I am a middle school student in China.I think your video is easy to understand and it can help me to learn the hardware.I am learning to make a 6502 computer and run BASIC on it.Thanks for your videos!
It isn't a lot, but the holidays are here and I wanted to express my profound appreciation for all the knowledge, passion and interest you generate and spread via your amazing videos. Your videos are absolutely the best tutorials and knowledge based videos I've ever viewed related to computers and electronics. As a software engineer, you really have bridged my knowledge gap between the software world and the hardware it runs on. Thanks again for all that you do and I hope that you and your family and friends have a safe, happy and healthy holiday season
This is so cool! I've used "debounce" methods in web programming for years and years to limit how often a function is triggered within a time frame and never really thought about why it was named that. Knowing that it comes from a physical phenomenon in electronics is super cool.
@@tailslessons9634the term "bug" as it relates to a technical error predates that, yes, but the term "debugging" did actually start with the Mark II moth incident.
I remember stumbling across your channel a long time ago & thinking to myself "One day I will be ready to come back and learn this stuff" I started programming in C#, and after being constantly dissatisfied with not understanding what the heck was happening underneath all the abstracted high level concepts, I worked my way down. I ended up getting an arduino last christmas. Now I am back to your videos & learning everything. Thanks for your channel, you are a blessing. You have the best videos that explain everything so thoroughly and well.
Best explanation of the operations of the 555 timer I've ever heard. Thanks to Ben for his clear and easy to understand delivery. He makes 555 timers fun!
I noted a flaw in the typical 555 monostable circuits, particularly for debouncing. The denounce is only 100% effective in the rising edge of the button. On the falling edge when you release the button, it is only effective if you released it sufficiently before the 555 times out. This is because the timer is not retriggering in this configuration, other than staying in triggered state as long as the button is pushed. What you really want is the output logic to stay high a certain amount of time after the button is released and not sooner. This can be accomplished if a circuit prevents the capacitor from beginning to charge until the button is released. Although button release bounces can't be eliminated, adding a .1uF capacitor across the switch cut it down considerably. Lengthening the on time from the current. 110mS or so to .250mS or more would do better without being annoying. Subbing the .1uF with 1.0uF electrolytic was effective but lasts over 1 second which can be annoying.
I'm currently studying for an exam on Op-Amps and it turns out that the schematic in my textbook was wrong! The guy had the SR latch upside down. You made it absolutely crystal clear. Nice channel. You got a new subscriber. Cheers from Belgium.
I played with those 555 timers growing up. I really appreciate your knowledge and the way you share this information. You may be the best teacher of electronic circuits in the world for enthusiasts.
I'm a electronics student, and the past week my teacher assigned us this circuit as our project for the 1st partial. I was a one step away of quitting the project because my circuit was a disaster, and i was so stressed. But then, i discovered your channel, and i watched your Breadboard 8bit computer. Then, i told myself "if this guy can make a freaking computer using breadboards, then, i can finalise my project" and i did it. And if i hadn't see your video, i would fail the project. You're a source of inspirarion for me bro, thank you.
That’s rough! I built these circuits on breadboard in my first weeks of high school EE, but in class with the teacher’s help, not as a homework assignment! I didn’t start to really “get” the rhyme or reason for circuit layouts until I was a dozen or so circuits deep in the course, all done in class with access to help. This knowledge has been really helpful in life, but I probably would’ve failed if I had to do it at home from the start! Still, I’m glad you’ve been able to hang on and continue the course!
saw this channel when I'm in junior high... not really interested back then. Didn't Know I'll stumble back here to learn ^^ I'm in 2nd year in Electronics engr course
Great content from all angles. The presentation is so organized. The audio is clear. The video is clear. The lighting is even nice and diffuse. Exposure is correct. What's supposed to be black is black. What's supposed to be white isn't blown out. And nice closeups. I like the approach of "not asking you to take anything on faith." Well done, and thanks.
I really appreciate your videos. I struggled to get my head around basic electronics for a long time, and your explanations have been very helpful to me. Thank you!
Mech engineer here, I want to build a little 4 bit proc, started watching these videos... so far so good. You explain all things in a very intuitive way with examples and real measurements, you should consider being a teacher as a professional.
This series is properly well sorted. Beginner topics and expert topics are well covered on the internet. Those of us looking to find some intermediate content are pretty stuck. I'm looking forwards to learning somre more computer related topics in future videos. This start has been a great refresh on astable timers
He has a gift for teaching and covering it from all aspects, I like his "system" approach towards things. Many teachers just can't teach like this, it is an art in itself.
I just love those videos. I'm about to make z80 computer and most likely some analog synth boxes. Thank you for explaining the basics so well. Great job!
I just bought a Z80 CPU the other day. I've yet to receive it, but my first planned project is the LED flasher Julian Ilett made out of one. Tbh I never thought I'd do anything with the Z80, much less use one in my first CPU based circuit. I always thought I'd end up using a 6052 or 8086 since I'm more familiar with them. I know almost nothing about the Z80. But it'll be a fun adventure learning.
@@VoidHalo the Z80 is a great cpu. I built my first computer using an 8080 with front panel switches and LEDS, serial I/o, 16k of memory, and 16k of ROM for a custom o/s I wrote. I wrote hundreds of thousands of lines of code on it. And later modified the machine for. Z80 and 64k of memory and adopted CP/M on it.
I've been fiddling around with this circuit for a while and I think I found a design flaw. Consider the scenario where we're in manual mode and continuously pressing the button. After a very short time, the capacitor for this 555 will be fully charged. If the button is released and it bounces (thus the trigger first goes high for a moment, than back low, before it finally goes high again), then the output goes low for a moment, but this will be followed by another high pulse (duration: about R*C*1.1). I solved this by also connecting the trigger input to a PNP transistor's base (BC556) through a 10k resistor, grounding the collector of this and connecting its emitter to the positive terminal of the capacitor. This way, while the button is pressed, the capacitor will be continuously discharged through this transistor and its charging will only start when the button is released.
You can also use a transistor as a switch for the input voltage to the capacitor so that the capacitor is disconnected from 5 V when you're pressing the switch. I've tested this and it seems to work reliably. See a modified schematic here: imgur.com/a/7uHehRF
When the button is released don't we want the capacitor to discharge at that time, and then when the button is pressed the capacitor charges and then discharges quickly for the circuit to work? I don't understand why continuously discharging the capacitor through the transistor when the button is pressed and charging it when the button is released would make the circuit work. :/
@@suuuken4977 That's because if we let the capacitor charge while we press the button, after a while, the charged capacitor will activate that "threshold" comparator. That would activate the "reset" on the SR latch. But if we keep pressing the button, you can see that the "trigger" comparator would also be on (the 1,67V on the "+" terminal at the comparator is bigger than the 0V on the -). At that point, we would have a signal both on the S and R terminals of the SR latch. On this type of latch, we can't have both terminals (S and R) set to 1. This would make the outputs unpredictable (Ben also has a video on the subject). For that reason, we need to make sure that the capacitor won't charge while we press the button, to avoid having the reset terminal bein on with the set terminal.
Understanding Electronics is an Art. you are an Artist 🤴we love to hear and learn from you. Lots of love and respect for you! ❤❤❤ Thank you for making me a better engineer.
Not so long ago, I came across your YT channel quite accidentally. :) Among the hundreds of other creators, the quality and high level of your films arouses my admiration and true respect. I have seen so far what you have prepared for 555 timer. Thanks a lot for that.
you are able to explain everything so good in these videos! im glad i can easely follow and understand these videos without being an expert in this kind of stuff myself
thank you very much! this circuit was very useful for me as the debounce circuit for the input of a t flip flop! it works very well and your explanation really made me understand why it works
Very nice video's. I am following along and doing the projects. You have an excellent way of explaining things that even I can understand. Thanks for taking the time to share your knowledge with us.
SPOILER ALERT! For those playing along at home, at 2:39, when Ben added the 555 timer to the button, he changed the button from operating at 5V to operating at ground. If you rewire your button, you’ll have effectively inverted the button from normally open to normally connected.
I experienced this bouncing when learning about a shift register (8 bit) that I was trying to manually clock. I noticed that at least 1 out of the 8 clock cycles it would just "freak out". I thought button was faulty but swapping it with other ones exhibited the same behavior. Now I now why! I had no idea contacts on the switch bounced! Thanks for these videos!
If you hold the button for longer than the RC constant, the output will become unstable and cause the computer to stop working. Although neat as a simulation for a bug, it doesn't work well for the intended purpose. I found the easiest way to eliminate the issue was to place a capacitor in between the button and the rest of the circuit (with a resistor to v+/gnd on either side). That way, only the negative-going edge makes it into the circuit and it can only pulse once per button press.
Yeah I just found this too. I gather that the debounce RC timer starts ticking on *button down*. That’s great for button down. But if hold any longer than the RC time it’ll just bounce on button up! So a) make quick button presses. And/or b) adding extra capacitance at pin 6 made it feel better. I wasn’t racing to get the button down and back up.
I know a lot about what you're doing in these videos, having taught myself as a youth in much the same way you're walking through the lessons in your videos. These are fantastic instructional videos. I encourage you to do as many of these as you can. They are more valuable that you might realize. I do have a nitpick about this monostable clock video. You mention that when you hit the button, as soon as the capacitor charges, the flip-flop switches the LED off. That isn't exactly true, as the video shows. It only turns off the LED after the capacitor charges AND YOU RELEASE THE BUTTON. That indicates that if both Set and Reset are asserted in the 555, the Set takes precedence. As I said, it's a nitpick...please don't see it as a criticism. These are all great videos!
I think it's great that you have 1.16M subscribers. It seems amazing given the technical level of your videos. But I do sometimes wonder, ... UA-cam is not necessarily right about these things. How could we ever know?
I do not have the parts, but this is a great video!!! You made 23 videos in the playlist I am watching. I focused more usually on analog/digital synths.
Why is another resistor required at 1:37? If the switch is off then LED has no power and this other resistor does nothing? Otherwise if switch is on then it will go through the LED and to ground, so what is the extra one for instead just a wire to ground?
aaaaaand subscribed. I really enjoyed your explanation of logic gates, and now thanks to you I'm building my knowledge on how computing works. Maybe for some basic aplication I won't need to use and arduino no more.
Oh, does this bring back memories - of me considering parts for a TTL based computer in 1974. My only computer experience was IBM mainframes, so my clock was going to have a start, and a stop button, and the mainframes had a "single step" button. I decided to go one better - so holding stop and pressing start, single stepped it. My clock was 2 flip-flops decoded to 4 states - (1) fetch instr; (2) decode instr; (3) execute; (4) increment program counter. WELL, looking on my scope, it clocked 0 1 2(0) 3 -- I was getting a 2nd phase 0 because of using ripple carry - sort of like your pushbutton debounce. The answer was to (I wonder where I found it) change from ripple carry to synchronous clocked. Unlike you, my "build" stopped at this point - because the Altair came out on the January '75 Popular Electronics, and I bought one, then built my own selectric and floppy interface boards.
at 7:34, you mention that the trigger pin (pin 2) will initially be at 5V. Is there not a voltage drop across the 1K resistor that would cause the trigger pin to initially be at 0V? I don't understand why the trigger would be at 5V if it is in series with that resistor when the button is unpressed. Any help would be appreciated.
3:06 - For a moment, I thought you were going to say to use an SR flip-flop switch (I was taught to do it this way). I actually didn't know you could use a 555 timer for a debounce circuit but I guess you could jack the SR latch inside of it and take advantage of the discharge circuit to create that automatic falling edge... Nice
3:48 - Quick question as I'm trying to make sure I fully understand this. Is it R*C, or is it 0.693(RA+2RB)C as it was in the previous video? I realize the difference is very small (0.1s vs 0.0693s), but I'd like to know just for my own understanding.
At 8:13, why does the 5v flow into the discharge circuit instead of into the top comparator? Is the resistance of the comparator and SR latch higher than the resistance of the discharge transistor?
Thanks for the great vid series! At 10:00, Ben says "it stays off". Now if you are holding the button down, doesn't that mean the bottom compare is still on and thus S = 1 which starts the process again, so won't start slow cycling on and off while the button is held? But maybe I'm missing something. Thanks!
Hi Ben, a question. What happens when the capacitor is too small? If its time period expires before you release the button, does it stay on? Or does the time period expire only after you release the button? Specifically I'm confused about what happens when S goes high so Q'(Q bar) goes low and the transistor doesn't discharge current anymore, charging the capacitor up. Eventually it'll exceed 3.3 and cause the R to set, and so S and R both are set to high. What happens then?
Looking at various datasheets, it's probably undefined behavior. It depends on the exact design of the RS latch, some keep state when they get the illegal input, some set, some reset. Since you said it should switch states: that'd be a JK latch.
If you really want to find out you can download a free Java based program called CircuitMod. It's a really nifty circuit simulator. Kinda fickle at times, like you can't connect capacitors directly together cuz it doesn't consider wires to have any resistance so it breaks the math, so to speak. But it's been an invaluable tool to me for learning electronics and it comes with literally oodles of example circuits, including maybe 5-10 circuits with the 555. It's been wonderful for helping to visualize and gain an intuitive understanding of how circuits work. CircuitMod combined with videos like this has been the majority of my non-hands-on education in electronics. I might check out an article on All About Circuits or Electronics Tutorials once in a while, but I have ADD so I find it very hard to read anything more than a few paragraphs. I'd much rather learn hands on. I believe there's also an online version available which you don't need to download. I think the site is called falstad. Definitely worth looking into.
If you look at commons.wikimedia.org/wiki/File:NE555_Internal_Circuit.svg I believe that if you set the S first then the R cant change the latch state. The lower left transistor in the purple section will be on so the output of the other comparator has no effect. It is a limitation of the block diagram.
By the end of the video, with the button circuit set up, you mentioned the behavior of the circuit as the capacitor charges, and then mention what happens once it's charged enough to trigger the R signal in the latch. However, you only mentioned what happens assuming the button is unpressed by then. At 9:30. I had a question, which is relevant for when the capacitor discharges very rapidly (unlike the one you hooked up to the oscilloscope that took 2 seconds to charge). What happens if the button is still pressed by the time the capacitor charges enough to hit the R signal? Both the R and the S will be active at once. What happens then?
for an sr latch if both the reset and set are active at the same time, then the latch goes into an unstable state. Simply put you can't predict its output.
you should use a transparency sheet over your diagrams to draw current flow, or for other reasons, so you can draw on your diagrams without drawing on or re-drawing your diagrams. Just a thought.
8:40 I don't understand this part. When the capacitor goes above 3.33 V, the comparator above outputs HI. However, the comparator below also outputs HI if the button is still pushed on, so we will get to a forbidden state for Q, since S=1 and R=1. Do we need to assume that the user instantaneously releases the button when R is set to HI?
I just understood that the 555 timer does not use an SR latch but a JK flip flop. Therefore, there is no forbidden state. When S=1 and R=1, Q toggles. Then everything holds true in the video.
Hi Ben, This is by far one of the best explanations series I've ever seen in 555 / Logic ICs!! Cristal clear and well balance between theory and proactive! Hats off! NOOB QUESTION: Why use 1K pulldown resistors VS 10k ?? is there any technical reason or any particularity of the TTL family ??
Ahh the wold famous "debouncing" circuit. Can you imagine if it was missing on our phones, every time you're trying to blank the screen it would flicker randomly. ;)
The tricky part for me is understanding the flow of electricity. When I was younger I had a kit like this from radio shack, but I could never wrap my head around the diagrams to truly understand what was happening with the flow through the circuit. I need an eli5 for electronics...
Same here. Possibly, instead of simply watching, it'd help to physically draw out the same diagram and annotate it the same way while watching the video? (I've not tried this myself - yet.)
@Duke Gibson correct not all the charges will flow through the path of least resistance but most will and if you have a short almost all the charges flow through that shorted path.you are correct if you want to know the current through each path just use ohms law
Before 12:32 , the pin 4 wasn't connected to any part of the circuit, so then it should have automatically been low. So how did R become high when you wanted it to be high ?
i have a question : at 9:00 isn't it a problem that there is no resistance ? that's basically a short-circuit right ? well sure it's only 0.1uF so that's not a lot of energy discharging at once, and the wires do have some resistance, but isn't it damaging to the components ? thanks !
Thank you for such a clear explanation! One thing I'm still confused about: if you hold the button long enough for the capacitor to fully charge, then let go, why doesn't the charged capacitor instantly trigger the reset?
I've just tried this on a counter with a 7 segment display I've made from a 4026. I was initially still getting some bouncing, but when I added a bypass capacitor it seemed to fix the problem.
How both R and S are low, when the Discharge Threshold is at 5V, which 5V > 3.33V and the comparator is on. Then the bottom comparator will NOT be on, because 1.67V at the positive is < 5 V at the negative?
I am a middle school student in China.I think your video is easy to understand and it can help me to learn the hardware.I am learning to make a 6502 computer and run BASIC on it.Thanks for your videos!
It isn't a lot, but the holidays are here and I wanted to express my profound appreciation for all the knowledge, passion and interest you generate and spread via your amazing videos. Your videos are absolutely the best tutorials and knowledge based videos I've ever viewed related to computers and electronics. As a software engineer, you really have bridged my knowledge gap between the software world and the hardware it runs on.
Thanks again for all that you do and I hope that you and your family and friends have a safe, happy and healthy holiday season
Awesome!
Thank you!
This is so cool! I've used "debounce" methods in web programming for years and years to limit how often a function is triggered within a time frame and never really thought about why it was named that. Knowing that it comes from a physical phenomenon in electronics is super cool.
It's not the only software term based on physical phenomenon. "Debugging" was coming by the removal of a moth from a Mark 2 computer.
@@tailslessons9634Fun as that would be, the term “debug” actually predated that incident!
@@GTLugo Really?
@@tailslessons9634the term "bug" as it relates to a technical error predates that, yes, but the term "debugging" did actually start with the Mark II moth incident.
"Tie the RESET_ pin 4 of the 555 timer to +5V" Completely solved the problems I was having with my circuit. You are a godsend. Thank you!
I remember stumbling across your channel a long time ago & thinking to myself
"One day I will be ready to come back and learn this stuff"
I started programming in C#, and after being constantly dissatisfied with not understanding what the heck was happening underneath all the abstracted high level concepts, I worked my way down. I ended up getting an arduino last christmas. Now I am back to your videos & learning everything. Thanks for your channel, you are a blessing. You have the best videos that explain everything so thoroughly and well.
Best explanation of the operations of the 555 timer I've ever heard. Thanks to Ben for his clear and easy to understand delivery. He makes 555 timers fun!
I noted a flaw in the typical 555 monostable circuits, particularly for debouncing.
The denounce is only 100% effective in the rising edge of the button.
On the falling edge when you release the button, it is only effective if you released it sufficiently before the 555 times out. This is because the timer is not retriggering in this configuration, other than staying in triggered state as long as the button is pushed.
What you really want is the output logic to stay high a certain amount of time after the button is released and not sooner.
This can be accomplished if a circuit prevents the capacitor from beginning to charge until the button is released.
Although button release bounces can't be eliminated, adding a .1uF capacitor across the switch cut it down considerably. Lengthening the on time from the current. 110mS or so to .250mS or more would do better without being annoying.
Subbing the .1uF with 1.0uF electrolytic was effective but lasts over 1 second which can be annoying.
I'm currently studying for an exam on Op-Amps and it turns out that the schematic in my textbook was wrong! The guy had the SR latch upside down. You made it absolutely crystal clear. Nice channel. You got a new subscriber. Cheers from Belgium.
Maybe been said before, but coming from web dev I've implemented/used debouncing functions a lot. So cool to learn where the term comes from!
I played with those 555 timers growing up. I really appreciate your knowledge and the way you share this information. You may be the best teacher of electronic circuits in the world for enthusiasts.
One of the best tutorials on youtube, for those confused the d capacitor reading/marking for mfd means double, MicroFarad Double..
While clever, let's not confused newbies. That is not a true statement. mfd= MicroFaraD
I'm a electronics student, and the past week my teacher assigned us this circuit as our project for the 1st partial. I was a one step away of quitting the project because my circuit was a disaster, and i was so stressed. But then, i discovered your channel, and i watched your Breadboard 8bit computer. Then, i told myself "if this guy can make a freaking computer using breadboards, then, i can finalise my project" and i did it.
And if i hadn't see your video, i would fail the project. You're a source of inspirarion for me bro, thank you.
That’s rough! I built these circuits on breadboard in my first weeks of high school EE, but in class with the teacher’s help, not as a homework assignment! I didn’t start to really “get” the rhyme or reason for circuit layouts until I was a dozen or so circuits deep in the course, all done in class with access to help. This knowledge has been really helpful in life, but I probably would’ve failed if I had to do it at home from the start!
Still, I’m glad you’ve been able to hang on and continue the course!
This is what I was delivering to K-12 students for 15 years. With sketches in resources and examples.
Great set of videos - subscribed.
saw this channel when I'm in junior high... not really interested back then. Didn't Know I'll stumble back here to learn ^^
I'm in 2nd year in Electronics engr course
Great content from all angles. The presentation is so organized. The audio is clear. The video is clear. The lighting is even nice and diffuse. Exposure is correct. What's supposed to be black is black. What's supposed to be white isn't blown out. And nice closeups. I like the approach of "not asking you to take anything on faith." Well done, and thanks.
I really appreciate your videos. I struggled to get my head around basic electronics for a long time, and your explanations have been very helpful to me. Thank you!
I've started building along with your videos. Extremely appreciative of all the hard work you've put into sharing this knowledge. Thank you.
Your videos make me understand why people like the 555 so much.
Mech engineer here, I want to build a little 4 bit proc, started watching these videos... so far so good. You explain all things in a very intuitive way with examples and real measurements, you should consider being a teacher as a professional.
I can't help but think that the ceramic capacitors are made of lentils!
I've always thought the same thing, and the electrolytics are made of mini coke cans
In fact in Persian language they are called Lentil capacitors (خازن عدسی)
It doesn't help that the ceramic caps are essentially the same color as raw lentils!
@@arashmousavi Same in Turkish
@@dijoxx yes (evet)
This series is properly well sorted. Beginner topics and expert topics are well covered on the internet. Those of us looking to find some intermediate content are pretty stuck. I'm looking forwards to learning somre more computer related topics in future videos. This start has been a great refresh on astable timers
Can't stop thinking of you as of a teacher I'd like to learn from.
Thanks for your efforts!
No text book nor any college class can make this understand in just 12 min!!
He has a gift for teaching and covering it from all aspects, I like his "system" approach towards things. Many teachers just can't teach like this, it is an art in itself.
My goodness this takes me back. WAY back.., 1974 study of CPU Logic Design at IBM.
Whoa. Im sure you could build something like that?
Using 2 of those 2uF capacitors in series will yield an equivalent capacitance of 1uF if you ever need it.
I built the first one works great and will now build the second setup. Thanks for sharing and explaining what exactly happening. Artie 👍👍👍
I just love those videos. I'm about to make z80 computer and most likely some analog synth boxes. Thank you for explaining the basics so well. Great job!
I just bought a Z80 CPU the other day. I've yet to receive it, but my first planned project is the LED flasher Julian Ilett made out of one. Tbh I never thought I'd do anything with the Z80, much less use one in my first CPU based circuit. I always thought I'd end up using a 6052 or 8086 since I'm more familiar with them. I know almost nothing about the Z80. But it'll be a fun adventure learning.
@@VoidHalo the Z80 is a great cpu. I built my first computer using an 8080 with front panel switches and LEDS, serial I/o, 16k of memory, and 16k of ROM for a custom o/s I wrote.
I wrote hundreds of thousands of lines of code on it. And later modified the machine for. Z80 and 64k of memory and adopted CP/M on it.
Excellent tutorial. I have studied about 555 timers 12 years ago. I never understood its working clearly until now. Thanks a lot mate.. :)
This is by far the best 555 video out there. Thanks for adding bits step by step.
I've been fiddling around with this circuit for a while and I think I found a
design flaw. Consider the scenario where we're in manual mode and
continuously pressing the button. After a very short time, the capacitor
for this 555 will be fully charged. If the button is released and it
bounces (thus the trigger first goes high for a moment, than back
low, before it finally goes high again), then the output goes low for a
moment, but this will be followed by another high pulse (duration: about R*C*1.1).
I solved this by also connecting the trigger input to a PNP transistor's base (BC556) through a 10k resistor, grounding the collector of this and connecting its emitter to the positive terminal of the capacitor. This way, while the button is pressed, the capacitor will be continuously discharged through this transistor and its charging will only start when the button is released.
You beat me to it.
You can also use a transistor as a switch for the input voltage to the capacitor so that the capacitor is disconnected from 5 V when you're pressing the switch. I've tested this and it seems to work reliably.
See a modified schematic here: imgur.com/a/7uHehRF
When the button is released don't we want the capacitor to discharge at that time, and then when the button is pressed the capacitor charges and then discharges quickly for the circuit to work? I don't understand why continuously discharging the capacitor through the transistor when the button is pressed and charging it when the button is released would make the circuit work. :/
@@suuuken4977 That's because if we let the capacitor charge while we press the button, after a while, the charged capacitor will activate that "threshold" comparator. That would activate the "reset" on the SR latch. But if we keep pressing the button, you can see that the "trigger" comparator would also be on (the 1,67V on the "+" terminal at the comparator is bigger than the 0V on the -). At that point, we would have a signal both on the S and R terminals of the SR latch. On this type of latch, we can't have both terminals (S and R) set to 1. This would make the outputs unpredictable (Ben also has a video on the subject). For that reason, we need to make sure that the capacitor won't charge while we press the button, to avoid having the reset terminal bein on with the set terminal.
@@olacolega7067 Thanks for leaving that comment, helped open my mind ;D
Outstanding explanation! We are so lucky to have people share knowledge like this on UA-cam.
Understanding Electronics is an Art.
you are an Artist 🤴we love to hear and learn from you.
Lots of love and respect for you! ❤❤❤
Thank you for making me a better engineer.
Not so long ago, I came across your YT channel quite accidentally. :)
Among the hundreds of other creators, the quality and high level of your films arouses my admiration and true respect. I have seen so far what you have prepared for 555 timer. Thanks a lot for that.
I love how you say we have the "guts" of the 555 timer laid out.
One of the best explanation and teaching person on youtoube, very good demo
and right tempo for me
thx a lot
The best tutorial on clocks with 555 that I have seen
you are able to explain everything so good in these videos! im glad i can easely follow and
understand these videos without being an expert in this kind of stuff myself
Been watching these breadboard, arduino and computer videos and these are the best explanations ive seen yet
thank you very much! this circuit was very useful for me as the debounce circuit for the input of a t flip flop!
it works very well and your explanation really made me understand why it works
Very nice video's. I am following along and doing the projects. You have an excellent way of explaining things that even I can understand. Thanks for taking the time to share your knowledge with us.
A beautifully and simply explained description of the 555 - thanks.
everything in the video is so simple;
I can easily focus on the issue ..
Like ASMR video ..
Health in your hands👍👍
Loving this video series!!
you can replace 2 555 timers for one NE556 Dual timer. Thanks for the videos. I learned a lot.
PLEASE START AN ONLINE ELECTRONICS COURSE... everything is easy to understand and builds as it goes.
These are possibly the best videos on electronics I've watched. Thanks a lot. Amazing work!
SPOILER ALERT! For those playing along at home, at 2:39, when Ben added the 555 timer to the button, he changed the button from operating at 5V to operating at ground. If you rewire your button, you’ll have effectively inverted the button from normally open to normally connected.
I experienced this bouncing when learning about a shift register (8 bit) that I was trying to manually clock. I noticed that at least 1 out of the 8 clock cycles it would just "freak out". I thought button was faulty but swapping it with other ones exhibited the same behavior. Now I now why! I had no idea contacts on the switch bounced! Thanks for these videos!
Pgysical switches are not perfect, and will never be. I had to build a debouncing board for my IC-testing using 7400 as a RS-FF.
If you hold the button for longer than the RC constant, the output will become unstable and cause the computer to stop working. Although neat as a simulation for a bug, it doesn't work well for the intended purpose. I found the easiest way to eliminate the issue was to place a capacitor in between the button and the rest of the circuit (with a resistor to v+/gnd on either side). That way, only the negative-going edge makes it into the circuit and it can only pulse once per button press.
Yeah I just found this too. I gather that the debounce RC timer starts ticking on *button down*. That’s great for button down. But if hold any longer than the RC time it’ll just bounce on button up! So a) make quick button presses. And/or b) adding extra capacitance at pin 6 made it feel better. I wasn’t racing to get the button down and back up.
I know a lot about what you're doing in these videos, having taught myself as a youth in much the same way you're walking through the lessons in your videos. These are fantastic instructional videos. I encourage you to do as many of these as you can. They are more valuable that you might realize. I do have a nitpick about this monostable clock video. You mention that when you hit the button, as soon as the capacitor charges, the flip-flop switches the LED off. That isn't exactly true, as the video shows. It only turns off the LED after the capacitor charges AND YOU RELEASE THE BUTTON. That indicates that if both Set and Reset are asserted in the 555, the Set takes precedence. As I said, it's a nitpick...please don't see it as a criticism. These are all great videos!
Thanks for this observation. I was scratching my head...
Ben sounding absolutely defeated by the 2 microfarad capacitors that say 1MFD is so relatable
The videos connect so perfectly
I remember seeing somewhere that 555 timer is the number one most sold chip, which is the most successful chip in semiconductor history!
Yep, some 40 billions (!) were sold since the beginning.
this is so much easier to understand than (or maybe in consideration of, after the) the last video lol
I really love how you explain things. i am learning so much from your videos
Awesome, your explanations and actual performance using the scope is fantastic, thanks.
You content is brilliant, Ben. Many thanks from Australia.
I think it's great that you have 1.16M subscribers. It seems amazing given the technical level of your videos. But I do sometimes wonder, ... UA-cam is not necessarily right about these things. How could we ever know?
I do not have the parts, but this is a great video!!! You made 23 videos in the playlist I am watching. I focused more usually on analog/digital synths.
Wesley Mays
Why is another resistor required at 1:37? If the switch is off then LED has no power and this other resistor does nothing? Otherwise if switch is on then it will go through the LED and to ground, so what is the extra one for instead just a wire to ground?
aaaaaand subscribed. I really enjoyed your explanation of logic gates, and now thanks to you I'm building my knowledge on how computing works. Maybe for some basic aplication I won't need to use and arduino no more.
Who is so stupid to give a dislike on this video???!
Someone who isn't happy to realise that their level of knowledge is not enough to understand what is being explained.
bad aim
Aldo Monteiro lol
dijox probably
not me
but a boomer that tried it with his 220v power supply he will
I really love this kit, it's so much fun to build.
I just realized, the 555 timer is basically the circuit version of a Japanese deer scare fountain.
Oh, does this bring back memories - of me considering parts for a TTL based computer in 1974. My only computer experience was IBM mainframes, so my clock was going to have a start, and a stop button, and the mainframes had a "single step" button. I decided to go one better - so holding stop and pressing start, single stepped it. My clock was 2 flip-flops decoded to 4 states - (1) fetch instr; (2) decode instr; (3) execute; (4) increment program counter. WELL, looking on my scope, it clocked 0 1 2(0) 3 -- I was getting a 2nd phase 0 because of using ripple carry - sort of like your pushbutton debounce. The answer was to (I wonder where I found it) change from ripple carry to synchronous clocked. Unlike you, my "build" stopped at this point - because the Altair came out on the January '75 Popular Electronics, and I bought one, then built my own selectric and floppy interface boards.
at 7:34, you mention that the trigger pin (pin 2) will initially be at 5V. Is there not a voltage drop across the 1K resistor that would cause the trigger pin to initially be at 0V? I don't understand why the trigger would be at 5V if it is in series with that resistor when the button is unpressed. Any help would be appreciated.
I already learned so much in your videos! Great!
Thank you so much taking time to share your knowledge. Really appreciated.
3:06 - For a moment, I thought you were going to say to use an SR flip-flop switch (I was taught to do it this way). I actually didn't know you could use a 555 timer for a debounce circuit but I guess you could jack the SR latch inside of it and take advantage of the discharge circuit to create that automatic falling edge... Nice
This is a really handy debouncer trick! Thanks a lot!
3:48 - Quick question as I'm trying to make sure I fully understand this. Is it R*C, or is it 0.693(RA+2RB)C as it was in the previous video? I realize the difference is very small (0.1s vs 0.0693s), but I'd like to know just for my own understanding.
Check the datasheet for the LM555(This is the IC Ben is using).
At 8:13, why does the 5v flow into the discharge circuit instead of into the top comparator? Is the resistance of the comparator and SR latch higher than the resistance of the discharge transistor?
Thanks for the great vid series! At 10:00, Ben says "it stays off". Now if you are holding the button down, doesn't that mean the bottom compare is still on and thus S = 1 which starts the process again, so won't start slow cycling on and off while the button is held? But maybe I'm missing something. Thanks!
Very well explained! The 555-timer is starting to make sense for me!
Hi Ben, a question.
What happens when the capacitor is too small? If its time period expires before you release the button, does it stay on? Or does the time period expire only after you release the button?
Specifically I'm confused about what happens when S goes high so Q'(Q bar) goes low and the transistor doesn't discharge current anymore, charging the capacitor up.
Eventually it'll exceed 3.3 and cause the R to set, and so S and R both are set to high. What happens then?
what happens if you keep pushing the button after discharge? Wouldn't the SR latch switch states?
i wanna know too
Looking at various datasheets, it's probably undefined behavior. It depends on the exact design of the RS latch, some keep state when they get the illegal input, some set, some reset. Since you said it should switch states: that'd be a JK latch.
Xiretza right, I was wondering this as well. S=R=1 is generally not allowed
If you really want to find out you can download a free Java based program called CircuitMod. It's a really nifty circuit simulator. Kinda fickle at times, like you can't connect capacitors directly together cuz it doesn't consider wires to have any resistance so it breaks the math, so to speak. But it's been an invaluable tool to me for learning electronics and it comes with literally oodles of example circuits, including maybe 5-10 circuits with the 555.
It's been wonderful for helping to visualize and gain an intuitive understanding of how circuits work. CircuitMod combined with videos like this has been the majority of my non-hands-on education in electronics. I might check out an article on All About Circuits or Electronics Tutorials once in a while, but I have ADD so I find it very hard to read anything more than a few paragraphs. I'd much rather learn hands on. I believe there's also an online version available which you don't need to download. I think the site is called falstad. Definitely worth looking into.
If you look at commons.wikimedia.org/wiki/File:NE555_Internal_Circuit.svg I believe that if you set the S first then the R cant change the latch state. The lower left transistor in the purple section will be on so the output of the other comparator has no effect. It is a limitation of the block diagram.
That bounce!!! this is one wizardry found!
Yesterday I measures a 1MΩ resistor at about 600kΩ. Tolerances aren't what they used to be.
By the end of the video, with the button circuit set up, you mentioned the behavior of the circuit as the capacitor charges, and then mention what happens once it's charged enough to trigger the R signal in the latch. However, you only mentioned what happens assuming the button is unpressed by then. At 9:30. I had a question, which is relevant for when the capacitor discharges very rapidly (unlike the one you hooked up to the oscilloscope that took 2 seconds to charge). What happens if the button is still pressed by the time the capacitor charges enough to hit the R signal?
Both the R and the S will be active at once. What happens then?
for an sr latch if both the reset and set are active at the same time, then the latch goes into an unstable state. Simply put you can't predict its output.
you should use a transparency sheet over your diagrams to draw current flow, or for other reasons, so you can draw on your diagrams without drawing on or re-drawing your diagrams. Just a thought.
What happens if you hold the button down for longer than the time it takes for the capacitor to charge (i.e. longer than 0.1ms)?
8:40 I don't understand this part. When the capacitor goes above 3.33 V, the comparator above outputs HI. However, the comparator below also outputs HI if the button is still pushed on, so we will get to a forbidden state for Q, since S=1 and R=1. Do we need to assume that the user instantaneously releases the button when R is set to HI?
I just understood that the 555 timer does not use an SR latch but a JK flip flop. Therefore, there is no forbidden state. When S=1 and R=1, Q toggles. Then everything holds true in the video.
Hi Ben,
This is by far one of the best explanations series I've ever seen in 555 / Logic ICs!! Cristal clear and well balance between theory and proactive! Hats off!
NOOB QUESTION: Why use 1K pulldown resistors VS 10k ?? is there any technical reason or any particularity of the TTL family ??
Theory+Well Explanation+Practical ..
Ahh the wold famous "debouncing" circuit. Can you imagine if it was missing on our phones, every time you're trying to blank the screen it would flicker randomly. ;)
Bill A huh?
Can someone explain me why at 0:30 two resistors are needed? wouldn't it work with one alone?
I would like to understand this as well.
The tricky part for me is understanding the flow of electricity. When I was younger I had a kit like this from radio shack, but I could never wrap my head around the diagrams to truly understand what was happening with the flow through the circuit. I need an eli5 for electronics...
Same here. Possibly, instead of simply watching, it'd help to physically draw out the same diagram and annotate it the same way while watching the video? (I've not tried this myself - yet.)
From an engineering perspective it flows positive to negative and current will flow through the path of least resistance.
@Duke Gibson correct not all the charges will flow through the path of least resistance but most will and if you have a short almost all the charges flow through that shorted path.you are correct if you want to know the current through each path just use ohms law
@Duke Gibson I'd recommend you take a look at open stax university physics 2 text book. It's free and a great resource
you should write a book Ben eaters computer. I would definetly buy it. 'cause not even 555 timer datasheets are explain how 555 works this clear...
What happens when you hold the button longer than the time it takes for the capacitor to trigger the reset?
Before 12:32 , the pin 4 wasn't connected to any part of the circuit, so then it should have automatically been low. So how did R become high when you wanted it to be high ?
i have a question : at 9:00 isn't it a problem that there is no resistance ? that's basically a short-circuit right ? well sure it's only 0.1uF so that's not a lot of energy discharging at once, and the wires do have some resistance, but isn't it damaging to the components ?
thanks !
From what little research I've done, it seems that for small capacitors with very little voltage, shorting them won't damage anything.
Wow , this is really cool, thanks a lot for explaining it.
Thank you for such a clear explanation! One thing I'm still confused about: if you hold the button long enough for the capacitor to fully charge, then let go, why doesn't the charged capacitor instantly trigger the reset?
Thanks for these videos! They're great!
I like the way you explain
Would you mind making a video about op-amps and how they work?
I've just tried this on a counter with a 7 segment display I've made from a 4026. I was initially still getting some bouncing, but when I added a bypass capacitor it seemed to fix the problem.
Thanks part 2.....
I love Relays....
How fast is the bounce displayed at 2:35? I don't know how to read an oscilloscope.
How both R and S are low, when the Discharge Threshold is at 5V, which 5V > 3.33V and the comparator is on. Then the bottom comparator will NOT be on, because 1.67V at the positive is < 5 V at the negative?