Stylus Synth Should Have Used A 555– And Did!

May 20, 2025 by 8 Comments

For all that “should have used a 555” is a bit of a meme around here, there’s some truth to it. The humble 555 is a wonderful tool in the right hands. That’s why it’s wonderful to see this all-analog stylus synth project by EE student [DarcyJ] bringing the 555 out for the new generation.

The project is heavily inspired by the vintage stylophone, but has some neat tweaks. A capacitor bank means multiple octaves are available, and using a ladder of trim pots instead of fixed resistors makes every note tunable. [Darcy] of course included the vibrato function of the original, but no, he did not use a 555 for that, too. He used an RC oscillator. He put a trim pot on that, too, to control the depth of vibrato, which we don’t recall seeing on the original stylophone.

The writeup is very high quality and could be recommended to anyone just getting started in analog (or analogue) electronics– not only does [Darcy] explain his design process, he also shows his pratfalls and mistakes, like in the various revisions he went through before discovering the push-pull amplifier that ultimately powers the speaker.

Since each circuit is separately laid out and indicated on the PCB [Darcy] designed in KiCad for this project. Between that and everything being thru-hole, it seems like [Darcy] has the makings of a lovely training kit. If you’re interested in rolling your own, the files are on GitHub under a CERN-OHL-S v2 license,  and don’t forget to check out the demo video embedded below to hear it in action.

Of course, making music on the 555 is hardly a new hack. We’ve seen everything from accordions to paper-tape player pianos to squonkboxes over the years. Got another use for the 555? Let us know about it, in the inevitable shill for our tip line you all knew was coming. Continue reading “Stylus Synth Should Have Used A 555– And Did!” →

The Magic Touch: A 555 Touch Switch

April 2, 2025 by 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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Chase Light SAO Shouldn’t Have Used A 555, And Didn’t

March 27, 2025 by 13 Comments

Around these parts, projects needlessly using a microcontroller where a simpler design would do are often derided with the catch-all “Should have used a 555,” even if the venerable timer chip wouldn’t have been the ideal solution. But the sentiment stands that a solution more complicated than it needs to be is probably one that needs rethinking, as this completely mechanical chaser light badge Simple Add-On (SAO) aptly demonstrates.

Rather than choosing any number of circuits to turn a strip of discrete lights on and off, [Johannes] took inspiration for his chaser lights from factory automation mechanisms that move parts between levels on steps that move out of phase with each other, similar to the marble-raising mechanism used in [Wintergatan]’s Marble Machine X.

Two thin plates with notches around the edge are sandwiched together inside the 3D printed case of the SAO, between the face and the light source. A small motor and a series of gears rotate the two masks 180° out of phase with each other, which creates the illusion that the light is moving.

It’s pretty convincing; when we first saw the video below, we were sure it was a row of tiny LEDs around the edge of the badge.

Hats off to [Johannes] for coming up with such a clever mechanism and getting it working just in time for Hackaday Europe. If you need to catch up on the talks, we’ve got a playlist ready for you.

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555 Timers Bring Christmas Charm To Miniature Village

January 2, 2025 by 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 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.
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.

Using The 555 For Everything

October 14, 2024 by 26 Comments

The 555 timer is one of the most versatile integrated circuits available. It can generate PWM signals, tones, and single-shot pulses. You can even put one in a bi-stable mode similar to a flip flop. All of these modes are available by only changing a few components outside of the IC itself. It’s also dirt cheap, so it finds its way into all kinds of applications its original inventors never imagined. There’s a bit of a trope around here as well that you ought not to use a microcontroller when one of these will do, and while it’s a bit of a played-out comment, it’s often more true than it seems. This video shows a few uncommon ways of using these circuits instead of putting a microcontroller to work.

After a brief overview of the internals of the hallowed 555, [Doctor Volt] walks us through some of its uses, starting with applications for digital inputs, including a debounce circuit and a toggle switch. From there, he moves on to demonstrating a circuit that can protect batteries from deep discharge, and a small change to that circuit can turn the 555 into a resetting fuse that can protect against short circuit events. Finally, the PWM capabilities of this small integrated circuit are put to work as an audio amplifier, although perhaps not one that would pass muster for the most devout audiophiles among us.

Even though it’s possible to offload a lot of the capabilities of a 555 onto a microcontroller, there’s certainly an opportunity to offload some things to the 555, even if your project still needs a microcontroller. However, offloading tasks like debounce or input latching to hardware rather than spending microcontroller cycles or pins can make a project more robust, both from reliability and software points of view. For some other useful circuits, some of which have been forgotten in the modern microcontroller age, it’s worth taking a look at some of these antique circuit books as well. While we are sure the 555 designers hoped it would be a big hit, no one imagined this giant one.

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Humble 555 Gets A Boost For ESR Meter

September 4, 2024 by 6 Comments

[Peter Demchenko] wanted to use a low power TS555 in an ESR meter design. The problem is, he needed to handle significant current sink requirements for cases where the capacitor under test had a low ESR. The TS555 wasn’t up to the task.

However, [Peter] made an interesting observation. the output pin of the device can sink or source current. However, the discharge pin is exactly the same output but can only sink current.

But what if you tied them together? Using some equalizing resistors, that’s exactly what he did, and this roughly doubles the rated current sink capability. According to [Peter], you do make the circuit more sensitive to power supply variations, but that could be an acceptable trade, depending on your application.

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