Announcing The 2025 Hackaday One Hertz Challenge

June 26, 2025 by Elliot Williams 51 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.

The Magic Touch: A 555 Touch Switch

April 2, 2025 by Al Williams 14 Comments

There seems to be nothing a 555 can’t do. We’ve seen it before, but [electronzapdotcom] reminds us you can use a 555 and a few parts to make a reasonable touch switch in this video, embedded below.

The circuit uses some very large resistors so that noise from your body can overcome the logic level on the trigger and threshold inputs. You can easily adapt this idea if you need a simple touch switch. Though we imagine this circuit wouldn’t work well if you were in a quiet environment. We suspect 50 or 60 Hz hum is coupling through your finger and triggering the pins, but it could be a different effect.

How reliable is it? Beats us. The circuit is a bistable, so essentially your finger pumps a signal into a flip-flop. This is old trick, but could be useful. Of course, if you really need a touch switch, you have plenty of options. You can get little modules. Or, directly measure skin resistance.

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Probably The Simplest Sequencing Synth

March 15, 2025 by Jenny List 31 Comments

With inexpensive microntrollers capable of the most impressive feats of sound synthesis, it’s not so often we see projects that return to an earlier style of electronic music project. The 1-bit synth from [Electroagenda] takes us firmly into that territory, employing that most trusty of circuits, a 555.

It’s a time-honored circuit, a 555 provides a note clock that drives a 4017 that functions as a sequencer. This switches in a set of voltage dividers, which in turn control another 555 oscillator that produces the notes. It’s a fun toy straight from the 1970s, right down to the protoboard and hookup wire construction. There’s a demo video with some lovely beeps below, and we think most of you should have what it takes to make your own.

If you’re seeking more inspiration, may we introduce you to our Logic Noise series?

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555 Timers Bring Christmas Charm To Miniature Village

January 2, 2025 by Tom Nardi 10 Comments

The miniature Christmas village is a tradition in many families — a tiny idyllic world filled happy people, shops, and of course, snow. It’s common to see various miniature buildings for sale around the holidays just for this purpose, and since LEDs are small and cheap, they’ll almost always have some switch on the bottom to light up the windows.

This year, [Braden Sunwold] and his wife started their own village with an eye towards making it a family tradition. But to his surprise, the scale lamp posts they bought to dot along their snowy main street were hollow and didn’t actually light up. Seeing it was up to him to save Christmas, [Braden] got to work adding LEDs to the otherwise inert lamps.

Now in a pinch, this project could have been done with nothing more than some coin cells and a suitably sized LED. But seeing as the lamp posts were clearly designed in the Victorian style, [Braden] felt they should softly flicker to mimic a burning gas flame. Blinking would be way too harsh, and in his own words, look more like a Halloween decoration.

This could have been an excuse to drag out a microcontroller. But instead, [Braden] did as any good little Hackaday reader should do, and called on Old Saint 555 to save Christmas. After doing some research, he determined that a trio of 555s rigged as relaxation oscillators could be used to produce quasi-random triangle waves. When fed into a transistor controlling the LED, the result would be a random flickering instead of a more aggressive strobe effect. It took a little tweaking of values, but eventually he got it locked down and sent away to have custom PCBs made of the circuit.

With the flicker driver done, the rest of the project was pretty simple. Since the lamp posts were already hollow, feeding the LEDs up into them was easy enough. The electronics went into a 3D printed base, and we particularly liked the magnetic connectors [Braden] used so that the lamps could easily be taken off the base when it was time to pack the village away.

We can’t wait to see what new tricks [Braden] uses to bring the village alive for Christmas 2025. Perhaps the building lighting could do with a bit of automation?

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Left: the traces of a flashy paper Christmas tree. Right: the finished tree on cardstock.

Flashy Paper Christmas Tree Does It With A 555

December 13, 2024 by Kristina Panos 11 Comments

‘Tis the season for holiday hacks, and [Ben Emmett] is here to remind us that we don’t necessarily need a fancy microcontroller in order to make flashy fun things happen.

Smoothing down the copper traces with a guitar pick.

Take this Christmas tree for example, which uses a 555 timer and a CB4017 decade counter in order to drive some blinking LEDs. The ICs are through-hole, making the circuit fairly accessible to new players, but there are a few SMD components that need soldering as well. (More on that later.)

Here, the 555 acts like a clock and drives a square wave. Using the clock as input, the decade counter toggles the output pins one after the other, driving the LEDs to blink in turn. Since there are only eight lights, there is a pause in the light-up pattern, but that could be fixed by wiring decade counter output #9 to the reset pin.

Although function was the main focus circuit-wise, [Ben] managed to lay the traces in the shape of a Christmas tree, which looks great. Having done a similar project in the past, he discovered that the craft cutting machine prefers thick traces and wider spaces between them. This is largely why [Ben] chose to use through-hole ICs.

After laying everything out in KiCad, [Ben] exported the copper layer image for use on the cutting machine. Once it was all cut out, he put it on transfer tape to weed out the extra copper, and get the traces onto cardstock, the final substrate.

This is such a fun project, and we love that the CR2032 that powers it also acts as the stand in its vertical holder. Hit up GitHub if you want to make one for yourself. Want something even more 3D? Check out this hollow tree we saw a few years ago.

Double Your Analog Oscilloscope Fun With This Retro Beam Splitter

November 24, 2024 by Dan Maloney 18 Comments

These days, oscilloscope hacking is all about enabling features that the manufacturer baked into the hardware but locked out in the firmware. Those hacks are cool, of course, but back in the days of analog scopes, unlocking new features required a decidedly more hardware-based approach.

For an example of this, take a look at this oscilloscope beam splitter by [Lockdown Electronics]. It’s a simple way to turn a single-channel scope into a dual-channel scope using what amounts to time-division multiplexing. A 555 timer is set up as an astable oscillator generating a 2.5-kHz square wave. That’s fed into the bases of a pair of transistors, one NPN and the other PNP. The collectors of each transistor are connected to the two input signals, each biased to either the positive or negative rail of the power supply. As the 555 swings back and forth it alternately applies each input signal to the output of the beam splitter, which goes to the scope. The result is two independent traces on the analog scope, like magic.

More after the break…

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Pushing The Plasma Limits With A Custom Flyback Transformer

October 22, 2024 by Danie Conradie 18 Comments

For serious high-voltage plasma, you need a serious transformer. [Jay Bowles] from Plasma Channel is taking his projects to the next level, so he built a beefy 6000:1 flyback transformer.

[Jay] first built a driving circuit for his dream transformer, starting with a simple 555 circuit and three MOSFETs in parallel to handle 90 A of current. This led to an unexpected lesson on the necessity for transistor matching as one of them let out the Magic Smoke. On his second attempt, the 555 was swapped for an adjustable pulse generator module with a display, and a single 40 A MOSFET on the output.

The transformer is built around a large 98×130 mm ferrite core, with eleven turns on the primary side. All the hard work is on the secondary side, where [Jay] designed a former to accommodate three winding sections in series. With the help of the [3D Printing Nerd], he printed PLA and resin versions but settled on the resin since it likely provided better isolation.

[Jay] spent six hours of quality time with a drill, winding 4000 feet (~1200 m) of enameled wire. On the initial test of the transformer, he got inch-long arcs on just 6 V and 15 W of input power. Before pushing the transformer to its full potential, he potted the secondary side in epoxy to reduce the chances of shorts between the windings.

Unfortunately, the vacuum chamber hadn’t removed enough of the air during potting, which caused a complete short of the middle winding as the input started pushing 11 V. This turned the transformer into a beautiful copper and epoxy paperweight, forcing [Jay] to start again from scratch.

On the following attempt [Jay] took his time during the potting process, and added sharp adjustable electrodes to act as voltage limiters on the output. The result is beautiful 2.25-inch plasma arcs on only 11 V and 100 W input power. This also meant he could power it with a single 580 mAh 3S LiPo for power.

[Jay] plans to use his new transformer to test materials he intends to use in future plasma ball, ion thruster, and rail gun projects. We’ll be keeping an eye out for those!

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