Classic Circuits You Should Know: Astable Multivibrator

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Classic Circuits You Should Know: Astable Multivibrator
HEY YOU ABOUT TO POST SOMETHING STUPID:
Yes, I know my hands are large/fat. It's because of a heart condition I suffer from called Congestive Heart Failure. Here's a link to some information about CHF: cle.clinic/2Td...
One of the symptoms is that is causes fluid retention, mostly in the hands, feet/ankles, and face.
It will kill me one day. I'm doing ok right now, but someday...
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2 окт 2024

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Комментарии : 222

@weerobot 4 года назад

"Only reason it works is cause nothing is perfect..." A Definition of the Universe..!!

@KaustavMajumder 3 года назад

Underrated Comment.

@BigSillyOrangeCat 2 года назад

Well, actually, the conditions for the universe have to be PERFECT for stars etc to form.

@tomety_tcg2073 2 месяца назад

Not really...

@isoguy. 5 лет назад

Its these basics in electronics that are so hard to find clearly explained, thank you for sharing your skills.👍👍👍 Just ❤ these vids.

@kwekker 4 года назад

why didn't I know this before I used 555's everywhere. THANK you so much for showing me this

@connormelton1635 4 года назад

You know someone's engineering skills are solid when they misspell simple words 😂

@mikeb4436 4 года назад

Every good engineer I know is a horrible speller haha

@Chris_the_Muso 4 года назад

For the same reason that doctors have the absolute worst handwriting. I have no idea how the pharmacist could understand some of the scripts the doctor wrote back in the day before it was all computerised, but they seemed to be able to figure it out. Oh, the reason? Handwriting is a right brain activity, while being a doctor is left brain (analytical). Yes that's an oversimplification of the issue because brains are complicated but it's pretty interesting how it holds true.

@adamedwards2435 5 лет назад

Very popular circuit design. I remember soldering together the siren kit from Elenco (SP-1A), with added caps, 555 timer, pot and 8 ohm speaker. Fun soldering practice for beginners.

@ash0787 3 года назад

I used to kinda get this one but looking at it now I still dont get where the charge goes on the transistor side of each capacitor, surely the cap cant charge if it doesn't have both sides connected ? I know transistor has a tiny bit of current flow through its gate but is it enough to charge up the capacitor ? also I don't get the purpose of the 10k resistor

@stevemaas99 5 лет назад

every time you explain things like this, I gain a bit more understanding, so thanks for posting these rather simple circuits that can be used to explain bigger concepts.

@vincesay2727 3 года назад

Teacher: Did you understand this lesson today? Me: I don’t understand everything

@davidjobe9876 5 лет назад

Great Circuit, that's like the Railway Crossing Lights ;)

@djberg3483 5 лет назад

These are my favorite of your vids, explanations are spot on, and easy for the newbie to comprehend.

@learnelectronics 5 лет назад

Thank you

@rish1459 5 лет назад

Nice demonstration on the classic astable multivibrator. That circuit works even better if you connect the capacitors between the diodes and the collector. What you are forming is a differentiator with R3/C2 so that when the voltage at the collector of the rightmost BJT goes low, the negative transition is coupled to the leftmost BJT base. Therefore, the leftmost BJT stops conduction. By placing the capacitor on the anode side of the LED, you are left with a lower valued negative pulse - it works, but may not through temperature ranges. As R3/C2 charge, the left BJT stays off and the right BJT stays on. This continues until Vbe on the leftmost BJT reaches 0.6V to turn it on. When it comes on, it comes on hard and pulls C1 towards ground (but the LED conduction of 1.8V + Vce(sat) of 0.4V keeps it from hitting 0V). R2/C1 form a differentiator; so the negative pulse pulls through to the base of the rightmost BJT - forcing the charge out of the base and turning it off. The cycle continues ad infinitum. If you placed your scope at the collector of the BJT, you would have had an easier capture, as the pulse pulls withing Vce(sat) of ground, Where you had it was pulling Vce(sat) + about 2V for a green LED (1.7V for red). You are spot on as to why this circuit starts up as it does! It is a race between the BJT's, Rs and Cs as to who gets to turn-on first. Since nothing is perfect, one of them wins the race!

@rish1459 5 лет назад

@learnelectronics, you should do a monostable multivibrator, too! I think that'd be cool. We'd learn about AC coupling and differentiators and how a small pulse can turn on (and keep on) a BJT using that trick.

@pepe6666 5 лет назад

i remember we learned this in 5th form electronics when i didn't follow and had trouble learning & stuff. i remember this circuit but had no freaking clue how it worked. i remember the teacher saying it started blinking cos the components werent perfect but thats all i remembered. its cool to know what it actually was now that im old and getting into electronics and can sorta get it now. i dont fully get it of course, but i will when i build it & put my scope on it. good video man cheers. please make love to lots of beautiful women and spread your genes & improve the human race

@kevfrets 5 лет назад

Thanks bro. I’m gonna try this. Cool.👍👍

@sylviaoliva1843 5 лет назад

Thanks. Nice explanation. For years in teaching I have found it a challenge to talk and write correctly simultaneously, so no apology!

@learnelectronics 5 лет назад

Thank you very much

@betta67 4 года назад

This was my first ever circuit I've built... and the PCB was etched in HNO3 after I've draw it with nail polish... somewhere around 1980... Behind the iron curtain it's obvious it was made with no LED's but bulb lights and with Ge transistors... :P

@robertedwards4113 5 лет назад

Thank you, very interesting and informative. You design your videos on the assumption that people are at the very beginnig of electronics, this is whats so good about them, they assume nothing. Excellent, thank you again.

@luckygen1001 4 года назад

I have a number of beginner electronics books and they all use bipolar transistors in the astable multivibrator build. So I looked up youtube videos about the same topic and they all use bipolar transistors. So why does everyone use them? Why not use mosfets or I.G.B.T.s or is there a reason why they are never used?

@petergazdag3020 3 года назад

Man, thank you for this video, you made my day! I have learned this circuit from my grandpa 30 years ago. I will build one again.

@Infinitesap 4 года назад

Larger resistor should increase the time of charging the capacitors hence frequency ought to decrease. Am I correct?

@daanhaeyen 4 года назад

Thanks for the video. First you say that the manufacturing tolerances are the reason why the LED's are oscillating, but later on you say that that's the reason why one LED blinks on first. I think only the latter is true. The oscillation happens because of one side of a capacitor dropping the voltage when a transistor opens, and then charging up again.

@larrybud Год назад

I think it would have been more beneficial to figure out why changing the resistor to 1k didn't work other than "oh well". Flashing 4x as fast wouldn't have created a solid led. It was clear from your scope that it wasn't working.

@PeetHobby Год назад

9:10 There is something wrong with the circuit, I guess bad connection or so, work just before. the blinking should still easily be visible to human eye, about 3-4Hz or so.

@dancoulson6579 4 месяца назад

I can get this circuit to work, and I'm taking a pin-out from one of the transistor collectors (to give me an alternating output between +vcc and 0v) however, I notice that I'm not getting a square wave. It's dropping to 0v quickly, but slowly raising to the +vcc. Is there any way to stop this? (_---^^_---^^_---^^ instead of ___^^^___^^^___^^^) I'm trying to drive the gate of a mosfet to drive a SPDT relay coil, so that I can power two channels of incandescent lamps for a halloween prop. The issue is that the intermidiate state of the output going to the mosfet gate is causing an asymmetrical duty cycle (maybe high for 90% as opposed to the intended roughly 50%) I've tried using a pull-down resistor and a zener diode before the mosfet gate, but that results in an unbalanced load (where the resistors would be) again, causing the asymmetrical duty cycle. I've designed an alternative circuit using a 555 timer, which works, so it's no matter of life or death. But it would be nice to know a solution to this, if one exists... Perhaps it's just the nature of this circuit?

@igxniisan6996 5 месяцев назад

The moment you said the name of it, my gf became very intresting in what I'm seeing but then she looked so disappointed LoL

@dheujsnrhfydhehehshshhdggsd 5 лет назад

Great topic series. There was a large library size dictionary book of circuit examples (80's) vintage that I really enjoyed. Anyone know the title? (My assumption is that it would be a common book amongst students/designers)

@panthLeoJTm Год назад

Excellent. Plz van you help me? I need To make a same circuit with short time ON (10000 miliseconds) and a long time OFF (2hours). What can ranges of capacitors and résistances?

@c.f.beeble 2 года назад

Great video, but you left us hanging about why the 100k resistors didn't seem to let the circuit oscillate at 4x the speed, or even oscillate at all! You concluded that it was going too fast to detect, but your scope couldn't detect oscillation either! You ended the video just as things were getting REALLY interesting! Maybe the two 100k's just happened to be almost exactly equal, (it could happen!). I suspect, though, that the problem occurred because the two capacitors were both charging too quickly, (due to the lower input resistance), and so neither one discharges quickly enough to stop powering their respective LED's. The speed of oscillation should only be changed by altering the capacitance, in my opinion. By the way, instead of relying on manufacturers' tolerances, to trigger oscillation, maybe you could simply add a couple ohms of resistance to one side of the input? 🙂

@dioszegizoltan4493 5 лет назад

I made the same circuit and it works for me but when I plug it in both of the leds light up and I have to short the resistors with my finger to make it work

@sundeep24jan 4 года назад

Hi...what changes would be required to run it off 48VDC 100mA ... Thank you

@LostInLeiden Год назад

I feel so stupid but I'm struggling to understand why the caps charge through the 470k resistors, not the 1k resistors (or both)? Both R1 and R2 are tied to 5V, how do you know how the cap will charge?

@sumbum3461 Год назад

Maybe I'm stupid, but a 2N2222 needs 1.3 volts at the base to trigger, and if this is putting 0.6V at the base and its working, either these aren't 2N2222 in the video or all mine are labeled wrong.

@asunasposibol 5 лет назад

Great video and explanation! What about the tolerance of the capacitors? Could they play a role as well? I love the conclusioni: "It works because nothing is perfect" ;)

@learnelectronics 5 лет назад

To a small amount the capacitor tolerance plays a roll, but its very very tiny. The resistors control the speed at which the caps charge.

@yootoobvyooer 2 месяца назад

If it's about resistor tolerance, both LED would light with one dimmer than the other. Resistor tolerance isn't the reason for blinking.

@michaelpadovani9566 5 лет назад

Good 'ol RC circuits. Neat concept to show tolerances. I believe you had a video on oscillating two LED's like this with an NPN and PNP transistor. Similar effect for a completely different reason.

@learnelectronics 5 лет назад

roger roger

@beeman1885 4 года назад

I track the whole explanation except the purpose of the 1k resistor. If the capacitor only charges through the 470 ohm resistor, it seems like the circuit should work without the 1k resistor. Must be missing something.

@derriusdunn-jk3gf Год назад

I was thinking a current mirror coming from the astable multivibrator would compress the solar kinteic current into a power form it it starts with a bridge refticer that's loaded back backwards into it's power loads would that stabilize my compression power I'm making from light

@Popsimath 3 года назад

I know this video is a year old but it's still relevant. Unfortunately almost all of the Amazon links are broke and yes, I do hope buying equipment will make me smart.

@Teister9 Год назад

I dont understand how it works, shouldn't all the leds always be on because the capacitor always gives an output? why does the capacitor discharge while charging?

@charlesklein7232 4 года назад

actually i dont write stupid things i generally comment on people who think that DRUG music helps them make their video more interesting. nobody in college is giving lectures with music going. we could have an extensive conversation about this. im curious if people are commenting on the size of your hands? never occurred to me but i could tell from your voice that you have a heart condition. what i am writing about is that i really like that you are not using an arduino to do this. i thought and still do that its great but the programing is a hassle and if you can do it with out one thats great not only did you do it but you explained why its done. i understand the changing of the resistor and capacitors but if they were exactly the same it would not work. that would have never occurred to me.

@helpfatbloke 4 года назад

Why does this work in a simulator? The manufacturing tolerances wouldn't exist.

@sokoloft3 10 месяцев назад

Going to give this a try instead of using a 555 ic in astable mode. Ah damn, I only have a 47uF cap

@johnf3326 4 года назад

"What's happening guys?" Looks like 2 green LED's are flashing! 🤣

@stevedresen8497 4 года назад

As an old journeyman certified technician, your videos are a good refresher.

@print4life Год назад

can you post a circuit diagram image or something it would really help... Thanks!

@gregferguson7737 3 года назад

I tried pretty hard to figure our why it was oscillating at the question portion and drew a blank. Tolerances (i.e. real world) I did not think of (stuck on theoretical). Thanks for these mental exercises as LRC does take me some time to figure out and I am learning from your videos.

@Cern2024AR Год назад

I buillt t his circuit but both led's turn on anyone know why?

@aodhanking2539 3 года назад

Astable Multivibrator, what a name . Do they come in an assortment of colors and their own lube?

@strokebootcampbydrparit 3 года назад

thank you enjoyed watching the video very much.

@JaimeWyant 5 лет назад

Thanks for the video, i learned something!

@robertoguerra5375 Год назад

Is it possible to daisy chain 2 astable multivibrators and get 4 cycling states?

@johnmoney910 3 года назад

Mine wont work and ive been trying for months😪 its really frustrating

@jesterbob828 5 лет назад

Really good videos. Much appreciated.

@sarachai 3 года назад

Thank you, everything in this video was so well-explained and very clear. I loved the walkthrough as you drew the schematic. Subscribed!

@sjoervanderploeg4340 9 месяцев назад

If you measure across the discharge resistor you will get a pulse!

@jonerasmus9399 Год назад

Ill give thumbs up for the transformer icon at 5:43 😀

@dominikbaricak9589 Год назад

I spend whole two days to understand this a fuck it I still don't get it.

@burpcoolgt8622 Год назад

Can this oscillator drive power transistor for smps circuit?

@bertspeggly4428 10 месяцев назад

Good interesting video. I have looked at a lot of these videos, and many others include blatant errors that will destroy your LED's, or they don't give you component values, etc. I would have liked to have seen alternative values for the base resistors that would show different speeds, and a non-symetrical duty cycle. That would have been interesting. Thanks.

@EEE-iw3fk 9 месяцев назад

You might be interested in my lasted post about this circuit

@eladioh3858 5 лет назад

Love this easy simple circuits Thank you Paul Have a nice day and take care

@ronsone8373 2 месяца назад

Why should i know this circuit? Use cases?

@alchemy1 2 года назад

For some reason I think the frequency is determined by the value of the capacitor and the duty cycle is determined by the value of R. Large R1 compare to R2 give you longer on time (pulse width) and less off time ( space width). If you swap them R values ( swap R2 and R1 and the same with R4 and R3, you will end up with long on time and less off time while your frequency remains the same. Right? If I want to see what the value of C must be to get 60Hz F= 1.44/ [ R1+2(R2)] x C. C=1.44/[R1+2(R2)]xF Most likely they are all tied up with each other from the looks of it all. Did I miss something?

@captainamerica949 3 года назад

Hello, thank you for your video. Question please, why does this still work if the inside of the circuit capacitor is positive or negative? I thought capacitor needs to be positive to discharge? thank you

@learnelectronics 3 года назад

Capacitors discharge when they are no longer charging. So in DC operation when there is no longer a current at the anode, the charge accumulated in the cathode basically just runs out. Things are much different in AC operation.

@OregonDARRYL 3 года назад

That's funny... I use two three-pin headers with my alligator power clips and split my positive and negative to each side of the breadboard too! Geniuses think alike.

@dreznik 3 года назад

u explained why the circuit gets started but not why it keeps going orderly

@learnelectronics 3 года назад

Once it gets going, the caps discharge into the opposite transistor so they just switch back and forth

@alchemy1 2 года назад

So frequency means how many times the LED turns on and off in one second and the duty cycle means how long in that one second it stays on. Say it is one time on and off per second. And duty cycle determines how long in that one time it stays on, in other words in may not be 50/50, it could be 3/4 of the second on and 1/4 off. Is this right?

@learnelectronics 2 года назад

You hit the nail on the head. Frequency is the same as cycles per second. You might even see that in some of the older textbooks or literature. Duty cycle also known as Mark space. Is the ratio of on to off. So we could have a frequency of 20 kilohertz. And a duty cycle of 50%. And a VCC of 5 volts. Whatever is on the load end of that circuit it's going to see 2.5 volts.

@alchemy1 2 года назад

@@learnelectronics Oh, that is interesting. So even though you are applying full voltage say for 1/2 second, the voltemeter will show 1/2 of the applied voltage. In other words just like current, Voltage is also measured by the second. I never had straightened that out in my mind. So I can use a Treadmill power supply that operates on PWM and not LWH ( pot) as a controllable high power DC source. And the only difference would be that I won't be able to set current constant if need be. Does this sound right.

@Sizzlik 3 года назад

Does this circuit only work with non polarized capacitors? Or can i use polarized electrolyte capacitors aswell? Does the flow direction change when it switches?

@learnelectronics 3 года назад

You can use any caps

@ertutorial4776 3 года назад

Thank you so much for your tutorial sir

@pulsartgaming4213 5 лет назад

I really appreciate the in-depth video describing how it works. It really bothers me that there aren't to many good quality videos and like yours. Subscribed!

@pulsartgaming4213 5 лет назад

I actually also really enjoy watching it too compared to other videos

@learnelectronics 5 лет назад

Thank you very much

@crisgetcrucified6972 Год назад

that is so cool. its like a perfect imperfection

@tankominos56 5 месяцев назад

you're the BEST!! I just started a hobby project of mine to make electrical stuff and i spent half an hour looking for videos and i saw your video and you are the only one who has a good explanation! (You should show how you connected the bits in the breadboard) THANK YOU!!

@russellslater4037 10 месяцев назад

I know I'm late to the party, but I'm learning by building these circuits and ensuring that I understand what's going on. I absolutely love your presentation, it makes me feel that I am learning, thank you. However, I may have misunderstood why this circuit works - I carefully matched my two 470K resisitors to 473.1K each and the LEDs still blink. What have I missed?

@learnelectronics 10 месяцев назад

Capacitors

@russellslater4037 10 месяцев назад

Matched those to within 10's of nF, or is that enough?@@learnelectronics

@freddythreepwood3519 3 года назад

Thanks for the explanation. I have a dumb question (I think).. at 4:30 you say that the capacitor on the right charges up enough to turn on the transistor on the left. Why does it need the capacitor to do this? Isn't its base also connected directly to Vcc via R3, like ALL the time? So it should NEVER turn off, right?

@vyratron839 4 года назад

I think it's called a multivibrator because there were also single vibrators and they were used with transformers to convert DC to AC in cars to power tube radios in the mid 20th century. Maybe google "radio vibrator".

@snorman1911 2 года назад

Learned this circuit from my radio shack 10-in-1 circuit kit. Never could figure out why it worked and the book didn't explain it except in the most basic sense.

@johnray854 Год назад

Something I do is add a tiny speaker in place of the led when it switches really fast to hear the ear can hear faster then the eye can see in terms of frequency

@learnelectronics Год назад

Great idea!

@friedmule5403 4 года назад

OH now do I understand!! :-) I did for some time ago look at a schematic of an astable multivibrator but could for the life of me not see the logic in how that should work, no matter how I did look at it were there no logical explanation on how that should start blinking! But electronic is fun and investigation could only add to the fun, so I did thought, I'd just draw the circuit in an visual simulator and then I know what's going on. But to my surprise did both diodes just glow and nothing else happened. I did redraw the circuit several times but every time with same result. :-)

@felixgottlieb654 Год назад

Amazing video Thank you!!!!

@arthurfricchione8119 4 года назад

If I can ask what is a good brand of transistor to purchase. Going to purchase a assorted pack just need to know a good name brand. Thanks for any info Artie 👍 also the blue small resistors are they 1/8 watt

@sebtodd97 3 года назад

does anyone know what state the transistors are in

@fetmar 10 месяцев назад

I remember buying the parts from radioshack and twisting this together myself when I was 13. Thanks for the awesome video.

@timstoriger3927 4 года назад

My goal is to identify the functions of the devices in a given circuit diagram? Or spoken more general. How can I learn this general skill? When do I see a random circuit diagram in all kinds of electronic fields that I can recognize the devices and their functions? What is the best strategy to acquire this skill? Do you know good information recourses specially designated to acquire this skill? I do not want to handcraft things on my own and I do not want to study at a university to acquire a bachelor's degree in electrotechnology. I just want to be able to read and being able to understand more or less the circuit diagram. Thank you in advance

@learnelectronics 4 года назад

Have you watched BigClive?

@timstoriger3927 4 года назад

@@learnelectronics no what is this?

@shwetankjain414 3 года назад

the slight change in the actual values of the resistors must affect the blinking or oscillation of LEDs continuously like the right LED showed in the beginning but they seem to oscillate at a regular interval why and how?

@kolinevans9127 5 лет назад

The two resistor are controlling the charge of the condenser but the quirkiness is that in your first example explanation following the 1k resistor that would charge one side of the condenser but this would cause a polarity potential difference between those two points, I mean obviously either end of the condenser then that equalization causes the rise to the gate potential, so I think it is tolerance differences but mostly the key is the condenser disequilibrium. No?

@ovidius2000 Год назад

failedTestingWithOtherResistors.

@batticha462 5 лет назад

Why You not examining the 1K resistors, they also not equal and not perfect ? And I think if we let the circuit run for long time there will be a moment in which the two led will lights at the same time. The chaos low :) I build the circuit and it's blink only when I use electrolytic capacitors instead of ceramic ?!

@thewhitedragon4184 4 года назад

So when I turn on power to the circuit the leds are just on, but when I reconnect stuff it stars blinking. What's causing it to not immediately blink?

@jonelectronics510 5 лет назад

They should get rid of the auto button on scopes they are just useless! I was working with a 5v supply last week and autoed my scope and it set to 100V per division...what???

@AaronB99999 3 года назад

What’s the frequency, Kenneth?

@alexmcd378 2 года назад

I've done basically this circuit with 555 timers. Setting it done without ICs is pretty cool

@jannh7569 2 года назад

Thank you kindly for all your informative videos, they have been a tremendous source of great information and pleasure for me. They have brought me many joyful evening playing with breadboards. I wish you all the best!

@KaustavMajumder 3 года назад

10:13 - Summary of the lesson.