555 Timer as Astable Multivibrator (Working, Design and Derivations)
ฝัง
- เผยแพร่เมื่อ 28 ก.ย. 2018
- In this video, the Astable Multivibrator is designed using 555 Timer.
After watching this video, you will learn the following topics.
0:23 What is Astable Multivibrator
0:50 Astable Multivibrator using 555 timer
1:18 Working of the circuit
9:08 Duty Cycle of Astable Multivibrator
13:25 Design of Astable Multivibrator with 50 % Duty Cycle
15:02 Derivation of the Timing Equations
What is Astable Multivibrator:
In Astable Multivibrator, both output states are unstable state and output continuously changes between the two states.
The main application of this astable multivibrator is in the design of relaxation oscillator.
In this video, the astable multivibrator is designed using 555 timers and the working of the circuit is also explained.
In the designed astable multivibrator circuit, the duty cycle of the output signal will be always more than 50 %. To achieve a 50 percent of a duty cycle, the modification in the circuit, as well as another alternative circuit, is also suggested.
And at the end part of the video, the equations used in the design of this astable multivibrator circuit has been derived.
This video will be helpful to all the students of science and engineering in understanding the design and working of astable multivibrator using 555 timer ic.
The more videos on 555 timer ic:
Introduction to 555 Timer :
• Introduction to 555 Ti...
555 Timer as Monostable Multivibrator:
• Monostable Multivibrat...
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The Timestamps for the different topics covered in the video:
0:23 What is Astable Multivibrator
0:50 Astable Multivibrator using 555 timer
1:18 Working of the circuit
9:08 Duty Cycle of Astable Multivibrator
13:25 Design of Astable Multivibrator with 50 % Duty Cycle
15:02 Derivation of the Timing Equations
Beautiful video with great explanation,worth watching.
Nicely explained
Tq
I liked you explanation , thanks, very helpful for beginner
Sir, according to the diagram of 555 timer, the output of the timer = Q bar. but you are saying the output will be equal to Q. Pls can you clear this ambiguity. Thank you!
Twenty minute video and still took one hr to finish with notes ,so much knowledge 👍🏻
Exactly bro
Notes banaya kya @Mohit Jangra
Can you send notes
@@veergupta4807 bhai ek saal pehle bnaye the , or aisi writing mein likhe the paper se ek din pehle ki mujhe b smjh nhi aaye paper se 5 min pehle 😂😂
@@mohitjangra323 engineer ho bhai?
Your work is much appreciated, thank you so much for making everyone pass in their semesters.
Thanks a lot bhaiya.
pure class ! i was struggling to understand astable multivibrator function. u have explained all concepts so well especially the time peroid and diode for bypassing . hats off to u sir . pls keep up the good wrk
A real masterpiece in explaining the 555 timer astable multivrator.
I watched your whole digital electronics playlist i dont think there is any better explainer on youtube but your videos are pure gem. Truly loved your work sir, keep it going.
u wont believe, today morning i was studying this topic
Great detailed explanation all the way through! thank you.
Thank you very much sir. We need more tutorial videos like this.keep it up sir! It helped a lot.
In my view the one who designed this 555 timer IC is LEGEND🔥🔥🔥🔥, Just think how difficult is to get this idea to build something wonderful..............
Much required one! Thanks a lot
You helped me alot in preparing this topic for exam... thanks Man!
Thank you so much........ each vedio of your channel has set a high standard of learning. I like this channel the most!!!
Great detailed explanation!
Thank you so much please keep uploading
thanks a lot bro, it really helps me. Carry on....
really i can just understand how the circuit works exactly . thanks man i really watch u videos more than reading text books
You are a life saver, man!!
awesome video. It would be really helpful if you upload videos of multivibrators using transistors.
Such a great explanation sir🙏
excellent and clear explanation
Really awesome explanation..👍👍
excellent explanation each and every doubt cleared
Super awesome explaination concept is soo clear
Excellent. Hats off to you.
Loving your videos
elegant explanation sir
great video, subbed!
Very well explained
i am being vibrated ,seeing your ability of explanation.thank you so much.
oh my god . This help me a lot thanks mate
fan for your explanation sir
Awesome work
Very nice video thanks a lot.....🤗
Thank you so much sir today was my electronics exam and there is one complete question about the astable multivibrator of 9 marks which I understood from you yesterday and the exam went well 🙏 now I am sure that I will pass the exam with shining marks.This happens just because of you.Thank you so much sir ❤
Good luck 👍🏻
@@ALLABOUTELECTRONICS ❤
You're videos are a lifesaver, I wish you put some effort into your english pronounciation too.
Thats an awesome on..My concepts got crystal clear.Thanks a lot
That’s epic!!!
Thanku so much sir
thanks a lot for this mate!
Thank GOD for subtitles! (just saying)...
Great session
Thank you so much
Superb explaination
Thank you sir
Really Awesome
Awsome bro
thanks andi...maa college lo untaru.,..enduko telidu
EXCELLENT
Thank you
Luv your videos... Subscribed also...
What do you do for living? I mean really. You are so good at making explanations, you should be professor.
Good job bro.
Hello sir,
Could you please explain how to select switching frequency , resistor and capacitor value previously while designing pwm controller for LED flash . Are these values depends on load wattage if is then how to select above parameters??
Perfect sir
Sir how would we go about calculating the resistor values when using a 40% duty cycle?
Sir at #5:16# u have told that the voltage at second pin is less than the ref voltage in such case the output of the comparator should be 1 ryt!!?
Same doubt........have you cleared it?
thaank you. :)
Thanks a lotttttt😘
Thank u thank u sir
By using multisim simulation, on increasing C by keeping C1=0.1uf and R1=R2=720, I am getting different values of Duty cycle (increasing). But according to duty cycle formulae, Duty cycle should be independent of C value... kindly explain
wow explanation
Thnku
Nice video☺☺☺
There is a way of calculating the frequency of an astable circuit using a chart called a nomograph and cannot find any explanation of how to do this and would love to see a video with a step by step explanation of how to use this chart.
I am having problem to understand the derivation part the beginning expression I cannot understand
The capacitor voltage part
Super sir
sir i think both the input is given to inverting terminals of the opamp , but here the second comparator input is given to non inverting terminal
I think you should have also provide notes as pdf in discription 👍, it would be useful 👍.
It would be better if you derive the expression for charging and discharging time just before computing the duty cycle results. But still great video, thanks ya man!
Thank you
I understood it clearly
During this lockdown situation your videos are life saver sir
Sir I have one doubt
While calculating t1 we took vf= vcc since capacitor is charging towards vcc but why we took VC(t) =(2/3) × vcc and during first cycle vi= 0 then why we didn't considered that case for calculating t1, sir
Because we want to find the time t at which the capacitor reaches 2/3 VCC. That's why Vc(t) = 2/3 VCC is taken.
I hope it wit clear your doubt.
@@ALLABOUTELECTRONICS yes sir, my doubt is cleared
Thank you
To calculate charging time you have to consider time taken to charge from 0 to 2Vcc/3 and time taken to charge from 0 to Vcc/3, subtract second value from first value...
If u see 11:05 the pin number 2 and 6 should be interchanged, u can verify with internal block diagram
Can you give link of video on which you explain to derive the expression of time period(for capacitor , using initial and final voltage)
Here is the link: th-cam.com/video/KylJ2v1_c-o/w-d-xo.html
Dear Aamir, I will make a video on this topic....
subtitles are not required, ur voice is very clear, sometimes because of subtitles some parts of the circuit are hidden and we face problem to understand.
If required, you can manually turn off the subtitles in the video settings.
We're can I get circuits for bistable MV using 555 timer and Op Amp..
supr sir
Your video is good, but at 5:14 you mentioned that output of 2nd comparator is 0 as reference voltage is greater than voltage at node 2, but the opposite happens.. So will u plz explain?
Actually the output driver circuit is inverting buffer. There is a tiny bubble at the beginning of the block. I should have specified that explicitly. But anyway I hope it will clear your doubt. And still if you have any doubt then please let me know here.
@@ALLABOUTELECTRONICSok I understand.. But without that if I use it normally then also I am getting desired output i.e. astable multivibratör. Is that okay? Or I have to follow this way? 1 more question i.e. Basically you are using a not gate at the output as you are taking it from Qbar instead of Q
But here in this circuit ,you have not shown it....please clear my doubt.
sir, actually I have a doubt related to this video and previous 555 timer video also. if when output Q=1
then value of Q' must be 0 because of its complimentary of output Q according to the truth table of S-R flip-flop. Sir, please clear this doubt.
Yes, that's how it works. I think if I am not wrong, you got confused because Q' is given to the output driver circuit (which is actually inverter). So, the output of the 555 timer will be Q.
I hope it will clear your doubt. If you still have any doubt then do let me know here.
You are right, when Q=1, then Q' must be 0
Sir, At pin 5,if we provide external voltage it gonna affect Ton but Toff is independent of external voltage ..why?(In diode condition)
There is no role for Pin 5 or upper comparator during discharging of the capacitor.....
At 5:17 output oof second comparator will be 1, as Vc/3 is greater (refrence) and connected to + of op amp.
👌
Is it necessary to connect the control pin to ground via capacitor? What is the role of it using here ?
The reference voltage at the upper comparator should remain 2/3 Vcc right !! (Just check at 1:46)!! If there is any fluctuation in the supply voltage then it may affect the operation of the timer. (Because the reference voltage will change because of that). This capacitor reduces any fluctuation and tries to maintain a constant voltage. I hope it will clear your doubt.
Sir how do we determine the amplitude of the square wave obtained???
Is it Vcc???
Yes, it's close to Vcc.
@@ALLABOUTELECTRONICS thanks
at time 14:57 I can see a mistake I think that formula is for t1 not for T. T has 2R2 not only R2
Yes you are right....
👌👍
u wont believe i was studying this just before the day of exam
Njanum
me too
Me just before an hour 😂😂😂😂
Please include design of astable multivibrator with less than 50% duty cycle
At 9.13 ,since t2 is the time for discharging then shouldn't there be t2=0.368×R2×C?
15:05 onward, the equation for t1 and t2 have been derived. Please go through it. You will get it.
1.can the output be considered as square wave if 50 percent duty cycle or we have to clamp below zero I am confused.
2.why can't we connect Q directly to output instead of an additional inverter.
1. Yes, Just 50% duty cycle is enough.
2. It is just to boost the output current capability. So, that it can properly drive the load connected to output.
Q equals to 1 and output is connected to the Q bar pin..then how the output is becoming high at that time?
Because the output driver circuit inverts the Q-bar output. It is actually inverting driver circuit. (that's why I have put a bubble on the left-hand side of the output block.)
Output is Q as Q' is inverted before connecting to output, or there is an inverter between Q' and output of 555
Sir make the video on v to f converter by NE/SE566
5:14 did you mean the voltage at the pin number 2 is still more than the reference voltage (1/3)Vcc . Please clear my doubt?
Yes, the voltage at pin 2 and pin 6 is less than reference voltage.
@@ALLABOUTELECTRONICS thanks sir your videos are very very helpful
@ 8:33 why we taken time period (t1) in second wave why not in first wave?
The initial output waveform is due to transient. In the steady state we will get the waveform which shown from the second wave. Thereafter, until you turn off the supply, you will get the waveform which is shown from the second wave onward. I hope, it will clear your doubt.
Around 3:31 if S=0 & R=0 how can you term it as "retains its previous state"?
thats how flip flops work
For a SR flip flop if both inputs are logic 0, output will not change, flipflp retains the previous output....
Sir can you please explain what is the requirement of C1 here????
Through pin number 5, it is possible to provide the control voltage to the timer. (other than 2/3 Vcc). When it is not in use, it can be left open. But in that case, it can pick up external noise and may override over reference voltage. To prevent that, capacitor C1 is connected. Which prevents any abrupt changes in the voltage or pick up due to external factors.
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS
Thankyou sir....now it's clear to me
..Thankyou so much
If Pin 5 is left open, there is a high possibility of noise pickup
just had a small piece of doubt, in the earlier figure u mention R2 was between pin 7 and 2(when u considered, 555 ic as a box, but when you started showing its internal parts as well, R2 is shown between pin 7 and 6 hows this possible?
If you notice, 2 and 6 are connected together.
Pin 2 and Pin 6 are shorted and R2 is connected between Pin 7 and Pin 2 or Pin 6....
One query that is do the time required for capacitor to charge about 2vcc/3 is as same as the time required to capacitor to charge Vcc
No it won't be the same. Here capacitor starts charging towards the Vcc. But as soon as it reaches 2/3 Vcc, the output of the comparator changes. So, it won't be able to go beyond that, although it was going to charge to Vcc. I hope it will clear your doubt.
Yes sir thank you
Time taken by capacitor to charge is different .... Vc = Vc(0)×Exp (-t/RC)
i don't know if you explained why C1 was used from pin 5 to ground?
If Pin 5 is kept open, there is a possibility of noise pickup at Pin 5, so C1 is used...
Sir can you please make the video on multiplexer
I will make a video on 2:1 multiplexer for you....
2:41 Sir, the animated video is showing that capacitor C is charging through R1 and R2 but you said capacitor C1 is charging through R1 and R2. Could you please clarify doubt sir .
Since the transistor acts as open circuit, so the capacitor will charge through R1 and R2 (as shown in the video). I hope, it will clear your doubt.
@@ALLABOUTELECTRONICS capacitor C is charging right sir.
Yes, it is charging through R1 and R2.
Yeah