Round Displays Make Neat VU Meters

May 5, 2025 by 11 Comments

You can still get moving-needle meters off the shelf if you desire that old school look in one of you projects. However, if you want a more flexible and modern solution, you could use round displays to simulate the same thing, as [mircemk] demonstrates.

At the heart of the build is an ESP32 microcontroller, chosen for its fast clock rate and overall performance. This is key when drawing graphics to a display, as it allows for fast updates and smooth movement — something that can be difficult to achieve on lesser silicon. [mircemk] has the ESP32 reading an audio input and driving a pair of GC9A01 round displays, which are the perfect form factor for aping the looks of a classic round VU meter. The project write-up goes into detail on the code required to simulate the behavior of a real meter, from drawing the graphics to emulating realistic needle movements, including variable sweep rates and damping.

The cool thing about using a screen like this is the flexibility. You can change the dials to a different look — or to an entirely different kind of readout — at will. We’ve seen some of [mircemk]’s projects before, too, like this capable seismometer. Video after the break.

Continue reading “Round Displays Make Neat VU Meters” →

Printed Perpetual Calendar Clock Contains Clever Cams

April 21, 2025 by 12 Comments

At Hackaday, it is always clock time, and clock time is a great time to check in with [shiura], whose 3D Printed Perpetual Calendar Clock is now at Version 2. A 3D printed calendar clock, well, no big deal, right? Grab a few steppers, slap in an ESP32 to connect to a time server, and you’re good. That’s where most of us would probably go, but most of us aren’t [shiura], who has some real mechanical chops.

The front face of the perpetual calendar clock.
There’s also a 24-hour dial, because why not?

This clock isn’t all mechanical. It probably could be, but at its core it uses a commercial quartz movement — you know, the cheap ones that take a single double-A battery. The only restriction is that the length of the hour axis must be twelve millimeters or more. Aside from that, a few self-tapping screws and an M8 nut, everything else is fully 3D printed.

From that simple quartz movement, [shiura]’s clock tracks not only the day of the week, the month and date — even in Febuary, and even compensating for leap years. Except for the inevitable drift (and battery changes) you should not have to adjust this clock until March 2100, assuming both you and the 3D printed mechanism live that long. Version one actually did all this, too, but somehow we missed it; version two has some improvements to aesthetics and usability. Take a tour of the mechanism in the video after the break.

We’ve featured several of [shiura]’s innovative clocks before, from a hybrid mechanical-analog display, to a splitless flip-clock, and a fully analog hollow face clock. Of course [shiura] is hardly our only clock-making contributor, because it it always clock time at Hackaday. Continue reading “Printed Perpetual Calendar Clock Contains Clever Cams” →

Clock Mechanism Goes Crazy For Arduino

March 9, 2025 by 28 Comments

You’ve doubtless seen those ubiquitous clock modules, especially when setting clocks for daylight savings time. You know the ones: a single AA battery, a wheel to set the time, and two or three hands to show the time. They are cheap and work well enough. But [Playful Technology] wanted to control the hands with an Arduino directly and, in the process, he shows us how these modules work.

If you’ve never studied the inside of these clock modules, you may be surprised about how they actually work. A crystal oscillator pulses a relatively large electromagnet. A small plastic gear has a magnetic ring and sits near the electromagnet.

Each time the polarity of the electromagnet flips, the ring turns 180 degrees to face the opposite magnetic pole to the electromagnet. This turns the attached gear which is meshed with other gears to divide the rotation rate down to once per 24 hours, once per hour, and once per minute. Pretty clever.

That makes it easy to control the hands. You simply detach the electromagnet from the rest of the circuit and control it yourself. The module he used had a mechanical limitation that prevents the hands from moving well at more than about 100 times normal speed.

We wondered how he made the hands reverse and, apparently, there is a way to get the drive gear to move in reverse, but it isn’t always reliable. Of course, you could also replace the drive mechanism with something like an RC servo or other motor and it sounds like he has done this and plans to show it off in another video.

We’ve seen the opposite trick before, too. If you really want an easy-to-control analog clock, try this one Continue reading “Clock Mechanism Goes Crazy For Arduino” →

Tech In Plain Sight: Speedometers

August 22, 2024 by 29 Comments

In a modern car, your speedometer might look analog, but it is almost certainly digital and driven by the computer that has to monitor all sorts of things anyway. But how did they work before your car was a rolling computer complex? The electronic speedometer has been around for well over a century and, when you think about it, qualifies as a technlogical marvel.

If you already know how they work, this isn’t a fair question. But if you don’t, think about this. Your dashboard has a cable running into it. The inner part of the cable spins at some rate, which is related to either the car’s transmission or a wheel sensor. How do you make a needle deflect based on the speed?

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Clock Mixes Analog, Digital, Retrograde Displays

May 30, 2024 by 6 Comments

Unique clocks are a mainstay around here, and while plenty are “human readable” without any instruction, there are a few that take a bit of practice before someone can glean the current time from them. Word clocks are perhaps on the easier side of non-traditional displays but at the other end are binary clocks or even things like QR code clocks. To get the best of both worlds, though, multiple clock faces can be combined into one large display like this clock build from [imitche3].

The clock is actually three clocks in one. The first was inspired by a binary clock originally found in a kit, which has separate binary “digits” for hour, minute, and second and retains the MAX 7219 LED controller driving the display. A standard analog clock rests at the top, and a third clock called a retrograde clock sits at the bottom with three voltmeters that read out the time in steps. Everything is controlled by an Arduino Nano with the reliable DS3231 keeping track of time. The case can be laser-cut or 3D printed and [imitche3] has provided schematics for both options.

As far as clocks builds go, we always appreciate something which can be used to tell the time without needing any legends, codes, or specialized knowledge. Of course, if you want to take a more complex or difficult clock face some of the ones we’re partial to are this QR code clock which needs a piece of hardware to tell the time that probably already has its own clock on it.

Synesthetic Clock Doesn’t Require Synesthesia

April 10, 2024 by 15 Comments

We often think of synesthetes as those people who associate say, colors with numbers. But the phenomenon can occur with any of the senses. Simply put, when one sense is activated, synesthesia causes one to experience an unrelated, activated sense. Sounds trippy, no?

Thankfully, [Markus Opitz]’s synesthetic clock doesn’t require one to have synesthesia. It’s actually quite easy to read, we think. Can you tell what time it is in the image above? The only real requirement seems to be knowing the AM color from the PM color. The minute display cycles through blue, green, yellow, and red as the hour progresses.

Behind that pair of GC9a01 round displays lies an ESP32 and a real-time clock module. [Markus] couldn’t find a fillArc function, so instead he is drawing triangles whose ends lie outside the visible area. To calculate the size of the triangle, [Markus] is using the angle function tangent, so each minute has an angle of 6°.

[Markus] created a simple but attractive oak housing for the clock, but suggests anything from cardboard and plastic to a book. What’s the most interesting thing you’ve ever used for an enclosure? Let us know in the comments.

Do you appreciate a good analog clock when you see one? Here’s a clock that uses analog meters for its display.

A Clock Made Out Of Electromechanical Relays

February 13, 2024 by 11 Comments

Electromechanical circuits using relays are mostly a lost art these days, but sometimes you get people like [Aart] who can’t resist to turn a stack of clackity-clack relays into a functional design, like in this case a clock (article in Dutch, Google Translate).

It was made using components that [Aart] had come in possession of over the years, with each salvaged part requiring the usual removal of old solder, before being mounted on prototype boards. The resulting design uses the 1 Hz time signal from a Hörz DCF77 master clock which he set up to drive a clock network in his house, as he describes in a forum post at Circuits Online (also in Dutch).

The digital pulses from this time signal are used by the relay network to create the minutes and hours count, which are read out via a resistor ladder made using 0.1% resistors that drive two analog meters, one for the minutes and the other for the hours.

Sadly, [Aart] did not draw up a schematic yet, and there are a few issues he would like to resolve regarding the meter indicators that will be put in front of the analog dials. These currently have weird transitions between sections on the hour side, and the 59 – 00 transition on the minute dial happens in the middle of the scale. But as [Aart] says, this gives the meter its own character, which is an assessment that is hard to argue with.

Thanks to [Lucas] for the tip.