Modeling The Classic 555 Timer On A Breadboard

Over the years, readers have often commented that microcontrollers (or more specifically, the Arduino) are overkill for many of the projects they get used in. The admonition that the creator “Should have used a 555” has become something of a rallying cry for those who think modern electronic hobbyists are taking the easy way out.

But what if you think even the lowly 555 timer is overkill? In that case, perhaps you’ll be interested in a recent blog post by [TheMagicSmoke], where the reader is walked through the process of creating an analog of the classic integrated circuit on a somewhat larger scale. Finally, we can replace that cheap and handy IC with a mass of wires and components.

Alright, so you’ve probably guessed that there’s no practical reason to do this. Outside of some theoretical MacGyver situation in which you needed to create a square wave using parts salvaged from devices laying around, anyway. Rather, the project is presented as a good way to become more confident with the low-level operation of electronic circuits, which is something we think everyone can agree is a good thing.

The components used include a 74S00 quad NAND gate, a LM358 dual operational amplifier, a 2N2222A transistor, and a handful of passive components. [TheMagicSmoke] not only explains how the circuit is constructed, but shows the math behind how it all works. Finally, an oscilloscope is used to verify it’s operating as expected.

We respect a hacker on a mission, just last month [TheMagicSmoke] put together a similar “back to basics” post on how to interface with an I2C EEPROM.

Fizzle Loop Synth Does It With 555 Timers

For every project that uses an Arduino to make soup or an ESP8266 to hash bitcoin, there’s always someone out there uttering the same old refrain. I could have done it with a 555. More often than not, this is true, even if it is tangential to the discussion being had. In this case however, such a statement is moot. [lonesoulsurfer] has built the Fizzle Loop Synth, featuring not one, but three triple-nickel timers.

It’s a build that delights in both presentation and performance. The hardware is elegantly slotted into a vintage metal flashlight case, which is absolutely covered in controls. It’s an aesthetic that gives us an irresistible urge to start twiddling knobs and flicking switches. Inside, two 555s are set up as basic flasher circuits, each feeding a vactrol – essentially a resistive optoisolater. Inside is an LED, which is optically coupled to a light-dependent resistor. The LEDs are flashed by the 555s, and this creates a varying resistance which is used to feed a third 555 which generates the tones.

The final result is a fun little noisebox that’s capable of generating quite the variety of bleeps, bloops and blops. There’s an onboard speaker for noodling on the go, as well as a line-out if you need to record your work on external hardware. It would be great fun to hear this circuit hooked up to a modular synth, too.

For a history lesson on the venerable 555, we’ve got you covered. Video after the break.

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The Three Faces Of The 555

In these days of cheap microcontrollers, it is hard to remember there was a time when timing things took real circuitry. Even today, for some applications it is hard to beat the ubiquitous 555 timer IC. It is cheap, plentiful, and reliable. What’s interesting about the 555 is it isn’t so much a dedicated chip as a bunch of building blocks on a chip. You can wire those building blocks up in different ways to get different effects, and [learnelectronics] has a video showing the three major modes you typically see with the 555: astable, bistable, and monostable.

The 555 is really only a few comparators, a voltage divider, one or two transistors, a flip flop and an inverter. The idea is you use a capacitor to charge and the comparators can set or reset the flip flop in different ways. A reset input or the flip flop can turn on the transistor to discharge the capacitor.

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Making The World’s Fastest 555 Timer, Or Using A Modern IC Version

If you’re not familiar with the 555 timer, suffice it to say that this versatile integrated circuit is probably the most successful ever designed, and has been used in countless designs, many of which fall very far afield from the original intent. From its introduction, the legendary 555 has found favor both with professional designers and hobbyists, and continues to be used in designs from both camps. New versions of the IC are still being cranked out, and discrete versions are built for fun, a temptation I just couldn’t resist after starting this article.

If you think all 555s are the same, think again. Today, a number of manufacturers continue to produce the 555 in the original bipolar formulation as well as lower-power CMOS. While the metal can version is no longer available, the DIP-8 is still around, as are new surface-mount packages all the way down to the chip-scale. Some vendors have also started making simplified variants to reduce the pinout. Finally, you can assemble your own version from a few parts if you need something the commercial offerings won’t do, or just want a fun weekend project. In my case, I came up with what is probably the fastest 555-alike around, although I spared little expense in doing so.

Follow along for a tour of the current state of the 555, and maybe get inspired to design something entirely new with this most versatile of parts.

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The 555 And How It Got That Way

There’s a certain minimum set of stuff the typical Hackaday reader is likely to have within arm’s reach any time he or she is in the shop. Soldering station? Probably. Oscilloscope? Maybe. Multimeter? Quite likely. But there’s one thing so basic, something without which countless numbers of projects would be much more difficult to complete, that a shop without one or a dozen copies is almost unthinkable. It’s the humble 555 timer chip, a tiny chunk of black plastic with eight leads that in concert with just a few extra components can do everything from flashing an LED a couple of times a second to creating music and sound effects.

We’ve taken a look under the hood of the 555 before and featured many, many projects that show off the venerable chip’s multiple personalities quite well. But we haven’t looked at how Everyone’s First Chip came into being, and what inspired its design. Here’s the story of the 555 and how it got that way.

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555 Timer Robots Will Rule The World

A running joke we see in the comments by Hackaday readers whenever a project includes an Arduino or Raspberry Pi that seems like overkill is to proclaim that “I could have done it with a 555 timer!” That’s especially the case if the project amounts to a blinking light or anything which oscillates. Well [Volos Projects] has made a whole robot out of a 555 timer circuit.

Okay, it’s really a dead bug circuit in the shape of a robot but it does have blinking lights. We also like how the base is the battery, though some unevenness under it seems to make the whole thing a bit unstable as you can see in the video below. There are also a few parts which are cosmetic only. But it’s cute, it’s a 555 timer circuit, and it’s shaped like a robot. That all makes it a win.

We do wonder how it can be taken further. After all, a walk cycle is a sort of oscillation so the 555 timer circuit could run some servo motors or at least some piezoelectric feet. Ideas anyone?

On the other hand, if you’re looking for a dead bug circuit which belongs in a fine arts museum then you need look no further than The Clock.

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LED “Candle” Gets The 555 Treatment

Regular readers may recall we recently covered a neat Arduino trick that allowed you to “blow out” an LED as if it was a candle. The idea was that the LED itself could be used as a rudimentary temperature sensor, and the Arduino code would turn the LED on and off when a change was detected in its forward voltage drop. You need to oversample the Arduino’s ADC to detect the few millivolt change reliably, but overall it’s pretty simple once you understand the principle.

But [Andrzej Laczewski], like many of our beloved readers, feels the Arduino and other microcontrollers can be a crutch if used exclusively. So he set out to replicate this hack with that most cherished of ICs, the 555 timer. In the video after the break, he demonstrates his “old-school” LED candle for anyone who thinks the only way to control an LED is with digitalWrite.

Not to say it’s easy to replicate the original Arduino project with a 555, or that it’s even practical. [Andrzej] simply wanted to show it was possible, which is something we always respect around these parts. He goes into great detail on how he developed and tested the circuit, even including oscilloscope screenshots showing how the different components work together in real-time. But the short version is that a MOSFET is used to turn the LED on and off, a comparator detects change in the LED’s voltage drop, and the 555 is used to control how long the LED stays off for.

Ever the traditionalist, [Andrzej] wrapped up this build by etching his own PCB using a variation of the classic laser toner transfer method. If this all looks a bit too much like Black Magic to you, there’s no shame in sticking with the Arduino version. At 1/20th of the parts count, and with no calibration required, who’s to say which version is “simpler”.

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