How 555 timers Work - The Learning Circuit

[@chrisg8709]

Honestly hands down the best explanation of the 555 for me. I’ve watched many videos and read many explanations for years but had no clue until now

[@alexvonbosse5090]

this is one of the best explanations of the inner workings of the 555 timer that I have seen in a long time!

[@Dingomush]

I’ve watched four different explanations on the NE555 internal workings and so far this one has made the most sense. A bit fast in places but it’s a video, I can go back and watch it again and try to pick up what I’ve missed. Thank you so much for your time and expertise on the subject matter and for “dumbing it down” in plain words and diagrams so that more people can enjoy electronics.

[@MAYERMAKES]

i used them a lot but never looked closely opn how they work, very informative, thx Karen!

[@migalito1955]

Very nice tutorial, especially given it can be configured 3 major ways. I am a math guy that hobbies in electronics and studied the 555 a few months back. It was nice that your video mentioned that the integrated flip flop actually used only one of the outputs which is a detail that often is overlooked in other explanations. I ended up building an astable Multivibrator so that I could put out a weak signal in the AM broadcast band spectrum in order to test reception capacity on regenerative radio receivers that I assemble from parts at hand. It worked, barely. By barely I mean that high a frequency was kind of pushing my luck. Without filters it was also broadcasting everywhere much like a skipping stone across a pond.

[@akashsunil7464]

How did u manage to do that how could you send out a wave using the 555 timer never mind I am a late bloomer my brain would take too much time to process but I would very much love an explanation

[@migalito1955]

@@akashsunil7464 Its been a year or two, but as I remember I set the IC555 to the highest frequency that I could get it to oscillate at using the configuration shown on the data sheet. This was a matter of selecting as I remember resistors at specific pinouts. The frequency that I was able to get was around 500KHz. I then added an audio transformer to the endeavor so as to inject audio such as a tone, into the signal it was generating thru being allowed to oscillate. It was a lousy transmitter but it did put out enough mili-watts to be heard by a radio in the next room. It also had a square wave & produced harmonics all over the place. Its kind of funny in that back then I spent a day or two understanding the entire innards of the chip & what could be done with it. I barely remember any of the details anymore. None the less its better suited for turning your car's dome light of than using as a low power transmitter

[@solapowsj25]

This is one of the best presentations for working of the 555. We've used the 556 as astable and monostable together to produce a PWM signal for a Boost Converter, 12v t0 48v DC at St. Joseph's Research, BLR, IN.

[@markedwards4879]

I wish we’d had resources like this when I was studying Electronic Engineering and building 555 circuits back in 1981! Such a great little timer, I built all kinds of alarms and flashing lights etc with them, but getting across all of the concepts etc was much more of a dry subject than it is today. I really like how simple and clear you made this for people starting out. Great stuff.

[@larrybud]

I mean, that goes for any tech, right? I learned programming in the 80s, and you'd buy a single book on a single topic, for 80 bucks.

[@awaitingthetrumpetcall4529]

@@larrybud I'm 68. In the 70's they had mainframe computers behind glass doors in my college that ran tape. I thought writing instructions with zeros and ones was tedious. In 2008 I discovered I could control the behavior of motors by writing instructions. I was hooked and realized I had wasted my college career.

[@markedwards4879]

@@larrybud I still have some of those overpriced and dull books on the shelf lol. There was very little choice of content at all and most of it was presented in a way that made things more difficult than they needed to be. I don't know about you but I had a mix of some very good lecturers and some that were just terrible. Luckily I worked with some very helpful people while studying and was given projects that helped me learn and keep it interesting.

[@markedwards4879]

@@awaitingthetrumpetcall4529 In the early 80s I was initially more interested in electronics (and cars/motorcycles lol) than computing but got exposed to personal computers as well as the mainframes in the telco space. In the early days most of the electronic projects that I built for myself were for cars and bikes - I built a full car computer that monitored fuel consumption and distance etc, car and bike alarms, electronic central locking. I got into computing outside of work in a big way when the Amiga 1000 came out (prior to that had a z80 machine at home), but the Amiga was a game changer. It could be programmed to play music properly and could display quality photos - something that the IBM based business machines just couldn't do.

[@awaitingthetrumpetcall4529]

@@markedwards4879 I would have seen you as as an intelligent nerd. My only involvement with computers was playing "Pong".

[@mehran_sk]

I have seen so many videos about 555 in my native language but somehow they were confusing until i found this video simple and understandable even with a foreign language description

[@gamergamer6241]

Great channel! Your explanations are so clear

[@antonnym214]

First time I've seen an understandable description of this chip. Thank you. By the way, I have a friend who says he's bistable, but practicing as monostable because it's just easier to live that way. All good wishes!

[@edinfific2576]

6:30 "If pin 4 is ever grounded, going low, the transistor is turned OFF." Actually, it's the opposite because this is a PNP transistor, so it is held OFF while pin 4 is high, and it turns ON when pin 4, its base, goes low.

[@LeoStarrenburg]

A good 50 years ago I started in electronics making my first medium wave receiver with an ECC82 valve. A year or two later, in 1972 the 555 was introduced and I've been dabbling with it ever since. Thank you Hans Camenzind ! Nice video BTW 👍.

[@zetaconvex1987]

A little bit fast in places, but a very useful video nevertheless. It certainly helps to demystify what's going on in the chip.

[@bananascannotfly2896]

My understanding for electrical concepts is not enough yet, but I loved how every pin was explained in detail. Hopefully I can comeback to this video to understand it. Thank you for such a descriptive video.

[@armincal9834]

I'm by no means an expert in electronics yet the way you explained it was so good that even I understood everything.you deserve a sub

[@Raaddller]

Wow, I wish I had a teacher like you, decades ago. It could've been career changing. Nice to learn the basics. Kids these days leap jump straight to a raspberry Pi and they find basics, pointless.

[@spudnickuk]

This has got to be the best video i have seen that explains how to use a 555 chip with proper illustrations of how it works

[@gusel9]

If I’m correct, Pin # 4 is the Base of a PNP transistor which Is set Hight turning the transistor OFF, and when the switch is pressed the base is grounded, an therefore the PNP transistor should go ON. Thank you

[@bingojamas4786]

gusel9 I agree. That is why the emitter is connected to Vcc internally as shown.

[@samcrowther3942]

I'm so glad someone else caught this it was driving me crazy!

[@cep5618]

I've never seen a high quality explanation like that. Congrat!

[@Valleedbrume]

Arguably the most used timer ever.I started using this in the 70’s.(okay I just dated my self:-)Great explanation.!

[@gregbrockway4452]

Don’t feel bad, me too. One of my favorite ic’s.

[@TCGCEOGuy]

Great job Karen! Wonderful job explaining. You are getting very good at quality examples and the discussion of complex items.

[@jimhenderson2308]

Great video. I’d also add that the rs latch is basically an electrical version of a mechanical toggle switch. But unlike the mechanical toggle switch the rs latch has 2 dedicated physical quantity inputs (either high or low) to change the state of the output. The mechanical toggle switch has a single algebraic input consisting of the application of a + force or a - force to change states. This 555 timer is an example of an application of the rs latch thru the use of the 2 comparators assigned to each of the 2 physical quantity rs latch dedicated inputs. Such a configuration can be used for automatic temperature control as set with a thermostat . And so that’s potentially an additional practical implication (besides an oscillator) of an rs latch configured with a couple of comparators to change states to turn furnace on or off to reject heat loss effects thru the walls of a heated building. Unlike the oscillator both the period and duty cycle of the 555 output behavior in the furnace example will change depending on outside temperature.

[@RC_Cola2020]

I had to watch this 5 times to wrap my head around it. Not your fault. Thank you.

[@Inquire98]

"Thank GOD", and thank you, thank you very much for your presentation 😉 REALLY Really really good 😎

[@_aakash.a5548]

I usually don't leave a comment for most of the videos but this one was Awesome explanation

[@NkanyisoSatywa]

The explanation that left me with no questions. THANK YOU

[@hubenbu]

Finally I get the hang of the circuit inside NE 555. Thank you!

[@juliuscesar4176]

this is better than the videos that just show projects with the 555

[@MehrdadKarami-x9w]

Great explanation, Great visualizations, Great tutorial. Thank you very much for this.

[@element14presents]

Glad it was helpful!

[@StuartWoodwardJP]

Much better than my university electronics course!

[@Gliese667cc60]

I loved your way of explaining...Very grateful!

[@element14presents]

You should consider checking out DC to Daylight too: kzbin.info/aero/PLwO8CTSLTkiiBLUDE3vfOGjvIuQONT4AC

[@eddierestauro277]

I allready use this when i made an inverter 12volt dc to 220 v ac since 1995, i was happy that it's clear explanation thank karen, thank yuo very much....

[@seuyt88]

So excellent in explaining!!Coming upon a female electronics engineer made this more exciting to learn. Good for you, indeed! I thoroughly enjoyed this!!

[@marksminis]

LoL. And all through college we just slapped them in and looked up what C and R needed to be. Never dug inside them like this, thanks!

[@gaminghighpriest5293]

omg finally a fully detailed tutorial for people who hav 0 knowledge

[@RI-ns8wz]

Superb, Milady! I always have some..10 or 15 of them in mi parts bin. I had even made some NCG control boxes for cars and there They are, working almost 10 years later! I had a book (ugly, fat,big book) that I can't find nowadays, about the 555, and it stated somewhere; "555's are like rice....there are more than 1000 recipes wit them!". Thanks a lot for your videos! And "hi.5!" from Argentina!

[@johnchildress6717]

556 can be used for many circuits.You probably know but others might not.2 555,s on a single chip was a good idea.

[@koszynek]

Super prezentacja, doskonale wytłumaczone. Dziękuję.

[@REXXSEVEN]

Do you see anyone else here speaking that?

[@Rodderick45]

Fantastic job done! Well defined and explained. She is great!

[@stever3886]

Well arranged presentation! Lots of good points for operation and I will watch the modes presentation next!

[@SLB_Labs]

I really appreciate this explanation, but I think I'm missing something about how the reset pin (pin 4) works. Since it's connected to the base of a PNP transistor, doesn't that mean that when pin 4 is set to low it will allow the Vcc current into the flipflop and set Q to LOW. From how I'm understanding your explanation, you are considering this transistor to be NPN. Let me know if I'm misinterpreting though!

[@tinfever]

I agree. I think there may be an error in either the diagram or description.

[@ICONICKABIR]

Awesome tutorial I m new to electronics but well understood thanks Maa'm

[@claytonbenignus4688]

Great Graphics!!! Contrast and highlighting is properly used without unnecessary distractions. The “ how it works” part is fascillitated by Karen, who shows both Teaching Experience and Knowledge of the subject. As a Presenter, she is comparable to Liliana de Castro, who does Group Theory for Socratica. All pins were covered without the dismissive “ this pin is seldom used” . I hope to see Karen in more videos.

[@davidcross30]

Awesome thanks. Very well presented and I’m looking forward to learning more now!!

[@MrZiolelle]

Sorry, but just to be sure I have understood: At moment @6:26 when you explain the Reset pin, it seems looking at the video that the behaviour is the opposite: if Q2 is a PNP transistor, when base is connected to Vcc, it is OFF and set RESET of FlipFlop to LOW (resetting it), but from the video it seems that vhen the base is HIGH, the current is flowing from Vcc through Collector to Emitter and to RESET (tipical for a NPN transistor). The final effect is correct but I think the animation should be the opposite. Is it so ? Thanks

[@octavioossa7705]

Q2 is off when switch is off, and halfway on when switch is on.

[@IFixOldStuff]

Great work here showing how the basic building blocks become more complex circuits

[@MrGato516]

Correct me if I am wrong, however there is a minor error: At minute 6:37 you state Q2 is off. A PNP is ON when the base is lower than the emitter. Additionally, the current limiting resistor should be placed between switch and Q2 base.

[@ManiKandan-xb2yk]

Wonderful video but only at 6:33 you made a mistake. That pnp is connected to reset. Only Grounding it will turn on.

[@fieldsofomagh]

Nice presentation, Karen and thank you for the information on the internal operation of the 555 engine.

[@johnthomas5166]

Yup, that didn't even bump my head as it went over. Her well executed explanation still left me just as confused as whence I came. I just need a 3 second delay on a 12 volt circuit.

[@BiscuitVillain]

This was such a helpful video, thank you!!

[@dmitripogosian5084]

Am I right that if one measures the resistance between pin 8 (VCC) and pin 5 (control voltage) one should get 5 kOhm ? Or is it more complicated ? ( I am trying to troubleshoot some PSB, and my on board measurement between these pins gives 120 kOhm)

[@tuananhnguyen8998]

Nice explaination. I have 1 question. In the block diagram, transistor at pin 4 is appeared to be PNP type. To turn it "ON" isn't that mean BASE voltage need to be negative compare to EMITTER? In the video you said when ever pin 4 is grounded, the transistor is "OFF" which is contradict with what I understand about PNP transistor type.

[@zeeebrenn]

Yes, you are right, the pnp explanation is wrong, when the reset pin is pulled high to VCC the transistor is off. But her schematic is correct.

[@GrowlyBear917]

@@zeeebrenn I was just going to say the same thing but you beat me to it by about 17 hours. Note to self: Wake up in the MORNING, not the EVENING. And, Happy new year.

[@dmitripogosian5084]

@@zeeebrenn Yes, and I guess that is why in applications when the reset pin is not used, it is permanently connected to VCC.

[@JojoDajay]

Your observation is accurate. The IC indeed becomes active when pin 4 is high, and applying a low signal at pin 4 resets it. To rectify this, we can interchange the positions of the switch and resistor. Specifically, we can connect the switch between VCC and the base of the PNP transistor, while the resistor should be connected between ground and the transistor's base.

[@solarflare4259]

Nice vintage scope in the background.It seems to be a Tektronix...Great, detailed explanation of the 555...Thank you for posting.

[@WACkZerden]

Thank You, this was a great intro video.I found Your explanation easy to follow and understand!

[@lucyalicenox5871]

Thank you so much for helping me figure this out!!!! It took me a long time to conceptualize how ICs work

[@anthonyshobbycorner]

What an amazing video explaining the workings of the 555 ... So well explained .. Gave me a far better understanding of it ,and how to use it , in all 3 forms ... Excellent video .. I also checked out the 2nd video you did as well .. Regards, - Anthony

[@michaelbenard6758]

Would you please explain in brief about pin 5 of the ne555 timer ic.

[@victimovtalent6036]

Wait,pin 4 consists of pnp transistor,as you said if pin 4 grounded its turning off?🤔

[@teku3985]

No it’s an npn but it is shown as a pnp in this drawing.

[@jamienewman1488]

So does the capacitor when charged make the comparator go high then as it drains the voltage goes low?

[@magicpike86]

I was wondering the same thing

[@spiculum1836]

My EE professor, prof Rigby (back in 1985 ) and his friend entered a contest to create a timer circuit in the late 60s. My prof said his timer circuit was the best functionally but lost to his friend's timer design even though his friends timer design was not as good as his. Apparently the reason why his friends timer design won the contest because it did the function with minimal components. His friends design is known as the 555 timer 🙂. The moral of the story during class was that a better design circuit is not always the best solution.

[@sreekumarvr6609]

how does the capacitor triggers the reset ? 7:03

[@youtube-username-placeholder]

I believe they forgot to present a few more connections from the capacitor (and one resistor is missing) to PIN 2 and PIN 6. Just look up ‘555 timer astable’. I might be wrong tho

[@dk3212]

I don't understand how the capacitor charging triggers the reset?

[@villagerse]

Charging and dischrgjng

[@GlynWilliams1950]

Very useful We call it Triple 5 (timer), in my area in Australia We also say 5k (for the resistor, five Kay), We are already metric so we understand 1K etc

[@MsRamesh21]

Wow! great to find this channel. Superb explanation

[@clayz1]

My one and only breadboard slash 555 timer electronics project. Has a battery, a pot, an on off switch and a variable time on off LED. Cool.

[@dangacoscosim]

Can you show a diagram using ic555 connected wit spdt relay, capacitor, potentiometer, and digital clock display?

[@richardpayne9640]

I would have to put this to practical use to get this into my memory Thank you!

[@freescientist1826]

in 6:31 if pin 4 is connected to Vcc, the PNP transistor will be off, right!?

[@harriusk4u]

Incredible lecture! Just have a question. What is the triangle attached to the output pin? Look like it inverts the !Q output.

[@maker_karen1785]

That's exactly what it is, an inverter.

[@vmsrao2125]

Excellent explanation madam.Thank you very much

[@guilletrost1319]

the best ... simple and clear, applause...

[@M4U999]

your explanation is perfect

[@ranjitfernando5241]

Fine explanation. Had watched many tutorials but this was the best. Thank you so much. A small point. In your next videos please try to make a little bit slow in words. As some of my friends felt so. Then persons who are not very conversant in English will enjoy it more

[@tusharpotdar5762]

Very nicely explain the working of 555, love u thanks

[@tcroyce8128]

Loved the presentation for the schematics.

[@oompaloompa7280]

This is the first video I watched from you and I loved it. I used the 555 many times over decades but never understood it in such depth. Very useful and helps with troubleshooting circuit design. One thing I may not be understanding is that when you said that when pin 4 is grounded, the transistor turns off. Being a PNP, shouldn't it come ON when the base is brought to ground? Maybe i misunderstood?

[@robinhood007ful]

Very good explanation of working

[@Mrusama93]

Thanks ma'am i have never learnt ne555 ever like you told love you.

[@flamencoprof]

I am so old I had forgotten when I was taught about this cct. Now I am not sure if I understood it then nor if I cannot understand it now. I am looking forward to seeing how the application of its properties is done.

[@apnamultitech786]

I like ur way to explanation in detail, thanks

[@JoshuaPritt]

The Makers Local 256 makerspace used a 555 timer to make a soldering learning kit to build a board that "rolls" a 6 sided die made of LEDs. Pretty neat!

[@maker_karen1785]

Joshua Pritt I soldered a similar kit in the project episode that followed the overview of ICs. Though my kit used a phase locked loop IC and a binary ripple counter. Would be neat to see a similar circuit but with a 555 instead!

[@BertGrink]

Joshua Pritt That sounds quite interesting, you wouldn't happen to have a link to that, would you?

[@sinewave3323]

Thnx a million for you're videos! I really appreciate them! Alot! 😎

[@howwitty]

Hey, why is usually 5 < Vcc < 15? Is it possible to leak less current with higher Vcc or what is the tradeoff of using different Vcc in a circuit that has a variable electric potential?

[@PankajYadav-hr8tp]

Nice one ...super excited for the next episode ...now I can make my own clock...please explain by using a clock in the next video

[@mediocreman6323]

If you want to make a clock, use a quartz oscillator.

[@PankajYadav-hr8tp]

@@mediocreman6323 thanks for the reply ..but I want an alternative option also...let's do something new

[@mediocreman6323]

@@PankajYadav-hr8tp - Why? If you want a clock, a crystal-based oscillator is the way to go. You can cut bread with scissors, yes, but why not use a knife? Given the fact that ohmic resistance changes with temperature and even a 1% tolerance in capacity and resistance is a huge deal for a clock (problems a quartz does not have, by design) would make a 555-based clock pretty darn inaccurate. Sufficient for processor clocks or something I guess, but not for an actual clock.

[@PankajYadav-hr8tp]

@@mediocreman6323 well actually ,there is much more than the clock ,and it's a part of it...since the video was for education purpose, I guess the extra part will not be relevant.....and moreover the scissors are pretty much used than knife whenever you want to create something special than the usual work to do...

[@RobiBue]

@mediocre man: ok, scissors are two knives with a hinge, but the 555 is not made of two quartz oscillators, so if someone wants to use the 555 as a clock, there‘s nothing wrong with that. It is not necessarily going to be accurate, but even to cut bread, cutting it with a paring knife, or a chef knife, or even a Swiss Army knife is not going to give you the same result as cutting it with a bread knife, although either one of them is a knife... 🤪 ✌️

[@sangarp2001]

i would like to know more about pin 4. It is PNP transistor. How it is on when it is connected to Vcc?

[@benjaminlindquist8530]

I’m very new. I’m confused with the digital signal of “low” and “high.” Is it 1/3 Vcc and 2/3 Vcc or the highest of the inputs and lowest of inputs? I’m wondering about building circuits off pin 3 if you don’t know the voltage.

[@LeventeDaradici]

it is explained superbly! thanks and respect!

[@briancoverstone4042]

Hi Karen. I have a question about the 555. Why take the output from Q bar and invert it, instead of just wiring Q to the output pin directly?

[@mediocreman6323]

I do not know if this applies to the 555 specifically, but you can use inverters to “clean up” the input, make signals that are below a certain threshold be a clean low and the ones which are above that threshold a clean high. But, as I said, I do not know if this particular inverter acts like such a trigger (Schmitt-trigger as far as I remember), if anybody could enlighten me, it would be highly appreciated.

[@maker_karen1785]

I don't really know. I didn't design the 555. [shrug] I'm sure there's a reason, but it is more advanced than my current knowledge.

[@curtispazderka1336]

One of the drawbacks of "conceptualising" circuits, is that it can make how they work apparent, but not why things were done that way. In an IC, you don't have a "flip-flop", you have a network of transistors. The transistor networks of all the conceptualised parts are joined together as one part. So whilst an "inverter" is known as a discrete component, in this IC it is just another couple of transistors. In this IC, the output of the flip-flop transistor network is not powered to drive the output pin; so either a buffer or an inverting buffer is required. Seeing as the inverted value is required internally, it makes sense to use the same flip-flop output to drive both signals.

[@jacobbronson9947]

How does the cap charging on pin 7 trigger the reset?

[@jamesyount2423]

What she doesn't say is that discharge is also connected to threshold or trigger to cause timing. In her graphic it wouldn't do much but charge up a cap.

[@bru2al1tyusa82]

I think this series is a great idea 👍

[@michaelbenard6758]

Could you explain the IR2110 ic

[@thunderbird1454]

Hey Karen, does that old valve tektronix CRO in the background actually work and do you know how to drive it ????

[@aryanabdolahi8469]

Thanks for the video. I learned and enjoyed.

[@rupertmurdoch469]

Thank you. Nice explaination

[@gerrys6265]

Great explanation, thanks...except I am stuck on some point I obviously don't understand. sWhen the output is high (S is H) and Q bar then being low there is no power flowing to pin 3, so no power going to pin3 - even though one would think it would if there was power getting through the flipflop. When S is Low Q bar is high and although there is power flowing through the flipflop, does it not then (through its inverter) cut off the power to pin 3? So how/when does power get through to pin 3? Sorry for such a dumb (I think) question... Ahhh...I watched the next video and it became clear Thanks

[@ثامرالبياتي-ض3ه]

Please when we see for the circuit electronic .we make short between pins 4and 8 .while pin 4 it is pin of base of transtor .

[@khan691]

Excellent learning program 👍

[@christopherbrown3614]

Thanks for the explanation!

[@kev_mclernon_family_channe4745]

Wow. The number 5 in spoken Thai is “Ha”. So 555 is like lol, 555. I was looking for video to send for the 555/lol and am now subscribed to your channel 555.

[@fmphotooffice5513]

Excellent presentation. A transcript of the script in the description wouldn't be too long and would be very useful. Regards.