SR latch
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- Опубликовано: 30 июн 2024
- Digital logic gets really interesting when we connect the output of gates back to an input. The SR latch is one of the most basic memory circuits that we can build on to make counters, registers, and all sorts of other interesting things.
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You can get all the components used in this video from any online electronic components distributor for a few dollars.
Complete parts list (everything in this video):
1x 74LS32 (Quad two-input OR gate)
1x 74LS02 (Quad two-input NOR gate)
3x 330Ω resistor
3x Momentary "Microtivity 6mm tact switch"
3x LEDs
Solderless breadboard(s)
22 gauge wire
USB charger and cable or some other 5v power source
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6:46
"if we push this button..."
*Dramatic pause*
"Nothing should happen..."
*Pushes button, nothing happens*
"...and in fact, nothing happens!"
That was palpable. I really felt it.
Q.D. White yeah, you can palp it!
@@0oh_no Palpatine would be proud
Same here
Dear Mr. Eater, I've been watching your videos now for the past couple of days, and I wanted to give you a sincere thank you, from the bottom of my heart, for finally explaining the fundamentals of computer logic and, basically, how CPUs really work, deep down inside. Throughout my life, I've been fascinated with hardware and assembly programming. Your vids are the first explanation, whether it be a book, article, video, etc., that I've come across that actually breaks it down in a simple, clear, and easy to understand way. Again, Thank You!
I want to repeat the words of "Eric Parent" as well because I feel the same way -
{..Dear Mr. Eater, I've been watching your videos now for the past couple of days, and I wanted to give you a sincere thank you, from the bottom of my heart, for finally explaining the fundamentals of computer logic and, basically, how CPUs really work, deep down inside...in a simple, clear, and easy to understand way.}
A sincere thank you from me too.
I would have to agree, your way of explaining the concepts in these videos is clear and makes sense. Also your choice of using breadboards makes it quite a good way to follow at home.
I want to follow up on networkmist and repeat the words of Eric Parent because i also feel the exact same way-
"Dear Mr. Eater, I've been watching your videos now for the past couple of days, and I wanted to give you a sincere thank you, from the bottom of my heart, for finally explaining the fundamentals of computer logic and, basically, how CPUs really work, deep down inside. Throughout my life, I've been fascinated with hardware and assembly programming. Your vids are the first explanation, whether it be a book, article, video, etc., that I've come across that actually breaks it down in a simple, clear, and easy to understand way. Again, Thank You"
A Huge Thank you to Mr Ben Eater for providing us with these precious explainations.
Right? I've wondered about it all my life. Now it makes sense. Partly because of the 8-bit guy, but mostly because of Mr. Eater here. Actually, I had designed an SR latch in Minecraft before I ever saw this video. But I never would've know what I had made, or that it's actually used in the real world. But these videos have inspired me to forego the virtual world and set these circuits up on breadboards. 8-bit computer, here I come!
Thank you Mr Eater. Good job on the videos. It is wonderful how such simple things as shareing what you know blesses so many. It is a reflection of Gods love for us all. Whew that went deap fast...
Ben, one of your teaching strengths is knowing the questions a student should ask but doesn't know to ask. For example. "Why isn't a current limiting resistor needed from the output of chip toe the LED?" Keep up the great videos. Well done in all regards.
I have question is it current limiting or voltage limiting ?
Because you don't want your LED to go up in a puff of smoke. ;)
@@stefanjovanic7725 mainly current. Just realised that comment is months old
This skill comes from being a student yourself and documenting your thoughts as you learn.
1:18 "We already have this 120 Ohm resistor built into the chip, in this case that's going to limit the current so we should be ok with that LED"
Thanks for building the circuits to go along with the logic. That really helps.
These videos are the benchmark of how electronics should be taught. If you were a teacher and I was back at school I listen to every word you have to say. Thank you
That´s exactly the art of presentations that i needed as a young scholar. Where were you my friend 25 years ago?
dont worry vevery age is right to learn
It's never to late Mr. Truman!
I'll raise you 15. Where were you 40 years ago ;-)
He probably wasn't even born.
@@rishitsingh6621
Pretty sure he's 35+ so he was born 25 years ago
*Never* have I seen electronics explained so well. I have been a programmer for 40 years with a hazy understanding of the 74LSxxx family and breadboards. If I had seen these videos 40 years I might have become and hardware engineer instead of a software engineer. Who knows? I am now addicted to watching these videos for my own entertainment and just for the shear wonder and joy of it all. Thank you Ben, you have made the world a better place.
I was here 4 years ago for my first course in logic gate. Now, I am back here for my master's thesis to review. Thanks for the video.
Oh. My. Goodness. This is actually crazy useful. I've only watched like four of your videos but already I want to know more. I'm especially curious about computer architecture and can't wait to see if you've talked about it!
Right?! These wonderful video just suck you in and keep clicking on more. Hungry minds want to know! ;)
Damn, one video better than multiple lectures and tutorials during the semester. Wish I had found this video before the final exam
What an excellent video. Explained in a simple but precise way. Thank you.
+
Ben, these have got to be the best videos I have ever seen. Explained in full detail, and dumbed down to basic esentials. Thank you very much.
+
Yeah a 1000 times better than the professors I had in UCI
Amazing video. Showing the circuit alongside the logic and diagrams is really an excellent way of putting your point across and effectively putting it into the viewer's mind.
Thanx Mr Eater , computer logic was never this easy to understand Thank you from the bottom of my heart :)
Sir I just want to say thank you so much, The 2 minutes of your video is better than 2 hours talks from my Indian computer science teacher!
Your breadboarding is so nice and clean, mine always ending up looking like a bird's nest lol
hey, at least a bird's nest not a rat's nest like mine
Amazing explanation!
I made an SR latch from NPN transistors in a NAND configuration. Great stuff. Looking forward to watching your other videos!
This came in my recommended. I'm studying Electronics at A-Level and I didn't really understand the concept in lesson. This is my first video I'm watching of yours and I have to say that this is amazing. You keep it simple yet say how it works, with schematics and demonstrations. I've basically revised a 2 hour and 10 minute lesson in just under 15 minutes. Thank you, I'm subbing.
Another thing I really appreciate about your videos is the fact your presentation is smart and clear. Thank you for taking the time to color code the 1s and 0s on that piece of paper. Thank you for making your breadboard neat and tidy. Also you explain the logic clearly. I decided I wanted to learn more about electronics for work and you are demystifying the whole thing for me.
I have been wondering about the current flow in a SR latch for years now. Even my teacher could not provide me with a concrete idea about it. And you have cleared one of my biggest doubts in electronics. Hats off to you sir.
After lots of theoretical stuff on the topic from mr. Tanenbaum (Structured Computer Organization), your practical stuff is just what I need. Thank you!
I wish you were my course teacher. So much respect for you. The way you have taught us this is super helpful. Also thanks to the youtube algorithm for suggesting your video.
you're thanking a youtube algorithm?
@@CleoKawisha-sy5xt lol yeah 🤣🤣
6 years later and you save my life for my exam. I have no words… Thank you so much . I don’t usually comment but you deserve at least a like and a comment. Thank you so much from Switzerland 🇨🇭
This tutorial was fantastic, thank you so much. I went from knowing nothing about SR latches to having a good understanding in only 13 min!
This channel is truly amazing. It really shows the power of the freedom of RUclips. Thanks a lot.
I just found your channel and I have to say THIS IS AMAZING! Thank you!
That was SUCH an amazing video! Thank you for explaining this concept very clearly. I loved how you introduced the latch with the example of the OR gate by itself and then made a logical progression to the latch.
This has got to be the best video on basic computing there is in the world. Terrific. If you can understand this you are already more than half way through understanding how computer memory works, and so many other things. Thank you for this knowledge.
Beautifully explained and demonstrated, Thank you!
I really enjoyed this lecture thank you for showing us the circuit while explaining the logic behind it!
This is hands down the best video on SR Latches/Flip-Flops online. My dad and I have been trying to figure out how they worked for a couple days, consulting many sources of info and I have to say your video was the only video that explained every question I had. Especially the one at the end of how a light turns on without pressing the buttons at all with the power plugged in. Thank you so much for making this video.
Thanks so much for this. I appreciate that you broke it down step by step *and* you clarified that there's nothing stopping either LED from coming on first!
This kind of explanation is what i have been looking for and needless to say, this is one of the best explanations I have found on the internet
You have explained what I "learned" in my Digital Systems course in a much more understandable way!
When I was around 10 I got a breadboard and some components as a gift. These videos bring me back to that time. Thank you for giving a clear and deep explanation to crucial concepts of our lives today!
Z
Brilliant chap, no hype, no distracting music and explains it very clearly. I wish more others would do their presentations the same.
Ben, I would like to thank you so much for these videos! I have been working on designing an 8 bit mechanical computer (pneumatic) and have been 3D printing my own pneumatic variants of AND, OR, and NOT gates but am coming across issues with the storing information in a latch. anyways, once again thank you so much for taking the time to make these videos and make this knowledge available to all who wish to learn.
Tyler Reeves do you have any plans on sharingg that at some point? I'd love to hear more about it it sounds truly fascinating
Yeah I actually do! I am currently getting my degree in computer engineering and hope to use the project to get some scholarships. Currently trying to get a 4 bit adder with 2 registers and the ability to subtract along with a binary to 7 segment display decoder working as a proof of concept. The proof of concept will be entirely mechanical and I hope to use it to do a little crowed funding so I can start building the real project. But I promise to remember to come back and comment here to let you know when I post a video of the working proof of concept.
oh my god ! this is awesome ! really appreciate made this kind of video !so clear and so impressive with the implementation circuit!
This is the best explanation on S-R on the net. Thank you so much- you explained in 12mins what my lecturer failed to do in one hour- TOP MAN
This video is amazing!!!! I finally can understand the real concept of latches! Very much appreciated, thanks. My mind got literally blown since the Or gate demo
There's this really cool software I found called Crumb. It's a breadboard simulator. I have breadboards and components, but this software makes it so you don't have to deal with the mess and annoying meticulous wire placement. It's not perfect, but I was able to create the CPU Timer. I'm running into issues replicating the latches demonstrated in this video, but the issue is related to the fact that adding the LEDs throws in enough resistance to drop the voltage so a latch signal isn't high enough to complete the latch. However, the software allows you to view real-time voltage so without the LEDs you can see the effect at least.
Incredibly helpful.If only the idea of building intuition was more prominent in education.You are pretty awesome.
Finding your yt channel is truly the greatest gift ever. THANK YOU VERY MUCH. There are no words to describe how helpful and spot-on your videos are.
As a kid I got a breadboard experiment kit as a present. The book guided into building this (although without the reset), but it didn't go into detail much for how it actually worked. Thank you for your explanation, in just a few minutes it is totally clear to me!
Not to make fun of what you do or anything, I just thought it was amusing that after a few minutes of watching this all of a sudden I was like “OH! I already know all this. This is an RS NOR latch I use and see used in Minecraft all the time.” Haha. Great video by the way. Very well explained and done so in a way most people should be able to grasp what’s going on. Definitely checking out more videos later. Haha
Minecraft is the best way to learn electronic and programming.
rs nor latch stands for Reset Set Not Or latch
@@borekworek69 Definitely one of the best ways to get interested in electronics and programming. Being pretty good at redstone is the only reason I understand the very basics of electronics and think it'd be a very interesting field. Haha
@@alyxbruno-bamford8414 Duh. Haha
that is so nice when i watch minecraft redstone videos i already knew all this so i think of these digital building block instead. so that is kinda the other way around :)
I hardly subscribe to channels even when I like them but I couldn't stop myself from subscribing to your channel. You're such an awesome teacher. It's really hard for me to learn things till I know their practical use and your videos are just the thing that I need.
Dear Eater, You have explained timer in excellent manner. I do not have words to thank you. I believe world needs more videos related this topic from you. Thank you so much Eater.
Seeing this I am sad now when in University of my professor would have thought this latch like you did I would have developed a passion for electronics
A very helpful explanation, though one thing confused me. The two resistors connected to the buttons are called pull down resistors and are needed to keep the chip in operating range. I couldn't get the circuit to work until I watched another video that recommended 10k ohms instead of the 330 ohms I had assumed. Ben might have mentioned it somewhere and I missed it.
Thank you for clearing that up
Hello, I just found your channel and I've watched a couple of videos. I instantly felt in love with this learning material. Thank you very much for the work you've done here. You really shed some light on the subject, at least for me. Thank you again!
I love your videos. They saved my life. I am studying at rose-hulman. You explain everything perfectly better than my instructors. I watched some open courses from Carnegie, you are better than most instructors there also. I wish I could learn computer systems with you. Best wishes. I appreciate your help.
I’m on my fourth viewing of this series while building my own computer at the same time.
The reason the top was getting priority was because it’s connection to the bottom one was shoter letting it turn that one off faster I do not know for shure if it was mentioned in the video but in case people didn’t here or understood why 12:30
Yeah but if we use his drawing where in theory the distance doesn't matter, it's the reason why.
Mate, this is excellent. I've been looking for an easy to understand tutorial on logic principals for a while now and this video is by far the best on youtube. Having the physical circuit laid out as an example is immensely helpful too. I've subscribed and will recommend you to everyone. Thank you for putting in the time to make this.
The only small bit of feedback I have is, the speed at which you narrated the video was perhaps a tiny bit too fast for me to keep up at some points, and I found myself having to stop and re-watch a few sections. However, this is only nit-picking on a practically PERFECT explanatory tutorial. Thanks again!
Thank you very much for this great video , i think if you start a series of introduction to Digital Design tutorial that will be great
For beginners to experts , i hope you think about it.
In case someone is having trouble following the first example in this video, for me it was necessary to use a 220Ω resistor between the LED and ground. It seems that the B input was not getting enought power to set it high.
...yeah! Ben's technique of connecting an LED directly to the TTL output is quite clever, BUT it'd be a bad idea in so many cases, it's hardly worthwhile just to save one resistor.
E.G. A red LED would bring a high output to 1.7V, which is too low for a TTL high input. Green and Blue, though, *might* be OK, depending on its forward-voltage AT the current it gets, which may be way lower than you'd calculate from ohm's law if you forget there's a transistor inbetween.
Doing-so means looking at the specific chip's (and specific LED's) specifications very carefully. Is it a 74HC 74LS. What's VIH? What's IOH-Max?
Frankly, I'm kinda surprised he thought this was a good idea to show newbs, at all, except maybe as a lead-up in an entire lesson about how bad a habit it is.
Mine always jumps back... will this help??
@@ericwazhung i fixed mine by using a blue led but the nett Problem is that the Second led is pretty weak, Do you know a solution?
@@OneMilian I updated my earlier response, which may help. Dunno about your specific components/circuit, but maybe you've got an older blue-LED which would require nearly 20mA just to be visible, as opposed to a newer blue LED (they used to be called "ultrabright," but now are pretty much standard) which might be too bright even at 1mA?
@@ericwazhung i fixed it by using a Weaker resistor. Thank you your help!!
The explanation from11:40 to 12:30 is extremely useful and cleared up my confusion no other video addresses. Thanks!
Thanks so much, i've been trying to understand logic circuits for awhile and you finally explained it properly
much appreciated
I remember the first time I heard of this was in a Minecraft video, called it an RSNor latch. Now I know where the name came from
3:30 - How about adding a resistor between OUT and B and another button that pulls B to GND? That would give you a reset button to reset the latch OUT to zero.
i was about to comment this... was looking if somebody else spotted that... in my opinion that should be a valid choise
Or, just have a normally closed button between OUT and B if you're going for least amount of components.
This is the first time i've seen videos like this explaining circuits where i have understood. Thank you!
Wow this video was amazing.
I finally understand the foundations of how a memory Latch works.
You are an Expert explainer.
Thank you a million billion times !!
For the sake people that more of a novice to electronics, you should very briefly explain the need for the grounded resistor connected to one leg of your gates.
Me, a Minecraft Redstoner: so it's an RS-NOR Latch!.
Ben: Well yes, but no.
Well yes, but yes. That is exactly what it is.
Minecraft redstone builds up in a lot of real life Electrical engineering terminology and circuits.
For example, if you look up the standard minecraft XOR gate design you will notice that it's made of an AND gate a NOT gate and an OR gate in the same configuration as what ben showed in the logic gates video.
My college lab TAs literally recommended your video for clear explanation, very well explained...thanks for this🙏🙇♂️
You are a pro in explaining things so easily! Amazing!
So, in an ideal setting where everything is timed perfectly, would the latch initially flicker both outputs on and off over and over at the same time until an input is activated?
Hey I tried out turning the circuit On and Off many times. Majority of the times one of the LED gets on, sometimes the other LED gets On, and sometimes both LEDs turn on and one of the LED is very dim, and the other one is also dimmer than normal. An oscilloscope might help to see things better
yeah they would both go on, off, on, off, etc. in sync indefinitely until an input comes in, then would act normally assuming the input lasted through the off state of the cycle
@@RoboGenesHimanshuVerma So, you could actualy use it in a random number generator?
@@chomo54andbabyaisha97 that's so interesting
I feel like crying, in a good way
so you are getting some FREUDENTRÄNEN thats the german word for tears of happiness
Thanks for explaining which gate outputs 1 first, really good explanation!!
Many thanks, I have experienced these gates in coding many times (coming from non-electronics background) and as someone in the organisation had already prepared a truth table I would use those outcomes for my code- but you explained it so well- thanks for you work.
I really like your videos. In this one, however, you never explains where the power to the LED comes from when no switch is pressed.
Only a careful study of the diagram reveals that the chip is connected to plus at leg 7 and it is up to the viewer to guess that this somehow allows current to flow when no switch is pressed.
This really needs to be explained.
don’t worry, he explained the basics of how such chips that contain logic gates work in previous videos. You can’t re-explain every little thing in every video
at 2:50, how is B still getting an input? where are the electrons coming from if the current cant even make it though the switch?
yeah, I don´t understand this either..
Remember that the IC is always powered from an external power source. The output doesn't (necessarily) come from the current into A and B, those are just "signals" which tell the gate to send output or not. The current on the output comes from the external power source.
Robert Anderson Thank you. I was wondering the same thing, but your answer makes sense.
That's the latch part of kt. It latched onto the signal and is keeping that signal alive with the power coming from the board
The thing to remember is that the logic gate representation of the schematic here is simply an abstraction of what is going on, in reality a more complete diagram could be drawn showing the actual transistors that make up the logic gate switching the chips power and ground lines to it's output pin it's just that this additional level of detail is not necessary in practice.
Oh my goodness, thank you for walking us through the flow of signal of the SR Latch. Now I understand it clearly. Thank you once again. Cheers.
Mr.Ben Eater you are a master at explaining & make understand concepts with practical scenarios. It's Incredible. God bless
could u make a video for jk flip flop and master slave
If you make an SR latch that is used for turning on or off something, because of the arbitrary initializing of the 0 0 state, would the on and off buttons switch at random every time you unplug power? Because I'm pretty sure it does, do you have to slightly delay one of the signals upon startup to make sure they give the same truth table everytime?
That's my question also. With 2 outputs (LEDs here), we don't know which will come on first, so doesn't that also mean we don't know before hand which input will be R and which will be S. That also seems to mean we don't know which output is Q or not Q. I'm sure I'm missing something here ... time for researching SR latches!
last night I saw the diagram for the SR latch for the first time, and I was pretty much sure I could never learn it. Then it struck me that maybe YOU have taught this, I googled and I found this video. I now understand! THANK YOU❤🌼
I know from Minecraft that this is called a RS Nor Latch (since there are other types of latches). Your explanations are AMAZING. Thanks for putting the time into this!
So i dont have NOR gate chips. I've tried using OR gate and add inverter made out of transistor and resistors to each OUTPUT of OR gate, but my SR latch wasn't latching. Is it because I wired something wrong, or there is some reason that it can not work this way?
Ice Carpenter you would have to reverse the inputs as well.
LittleRainGames Why would you? That would make it a Neg-NOR. The outputs for the Nor would be 0 0 0 1 therefore you have an inverted latch. Tell me if I'm wrong there, but that doesn't seem necessary and wouldn't fix his problem.
NOR is exactly that, OR with an inverter at it's output, there's no magic going on there, so yeah, he did something wrong, and you wouldn't need to invert inputs.
Whats the reason for using resistors with switches, please?
That is a pull down resistor so the A input does not accidentally go high. B is being held down by the output, which is a solid 0. Once A goes high, game on!
@@jimedgar6789 the resistor cause a voltage drop across it so A always remains 0 at the start ?
@@gokuvegeta9500 The resistor is necessary to allow the voltage to the pin to be 0V (logic low) and have enough resistance to current to prevent blowing the logic gates out at that pin. Adding the resistor keeps the pin at low at the start of energization of the circuit, yes. It is a well known way of setting a logic state.
@@jimedgar6789
I don't understand how to we determine what value of resistance should be required to keep the logic near to 0 using network theory
Like how do I show it mathematically. Do you know the answer to this ?
@@gokuvegeta9500 The value of the resistor is not critical, it just has to be enough to prevent the current from the 5V destroying the input pin. I would recommend 10K Ohms as a safe value to give the logic low (or high).
There are lots of channels that explain how computers work, but this is the ONLY one that I could find that explains how it all works, completely, without abstracting away all the important details.
Picked up a 74LS02 from my local hobby shop and made this circuit. Worked beautifully, thank you!
I've done a whole bunch of Arduino stuff over the years, but not straight logic stuff. I want to make a little circuit to allow my 2 year old to turn her own light on and off on the bed, but specifically wanted separate on and off buttons to teach her the concept of on and off. The SR Latch is therefore perfect. And I figured while I could easily make this circuit with an Arduino, for a simple light on/off circuit, it would be massively overkill, so this hugely simplified it for me!
This videos are really informative and interesting. I'm proud to admit that i found your channel while learning how to improve my redstone circuits in minecraft tough.
Nice job, Ben. Really like your style and clear & comprehensive explanations.
Best Lecture on SR Latch I have seen. Thanks a lot for making it.
Very useful . I wasn't able to understand this from books, but by watching your video , I understood it. Thank you. I will watch more videos on your channel.
Your videos are making me wanna dive head first into 74 series logic. thanks!
Thank you Bean Eater, your videos alongside NandtoTetris course are the most valuable resources about the fundamentals of computer logic we have on the internet and this thrills me
Lol @ Bean Eater, great typo!
Thank you so much. Very good video. I was struggling a lot to understand this, a looked a it it in books, other internet pages and I just couldn't get it. You explain it in a very simple and direct-to-the-point way.
Best explanation I have found. Circuit helps a huge amount
really appreciate it ben for putting together such a great video
Thank you, the best ever in explaining the basics of computer logic. I wish I have found this years ago.
Damn, I wish my tutors would be so interested in delivering knowledge like this guy, not only show absolute Basic what you are paid for
Explanations very simple, but enlightening.
Congratulation!
Man I love how neat you connect your components. And your videos are major help thanks man
The way you teach this is absolutely brilliant! You just gained a subscriber.
Brings back memories of navy BE &E school. Fun times for sure.
Thanks.a better explanation than any teacher, book and video. Struggled hard for this to understand.
I sincerely wish you all the hapiness, peace and health in this life. You have done an auspicious video for the humanity, and helped me a lot. Thank you.
I was going to ask how one can be sure which output goes on in initial state and you've covered them up. Like I learned I have nothing else than appreciation to put in the comment section lol
Thanks a million, sir!
I really feel blessed to meet your channel because you turned me from absolute zero interest in building circuits learning electronics, to someone already learnt quite a bit enough to go build one for myself.
Feed the power line to one of the inputs through a large capacitor. The step function produced by switching on the power will be converted to an impulse function by the capacitor and that would set or reset the latch at power on (Depending on the input the cap is connected to).