555 Timer Circuits
555-timer-circuits.com
555-timer-circuits.com
Today, it's essentially obsolete. You're quite unlikely to find it in any competently-done commercial designs. Every analog trick you can do with it can be done more cheaply, more reliably, with better power efficiency, and with fewer external components using a modern MCU.
It's not that analog is dead, but it's solving different problems now. Including how to keep ultra-high-speed digital signals usable within the footprint of a PCB - which wasn't that much of a consideration in the golden days of the 555.
But even there, it's high Iq limits its applicability.
https://en.wikipedia.org/wiki/Bang–bang_control
There's still plenty of analog control out there, it's just all hidden away as parts can integrate the sensor, controller and actuator, all in one magic IC. And it can definitely be lower power and cheaper, in volume. The main weakness is the NRE is higher than the typical MCU project so it's not really seen in low volume or hobby level stuff.
You'll find them in tons of commercial designs - your modern headlights (which I manufacture) and off-road lights use them in droves. Short-timed lighting like automatic UVC sterilization lighting and such also still relies heavily upon a 555 timer just to act as the on/off switch for the power driver pushing the LEDs.
I have a bit of a pet peeve about car lights (usually exterior lights that aren’t the headlights) that are visibly pulsed. They can be distracting. I think they should all be designed to operate either at silly frequencies that are genuinely undetectable by human eyes (30kHz?) or to genuinely operate at DC.
Newer headlights use the 555 timer as a quick comparator to turn off the headlight when the corresponding turn signal is activated, and control the turn signal simultaneously.
[0] Why do cars have special names for microcontrollers?
They aren't needed when the lighting is LED. The wiring harnesses going to more modern headlights are quite thin.
"I always imagined that newer cars would have a single CAN link to an ECU [0] in back, and that ECU would control all the lights near it."
They do but some are moving away because of the total lack of security and ability to compromise the CAN bus through the headlights to steal vehicles - read https://www.autoblog.com/news/vehicle-headlight-can-bus-inje... for what's going on there. They're too cheap to actually spend the money on real hardening so they're moving back to pure hardware control in many cases.
Haven't seen 555 in a commercial product with modern design for a long long time.
Wait what? Why is a headlight influenced by a turn signal??
I realize that American brake lights and turn signals are more intertwined than is reasonable, I've seen the Technology Connections Youtube video. Are you telling me something similar is going on with headlights?
Some new cars, mainly luxury ones, dim headlights. It is to avoid blinding other drivers who may be looking at your turn signal.
All cars with "Daylight Running Lights" (housed in the headlight assembly) turn them off for that side when the turn signal is active. I assumed this is to make the turn signal more obvious (as the change in brightness is more prominent).
For more modern vehicles, they have to turn off the LED/Laser-phosphor unit entirely because the lights design is too radiant and glaring for the turn signal to be seen. GMC and Ford big-ass trucks made within the last 5 years are an example.
It makes a nifty missing pulse detector, though.
“Hi, Jeff H., I have almost never used a 555. Maybe never? I use op-amps, LM324's, LM311's, LF356's. I use 74HC04's and 74C14's but not 555's. I've used ECL fast logic, and discrete transistors. But the 555 just does not do anything precise, or even semi-precise, that I need done. So that's one thing I can "share" - my favorite circuit to use a 555, is: a blank piece of paper. Never touch the things. Go ahead and print that. / rap”
It’s a shame that Arduino has effectively truncated kids learning with a full MCU as the “building block” of their learning
I see it also bite them in the arse with wasteful solutions. Often a BJT or power fet is all they need (say for a basic relay trigger). But if they aren’t presented with a shiny arduino compatible module explicitly designed for what they want, they get nervous
About half the kids I see make the intellectual jump, half end up not coming back
I do wish kids were taught basic soldering, it would make the learning process a lot less worrisome
The 555 and LM741 are still supreme learning tools. They are even simple enough to breadboard out with BJTs and analogue components. I’ve only seen a few extremely hardcore guys bother to conceptualise under the hood that deeply
Why? I think the vast majority of hobbyists used the 555 as a "black-box" chip. They now have a more intuitive, cheaper, and more power-efficient way of doing the same thing.
Pre-Arduino, learning electronics wasn't more profound. It was just less accessible. Nowadays, you have the same number of determined and talented hobbyists who eventually master some of the more arcane topics. You also have more people who learn just enough to get their art project done, and it's easier than it used to be... but why is that a bad thing?
There's a temptation to demand that others do things the hard way just because we had to. But is it healthy? I don't lament the demise of the 555 any more than I lament that the youth no longer knows how to put shoes on a horse.
I agree with both you and the GP. Arduinos tend to make goofing around with electronics more accessible to more people. At the same time a lot of projects could be built very simply with just a couple timer chips. It's unfortunate people reach for a relatively complex solution (Arduino etc) to what's ultimately a simple problem. They would benefit a great deal from just knowing a blinking light can be made very simply with a simple circuit.
An Arduino is very approachable in that you can just plug it into a USB port and tell it to blink a light following a very simple tutorial. No breadboards even, just plug in a device and open a program. Under the hood the Arduino is very complex but for the end user it's very simple.
A lot of Arduino compatible modules are also simple for the end user despite being very complex under the hood.
The simplicity for the end user is I think the biggest attraction for the Arduino. In your K8s analogy, it is not simple for the end user. Someone may build some K8s monstrosity because that's what a tutorial or bootcamp taught but it's very obviously complex. The hosted JavaScript app is a better Arduino analogy, it's a complex solution under the hood but presents a relatively simple user experience.
I’m thinking RC timing and voltage dividers. These have practical application. Would it ever get used elsewhere? That is where my thinking merges to yours.
Forty years from when I started that journey, not sure it can’t be learned from a wiki.
(The power supply sitting next to that MCU has a divider-based feedback loop, usually.)
These possibly can't be learned from a wiki, but they can absolutely be learned from the Art of Electronics for a low price.
But I always dreamed of a digital future. When I was very young, microprocessors fascinated but intimidated me with their need for special support chips, and I would design 4 bit computers I couldn’t afford to build using 7400 logic and 4 bit SRAM.
For a while, I strayed from the path and learned to program on my C2-8P computer that my brother and I bought. By middle school, I was more or less distracted, and came back to technology later with the TS1000 and later the c64. Eventually, the AT2323 brought me back into electronics with MCUs, and I found it was the world I always fantasised about as a 7 year old kid designing 4 bit ALUs. I don’t know why I missed out on the early PIC days, but I think it was girls, cars, and LSD, mostly lol.
Anyway, since then, I’ll unashamedly put a 6 pin mcu in just to flash a light, but I’ll make it flash in a better way, so that it grabs your attention when it is starting or stopping flashing, for example. Or it will flash in a way that communicates just a little more about what it’s telling you. I find with MCUs your stuff can be just a little bit better in a thousand subtle ways, and despite 10000x the parts count, more reliable and resistant to environmental factors. With modern mixed-signal MCUs that can drive 60ma on a GPIO, most things can boil down to a single chip with a few external parts.
Then you get to stuff like the esp32 platform, where for $1 you get a single chip solution that puts my first 486 PC to shame playing DOOM, even while bit-banging the video output. There’s no point in using something less capable unless you are making more than a thousand units, in which case you can still end up with a $0.10 risc-V running a respectable 24 mhz at 32 bits, with more flash and ram than my old C2-8P.
Lol this also happened to me, I wonder how common this is?
Sex derails the potential of young humans in so many ways, yet the process of reproduction is so arduous that it makes sense that we’d end up wired to prioritise it heavily. All it would take is for young people to wise up and we’d be extinct within a century and a half lol.
We’re seeing the results of not valuing the labor that is creating a home and raising children in systematic rapid population decline. (Which might seem ok, but in most situations, it is socioeconomicly catastrophic)
We need to learn to overtly value the huge labor sink investment that motherhood , fatherhood, and family stewardship entail.
There are things more valuable to humanity than the ability to concentrate wealth and power at the expense and to the exclusion of others.
The whole drive to concentrate wealth and power is fundamentally based on sex anyway. It seems a great poverty to not acknowledge and socially celebrate the skills, labours, and sacrifices of parenthood.
This absolutely matches my experience. I was very interested in electronics growing up in the 80s. I took everything apart (occasionally without breaking it), I had those spring terminal "200 in 1" kits, a crappy soldering iron, and tons of enthusiasm and energy to channel into it. But I very quickly hit a wall trying to understand analog circuits, and I gave up (and redirected my interest to computers).
Some of it could be the limited information I had access to, in a small town, pre-Internet. There was a lot of math, and this was when I was like 8-10 years old, so it was way over my head. But I tried several times over the following decades to get back into it, and I just couldn't find a way in that connected with me.
The point of all of this is that in 2012 I stumbled across an Arduino kit and everything changed. Now I could apply the digital logic and programming concepts I understood to make things that did stuff. I rediscovered my interest in electronics, and the part that's most relevant here is that because it was accessible and fun, it gave me an on ramp to start to explore the analog world a bit more. The concepts began to make sense and build on each other as I developed an intuition for how they worked, and now I feel reasonably comfortable with analog circuits.
So I don't see it so much as nobody is going to learn other things because they can just throw a MCU at it, I think it's a great way to get started and then go on to develop a more thorough understanding of electronics (if that's your thing).
I got into electronics (and to some degree, computers) as a means to do something cool. I don't have the drive to memorize data sheets spend hours playing component golf. I just want my circuit to work, even if it's not the most efficient way possible to do it.
That said, some analog principles are still needed in the back of your mind when making digital stuff. Input impedance, rise time, ripple etc.
I was 100% self thought and teach electronics in art university now. And I have to say I can't really confirm your suspicions about "the kids", sure many stay at the module level (totally okay, they study arts not electronics), but many don't. I had a student who over the course of 2 years built a brain wave reading circuit with a specialized instrumentation amplifier IC, to filter out grid EMF she built an opamp based notch filter and that woman had nearly no help from me and no prior education in the field. That analog stuff isn't going away anytime soon.
For art projects I totally get using a MCU. You're probably only making one and the product is the art. The engineering just gets in the way so minimizing man hours, which includes the time to learn to do the thing, is critical. It will be tough to beat a MCU on that metric.
Not every project is mass produced or must be highly optimized when it comes to size, cost or power consumption. People use what they know, and what they know depends on when they grew into it.
555 is obsolete tech. I see this as equivalent to suggesting someone buy an Apple II instead of a modern PC.
This is a good question. I think that "Arduino" means a couple of different things, and it's sometimes hard to guess what someone means from context.
There's "Arduino" the old 16-bit MCU board, and there's "Arduino" the development platform supporting a huge ecosystem of MCUs, libraries, and accessories.
For instance, I use the Arduino IDE, but with a variety of dev boards to suit my needs. For my work, I don't need to cost-engineer anything, so I'm satisfied with pre-made modules that I plug into my own application boards.
A lot of engineers dismissed Arduino long ago, and are utterly unaware that the broader ecosystem even exists.
I don't object to a beginner choosing the original Arduino board, for which there's huge amounts of tutorials and documentation. And then, maybe graduating to a more performant board if they take an interest in more advanced or specialized projects.
The second the conversation steers towards actual product selection… that is the time to introduce the MCU space and steer them to the right fit. You do always have to remember that most of those arduino MCU’s have a 5 volt logic level that is more compatible with “LEGO part style electronics” than things like the ESP chips.
I grew up interested in stuff like that, taking walkie-talkies apart and building electromagnets with nails etc. - despite the availability of the world wide web & DAB radio.
There is a reason I didn’t truly get into electronics as a kid. Only in adulthood with the introduction of the arduino (really esp8266) did any of that stuff click enough to get my interest.
All that analog stuff just got in the way from what I actually wanted to do. Build cool stuff. But back then there was way too much “complexity” between me and whatever cool thing I wanted to build and none of it was the good kind of complexity.
Starting out with modern MCU’s take all that away and let me build at the level of the project where what I do actually impacts things. If I had to worry about all that analog stuff, I never would have bother, just like as a kid I never bothered—I just did all my cool shit on the computer instead!
Perhaps you mean BJT+resistor+diode+relay or FET+diode+relay is all they need?
The value in the module is that it includes the necessary components required so that the circuit doesn't break. And such breaking is highly destructive to the learning process. You need to get kids excited about what they might be able to do on a larger scale, before you can trick them into studying the lower level details and diligence required to make it happen.
My own childhood explorations in electronics were stunted due to not understanding that BJTs were current devices, and what all those resistors were for. I'd try to modify a circuit, destroy a transistor, and then no amount of playing around would get things working again. Especially on those toy kits where every component was broken out into spring terminals - I basically learned that the transistor section was verboten unless I was building something exactly from the manual. Sometimes I ponder how much earlier I would have understood electronics in an alternative timeline that emphasized 2N7000's instead of 2N3904's.
When circuits become larger than trivial, the analog way is noise and temperature sensitive, you will spend a lot of time on tweaking those aspects by themselves.
And while scopes do take time to learn, learning about scopes themselves will convey a lot of fundamental information about electronics. I also wouldn't underestimate the difficulty in learning how to use microcontrollers. While using something like Arduino (boards, shields, development tools, and libraries) may be straight forward, the learning curve rises steeply as soon as you try to do anything truly independently. More steeply, I would suggest, than learning how to use an osilloscope. Besides, most of those development boards cost a lot more than a bare chip.
For some reason I always struggled to remember the different operating mode configurations, what they are called, and how to set them up. But one day I was trying to build a specific thing and decided to sit down and actually understand the 555. To my surprise, it's really simple in operation and requires relatively little electronics theory to understand and derive the different configurations yourself. Once I did that, I haven't forgotten it and I can come up with more creative uses for the 555.
You mentioned only ten functional components inside it, but if you look at individual transistors and resistors, there are quite a few more.
Here is the through-hole component version:
https://shop.evilmadscientist.com/productsmenu/652
And a surface mount device version:
https://shop.evilmadscientist.com/productsmenu/922
I built the through-hole version, and it worked the first time I wired up a circuit around it.
Highly recommended!
You could make it so you could control it with a light pen. It would integrate over a window of a single scan line?
A slightly more complex device could retrigger and sum into a bucket brigade and integrate over a region.
https://climate.nasa.gov/vital-signs/global-temperature/?int...
At any rate, I do own his books on electronics as a kind of an amusing look into the history of how electronics were taught, but I do find it to be a positive thing in the world to have curious individuals like himself.
People from all walks of life believe all sorts of kooky shit. That’s the spice of it I suppose.
https://answersingenesis.org/theory-of-evolution/12-the-basi...
My biggest critiques are that it consistently fails its predictions. You’d see an endless stream of intermediate forms going in so many directions. Instead, we saw few if any, nature organized more hierarchically, and organisms just appear out of thin air after extinctions (eg Cambrian Explosion). Instead of falsification, scientists keep making excuses for it like it is a religion that can’t be wrong.
I’ll add that humans have observed creatures, in their areas and in captivity, for a long time. We haven’t seen the chickens start giving birth to different animals. I’m grateful the fire ants and poisonous spiders we’re dodging haven’t turned into something more effective. Dumb evolution would have a crazy number of adaptation streams happening, many attempts per species, to create all the life we see. Instead, we see exactly zero movement from one kind of animal to another with changes only happening within kinds.
Whereas, studies of creation itself have proven the opposite. Everything from our non-life experiments to evolutionary algorithms show a creator who fine tunes is necessary. The universe itself has many constants that never change, they work together in precise ways, all has perfect reliability, and life on Earth depends on most of them. Complexity of most of biology is such that we’re incapable of manufacturing it. (See a lung vs a respirator.) It only gets more and more impossible over time the more we learned.
On time scales (X is millions of years old), they seem to assume the Earth didn’t change much at all over a long period of time. A specific thing changes at rate X. They’ll roll the clock back that much until they hit a point in their theory. Both human literature (esp Genesis) and the fossil record show catastrophes with huge effects on the Earth. It probably went through many changes. So, all time estimates that make that assumption are faith-based, likely-incorrect beliefs no matter how many textbooks they end up in. There is a minority studying Catastrophism or something like that to understand their effect.
Finally, godless science that broke from Christian scientists, like Newton and Pascal, all backed David Hume saying only material, observable things exist. Nothing else is ever allowed in scientific theory. A faith-based, unproven belief. While still making godless and materialism axiomatic, the same scientists tell us of a world outside our universe, exceeding the laws of physics, and maybe even having effects on observed phenomenon. Instead of things with evidence (eg Bible), they’ve shifted to purely-imaginary constructs outside the universe to support their claims which themselves contradict the Hume foundation they demand of us. They do it while denying the logical implications of the complexity and fine-tuning we’ve observed.
Those are some examples of counters to mainstream creation, like evolution and long timescales, being a pile of faith-based dogma that continues to fail in scientific experiments, historical writings, complexity theory, and global observations by laypeople. Outside of minor adaptation, evolution theory is provably false which leaves God as the primary hypothesis. From there, we consider whichever God claim has the most evidence and impact. That’s Jesus Christ. :)
Indeed, a small $0.23 mcu may have its own internal RC oscillator, or even a MEMS based resonator on a PLL. =3
Microcontrollers obviously have more than 1 bit of memory + 2x analog comparators + one 33% / 66% voltage divider (which is all a 555 timer truly is).
What is surprising however is how flexible 1 bit of memory + 2x analog comparators + one 33% / 66% voltage divider
For example, switch debouncer could be solved in code, resistor+capacitor or other methods. But you know what's one of the best performing switch debouncers?
1-bit of memory with an analog comparator. Aka: a 555 Timer.
> 555 is useless without multiple extra parts
Not needed for bistable multi vibrator (aka: just a flip flop mode). Which happens to be the debouncer circuit.
You can add the 555 Timer to an already completed design if it is later discovered that debouncing was an unsolved problem.
I don't think it is always appropriate to assume that code can be rewritten (or rearchitected) to fit your needs. Sometimes its easier to solve problems with a touch of extra external hardware.
What matters in production is that a 555-based circuit will use more power, that it's four components to source and install instead of one, and so on. Don't get me wrong, I like the 555, just like I like vacuum tubes, but it's nearly as dead.
The ATMega needs about ten components to get properly operational for programming vs a simple 555 timer circuit. Oh, and then you also need the programmer and toolchain for making the code.
Or you can just use some basic math and thrown down native hardware to do the job. One of the biggest off-road lighting manufacturers on the planet does exactly this with 555 timers.
I manufacture lighting controls of various sorts as my current profession.
As an example, here's a equalizer built around a 4049 quad inverter gate chip.
http://www.runoffgroove.com/mreq.html
As for digital gates, I couldn't recommend more the TTL and CMOS cookbooks by Don Lancaster: they're a goldmine of ideas. 2nd one is available for free at author's site.
More details if curious: https://www.reddit.com/r/amateurradio/comments/1eo9ki7/xiegy...
I cut my teeth on them, about 40 years ago.
1) https://www.talkingelectronics.com/projects/50%20-%20555%20C...
> This device is used tocure, treat and prevent any disease. It will cure anything.
The internal resistors should be connected to the upper comparator. Also, that diagram just seems confusing. Something like this makes more sense: https://www.theengineeringknowledge.com/wp-content/uploads/2...
https://hackaday.io/project/182915-555enabled-microprocessor
With everything going 3.3V these days with no 5V tolerance (can't have nice things ofc), is there some kind of 333 timer that would do the same job but down to those logic levels?