Cascading 555 Timers for Custom Blinking LEDs

[@timbodemi]

I am not an electrical engineer and just starting to meddle in electronics. Your videos are so logical, clear, and not overly repetitious that even I can follow them. Thank you so much!

[@jassheen5318]

I'm making a model of the A380 strobe lights and accidentally discovered that you could use the output signal from another 555 timer along with a diode and 10K resistor attached to pin 2/6 (negative end towards pin 2/6) of the LED timers to regulate whether or not the LEDs turn on for a certain number of times and then off. In this case I needed a timer for the strobes on the wing tips to blink twice @ 50ms and the red anti collision lights to blink once at 50ms. If i turn the chips on and off with transistors the timing in the signal was noticeably longer than 50ms on the first pulse before it settled into its normal width. Interrupting pins 2 and 6 with the signal from another 555 timer to regulate it (used your diode design to adjust the duty cycle) eliminated this pulse width problem. Total amateur here and not a math wiz but just wondered what your thoughts were on this.

[@samrjack]

I liked the video, but I would have enjoyed a heads up for this circuit earlier in the week so that I could contemplate and implement my own solution before watching yours. Is there anywhere/anyway to be notified about interesting circuits like this before the video is out?

[@fredblogs1931]

Would this circuit still work if you removed one set of led’s and 555? I need to make some led’s flash twice then pause but only one set of led’s, not alternate between two sets.

[@toGodbdaglory]

Love your videos on the 555 timers, you explain it all very well. Do you have a video on transistors and how to use them?

[@Skinnyrd]

Thanks for watching! I don't currently have a video on transmitters but I started looking into it before I took a break last year. I'll have to revisit the idea.

[@jhanthony2]

Thanks! That was so clear and logical. I never understood how to use a PNP transistor until I watched this.

[@lucasfalcon4079]

I'm pretty sure you could do this with only 2 ICs. For example have 1 555 with a period of 3s controlling where the output of a second 555 goes using two transistors. On one of the transistors the controlsignal from the 1st 555 should be inverted. And also, to keep the timing, the signal from the 1st 555 could pulse trigger reset on the 2nd. I'll challenge myselfe to do this

[@VoidHalo]

Great video. Cascading 2 monostable 555s was one of the first "puzzles" I ever tackled in electronics when I started 6 months ago. I'm currently trying to design a circuit that would blink one LED once, wait, then blink another LED once, then wait, and repeat using 555s and perhaps some logic chips if need be. I can totally relate to not being able to get an idea for a circuit out of your head until you work it out. Cheers.

[@christianwiksten4874]

great project , how do u add a fade effect instead of blinking , and with adjustable speed controller?

[@remintroy]

Can you create a circuit with exactly this function with npn transistors ???

[@kevfrets]

Just what I was looking for! Excellent tutorial and explanations. I’m going try this for myself. Thanks.👍👍 Looking forward to seeing more .

[@markwhitehouse86]

Jason, thanks very much for the informative videos on the 555, including all the math explanations in several of the videos. Just one confusion spot for me is that in the comments of one video you reply that the capacitor at pin 5 should be 0.022uF, in another you state 0.01uF. I have checked the Datasheet from Texas Instruments on the 555 and the Datasheet suggests 0.1uF. While I bow to your vastly superior knowledge, especially in the math department, I have been using the 0.1uF capacitor as stated in the Datasheet, but was wondering why you indicated 0.022uF or 0.01uF in different comment sections?

[@michaelgray8338]

Great lesson. Is there any way to get the full curcuit diagram. I am stuck on how to connect the rest of the circuit fully.

[@Skinnyrd]

The output circuit of the other two 555 timers are constructed by the same method shown here: kzbin.info/www/bejne/mqbOi5-ph9R2gNEm6s

[@michaelosmon]

If I wanted to use a trigger to activate and limit the cycles in this circuit, I could add another 555 in monostable mode and set the timing for the time it takes for the number of cycles I want, and connect pin 3 of new 555 to pin 8 of the first one in your drawing right?

[@noysantia2510]

very nice video. i have learned a lot. i have question instead of putting a led can i put a power mosfet to drive a tank ciruit that resonates at 30khz? or drives a zvs circuits? hoping for yr reply thanks

[@iwasai4606]

Very good video, your explanation is so good! thanks!

[@andrewferg8737]

Love your videos! Alternative scheme would be 2 monostable triggers connected to your carrier; one set high & one set low. Don't really like sinking too much current through the 555.

[@barbasbandas6665]

Nice circuit! What about pins 2, 4 and 5? Did you connect them like your video "How 555 timer works"? Thanks

[@4shellma]

navigation system is not: "one set of LEDs blinking twice and then other set of LEDs blinking twice". they are actually flashing twice (or 3 times?), gap 1.5 second and flash again. can you shorten the time in between "blinks" to do double flash, 1.5 second gap and the double flash again; and further on

[@mikelee1906]

I saw a video a while back of 3 rows of LED "chasers". 3 rows of LEDs consisting of 10 LEDs in each row each moving only from left to right . When reaching the 10th one starting again on the left side.The middle row moved across at half the speed as the top row and the bottom at half the speed of the middle row.They were all in sync. Any ideas of how this would be accomplished. Three 4017 decade counters maybe? With a 555 as a clock, Use pin 12 carryout to the input of the next one?

[@JustFun-iz9rf]

Thank you I was looking for the LED to be on for a short period of time and off longer. If I try this idea maybe I can make it work. 👍🏼

[@SkillWill22]

Great video! I would like to see the other ways of making this possible. Because I don't know much (more like anything) about microprocessors. Since I really enjoy your videos and like the way you explain things it would be awesome to hear from you how that would work. Thank you for your time

[@arunlal2104]

Hello Jason! I am really thankful to you for this series of informational videos regarding 555. I am trying to implement same kind of application in one of my project, and this video helped me alot to understand the working of 555 Timer. After watching them, I am now able to think out of the box and thinking to add some more features to my application. I have a question, I want to make single LED blink at two different frequency, lets say, 1 Hz and 2 Hz without the additional circuitory. So, do you think it is possible? Thanks

[@Skinnyrd]

I'm glad you found the series helpful. I'm not really sure what you mean be two different frequencies. Do you mean that you want the LED to blink with two different periods (a slow blink and then a faster blink repeating)? If so, you can sometimes feed voltage in on the control pin (pin 5) to change the frequency just slightly whenever you want.

[@jamykowshik]

Very informative and Understanding Circuit making... Thanks a lot !!!

[@ashwinshetty1961]

A really nice video on 555 timer ic application.may i know what kind of transistor did you use.will a bc 547 bjt suffice for this experiment

[@Skinnyrd]

Thanks. The BC 547 should work.

[@hopcounter]

Question, you appears to have connected pin 5 on each to GND with what appears to be a capacitor, is that correct? also Pins 2 are connected to pin 6, but are not in the diagram, is that always a given for 555 timers?

[@RandyFromBBlock]

Nice tutorial. Thank you. How did you know to put a 10K resistor between the 1st 555 output and the NPN base ?

[@Skinnyrd]

+Randy Gast I knew it needed something to limited the current being pulled, so I looked at some other schematics online and 10k seemed to be the magic number.

[@hamradiomanoz9448]

really cool. like the way you group breadboards together must try this

[@jimmyjohnny3779]

Nice video. Would this circuit be considered “intermediate” or “beginners” electronics?

[@fench1234567]

There's sort of no such thing as beginner or intermediate electronics. It's all math from the ground up. The lights, motors, and audio are just for show. There are approximate math formulas that are easy for anyone to use, and there are precise calculus ones. These formulas show how every component in the HUGE list behaves when you power it. As for where to actually begin? Just pick what topics you can find that interest you and run with them. It will be a LONG run to learn everything that industry has researched and developed in so many years.

[@starcitizenmodding4436]

How could i make a circuit that cycles leds in a row just by repeatedly pressing a single button. so one light is lit, press the button the next lights up and the previous goes out. and so on?

[@amrosama5417]

Nice Video , but i have a question which p-n-p transistor did u use

[@Skinnyrd]

Thanks! I used a 2N3906 transistor.

[@octaviob6078]

HI, great und usefull stuff, i´m starting in electronics, but i have more experience in clay sculpting, recently someone ask me to make a serie of some specific lighthouses. but the particular light characterisics of each one are tricky, for example, i need a 1 second blink followed of 6.5 second obscure ( 1sFL- period 7.4sec), other needs a serie of 1 flash of 1 second of duration following of two second obscure period, two flashes, and a 5 second obscure (1sFL, 1s obs, 2sFL, period 10 sec). how can i do?

[@herminigildojakosalem8664]

I would have loved for you to have shown the waveforms in a graph? (i.e the 2.8 sec. waveform in its time relation WRT the 1.5 sec. pulses waveform if you get what I mean.

[@amrosama5417]

thanks to quick answer i want to do this project in my college , did you have the circuit diagram or draw for this circuit thanks alot for your help and amizing work

[@Skinnyrd]

The circuit is drawn before you in the video. Is there a specific thing you need?

[@amrosama5417]

is the value of resistance 10k , 220k and two capacitor 10UF in the first 555 timer and other two 555 timers the same value of resistace and one capacitor 10UF(pin5) , 1UF(pin 6) Is this right ? and which NPN trasistor did you use with LED

[@Skinnyrd]

On the second set of 555 timers, pin 5 has a 0.022µF cap and pin 6 is as you say. I think the NPN is a 2N3904.

[@dergrunepunkt]

I'm totally noob to electronics, so bare with me if my question does not makes sense, but wouldn't be possible to use two 555 instead of 3?, one 555 that just blink the LEDs and one that switches between the two groups by changing the ground?

[@tkturbo_jsps]

Can this be done using Q and not-Q? This eliminates both transistors and the diode.

[@tobes9074]

Great video Jason! I feel it may have been helpful for some if you rearranged the formula to derive your Ra, Rb and C values. Or perhaps say your resistor values and then calculate the Cap value needed. Thanks!

[@Skinnyrd]

Thanks for the input. I'll try to do more examples in the future.

[@mattp9361]

Thumbs up for no music. Great explanation

[@patjosullivan1]

Can the 555 timer drive 4x Jumbo LED (for lighthouse project - slow rotating light) Would you have a circuit diagram? Thanking you in advance.

[@Ilaxffxi]

Is there a reason to have 2x 10k instead of 1x 10k and just connect base + diode together sharing the same 10k resistor?

[@wry468]

can i use this circuit to feed two cctv cameras to a recorder using 1 line?

[@loganpaul31]

Are the V (forward) and the I (forward) of the led important to determine the value of the other components ?

[@Skinnyrd]

Yes, it is. I made a video about it -> kzbin.info/www/bejne/jmicY3WrYtyirK8

[@laurentstrodiot8434]

Hi there, I really liked the video, I am learning a lot just watching it. One question: do you think you could do something similar with the exit of the pin 3 of the first 555 connected to a 4017 connecting the 5 first outputs of the 4017 to blink the first series of leds and the 5 other outputs to the other series of leds ? Thanks anyway for your videos.

[@Skinnyrd]

In what manner would you like them to blink? Do you want the first series to all blink at the same time and then the second series all turn on when the first series goes out?

[@laurentstrodiot8434]

Hi there, I though we could have the same blink patern as the one you describe in your video. I think it is possible to use the 555 in astable mode with output connected to the clock pin of the 4017. Use Q0 and Q3 as output connected to your first NPN transistor to command your leds of the first series and the Q7 and Q9 as outputs connected to another NPN transistor to command the second led series. You should have the first led series to blink twice, then the second one blink twice. What do you think ? would it work ? Thanks for your great video.

[@Skinnyrd]

Every output of the 4017 has a different frequency so the first series would just blink at a faster rate than the second series.

[@laurentstrodiot8434]

Hi there, I have found what I was looking for, kind of police lights: kzbin.info/www/bejne/qJ7KYoyvgL2eqNU. Thanks for your answers.

[@jj74qformerlyjailbreak3]

How many timers would I need to split a 16v source into 12 2v outputs?

[@ashwinshetty1961]

Just had one question can a 555 timer ic be used as a mosfet driver and if not are there any alternatives for a mosfet driver

[@Skinnyrd]

You could use the 555 as a MOSFET driver.

[@bitsurfer0101]

How would you create a circuit where the LED gradually turns on/off?

[@wr30025728]

This was interesting. I would like to figure out how to have a group of LEDs, in a star pattern, randomly blink (or strobe flash). One larger LED in the center (5mm white) and 5 smaller LEDs (3mm white) on each point of the star. I do not wish to use Arduino, just electronic components. 555 timers? It'd be interesting to have a field of these stars (50) that would randomly strobe while each LED in each star was doing it's thing. Creates a "twinkling" effect, in the mental image I have. I am the consummate novice, so definitely need help figuring this out. For all I know, I know nothing. Is this idea even possible? Also, here's part of my "novice", why would I choose a 4.7 µF or 47 µF or 470 µF or some other µF value electrolytic capacitor? I understand, I think, why I would choose a particular voltage of capacitor. When and why would I choose a ceramic capacitor? I built a kit that had a .1 µF round ceramic? capacitor in it. It was orange and had 104 stamped on it. I know that is it's capacitance - 10 0000. Works out to .1 µF. Last, how about transistors. There are a blue million options. Why a 2N3904 or a 2N2222 or some other NPN or PNP transistor? I have gathered they have characteristics like how much voltage and amperage they can handle, so that would certainly help in deciding. Is there a comprehensive list showing transistors (or caps or whatever) and their specs dumbed down so even this caveman can do it? I am sure I will have more questions. Thank you, in advance, for your reply.

[@GaryGrimley]

Great videos... I am not schooled in electronics, but learning. I am looking for a good video on how to strobe a low powered led - for tail marker on my RC Plane. I just successfully hacked servo board (from a servo with a striped gear) and tied it to a N channel mosfet (sp) to control the 10 W led landing light. Can you help. Gary

[@zainaabdin]

Though I am late but two 555 are enough and two transistors are connecting the leds to ground subsequently instead of supplying the timers

[@ateeqahmed6873]

i just came across your video , and it really helped me alot ,thank you for that . plus a question ,, is there any version of 555 timer that could be used with high voltages like 220 v or any alternative of 555 timer ?

[@Skinnyrd]

I'm glad the video helped. I've never heard of a 555 timer that could handle that large of a voltage.

[@ateeqahmed6873]

yeah there is non , but i figured out something else, i used a 9 v relay instead which really didn't worked somehow . you ever controlled the switching of a relay using 555 , if yes please help me out with that . i gotta submit my project by thursday . thanks again

[@abdelrahmangamalmahdy]

You made my day! I watched all your 555 timer videos :)

[@samuelcarpenter4576]

Where are you from? I grew up around the South Georgia accent and I can't quite pin you down. North Alabama, maybe? Thanks for the great tutorial.

[@Skinnyrd]

Grew up in Georgia and moved around a bit after college.

[@ShekaranJagadeesan]

Can you simplify the circuit for a chaser light (the in-line one) with more than 10 LED's... Your content is very subtle, loved it 👍

[@harrysingh4929]

how can you make it flash really really fast ?? like in construction vehicle lights.

[@daily-learning-with-me]

sir please describe the working of pnp , npn transister and diode little more ..thanks!

[@vjnarayan8416]

what are the other capacitors used in the circuit video not clear enough

[@Skinnyrd]

The second stage of 555 timers used 1uF for the timing capacitor.

[@vjnarayan8416]

what are all values of all capacitors used . thank

[@Skinnyrd]

The first stage timing capacitor is 10µF and every capacitor connected to pin 5 on a 555 timer chip is 0.022µF

[@TheAMFT]

Can you make a video better explaining the math associated with picking components? I have attempted to plug in values to the formula but I am not sure that I am formatting the numbers correctly.

[@Skinnyrd]

+Aaron Thomas Sounds like a great idea! I'll add it to my list of videos on my wall. At the moment I'm just finishing up some other things for my business but everyone been giving me some really good video ideas. I'll make sure this one gets some attention before long. Thanks for the comment!

[@jaypepper7029]

can you provide the complete schematic diagram, please i'd like to make it for my project. thank you

[@cotton4570]

First time viewer. Great videos! How about throwing in a 556?

[@Skinnyrd]

Sure. I'll add it to the list.

[@sharojalhasan7852]

Dear Can u please help me ? i want a timer circuit wich can Relay On for 10 seconds and turn OFF the relay 10 seconds it will happen contineusly When battery is connected

[@whateverittakes9000]

Hey how can I correctly depict the value of resistor required for the LED ?? Thanks in advance

[@30041983TCM]

It depends on the intensity of the current you want to run the LED on: R=U/I U= source voltage minus LED voltage. Ex.: Source 5V, Red LED 1.8V @ 10mA R=(5-1.8)/0.010 R= 320 Ohm for 10mA at 5V supply

[@emmanuelpenn1652]

Great video,but I do agree that using the 555 with the 4017 is a lot simpler. Again,great video.

[@Skinnyrd]

+emmanuel penn Glad you liked the video! No doubt the 4017 would be a little easier. I'm using a 4024 right now on an ultrasonic circuit and it's dead simple to use.

[@Inquire98]

"They You", thank you very much. That was very instructional...

[@Skinnyrd]

+Inquire98 Thanks!

[@andyfairman7812]

Fantastic video series! Keep up the great work! :)

[@Skinnyrd]

Thanks! Glad you enjoyed them.

[@ArunKumar-fm7yl]

cool videos on 555 timer! Explanatory and informative...

[@SeanHickeyMarineServices]

Can people hire you for modeling projects involving blinking lights?

[@MrKillanthony]

could you use a 556 for this project?

[@Skinnyrd]

+MrKillanthony There's a chance you could. I had a guy show me this (goo.gl/O5b2hD) circuit to do a similar thing. That particular way of blinking the lights could be done on a 556 if the circuit works at all. I haven't tried it yet, so I'm not sure.

[@Inquire98]

Hello, I have a challenge for you. I'd like to see you, repeat this project, with a IC 558 timer. I tried and got "lost". So let me know. I look forward to hearing from you... Thank you

[@Willam_J]

Inquire98 - It can't be done with a 558 timer because all four timers are powered by the same source. In his circuit, he's turning the power to the individual timers on and off. Not possible when they all have the same power source.

[@Inquire98]

Okay, what about some kind of power subsystem, to control the power and current to each 558 timer. Let me know...

[@petec6690]

At 15:14 the three lower LED"s blink four times, not two.

[@adamdavey6102]

which transistors did u use

[@Skinnyrd]

I used a 2n3904 for this video.

[@mrifixplanes1813]

what about the pnp please

[@Willam_J]

MrIfixplanes - 2N3906 is the complimentary PNP transistor to the 2N3904.

[@mrifixplanes1813]

Thanks!

[@rccanuck4473]

Perfect. Thank you very much your a genius I built one with a 4017 but going to do yours on my next RC build. I will let you know when it's done and post it on my rc Canuck you tube channel Once again thanks and I hope I didn't hurt your brain too much

[@Skinnyrd]

+RC Canuck I posted this same video to reddit and one of the comments mentioned a simpler solution: www.reddit.com/r/electronics/comments/3nendd/made_a_video_from_a_question_in_comments_about/ I am not sure if this works well in reality. I have not tried it on a breadboard yet, but it might be worth a look. Thanks again for the interesting project!

[@rccanuck4473]

like yours better

[@johnhenry3255]

What is the voltage of the transistor

[@Skinnyrd]

To which voltage level are you referring. Transistors have multiple voltage characteristics.

[@GMC997]

What does 1.44 stand for? 3:09

[@GMC997]

The link leads me to the KZbin Creator Studio of my account

[@Skinnyrd]

Sorry about that. Got a little ahead of myself. kzbin.info/www/bejne/fX-ydYyZrcqUg7s

[@thenimbo2]

Why 3 555's? Use 2 w/ a SPDT (1-2 demux) switch

[@markburgs8727]

how to increase the blink speed of a led after 5 seconds automatically?

[@arunlal2104]

Nice question ! I was also wondering this.

[@andyfairman7812]

You might be able to use an additional 555 timer (running slower at maybe 6 seconds speed?) to turn on/off a transistor placed in the circuit of the 1st 555 timer's R/C network. Through this transistor, an additional resistance could be placed in parallel with Rb. This would reduce the resistance of Rb in the first 555 timer and cause the 1st 555 timer's output (square wave) to increase frequency. It would be tricky to make sure that the transistor doesn't affect the proper operation of the original 555 timer's RC circuit, but it should be possible with a little thought.

[@diamony123]

Do a Time of flight circuit using 555 ic, some capacitors, photodiode and laser to measure distance via how bright the output led is...delay time to show people how this works

[@DefiantFox]

can you do a video for 3 blinks with a 5-10 second pause

[@30041983TCM]

3 blinks each side and the frequency can be adjusted kzbin.info/www/bejne/b6OoYZlum8aVbpo

[@naveenc8755]

this video is very nice plz upload full circuit diagram

[@Sarahbuildsstepsequencers]

P.S.S. Jason, for a video idea, how about a complete tutorial on how to make a (small, simple-ish) 4-function, 8 digit red led calculator using .36" digits? Another idea: how are 14 segment led's used and is there encoder decoder chips designed for them to simplify? LASTLY, I'd love to see these things done with stand-alone chips, NOT Arduino/other programmable chips. 'Old school' electronics is best for us uneducated lil' sprouts! THANKS, Sarah🙋🏻

[@avrajsri]

Sir,Skinny R&DTel me which transistor number you use in CKT.NPN transistor number...PNP transistor number...

[@Willam_J]

Anand Vijay Rajsri - NPN is 2N3904 and PNP is 2N3906.

[@avrajsri]

wjustic1 Thank you Boss

[@Willam_J]

Anand Vijay Rajsri - You're welcome. I'm glad I could help. :-)

[@godhasleftthebuilding3224]

thx for all your efforts

[@sarathigayu9049]

This video is very nice.please upload full circuit diagram sir.

[@blackhole7818]

This was so awesome.

[@keffinsg]

using 555s is a bit of an overkill. The same can be done with some transistors, capcitors and resistors.

[@josefaschwanden1502]

why dont you just simply use the control pin of the 555?

[@tecter100]

Enjoyed it, thank you..

[@Sarahbuildsstepsequencers]

Jason, I love you! Hi, I'm Sarah, and I just viewed this and...I appreciate very much HOW you presented this episode. It's the first of you and your channel I've seen, and you really hooked me, Jason! I've always wanted to be an electronic engineer while at the same time being lousy at maths. Do you have a solution for THIS problem, sir?? 😉 Again, thank you. I can't wait to peruse and watch your other channel offerings! Sarah🙋🏻 P.S. I did Like AND subscribe to your channel! Peace! 😃

[@Skinnyrd]

Thanks for the sub!

[@naveenc8755]

Thanks, really appreciated

[@Skinnyrd]

Thanks for watching!

[@mustafagurdag4883]

Hi my name is Mustafa I’ve just got into electronics, I’m having difficulties in reading schematics and translating them onto breadboard if you can help me out with this I would very much appreciate it, look forward to your reply Thanks

[@richardchartier3023]

Just now attempted this and had a 1uF capacitor pop. LOL😅😂❤ probably crossed voltage in source.

[@mohdtmeme6842]

you are on electronic beast mode

[@pomptang]

Great video! Thanks, really appreciated!

[@Skinnyrd]

+pomptang Anytime, glad you enjoyed it!

[@richardchartier3023]

Just now attempted this and had a 1uF capacitor pop. LOL😅😂❤

[@SushmaMantaganiYT]

Brilliant :)

[@Charlieglock]

Nice Video,Well Explained....

[@avetiszakharyan]

can't you just blink with 555, and then switch between led's with astable multivibrator circuit? Should be the cheaper alternative. (so just use one 555 instead of 3)

[@andyfairman7812]

The challenge was to blink each set of LED's twice before switching to the other set of LED's to switch those twice, then start over. Switching each set of LED's once is easy with a single 555 timer but that wasn't the purpose of this circuit.

[@avetiszakharyan]

To blink each of led's twice before switch. One can: switch between left and right using astable multivibrator circuit without 555, and then use one 555 to blink them twice.

[@andyfairman7812]

Yes you're right. You could use an astable multivibrator but I don't think it would work very well. Let me see if I understand what you mean by using an astable multivibrator and a single 555 timer: An astable multivibrator has 2 outputs with one HIGH while the other is LOW. These will reverse after a specified time determined by each of the two RC network of the astable multivibrator. You could (for example) take each of the two astable multivibrator outputs and connect them to the base of two separate NPN transistors. Only one of the two transistors will be switched ON at any given time. Then you can connect a separate set of LED's to both of these transistors which would pass the common output of a single 555 timer. The 555 timer would need to operate at exactly twice the frequency of the astable multivibrator so that as each transistor is turned on, it would allow the 555 output signal to pass two pulses to blink the LED's twice. Is this what you are talking about doing? If so, you can probably already see how timing in going to be a big problem for this circuit. If the 555 timer isn't always exactly synchronized with the astable multivibrator, then there will be times when the LED's will only blink once instead of twice (or possibly even blink 3 times instead of twice). Since the astable multivibrator and the 555 timer are operating in "Astable" mode, this implies that they will not be very stable, and since they are independently oscillating, they will never both be perfectly in synchronization. Using three 555 timers as shown in the video resolves this problem. As long as both of the second stage 555 timers (the ones blinking the LED's) are operating at at frequency that is slightly more than twice the frequency of the 1st stage 555, then it will work reliably and always blink the LED's twice before being switched off again. One thing you could do is replace the 1st stage 555 with an astable multivibrator circuit and have each of it's two outputs trigger two separate 555 timers. That would work as long as the components in both of the RC networks in the astable multivibrator are matched closely enough so that both outputs are HIGH for roughly the same amount of time (another limitation of the astable multivibrator). In my opinion it's just simpler to stick with three 555 timers since you're already using two in the circuit anyway (and you can buy several 555 timers for about one U.S. dollar - they are VERY cheap).

[@vijaysurya5769]

You are Awesome!!!

[@samsmith8853]

found using 280K Rb gave 2 seconds Thanks for the video

[@gerrys6265]

You are awesome!

[@rccanuck4473]

Have another challenge Can you use a 555 timer to slow down an rc servo for flaps or landing gear :)

[@Skinnyrd]

+RC Canuck I think you can. You would need to change the duty cycle of the timer. I've got one small electric motor out of a toy car I can experiment with. I'll let you know how it goes.

[@camaroz1272]

+Skinny R&D Sound good don't over work your brain on my behalf though Regards RC Canuck

[@Skinnyrd]

+RC Canuck I think I worked something out to help with the servo. I'm not sure if this helps you but it seemed to be applicable: kzbin.info/www/bejne/bouanId5iL96a6c