an FPS limitation caused by SMBus standard restrictions, rewrote his code to directly talk to the I2C device node, raising FPS from 2 to 5-10.

From there, question arose – what’s the best software route to take? He tried making a custom X modeline on the HDMI port the display was technically attached to, but that didn’t work out. In the end, he successfully employed the Linux capability called “virtual monitors”, and found out about an interesting peculiarity – there was no mouse cursor to be seen. Turns out, they’re typically hardware-accelerated and overlaid by our GPUs, but in [mitxela]’s case, the GPU was not involved, so he added cursor support to the picture forwarding code, too.

With partial refresh, the display could be redrawn even faster, but that’s where [mitxela] decided he’s reached a satisfactory conclusion to this journey. The write-up is a great read, and if videos are more your forte, he also made a video about it all – embedded below.

We first covered the ability to get I2C from display ports 14 years ago, and every now and then, this fun under-explored opportunity has been popping up in hackers’ projects. We’ve even seen ready-to-go breakouts for getting I2C out of VGA ports quickly. And if you go a bit further, with your I2C hacking skills, you can even strip HDCP!

We thank [sellicott] and [leo60228] for sharing this with us!

Continue reading “Making Your Own Technically-HDMI OLED Monitor” →

Custom Soldering Fume Fan Doesn’t Skimp On Features

August 27, 2021 by Tom Nardi 8 Comments

Prolific maker [sjm4306] tells us the first iteration of his soldering fan was little more than some cardboard, electrical tape, and a hacked up USB cable. But as we all know, these little projects have a way of evolving over time. Fast forward to today, and his custom fan is a well-polished piece of kit that anyone with a soldering iron would be proud to have on their workbench.

Cardboard has given way to a 3D printed enclosure that holds the fan, electronics, a pair of 18650 cells, and a easily replaceable filter. Between the marbled filament, debossed logo, properly countersunk screw holes, and rounded corners, it’s really hard to overstate how good this case looks. We’ve shamefully produced enough boxy 3D printed enclosures to know that adding all those little details takes time, but the end result really speaks for itself.

Fan internals, with a look at the custom PCB.

The user interface running on the OLED is also an exceptionally nice touch. Sure the fan doesn’t need a graphical display, and [sjm4306] could have saved a lot of time and effort by using a turn-key speed controller, but the push-button configuration complete with graphical indications of fan speed and battery life really give the final product a highly professional feel.

In the video below, [sjm4306] reveals that while the finished product might look great, there were a few bumps in the road. Issues with clearance inside the case made him rethink how things would be wired and mounted, leading to a far more cramped arrangement than he’d anticipated. Part of the problem was that he designed the case first and tried to integrate the electronics later, rather than the other way around; a common pitfall you’d be wise to watch out for.

It’s been proven that, without some external input, solder smoke is going to go right in your face. Whether or not you need to do something this complex is naturally up for debate, but if you want to keep all that nasty stuff out of your lungs, you’d do well to outfit your workbench with some kind of fan.

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