555

180 Articles

Thermostat? Do It With A 555!

April 7, 2026 by 19 Comments

It is a running gag around here that whenever a project posts, someone will inevitably point out that it could have been done with a 555 timer IC. [Stephen Woodward] went the opposite way and built a simple thermostat using the ubiquitous chip.

To be fair, this isn’t some sophisticated PID controller — it’s basically a bang-bang controller. Since the device has a comparator and the circuits use a thermistor, it seems like a clever but simple idea on the surface. However, there are some neat tricks. For example, if you tie the 555 threshold pin to Vdd, then the trigger pin acts as an inverting analog comparator. Another nice feature: the setpoint depends on a resistance ratio, so there is no need for a precise input voltage reference.

A simple circuit change can switch the circuit to power a heater or a cooler. The chip can handle a surprising amount of power, but for some applications, you may need some output drive circuitry. The simple circuit even has hysteresis, which you can set with a different resistor. Pretty impressive for a cheap chip, two resistors, a thermistor, and a battery.

We’ve seen a lot of strange 555 circuits in our contests. We even had a 555 Timer Contest.

A Novel 555 Circuit In 2026

April 1, 2026 by 22 Comments

The humble NE555 has been around for over five decades now, and while during that time we’ve seen a succession of better and faster versions of the original, the circuits which surround it are pretty well known. There can’t be anything new in the world of 555s, can there? [Stephen Woodward] claims he’s made a novel 555 circuit, with his 1 MHz linear voltage to frequency converter. Since he’s been in love with the 555 since 1974, we’re inclined to trust him on this part.

It’s visibly the 555 astable oscillator we’re all familiar with, given the addition of a current source in place of the normal charging resistor. This makes for a much more linear sawtooth waveform, but it still doesn’t fix the linearity of the voltage to frequency curve. The novel bit comes in adding an extra resistor between the threshold and discharge pins, with a value calculated for a time constant with the capacitor to match the 555’s own switching delay. This provides the necessary compensation, and gives the circuit its linearity.

This is so brilliantly simple that it’s almost a shock that it’s new, but it’s also a great example of the old-school electronic engineer’s art. We can’t think of an immediate need for a 555 voltage to frequency converter on the Hackaday bench at the moment, but you can bet we’ll come back to this one if we do.

We had someone pushing a newer 555 variant to its limit, when we ran our component abuse challenge.

Disposable Vape Becomes Breath-Activated Synth

March 24, 2026 by 11 Comments

Makers and hardware hackers have been collecting disposable vapes for some time now, usually to salvage their batteries or the unique displays many models now come with. But you can also repurpose them for other ends, such as playing music. [Becky Stern]’s vape synth is a perfect example of this.

The build started with an ElfBars BC5000 vape. [Becky] notes there may be similar models under different names out there that would work just as well. The vape is effectively gutted for parts, with the LiPo cell, USB charging board, and the low-pressure sensor the main things that remain. These parts are combined with a drop-in 555 synthesizer circuit complete with speaker, which has its pitch controlled by a series of six photoresistors. When the low pressure sensor is triggered by inhalation, the 555 circuit is triggered, and operates at a pitch depending on the resistance of the photoresistor stack.

The output of the vape synth is kind of shrill, and frankly a little bit annoying — which is somehow rather fitting for what it is. If you want to make a better-sounding synth at home, we’ve featured such projects, you’re just unlikely to fit them entirely within the housing of a disposable vape.

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Analog Siren For Psychedelic Soundscapes

March 21, 2026 by 4 Comments

For better or worse, there are a few instruments that have been pigeonholed into specific genres of popular music. For example, banjos are often heard in bluegrass or folk, harmonicas in blues, and a sick horn section will take many of us immediately to third wave ska. Similarly, there are certain styles of synthesizers tied to various genres and if you’re a fan a certain sub-genre of reggae you’ll be familiar with the dub siren. This unique analog synth has a few tricks up its sleeve and [Jakub] shows us how he built his.

He’s calling this build the Sirenotron, and its based on the venerable 555 timer It also features an LFO built on an LM358, with triangle and square wave modes, plus an additional “acid mode” for the square wave which adds a single capacitor to the circuit but makes a big difference in the sound. Like any siren synth, there are potentiometers to control pitch and the pulse rate of the siren as well and another switch controls whether it is outputting sound or not. He’s also included the ability to control it with a foot pedal so he can use it while playing the bass guitar during live shows.

[Jakub] has gone through several prototypes before getting to this stage, and not only uses it when playing dub but also creates psychedelic soundscapes in a side project of his where it also fits right in. He’s also made the schematics available for anyone who wants to reproduce it or build on his design.

We’re always interested in a unique synthesizer build around here, and some of our favorites include this synth built from Sega Genesis parts and this one controlled more like a woodwind instrument.

Continue reading “Analog Siren For Psychedelic Soundscapes” →

2025 Component Abuse Challenge: Pushing A 555 To The Limit

November 7, 2025 by 5 Comments

The humble 555 timer has its origins back in the early 1970s as the NE555, a bipolar integrated circuit. Over the years it has spawned a range of derivatives, including dual versions, and ones using CMOS technology. Have these enhancements improved the performance of the chip significantly? [MagicWolfi] has been pushing the envelope in an effort to see just how fast an astable 555 can be.

The Microchip MIC1555 may be the newest of the bunch, a 5-pin CMOS SOT-23 which has lost the frequency control and discharge pins of the original. It’s scarcely less versatile though, and it’s a fine candidate for an oscillator to push. We see it at a range of values for the capacitor and resistor in an astable configuration, each of which is tested across the supply voltage range. It’s rated as having a maximum frequency of 5 MHz, but with a zero Ohm resistor and only the parasitic capacitance of an open circuit, it reaches the giddy heights of 9.75 MHz. If we’re honest we find this surprising, but on reflection the chip would never be a first choice for super-fast operation.

We like it that someone’s managed to tie in the 555 to the contest, and given that it still has a few days to run at the time of writing, we’re hoping some of you might be inspired to enter one of your own.

2025 Hackaday Component Abuse Challenge
The weaving is on the left, a microphoto of the chip die is on the right.

The 555 As You’ve Never Seen It: In Textile!

September 10, 2025 by 12 Comments

The Diné (aka Navajo) people have been using their weaving as trade goods at least since European contact, and probably long before. They’ve never shied from adopting innovation: churro sheep from the Spanish in the 17th century, aniline dies in the 19th, and in the 20th and 21st… integrated circuits? At least one Navajo Weaver, [Marilou Schultz] thinks they’re a good match for the traditional geometric forms. Her latest creation is a woven depiction of the venerable 555 timer.

“Popular Chip” by Marilou Schultz. Photo courtesy of First American Art Magazine, via righto.com

This isn’t the first time [Marilou] has turned an IC into a Navajo rug; she’s been weaving chip rugs since 1994– including a Pentium rug commissioned by Intel that hangs in USA’s National Gallery of Art–but it’s somehow flown below the Hackaday radar until now. The closest thing we’ve seen on these pages was a beaded bracelet embedding a QR code, inspired by traditional Native American forms.

That’s why we’re so thankful to [VivCocoa] for the tip. It’s a wild and wonderful world out there, and we can’t cover all of it without you. Are there any other fusions of tradition and high-tech we’ve been missing out on? Send us a tip.