[HN Gopher] Doin' It with a 555: One Chip to Rule Them All
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Doin' It with a 555: One Chip to Rule Them All
Author : MonkeyClub
Score : 115 points
Date : 2026-01-27 15:02 UTC (3 days ago)
(HTM) web link (aashvik.com)
(TXT) w3m dump (aashvik.com)
| stackghost wrote:
| Obviously TFA is satire/tongue in cheek and while you can do all
| sorts of awesome stuff with a 555 you can't patch those
| implementations without physically rewiring them which in many
| cases means throwing out the board and fabbing a new one, whereas
| a microcontroller-based board can often be fixed with a simple
| jtag debugger.
|
| So, yeah, 555 timers are cool and doing things with analog ICs is
| groovy but there's a reason everyone just stuffs a small
| microcontroller in places where we used to just stuff a 555, and
| it's maintainability.
| nippoo wrote:
| And price. A PY32 is about $0.08 in quantity and can do a lot
| more than a 555 - which is at least 3 times more expensive...
| ofrzeta wrote:
| Puya? First time I hear of these things .. (having used
| ESP32, RPI Pico, Nordic and STM). Googling led me to OpenPuya
| https://py32.org/en/
| 15155 wrote:
| Puya is a major flash manufacturer who ventured into ARM
| chips.
| mrheosuper wrote:
| and it comes with new set of problems: Now you need a FW guys
| to write and maintain software for it, then your hardware
| team may need to wait that FW guy to release software to
| test, or the FW guy need to wait hardware to test his
| software, etc.
|
| Then in production, you need another stage to flash the FW,
| which add time and complexity.
|
| Then security, cheap MCU usually has bad software protection,
| that means your software can be read out easily, not a big
| deal since the FW replacing the 555 would be dead simple
| anyway, but try to explain it to a non-technical CEO when he
| read about it on his morning's newspaper.
| jeffwass wrote:
| Two thoughts on situations where the 555 may be preferable, if
| anyone has experience how these compare :
|
| 1. Low-noise applications. I'd naively expect the 555 to be
| less noisy than a clocked digital microcontroller, though it's
| been awhile since I've worked in this space.
|
| 2. Low power applications. How does latent power draw compare
| between a 555 and a typical low power microcontroller?
| tdeck wrote:
| > Low power applications. How does latent power draw compare
| between a 555 and a typical low power microcontroller?
|
| The 555 is very power hungry compared to a typical cheap low-
| power microcontroller. IIRC there are lower power variants
| but the 555 still fundamentally does timing by draining
| current through a resistor, which is going to result in
| losses.
| dubbie99 wrote:
| A micro is far superior on both these metrics.
| ErroneousBosh wrote:
| > I'd naively expect the 555 to be less noisy than a clocked
| digital microcontroller
|
| TTL ones were exceptionally noisy because the output
| transistors "shot through" - both output transistors would
| conduct for a moment shorting the supply rail to ground and
| crowbarring ridiculous interference onto other parts of the
| circuit.
| buescher wrote:
| And there's another reason not to recommend them - no one
| sane has used the bipolar version since the Carter
| administration but they're still out there and it's another
| pitfall for beginners.
| nurettin wrote:
| Obligatory
|
| https://youtu.be/mDhNQPt8An0?si=VlzHWK4Cxcxn9pSK
| solomonb wrote:
| When I was in college I was not in an engineering program but I
| was self-learning electronics. I was trying to learn to use a 555
| timer to do something and couldn't get it to work.
|
| So I went to the office hours of a random EE professor thinking
| they would help me out. Instead I got scolded about how 555
| timers are not real engineering and that I shouldn't waste his
| time.
|
| I never used a 555 timer ever since.
| foxglacier wrote:
| I used to salvage components from electronic stuff and was
| always looking out for 555s but never found any, in a whole
| range of vintages from 1970's to 2000's. I ended up with the
| same conclusion - it seemed to be a hobbyist's chip that real
| consumer products didn't use and felt amateurish for some
| reason I didn't understand.
| tralarpa wrote:
| That's funny because I have two objects on my desk for which
| I know that they use 555s. One is a no-name joystick with
| "autofire" function from the late 1980's. The other is a mass
| produced motor controller from the 2000's where the 555
| generates the PWM signal for a FET.
| leoedin wrote:
| The big problem I ran into playing around with 555s was that
| capacitors are very rarely the capacitance they claim. Unless
| you're speccing an expensive capacitor, you'll find your time
| constant varies quite a bit across devices and temperature.
| That's fine for some use cases, but completely a deal breaker
| for others.
| buescher wrote:
| Yeah, in the typical value ranges (nanofarads) of a
| 555-timer-class analog design, you'll need film caps.
| Ceramic C0Gs are too small and class 2 dielectrics are
| dismal for anything but bypass. They don't just have
| temperature coefficients, they have _voltage_ coefficients
| and are wildly nonlinear. And electrolytics are almost as
| dreadful as batteries. Worse in some ways. It 's a tough
| bridge for beginners to cross - once you figure out
| capacitors are not all equivalent you have to do a deep
| dive on dielectrics and it's a bit of a chicken-and-egg
| problem - you don't know what you're doing so you don't
| when you'll need what.
| blackguardx wrote:
| 555 timers were everywhere back in the day. It was one of the
| most mass produced chips at the time with over 1 billion made
| per year.
| buescher wrote:
| Sure, it's kind of cringe. I've shipped stuff with 555 timers
| in it. I'm not proud, but I'm not telling what either.
|
| You can do almost all of the 555 tricks with comparators and
| then some, and you'll learn more doing them. Check out the
| old National Semiconductor application notes for the LM393.
| You're more likely to see comparators used for little bits of
| analog/analogish-digital glue in professional designs.
| Zardoz84 wrote:
| I saw 555 being used to implement the "Turbo" buttons in
| these old 8-bit pads for NES clones and similar. Also, I
| think that the mythic Gravis game pad uses a 555 to implement
| the same function when it is in two button mode.
| jacquesm wrote:
| What a spectacular failure of education.
| rcxdude wrote:
| A little bit (scolding a beginner in this way is never
| acceptable), but I do feel like the 555 is really
| overrepresented in electronics learning materials. It's a
| quirky little chip, so learning about it doesn't really teach
| you much (most of the time it's just 'hook it up like so and
| it does this!', not 'here's how comparators and oscillators
| actually work'), and it's also now almost never the best or
| even a good solution for any of the problems it solves.
| jacquesm wrote:
| That's true but because it is a quirky _useful_ little chip
| it is for many people their first exposure to integrated
| circuits that are a bit more 'analog' than gates and micro
| controllers. Opamps are the other gateway drug I guess.
|
| It's excellent teaching material for that reason alone, you
| do learn about it if you try to understand what makes it
| tick (there are plenty of articles about it, including
| blown up versions). I agree it is not the best solution for
| most applications but I'm happy to admit that I've actually
| used it in production designs (more than once, actually)
| where it made good sense to have a component that didn't
| have to be programmed. If you have a soft component on a
| board and a spare io line then you are usually better off
| doing it in some different way.
|
| I've seen some interesting applications of 555s that would
| have taken a lot more hardware otherwise, one of which was
| an oven controller with used a thermistor to directly
| affect the PWM output of a 555.
| Tade0 wrote:
| It's true. They're not useful for anything not hooked up to
| mains.
|
| I was meaning to add footstep-activated lights to my stairs
| using vibration sensors and 555 timers, but then I learned
| that if I tried to operate them from a battery, the 555
| would drain it in hours, while a much more sophisticated
| ESP32-c3, would last a month in sleep mode on two coin
| batteries or one li-ion in the same form factor all while
| being part of a development board that greatly increases
| idle current.
| ghtbircshotbe wrote:
| Yes, but a successful way to prevent people from going to
| office hours. People generally don't become professors
| because they care about teaching, and universities don't
| reward professors for teaching.
| bigstrat2003 wrote:
| > People generally don't become professors because they
| care about teaching
|
| That's only true in the very twisted environment that is
| the modern research university. But universities _do_ still
| exist which are focused on teaching students as the primary
| goal, and the faculty there love teaching.
| solomonb wrote:
| I never went back to that engineering department.
|
| I ended up befriending a former Northrop RF Engineer and a
| (sadly) homeless genius who was involved in early silicon
| valley. Those two guys were incredibly impactful on me and
| got me all the way up to building RF equipment.
| jacquesm wrote:
| Very neat. I'm in the midst of some interesting hacking and
| I _really_ regret giving away a lot of my workshop tools in
| the mid 90 's when it all went to software. I still have a
| lot of hooks in electronics and such but I just couldn't
| justify lugging around a couple of cubic meters of parts
| stock & gear. But right now I'm seriously wondering whether
| that was a wise decision, on the other hand that world has
| definitely not stood still, and the prices have come down
| considerably. But I'd love to have my old frequency counter
| and pulse generator back :)
|
| I'm really happy that you found an alternate path because
| such a put-down is terrible and should have never happened
| in any mature education institution.
| solomonb wrote:
| > that world has definitely not stood still, and the
| prices have come down considerably. But I'd love to have
| my old frequency counter and pulse generator back
|
| My whole workbench is mid to late 90s HP equipment I've
| picked up very cheap at swap meets. I love this older
| stuff but it is really crazy what you can buy out of
| China now. The Rigol Oscilloscopes and Spectrum Analyzers
| are crazy. They can actually replace a lot of other test
| equipment and do some pretty complex analysis.
|
| > I'm really happy that you found an alternate path
| because such a put-down is terrible and should have never
| happened in any mature education institution.
|
| I actually had a near identical experience at a different
| university when seeking advice about how to read Hegel. I
| think this is a common issue with our academic system.
| Joel_Mckay wrote:
| That is a terrible learning environment. Our profs always leave
| a box outside the laboratory with free expired textbooks,
| partial part lots, and damaged/old test equipment.
|
| Some people get into Science, Software, and Electronics for the
| wrong reasons.. And end up miserable teaching after failing in
| the private sector.
|
| A few 555 can teach people a lot, and burning out parts is part
| of the learning process. Most fold the DIP legs under like a
| "dead bug", as that is the tradition to prevent its accidental
| re-use.
|
| In terms of component cost, ATTINY or PIC10 mcu have internal
| RC oscillators with configurable PWM pin hardware. Thus a
| single component is usually better than the accumulated
| precision error in discreet parts around a 555.
|
| I usually recommend an RC car/truck build,
| https://eater.net/6502 , and or an LDOmotors Voron kit. Getting
| your Ham Radio technician license will also introduce you to an
| intuitive understanding of EE component model limits.
|
| This covers a lot about discreet analog circuits, and I
| recommend trying to figure out how every circuit works on your
| own:
|
| https://archive.org/details/encyclopediaofelectroniccircuits...
|
| Simulators are not perfect, but they are a lot cheaper when
| starting out. =3
|
| Tutorials:
|
| https://www.youtube.com/@FesZElectronics/videos
|
| Tools:
|
| https://www.analog.com/en/resources/design-tools-and-calcula...
|
| https://web.archive.org/web/20200218212700/http://spectrum-s...
|
| This requires a GPU on Windows, but is a more advanced newer
| Spice simulator:
|
| https://www.qorvo.com/design-hub/design-tools/interactive/qs...
| teaearlgraycold wrote:
| How hilariously transparent that he didn't know how to use a
| 555 and didn't want to admit it.
| MisterTea wrote:
| I always get reminded of this when I see all the weird praise
| the 555 gets:
| https://www.electronicdesign.com/technologies/analog/article...
|
| It's one of those poor/early designs like the 741 opamp that
| has since been superseded by much better chip designs but is
| thoroughly ingrained in hobbyist and EE101 classes to the point
| where people think it must be a good design because it's so
| venerated. It's meme driven really.
|
| However, for educational and hobby use, eh whatever. If I was a
| professor and the curriculum called for 555 or 741 use I would
| thoroughly state to the students that A. these devices are
| historic and good teaching tools, however, in the real world
| their performance has been surpassed and you would use new
| designs. Maybe even present a few alternatives like the TL081
| and what Pease mentioned for timing.
| analog31 wrote:
| Indeed, my professor mentioned that we used 741's so we would
| learn all of its deviations from the idealized op amp model.
| Plus, we had a huge pile of them.
| buescher wrote:
| The TL081 family of op amps is definitely in the "old parts
| you should (sometimes) use" category (for price/performance)
| but there have been much better op amps for not much more
| money for a long time now. Both the now-ancient 2nd edition
| and the aging 3rd edition of Horowitz and Hill recommend the
| LF411 for a JFET-input general purpose jellybean, for
| example.
|
| For learning you some analog, I would recommend the LM358 op
| amp and the LM393 comparator and all the old National
| material on them. The LM358 has its quirks so you won't think
| op amps are ideal but you still see them in a ton of stuff,
| because they're dirt cheap and adequate for a lot of things,
| and the LM393 comparator is still so good you really should
| _know_ why you 're choosing anything else - micropower or
| exotically high speeds or whatever.
| buescher wrote:
| When the student is ready, the teacher will appear. What a
| wonderful fellow. Have you gone back and thanked him?
| moron4hire wrote:
| That's really too bad. 555 timers are a lot of fun.
| ryan42 wrote:
| I want to build an atari punk console with a 555 to learn basic
| soldering and electronics, fun stuff
| ErroneousBosh wrote:
| Do it. Build a couple, then build a simple opamp mixer (it's a
| single opamp and a handful of resistors, and a couple of
| capacitors across the power supply), and then - get adventurous
| - a PT2399 delay kit.
|
| Then take a look on https://yusynth.net at some of the VCF
| designs, and build one of them.
|
| You won't have a synthesizer, you'll have some crazy homebrew
| drone machine that you can make scary movie sountracks with.
| 0xEF wrote:
| Definitely do it.
|
| Obligatory link to Forest Mims' book:
| https://archive.org/details/555-designs
| cbdevidal wrote:
| Ah man I had that one. Total flashback when I opened your
| link. Thanks
| fzeindl wrote:
| The 555 is a versatile little thing. I used it at university for
| a simple circuit which allowed an arduino to cut it's own power
| for 5 minutes and then boot again.
| pkphilip wrote:
| :) that is actually pretty cool!
| gary_0 wrote:
| I designed the electronics for a heavy-duty industrial 3D printer
| and used a 555 in the failsafe circuit (alongside the manual
| e-stop). If it didn't get reset by a heartbeat from the embedded
| computer/software, it would unpower the heaters and actuators.
| buescher wrote:
| That's the only use for one that isn't (always) a design smell
| - it makes a really nice missing pulse detector, better than
| you can easily do with comparators. But if you have the budget,
| a purpose-made watchdog chip or a tiny microcontroller really
| can make a better watchdog.
| gary_0 wrote:
| I would absolutely not want to use a microcontroller or a
| complicated chip for something like that. Simplicity is the
| point.
| buescher wrote:
| Supervisor chips are not complicated. In some ways simpler
| than a homebrew analog watchdog, and the good ones will
| handle failure modes a simple watchdog won't, like those
| that result in an oscillating output.
| gary_0 wrote:
| Yes, a simple purpose-made chip designed to be used in
| safety-critical situations, with high tolerances for
| voltage etc, would probably be better. Although one thing
| the 555 design has going for it is that a seasoned EE
| could take one look at the physical circuit and know
| exactly what it does.
|
| But I would _never_ trust anything that _ran software_
| for something like this.
| 15155 wrote:
| Modern 32-bit microcontrollers are cheaper than 555s.
| reader9274 wrote:
| I built one from discrete transistors in a lab class in college,
| on a breadboard. Fun times debugging and getting it to work. Then
| I flashed an led with it right next to another led flashed from a
| 555 chip. With the same discrete timer caps, the flashing
| frequencies were different due to the extra parasitics in the
| breadboard discrete 555 version. So had to compensate the caps to
| make the flashes match each other's frequency.
| jacquesm wrote:
| That's a great exercise. The hard part is always that in chips
| you can pull stuff that is rather tricky discretely, for
| instance, a multi-emitter transistor. So you can't always do a
| 1:1 conversion but for a 555 it is still doable.
|
| I saw this a while ago:
|
| https://www.instructables.com/Designing-a-555-Timer-on-Discr...
| direwolf20 wrote:
| Only because odd components aren't marketable. There used to
| be 4-terminal MOSFETs, they weren't sold after ICs became
| normal. Never heard of a multi emitter transistor being sold
| discretely but it's possible.
| jacquesm wrote:
| I use dual gate FETs frequently for all kinds of tricks and
| they're super useful.
|
| Is that what you had in mind?
| squarefoot wrote:
| Dual gate mosfets were a godsend when building RF/IF mixers
| or preamps. Luckily I have a small stash as they're almost
| unobtanium and costly these days, but for most uses such as
| mixers and preamps they can be swapped with a pair or
| normal jfets in a cascode configuration like this one:
| https://i.stack.imgur.com/6Nyhg.gif
| cbdevidal wrote:
| Today I learned you can build an entire freaking CPU out
| of 555s lol
|
| https://hackaday.com/2011/08/05/building-a-computer-out-
| of-5...
| jacquesm wrote:
| > Dual gate mosfets were a godsend when building RF/IF
| mixers or preamps.
|
| _exactly_ :)
|
| BF901 FTW.
| analog31 wrote:
| Coincidentally, there were vacuum tubes with dual grids
| for mixer and AGC applications.
| buescher wrote:
| And there's someone with a stash of those too. Dual-gate
| mosfets are one of the ways you know something's been in
| the back catalog way too long.
| Zardoz84 wrote:
| Omg... and thinking that my mother throws a huge stash of
| components like that. my father was an electrical
| engineer and ham radio. At least, I managed to save a
| stash of electronic valves and some analog equipment like
| an old oscilloscope that could be in a museum (I saw a
| similar model in a museum).
| gus_massa wrote:
| Do you still have a video saved somewhere?
| morninglight wrote:
| Real men use Unijunction Transistors like the 2N2646.
|
| https://en.wikipedia.org/wiki/Unijunction_transistor
| buescher wrote:
| One of the books I first tried to learn from was _Miniature
| Projects for Electronic Hobbyists_ by one Ken W. Sessions. It
| was really a unijunction transistor project book. You know
| how some people will say you'll learn maybe not the best
| mental models for electronics from Forrest Mims' books? (I
| don't get it, they seem OK to me) Well, Forrest has nothing
| on Ken W. Sessions. The circuits worked, though.
| pantulis wrote:
| Have to love the tone of the article.
| aj7 wrote:
| The late Harold DuBose of Spectra-Physics, repeatedly used 555's
| as power inverters in the electronic design of a frequency
| stabilized ring dye laser. He liked the strength of the output
| transistor.
| MeteorMarc wrote:
| In the same voice as saying that some language is Turing
| complete, we can now say that an electronic component is 555
| complete.
| quijoteuniv wrote:
| That's why the Beach Boys made a song about the 409, the
| predecessor chip.
| TomMasz wrote:
| The 555 figured prominently in a digital circuits course I took
| back in the mid-80s. It was into its second decade of existence
| by that point, and it's still going strong.
| BoredomIsFun wrote:
| Depends what you want to achieve; from fundamental educational
| point of view it is not a good device, too high level; most of
| the stuff you can build with 555 you can do with standard BJTs,
| and you'd be able in fact in understand how it works. To me, 555
| is good only for dumbed down entertaintment, not true learning.
| nayuki wrote:
| > Doin' It With A 555: One Chip to Rule Them All
|
| > We also know that microcontrollers implement logic gates - AND,
| OR, NOT, NAND, etc. But you don't have to deal with those
| complicated logic functions, or worse, the software that runs on
| those microcontrollers. Get down to brass tacks and use hardware
| (555 ICs and 555 timer ICs, to name a few the only important
| ones) that just works!
|
| Come on, you haven't even described how to implement
| combinational logic using 555 timer chips. Just show us how to
| build NAND, please.
| jrmg wrote:
| The 'birthplace' of the 555 is in downtown Sunnyvale - an easy
| trip if you're in the Valley*. It's in an alley between Murphy
| Ave. and the parking lot off S. Frances. There's a realtor's
| office opposite the side entrance to Fashion Wok. That's the
| place.
|
| It was invented by Hans Camenzind**, who was doing contract work
| for Signetics in an office he rented there. What a great location
| for your office, even back then!
|
| There really should be a plaque or something.
|
| * Go there then have dinner at Dishdash, across the street.
|
| ** RIP - he died in 2012, but his web site is still up:
| http://www.designinganalogchips.com/
| ChrisMarshallNY wrote:
| I'm really looking forward to the LLM results of all these posts.
| relwin wrote:
| I won 2011's "555 Timer Contest" artistic category. As a bonus I
| got a phone call from Hans Camenzind, who offered to design a
| custom chip (for free) to perform the same function.
|
| LeDominoux vid: https://youtu.be/PQOjkuJtBfM?si=pS9Qloekm7JJKCoE
|
| 555 contest archive:
| http://web.archive.org/web/20120121212136/http://www.555cont...
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