Introduction to 555 Timer: The Internal Block Diagram and the Pin Diagram Explained
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- เผยแพร่เมื่อ 6 ก.พ. 2025
- In this video, the brief introduction to the 555 Timer IC has been given and the pin diagram (of 8 pin DIP 555 IC) and the internal block diagram of the 555 timer have been explained.
By watching this video you will learn the following topics:
0:20 Introduction and Application of 555 timer IC
0:50 Pin Diagram of 555 Timer IC
1:06 Internal Block Diagram of 555 Timer
1:48 Brief description of 8 Pins and basic working of the internal blocks of 555 timer
what is 555 Timer IC?
The 555 timer IC is a very popular timer IC and it is widely used in many timing related applications.
It can be used as an oscillator, LED Flasher, tone generator, Frequency division, and timing delay generation.
The 555 timer IC is available in many packages but most popular is 8 pin DIP (Dual Inline Package).
The following is the list of the individual pin of 555 timer IC.
1. Ground
2. Trigger
3. Output
4. Reset
5. Control
6. Threshold
7. Discharge
8. Vcc
In this video, the brief description of each pin is given.
If you see the internal block diagram of 555 timer IC then it consists of the following parts.
1. Voltage Divider Circuit
2. Comparator
3. SR Flip-Flop
4. Discharge Circuit
5. Output Driver Circuit
In this video, the function of each block is explained in detail.
By connecting the external resistors and capacitor to the different pin of this 555 timer IC, it can be configured as either Astable, Monostable or Bistable Multivibrator and can be used in wide range of timing related applications.
This video will be helpful to all the students of science and engineering in understanding the basic working of 555 timer IC.
#555Timer
#PinDiagram
#InternalBlockDiagram
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The timestamps for the different topics covered in the video:
0:20 Introduction and Application of 555 timer IC
0:50 Pin Diagram of 555 Timer IC
1:06 Internal Block Diagram of 555 Timer
1:48 Brief description of 8 Pins and basic working of the internal blocks of 555 timer
ok sir output block inverts the output.Awesome sir ,my bad .
Yeah MAN you got it right the OUTPUT block is actually a not gate..
10min video=10hr of reading about 555 timer...Very useful👌
These videos are like NCERT books. Every sentence is crucial and important to note. Otherwise, you will be lost. Loved it.
You're cringe
Great work.The concepts are explained in a lucid manner and provide in-depth conceptual clarity of the subject.Hats off buddy !!!!!
Can you also make such videos on microprocessor as it will be helpful for us.
Thank you so much for such a useful class....🎉
THANK YOU SO SO MUCH FOR HELPING TO STUDY FOR EXAMS !!!!
Wait it is for which exam
@@executorarktanis2323 diploma
@@executorarktanis2323 integrated circuits BTech
What exam
Excellent. Much better than the book I was consulting.
literally the best explanation.
Love u brother u cleared most of my confusions of my electronics course keep it up ❤️
U explained in a clean manner thank u so much
Thank you so much, your explaination is clear and right to the point.
अत्यंत प्रभावशाली।।। best video to explain 555 bro... Keep up the spirit high...
Yes you are right.....
Thank you sir this video made 555 timer very easy to understand
Great Job Brother 👌 you give us lot's of information which not give by our school/college. Excellent 👌🔥
Excellent video sir,
it would be great if you could enlarge the size of the cursor as it is very difficult to identify different blocks while you explain them
You are a God! You totally saved me!
average hindu
Amazing teaching. Thank you so much. :D
better than VIT teachers lol
@@lemonspatula2545is vit means vit vellore
am i right bro
Thanks, you are great teacher.
Awesome sir awesome 😊😊😊😊
Helped a lot sir THANK U Very much
Superb explanation bro
Thank you sir... Your videos are so helpful ... 💖
Great Sir, I am thankful
Very good explain...
Thanks 😍
sir tq somch I cleared my doubt
sir the output of ic 555 is taken from Q bar instead of Q .
As usual....great one..thanks sir
great job sir!!
Sir, you said that when the flip flop resets due to the high output from upper comparator, the output of timer is zero. But in diagram, the output is connected to Q'. So shouldn't the output be 1 at that time?
Okay sir, I got the reason. Isn't it because the output circuit is inverting? You said it later in the video 😅
Sir, the video is excellent. I loved it a lot from the signature tune all about electronics 😍
Wouldn't it just make sense to tie Q to the output rather than having to waste an inverter?
Same doubt I have
I did not understand how can Q' is high when the output us high
@@JayDubb410 i guess we are using an inverter usually a bjt amplifier circuit so that we are capable of driving a load
Sir, is this ic 555 timer analog or digital?
Please answer...
The output of the IC is analog.
Really great explanation 💔💔💔
excellent explanation brother..!!!..thanks a lot...
Sir plzzz do vedios on 555 timer as early as possible please sir😊😊
What happen if we don't connect pin no. 4 to pin no. 8 when pin no. 4 is not in use . . . . . . ???
bro great work! your explanation is really fantastic.
Excelent .... No words to say
Clear explanation sir
The transistor connected at Q bar of flip-flop should be PNP or NPN TRANSISTOR should be connected to Q of flip-flop
The diagram is incorrect sir. The output buffer is connected to Q, not Q' as shown in the video.
Please correct it.
bro if u connect to q u will hv to use inverter so meaning is same
@@ytstudy7007 please see 9:17 - 9:25 🙂
The output circuit is basically an inverter circuit. So since Q' is connected to the output, it will get inverted and we will ultimately get Q at pin no. 3
Tqs for ur video I'm cleared of my doubt
Here , when Q is zero u r saying output is zero but output is connected with Q bar so output should be 1.
There is a bubble at the output side, so the output is getting inverted after that. ( I should have specified that in the video though ). That's why Q' is applied. I hope, it will clear your doubt.
@@ALLABOUTELECTRONICS ok , thank u for clearing doubt .
sir, Can you say why we are using 555 timer ic instead of using opamp for astable & monostable multivibrators. Any specific advantage of using 555timer ic
Superb explanation sir☺Tq
shouldn"t it be a sr latch rather than a flip flop as we are not using a clock signal here?? I might be wrong tho
It's clear explanation.
If this 555 ic support only 15 volts, which ic need to be used for 230 volts energy in our real time scenario? Can you suggest?
The relay can be used at low frequencies with line voltage. And high voltage MOSFET switches are also available, which can be used at high voltages.
555 can be supplied with upto a max of 18V DC. You should use a rectifier to use it with AC....
I need to buy PWM for hydrogen production. Hydrogen unit need 220volt
2500watt. I have 220volt inverter. Which PWM should I selected
Thank you sir
I have a doubt on the voltage divider part
In the 1st node which is connected to the iverting terminal of the 1st opamp would be (Vcc/3) inspite of (2Vcc/3)
If you observe, at the inverting node, two resistors (R+R) are connected in series. So, the voltage at the inverting node would be (R+R)*V / (2R +R) = 2/3 Vcc.
Voltage drop across the resistor is only1/3vcc . So reduce vcc with 1/3vcc you will get 2/3 vcc is the voltage at the node
Plz tell me apnay yeh potential divider wala formula kesay derive kiya hy plz karkay bata dein yeh 2R kesay aya?
So sir we need to keep +Vsat and -Vsat of the two op amps as +1V and 0V respectively right
No, actually I was referring to the logic levels. Logic "1' And logic '0'. In 555 timer, the comparators are biased internally. We only need to apply the supply voltage to the Vcc pin.
@@ALLABOUTELECTRONICS ok sir ok sir
Thank you
@@ALLABOUTELECTRONICS oh sir so the Logic High is +Vsat and Logic LOW is -Vsat
So sir what are its typical/normal valies
Thank you
No, that is not right....
Sir
Is it true or a misnomer that the three voltage divider resistors are 5k Ohm thus the name 555 IC timer
Thank you
No, the name was chosen arbitrarily.
@@ALLABOUTELECTRONICS 👍
sir i can become an engineer just bu listen to this video
I have a question: at 7:07, the output is connected to Qbar, so i deem the output should be 1. Chould you please tell me where i am going wrong?
The Q bar is connected to the output driver circuit, which is the inverting circuit. That's why the output is 1.
I hope it will clear your doubt.
Oh ,yes. Thank you!@@ALLABOUTELECTRONICS
I too got this doubt... Thanks!!
at time 7.45 to 7.50 you say output of flip flop =0 (Q=0,Q'=1),because of this output of 555 timer is also =0 but the output of 555 timer connect to Q'.i did not understand here.
actually here the output stage is inverter. That is why Q' is connected to the output state. But I should have mentioned that explicitly. I hope, it will clear your doubt.
@@ALLABOUTELECTRONICS Thank you so much
While explaining the flip flop circuit you have considered the output as general circuit but when you are explaining discharge circuit you said it's an inverting circuit
What should we consider
can you upload a video about 74193 counter IC
Suggestion: use overlap symbol in your diagram else it's quite confusing.
@6:15
U mean
Trigger vlg=to Vcc vlg
Now Vcc vlg is which vlg (supply vlg (pin no 8) or reference (1/3Vcc) vlg )
Voltage at Pin 8
Nice video....keep on
Does it matter with numberings
When reset pin goes high then the output should be zero sir ?
please explain this to me sir and aslo the discharging part
@@neerajhebbar7313 When Reset pin is low then the output of the 555 timer will become zero (Because it is Reset -bar ). So, whenever it is zero, it functions and makes the output of the 555 timer zero.
For the discharge pin please check the video on astable and multivibrator using 555 timer. I have explained there in detail.
Here is the link:
th-cam.com/video/iJYm_BGqa1A/w-d-xo.html
And after that, if you have any doubt then do let me know here.
@@ALLABOUTELECTRONICS Thank you so much sir i am your student from 2 years and your teaching skill are great i wish i could get a sir like you next sem and sir thanxx for the quick response
@@ALLABOUTELECTRONICS So is it compliment of reset right so it makes out put of the 555 timer ic to zero if m ryt jst give it a like sir and thank you once again
Hi,
I need a circuit that every trigger can discharge capacitor. So whenever a new trigger the timing will reset, and output willl only off if after delay time no trigger anymore.
Is it possible ? And how to achieve this
What do you do sir?
Working or Student?
Can I contact you with a question where I think I can use a couple of 555 timer circuits? I used to work with 555 timers many years ago but have forgotten a lot about them now. I have a one-off situation where I think two 555 timers will work for me but I don't want to go through the whole theoretical refresh process again. I just want a circuit I can build.
You can contact me on either facebook or Instagram.
The link is given in the descreption of the video.
Bro how the time was delayed by changing input voltages can u explain me
Please go through the monostable multivibrator using 555 timer video, you will get it.
Here is the link: th-cam.com/video/ypV6gdIJJU4/w-d-xo.html
I want to build a ckt dat get triggered by sensor and high for 10 sec for indicator within dat time another push button get signal and after pressing push button another 45 sec the solenoid valve get activated.
How I can achieve this?
Pls help on this
You can use 555 timer as monostable multivibrator. The sensor output will act act as a trigger for monostable.
You can select the RC time constant to get 10s of time. Similarly you can also generate the trigger signal corresponding to push button and can give it to another monostable.
At the output of the monostable, you can connect the solenoid.
I hope it will help you.
Is my assumption that Q bar is high whenever Q and/or output pin is low, correct?
Yes, Q and Q bar will be always the opposite. And in 555 timer, the output of the Q bar is given to the output driver circuit, which is once again inverting circuit. So, the output will be opposite to Q bar.
Exactly.....
without clock how does flip flop works there sir
please clarify my doubt sir, I have a presentation tomorrow
Technically, here it is a SR latch. But in general there are called Flip-Flop. ( Both latch and Flip-Flop). And that's why you must have heard some people are using the word, clocked flip- flop. But I hope, you got the point. If you still have any doubt then let me know here. Good luck for presentation 👍🏻
@@ALLABOUTELECTRONICS I have got your point
Thank you for replying
How 2R is written in potential divider formula on 1st comparator
There are three resistors. And comparators are assumed to be ideal. So, using the voltage divider, the voltage across the node is found. See, the voltage at that node is the voltage across the two resistors. If the current flowing the resistors is I, then voltage at that node is I * 2R. And current I is Vcc / (R + R + R).
That means voltage at that node is 2R* Vcc / 3R = 2/3 Vcc. I hope, it will clear your doubt.
How 2 voltage can be supplied at the same pin in threshold pin?? Please explain. Would not spark come out at this point??
Actually, there is only one supply to the threshold pin. I think what you understood is 1/3Vcc pin and trigger pin are connected right. But actually, they are not. (see, there is no small blue dot, which indicates the connection of two wires)
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS ok thanks for replying.
Another......how value of control pin is made higher than the threshold pin while the 2/3Vcc remains connected to negative of comparator?? Does it mean when control is made higher, the 2/3Vcc remain disconnected?? Awaiting solutions again. Thanks.
@@tnamen1307 If you look at the internal digram, the 2/3Vcc is provided to the comparator using voltage divider right !!
And the control pin is directly connected to the inverting terminal of the comparator. Or just after the first resistor.
So, whatever voltage is applied at the control pin, the same voltage will appear as a reference for the comparator. Again here 2/3Vcc voltage is applied using a voltage divider, so KVL will not get violated even if we apply the control voltage to the same node. (As there is a resistor between the Vcc and control pin).
It would have been violated if the 2/3Vcc voltage is directly applied to the comparator from the supply (instead of using a voltage divider)
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS okok very clear explanation. I need to recall my concepts on KVL!!! THANK. Sir!!!!
i still cant understand why this ic called timer?
Top 10 unsolved mysteries of all time
I think maybe you'll find the answer in the astable and monostable multivibrator videos.
You can change the output after a predefined time ....
sir you explained bjt as switch using capacitor is it just for explaining or capacitor is connected to it. I'm confused.
While designing the circuit using 555 timer, the capacitor is connected externally to 555 timer. And this discharge pin provides the discharge path through this transistor.
I recommend you to watch the other videos on 555 timer (Astable and Monostable Multivibrator using 555 timer) in which the external capacitor is connected to the 555 timer.
th-cam.com/video/iJYm_BGqa1A/w-d-xo.html
Good my doubt is gone 👍
How to generate difference number of pluses using ic 555 and ic 4017 ?
9:34 how did you take Q' as 1 when your are saying output is zero at that moment
Because the output block shown in the diagram is the inverting buffer.
@@ALLABOUTELECTRONICS i got it thanks man
Thank you,sir
are u who i think you are
@@CooperStation01please elaborate
@@rahulanand3099 nah nevermind, thought I knew you
Sir u can make this video in 15 or 16 minutes so that we can understand it easily
You can go through my videos....
Sir what about Q bar in 3rd block
In SR flip flop isn't S connected to Q and not Q'?
Are you referring to the block diagram of SR flip-flop shown in the internal block diagram?
@@ALLABOUTELECTRONICS yes
@ursula das
No. R is always connected to Q. But when we make the diagram of flip flop using 2 nand gate, internally, S' is connected to Q and R' is connected to Q', and when we implement the circuit using 4 nand gates in which S' and R' are changed to S and R with a not gate in the front, which results in S connected to Q and R connected to Q'. Try drawing a diagram with the explanation given. You may understand.
It's a block diagram so connection from input to out are not shown. But he gave us the truth table and that is how it works. When s=1 r=0 Q is high, Q not is low and visa versa.
Output is NOT(inverse) of Q or Q' ??
FM Demodulation with 555 possible?
Well explained
since the output is taken from Qbar ,why it is not opposit of Q.??
in video 6.58 and 7.51 time
Q bar is given to the output driver circuit, which is inverting driver.
That means if Q bar is 1 then the output of the output driver will be 1.
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS thanks
Why to discharge the capacitors when the output is in low state?!
Capacitor is connected in such a way that it discharges when Q=0
Good
EXCELLENT
I wish you create a similar video for op amp
LM555 SOP-8 Timer IC and NE555N Timer IC between two of them what are the difference
LM 555 is a low power version. (CMOS version)
Somehow I missed that the output stage is inverting?
Also, a small thing (pun), your cursor is so small that it's very difficult to follow...
Block diagram acche se dikayi nahi de rahi.. scrn par typing ki wajah se....
Can upload designing of multivibrator
I have already uploaded a few videos on how to design astable and monostable multivibrator using the op-amp.
Very soon I am going to upload more videos on the design of these multivibrators using 555 timers.
Sire its a year now........ You're yet to
Sir.thank you
I see many tutorial, Web even book to learn 555 Timer IC, All of them frustrated me,
Now I got the clear picture, (Thanks dude)
I more question what about comparator's - and + sign means ?
Hope you will replay to me.
The comparator has two terminals. Inverting (-) and non-inverting (+).
When the voltage at the + terminal is more than - terminal, then output of the comparator will be high. Similarly, when the voltage at the negative terminal is more than + terminal, the output will be low.
For more info, you can check my video on comparator.
Here is the link: th-cam.com/video/k9zQjEaKtfk/w-d-xo.html
How can it be when Q is 1, Q’ is also 1 ? Q’ isn’t Q(t+1) sir.
No, Q' will be zero. But the output driving circuit is inverting circuit. So, the output of the timer will be 1. I think I should have specified that the output driving circuit is inverting driver circuit.
Anyway, I hope it will clear your doubt.
Sir why you take Q as a output why not the Q'
Q' is given to the output driver circuit. (The output driver circuit is inverting circuit). So, the output of 555 is the same as Q.
I hope it will clear your doubt.
IF you still have any doubt, let me know here.
@@ALLABOUTELECTRONICS kk sir
@@ALLABOUTELECTRONICS sir is we also use transistor at rest pin?
time period expression for the output wave?
Please check the entire playlist on oscillator and Multivibrator. I have made seperate videos on how to design a Monostable, astable Multivibrator using 555 timers with equations.
Three together means something as named it.
ty
"I still don't get the idea of using a bubble at the output side... Wouldn't it be easier if you hadn't used the bubble at the output?"
It would have been, but in the actual IC, that is how it is implemented.
Please explain about Hamming code generator
please explain the function of pin 4,5 and 7....its not clear
Pin no- 4: Reset pin is for simply to reset the output.
Pin no - 5: Control pin is used when you want to provide some other reference voltage to two comparators. (Generally, the reference voltage is 2/3Vcc and 1/3Vcc)
Pin no-7: Discharge pin is used to discharge the external capacitor.
For more info about the pins, please check the video on astable and monostable multivibrator using 555 timer.
Where in detail I have discussed the use of these pins.
Here is the link:
Astable Multivibrator using 555 timer
th-cam.com/video/iJYm_BGqa1A/w-d-xo.html
Monostable Multivibrator using 555 Timer
th-cam.com/video/ypV6gdIJJU4/w-d-xo.html
@@ALLABOUTELECTRONICS thank you sir...grt work