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LED Chaser Circuits – Knight Rider, Scanner, Predator, Slow Fade

LED Chaser Circuits – Knight Rider, Scanner, Predator, Slow Fade

The article discusses the construction of six best LED chaser circuits, which not only create beautiful running light effect but are also easy to build.

We also discuss how to modify these into a design popularly known as "knight rider" chaser circuit.

These primarily incorporate LEDs as well as mains operated bulbs through triacs. The proposed circuit is transformerless and is thus a lot compact and light weight.

What is a Light Chaser

Decorative lights arranged in different moving patterns look very interesting and are surely eye catching and that’s why these types of lighting arrangement have gained immense popularity in today’s world.

Though the more complex lighting might need the incorporation of microcontroller ICs, simpler yet very interesting light effects can be generated through ordinary ICs like IC 4017 and IC 555 as shown below. This design requires very few components for the configuration.

As can be seen in this configuration, in response to the pulses from IC555, the IC 4017 generates a running or chasing light pattern across the connected 10 output LEDs. The chasing pattern goes on repeating itself from start to finish as long as the IC 555 keeps pulsing pin #14 of the IC 4017.

The lights connected are mostly LEDs, however it can be modified for using with mains operated lamps also.

Although the above design looks great, it is possible to create even more complex and interesting light effects using the same IC 4017 and IC 555 combination, through some minor modifications, as described below:

The first concept presented here is basically a running light effect generator circuit, quite resembling the effect produced over the popular "knight rider" car.

The circuit mainly comprises of IC 555 and the IC 4017 for implementing the required functions. The IC 555 is used to generate the clock pulses which is fed to the clock input of the IC 4017.

These clock pulses received from the IC555 is translated into a sequencing or chasing effect over the LEDs connected across the various outputs of the IC 4017.

In its normal mode the IC 4017 would have generated a simple start to end sequencing of the LEDs wherein the LEDs would have lit up and shut off one after the other in a sequencing pattern with a rate determined by the IC555 cock frequency, this would repeat continuously as long as the unit stays powered.

However in the proposed knight rider LED light chaser circuit, the output of the IC4017 is configured in a special way using a group of diodes which enable the output sequencing to produce a to and fro chasing of the connected LEDs, albiet through 6 LEDs only in contrast to 10 LEDs as in the normal mode.

How it Works

As can be seen in the first circuit diagram, the design produces a reverse forward moving effect of the LEDs in response to the clocks generated by the IC555 which is basically wired as an astable.

The frequency of this astable can be varied by adjusting the associated 500k pot which in turn influences the LED sequencing speed.

The entire circuit is powered via a compact transformerless power supply circuit thus avoiding the need of bulky transformers or costly SMPS.

This circuit can be also modified for illuminating mains operated bulbs by incorporating a few triacs in conjunction with the LEDs present at the outputs.

The second figure shows the complete arrangement where we can see 6 triacs being rigged across the output LED ends via 1 K resistors.

Again, this mains operated knight rider light chaser does not depend on bulky power supply stages rather employs a simple capacitive power supply for implementing the proposed running light or chasing LeD effect.


knight rider chaser LeD PCB

Video Clip:


Knight Rider Circuit using 220V Mains Lamps

Knight Rider Chaser using 12V Bulbs

The above circuit can be also as effectively used for car installation by doing the following modifications to the above circuit. The circuit shows how the design can be used for illuminating 12V car automotive lamps.

2) Knight Rider LED Scanner Circuit Mustang Type

In next idea is also knight rider chaser circuit which produces a LED scanner type illusion through the various sequencing illumination modes over the attached LED arrays. The idea was requested by Mr. Danely Sooknanan.

Technical Specifications

Hi, I need your help.i want to build the new Knight rider mustang light for my car scoop.What i have read is. It's made up out of 480 distinct LEDs, arranged in three rows of 80 in each row, then divided up into two sides.

My question is how you build it. The size i want to work with is 12 inches in length by 1/2 inch in width. How many rows of leds will i get by that dimension. What kind of led to use ?What can i use for the diffuser case? What to use for the control box.

The Design 

In the actual knight rider LED scanner unit as shown in the video, there are as many as 29 number of functions to be precise, implementing those is virtually impossible using discrete components and without employing MCUs, however here we'll see how a few of these could be possibly made using just a handful of components.The main two functions of the proposed Mustang LED scanner circuit may be assessed as given in the following description:

1) LEDs light up in a bar mode fashion from the two ends of the strip and meet up at the center, illuminating the whole module brightly.

In the next sequence the LEDs begin shutting off in the same sequence as above from the outer extreme ends until all the LEDs are switched OFF.

The rate or the speed of the above procedures are adjustable through a pot as per individual preferences.
2) The second scanning sequence is similar to the above, except the shutting off procedure which is done for all the LEDs at once instead of one at a time.

The above two functions can be easily implemented using a couple of 74LS164 ICs and a 555 IC oscillator as shown in the following circuit diagram:

Circuit Diagram

Using IC 74LS164 as the Controller

In the shown mustang scanner LED light circuit, a couple of 8-bit parallel-out shift register ICs 74LS164 are employed, driven by the IC555 configured as the clock oscillator.

The circuit may be understood by considering the following two modes in the design:

As may be seen in the above circuit diagram, a 3 pole, 9 throw switch is used as the changeover switch for imitating the 2 functions explained in the previous section above.

In mode1 S1 is connected as shown in the circuit diagram, in this position the LEDs illuminate in an sequencing LED bar like fashion with every rising edge of the clocks from the IC555 until all the LED light up and the final "high" reaches pin16, when T1 momentarily resets both the ICs producing in instant shutting off of all the LEDs at once.In the actual prototype the LEDs from Q9----Q16 must be arranged such that Q16 faces Q8, while Q9 faces the outer end of the relevant strip.

As soon as the above happens, a new cycle initiates afresh and the cycle repeats for so long as the S1 position isn't changed.


In mode 2 let's consider the switch S1 connected with the positive supply, thus S1a gets connected with the +5V line, S1b gets hooked up with the collector of T1 while S1c with R5.Also the reset pin9 of IC1 and IC2 get connected with the collector of T1 whose base can be seen configured with the last output Q16 of IC2.

On power switch ON, the LEDs begin illuminating in a BAR like mode as before from Q1 to Q8 and from Q9 towards Q16 in response to each clock pulses supplied by the astable IC 555 at pin8 of the two 74LS164 ICs.Now as soon as the high across the shifting outputs reach pin 16, T1 instantly inverts and renders a low to the serial pins1,2 of the ICs so that now the LEDs begin shutting off one by one across the arrays in the same sequence as it illuminated in response to every clock from IC555.

The LED Sequence Keeps Recycling

The procedure keeps repeating as long the switch S1 position is not changed from its existing position.The above two functions are pretty easily implemented and we have our LEDs scan the whole array quite in the manner the actual Mustang scanner is supposed to do, however with the above two functions the features look much limited and we would want to insert a few more of the features as may be witnessed in the original video.

I'll keep the article updated with the new added features, but in the meantime let's learn how the LEDs could configured to the above scanner design as per the request made by Mr. Dannel.For ease of calculation and configuration we incorporate 32 + 32 LEDs on each left and right strips.

The arrangement and the connection details may be verified through the following diagram:

Enabling Rapid Up/Down Sequence

Another interesting scanner function that could be easily added to the above circuit with a feature producing rapid to and fro sequencing over the two strips in groups of four.

This could be easily done by toggling an arrangement wherein T1 would freeze once all the LEDs switch ON in bar like style.

Now in this position a 4017 with its own oscillator would come into the scene with its outputs switching OFF the lit LEDs rapidly in a reverse forward manner. The switching could be done using BJTs which would ground the relevant anodes of the LEDs in the process.

So now we have three interesting scanning sequences toggled in our very own homemade mustang LED scanner circuit, any more possible solutions are welcome from the readers.

Cascaded 16 Strip LED Sequential Switch ON Lights using 74LS164

The following figure show how a 16 LED strips or power LEDs can be illuminated using a 2 cascaded 74LS164 ICs, and by using IC 555 as the driver oscilltor.

The diagram was contributed by Mr. Norman Kelly:

LED Sequential Switch ON using 74LS164 circuit

3) LED Chaser Circuit with Slow Adjustable Fading Effect

The third circuit below discusses a cool chasing LED light circuit that features a timed delay fading slow transition effect across the whole illuminated sequencing LEDs. The idea was requested by Mr. Tamam

Technical Specifications

I want to design a circuit consisting equal no. of Red, Green, Blue, Yellow, Violet, Orange and White LEDs. I want to have these LEDs in a continuous and smooth transition effect like

At first, Red branch of LEDs lit for a preset time then slowly fade out and then Green branch of LEDs fade in and fade out then next branch fade in and so on.....

I would like to have control on transition time delay, light timing, fade in or out timing if possible. And I don't want to use any Programmable IC for this. So please please let me know if it possible without any programmable IC. It is okay even if I need several ICs to accomplish the job. You just show me the way !!

Thank you very much once again for your valuable time and for a quick reply! I am looking forward to you response!!


Circuit Diagram

The Design

The proposed chasing, fading LEd light circuit may be understood with the help of the above schematic and the following description:

The upper circuit is a standard LED chaser design comprising of a decade counter IC 4017 and a clock oscillator using IC 555 astable configuration.

This IC 4017 generates a sequencing high logic (equal to supply voltage)  across its entire output pins in response to the clocks at its pin14 from the IC 555.

If we connect LED directly across the 4017 outputs and ground, the LEDs would illuminate in a dot mode fashion from the first pinout upto the last in a sequencing pattern resembling a chasing effect.

This effect is pretty ordinary and we all probably have come across and built such light chasers circuits quite often.

However as per the request the effect needs to be enhanced by adding a slow transition over the LED illumination as it sequences across the entire channel. This fading transition on the sequencing LEds is expected to generate an interesting group LED chasing effect instead of an illuminated dot like appearance.

The above intriguing show could be easily implemented by connecting the LEDs to an intermediate BJT delay generator circuit.

This BJT circuit becomes responsible of generating the intended transition delay over the LED illumination and can be witnessed in the lower design.

This stage needs to be repeated across all the selected outputs of the 4017 outputs for achieving the desired chasing, fading slow transition over the LEDs.

As requested the rate of the above fading slow transition could be controlled by adjusting the given pot.

The circuit is basically a simple delay timer which sustains the illumination on the sequencing LEDs for a few moments depending upon the set value of the pot. The stored charge on the capacitor produces this timed delay effect on the LEDs which could be predetermined as per ones own choice.

The speed of the sequencing could be also altered by tweaking the 555 IC 100k pot as per individual choice which this could in turn interfere with the delay transition effect and thus is a matter of some trial and error until the most attractive set up is determined.

For Improved Fading effect

For an improved fading response the LED could be connected across the emitter and ground of the circuit, as indicated the below given diagram:

4) 18 LED Light Chaser Circuit Using Two IC 4017

The next fourth design explains how to build an 18 LED chaser circuit through a simple cascading of two 4017 ICs, and some passive electronic components.

Working Explanation

Here we are discussing how to make a simple LED running light which can be built by any newcomer in the field albeit the individual has some knowledge of soldering and regarding the commonly used electronic components.

The concept of a light chaser discussed here utilizes the popular Johnson’s decade counter IC 4017 for getting the desired light chasing effect. IC 4049 is used as the Oscillator

Another IC 4049 provides the clock signals to the counter ICs. We all have probably seen how the IC 4017 can be configured for creating the light chasing effect using LEDs, however the number of maximum LEDs supported by this IC is not more than ten. In this article we’ll learn how to make an eighteen LED light

chaser by cascading two of these ICs.

Cascading two IC 4017 Johnsons Counter for the 18 LED Effect

Looking at the above light chaser circuit diagram we see how the two ICs are configured so that the “chasing”  or "running"of the LEDs at its outputs are carried on for 18 LEDs. The diodes included in the circuit especially are responsible for switching the ICs into a cascading action.

The diodes make sure the IC outputs are carried forward from one IC to another, so that the “chasing” effect is pulled for the entire 18 LEDs in the array.

The whole circuit can be built over a general purpose PCB, and connected together by soldering with the help of the shown diagram.

The circuit can be operated in between 6 volts to 12 volts.


Parts List
R1, R3, R4 = 2k7,
R5 = 100k,
C1 = 10 uF/25V,
N1, N2, N3, N4, N5, N6 = IC 4049,
IC1,2 = 4017,
All diodes are = 1N4148,
PCB = General purpose

LED = as per choice.

The above 18 LED cascaded chaser circuit can be also conveniently built using a 555 astable circuit, as shown below:


18 LED chaser circuit two IC 4017 cascaded with each other

Video Clip of the above circuit in operational mode:

5) "Predator" Type LED Light Chaser Circuit

The next car tail circuit was requested by Mr. Danley Sooknanan, it's regarding the designing of a customized car tail light consisting of "running" or chasing LEDs arranged in Yautja language, as viewed in the movie "Predator", over the wrist of the "Alien" being. Let's learn more.....

Technical Specifications

I want to try the above chasing tail lights in my car .

But I want to add something to the design I need your help. The turn indicator i want to make it as a predator count down timer.

Let me explain the design in the predator count down timer their is a bunch of sequential lighting. Now what i want to do is have the indicator led move from one point to the other with the predator pattern of the the count down timer.

I would be grateful if you can help me .The other project I am thinking about is a Audio Spectrum Analyzer how i want to do this is place it on the led on the grille .

When the music plays the led moves upwards and downwards when the different frequency is played

Can you help me with the diagram n listing of the parts I need. It is been for years I have wanted to do this project but I dont know who to ask for the help on the circuit design .

Now i am greatful for the effort n time u help others with .

Thanks a million....

before i forget the predator turn signal the sequential count down mus be a little faster than the video i send you move from one point to the other then all the led will flash n light and the the sequential count down starts again

Please provide me with the exact pattern of the LEDs in lit position for the different sequences. you may send me the drawing of it so that I can understand how the LEDs should be laid down.


Once again Thanks for the reply . I am really excited of this project .Looking foward to your reply.

I think I have understood your requirement, the sequence will keep only one block illuminated at a time while sequencing.

After the five sequences are over, all the blocks with the relevant patterns will illuminate together and flash.

I hope this is what is required by you.2 by 13 inches will be enough for the design, however the display will not be understandable from a certain distance may be from 30 feet away.

I'll inform you when it's posted.

Good point " the  display will not be understandable from a certain distance may be from 30 feet away."

U know i was thinking about that before i read the email.Here is what we can do to tweak this. After the five  sequences are over the   chasing
light patterns comes on the indicator. then the five sequence.............

With this tweak the driver behind can see that the indicator is on .

Thanks a million looking foward to the post .

Here is the mazda 323 tail light .

I tried my hand on a photo editing software

Now this is the concept .In the above After the five sequences are over the chasing light pattern starts then the five sequence ...................

I would have have showed u each of the sequence predator pattern photo but that would take five more pics to do that .I think u understand the concept

If the LED PCB is put over the indicator area, it will block the actual bulb indicator lights of the car because the PCB will be opaque by nature.

How the Sequencing Needs to be Like

About the sequencing: when the blocks light up one by one (the previous block shutting-of as the sequence proceeds), the various lines (signs) present on each block will not make any action, the illuminated pattern will remain fixed on each block as the sequence proceeds....is it that way???

Sequencing Pattern

I googled n got information about retro fitting the taillight .My tail light has bulbs.The idea is to convert the whole tail light to led (LED PCB)

Now this project is all new to me I just have the ideas.What i want to do I want the chasing light feature as your diagram

Now all we are tweaking is the indicator .The indicator part will be converted to the LED PCB

Now this is the concept .In the above After the five sequences are over the chasing light pattern starts then the five sequence pattern...................

I just have ideas what do u think is the best way to display this on the tail light

The predator countdown has an awesome display.here are the examples....

I was thinking of the indicator do u think it would be better on the red part of the tail light.Your input would be highly appreciated ............ Now everything is clear, ......one last question though, I couldn't follow this statement of yours:"

After the five sequences are over the chasing light pattern starts then the five sequence pattern..................."

What I understood is, the predator signs would be displayed initially in the chasing pattern.....once this chasing gets over, all the sign-blocks would illuminate together and flash, may be twice and thrice.......what next?? what should be the function after this??

Using White LEDs instead of Red

I think the white section would produce better results.....under the red lens, the red LEDs would become too much responsive, and therefore difficult to distinguish.

I'm really glad that ur taking your time to understand and email me back .I'm am truly thankful.

What i meant in the quote after the five sequences are over chasing light pattern starts then the sequence pattern

It is like a cycle or loop?

Understanding the Chasing Pattern of the LEDs

The predator signs would be displayed initially in the chasing pattern.....once this chasing gets over, all the sign-blocks would illuminate together and flash, may be twice and thrice"

Then the predator sign chasing pattern would start all over again. after it it is over all the sign blocks would illuminate together and flash may be twice and thrice then the predator sign chasing pattern.

You understand now a loop Now we are using this circuit for the red part of the lens on the tailight

Thank you!This project is interesting, and the folks will love to read it when it gets published 🙂

We had discussed earlier, that the signs wouldn't be understandable from some distance and therefore after the initial sequences are over the background light should start flashing in order to make the light distinguishable to the distant vehicles.....

so I was actually referring to this operation, when should this happen? According to me after the sequencing and the flashing of the predator signs finish, the background lights should come into action.

If the predator sign sequences keep repeating, it will interfere with the actual flashing of the background lights. Since the operations are connected with signalling and safety issues, it needs to be taken care of seriously. This is what I was interested to know about, so it is the last part of the confusion.....:)

Okay good that you mention safety, lets do it with your method then ." According to me after the sequencing and the flashing of the predator signs finish, the background lights should come into action." so it is a loop cycle - predator signs-backround lights come into action - predator signs

This is just like a send u with the last email with all the pics

I'll do it soon, and inform you when it's published....Thanks! Great looking foward to the post .I have some great ideas for some other projects.like a spectrum analyser display for a car.

an antiteft device for a car

Designing the Predator LED Tail Light Circuit

As shown in the following circuit diagram, three numbers of IC 4017 have been used for implementing the required sequencing operations of the predator signs as well as the background LED indicator bars.

The different stages of the circuit operation may be understood with these points:

When the turn signal switch is turned ON, the 12V supply passes through the 7812 voltage regulated IC and powers the preceding electronic circuit stages.

N1 along with R1 and C1 forms the clock generator or the oscillator circuit which provides the necessary clocking to pin#14 of IC1 and IC2.

IC1 outputs immediately start sequencing in response to the above clocks.

The sequencing initiates from pin#3 of IC1 to pin#10 Since the predator LED patterns are connected with these outputs via transistor drivers, all of these signs become illuminated one after the other in the given sequence.

At pin#10 the last predator pattern illuminates. In the following sequences, pin#1, 5 6 and 9 of IC1 become high one after the other....however since these outputs are connected to the base of T1 (see next figure), T1 switches ON and it also switches ON T2.

T2 now starts providing 12V to all the driver transistors which are responsible for sequencing the predator signs, this action immediately switch ON all the predator signs together.
However the clocks (positive) reaching the base of T2 via D1 forces it to blink with every positive clock from N1.

Due to this operation T2 switches in a flashing mode and initiates a flashing response over all the predator which flash thrice until the sequence reaches pin#11 of IC1.

At this point the logic high from pin11 connects with pin 13 of IC1, locking its sequencing on the spot so that the IC now is unable to sequence any further and gets latched at this position.

But the above logic high prompt the output of N4 to go low, which immediately enables IC2 to begin its own sequencing  shifts.

The outputs of IC2 now begins sequencing and illuminates the connected LEDs from pin#3 to pin#11.

This sequencing starts repeating, and in the process the logic high at pin#3 of IC2 clocks IC#3 pin#14.

IC3 responds to these clocks and in turn allows its outputs to sequence. When its output sequence reaches at pin#5, the entire system RESETs, because the logic high from pin#5 of IC3 hits pin#15 of IC1.

The entire process begins all over again.

The outputs of IC2 are arranged as small vertical bars using high bright RED LEDs and are put in between the predator sign-block gaps and ahead.

When the predator sign stops, these bars take their position and continue the sequencing so that the indications become prominently visible even to the distant vehicles at the rear.

The following figure shows the method in which the bars of the predator sign may be wired using 3mm high bright red LEDs.

As shown, each of the lines in the signs are made by aligning three 3mm LEDs in series. Once all the lines are aligned with the LEDs, the anodes of each string should be connected with individual current limiting resistors.

The ends of the resistors should be made into a common for different blocks and these points should be connected to the collectors of T3, T4, T5, T6, T7 respectively.

The cathodes of all the LEDs in the blocks should be made into a single common point and connected to ground.

Parts List

R1 = 100 pot
R2 = 1M
R3....R12 = 1K
R13...R22 = 150 Ohms
R23....R31 = 1K
D1.....D5 = 1N4148
IC1,2,3 = 4017
IC4 = 7812
N1....N4 = 4093
T1 = BC547
T2 = BC557
T3....T7 = 8050
C1....C4 = 1uF/25V non polar

6) LED Chaser Circuit cum Blinker Using IC 4017

The sixth concept presented below is also another LED chaser circuit but includes a blinking effect to the design. The circuit was requested by Mr.Joe, one of the keen followers of this blog.

The circuit initially was intended to be used for generating LED strobe light effects and was asked to be modified such that it could be used as an LED sequencer as well as a blinker. The change over would be implemented via a toggle switch.

Circuit Operation

The IC 4017 is not new to us and we all know how versatile and competent this device is. Basically the IC a Johnson’s decade counter/divide by 10 IC, fundamentally used in applications where sequencing positive output signals are required or desired.

The sequencing or the orderly shifting of the outputs take place in response to a clock pulse that needs to be applied at the clock input pin #14 of the IC.

With every rising positive edge of the clock input, the IC responds and pushes its output’s positive from the existing pin out to the next pin out in the order.

Here a couple of NOT gates are used as a oscillator for providing the above clock pulses to the IC 4017. VR1 may be adjuted for determining or fixing the speed of the sequencing.

The outputs of the IC are connected to an array of LEDs in a specific order which makes the LEDs look like as if they are running or chasing during the operations.

If the circuit would be required only to produce the chasing effect, the diodes would not be required, however as per the present ask the diodes become important and allows the circuit to be used as a blinker also, depending upon the position of the switch S1.

When the switch S1 is positioned at A, the circuit behaves like a light chaser and produces the normal chasing effect over the LEDs which start illuminating in sequence from top to the bottom, repeating the operations as long as the circuit remains powered.

As soon as S1 is flicked toward B, the clock signals from the oscillator are shifted into the input of the transistor T1, which instantly stats to pulsate all the LEDs together in response to the received clocks from N1/N2 configuration.

Thus as per the requirement we have successfully modified an ordinary light chaser circuit with an additional feature through which the circuit now is also able to function as a LED flasher.

Do not forget to connect the inputs of the remaining unused gates from the IC 4049 either to the positive or the negative of the supply. The supply pins of the IC 4049 also need to be connected to the relevant supply rails of the circuit, kindly refer to the datasheet of the IC.

If all the ten outputs of the IC 4017 are required to be integrated with LED sequencing, just connect pin #15 of the IC to ground and use the left over outputs of the IC for the required sequencing of the LEDs in the order of: 3,2,4,7,10,1,5,6,9,11

Circuit Diagram

The following parts will be needed for making this LED light chaser cum flasher circuit:

  • R1, R2, R3 = 1K,
  • R4 = 100k
  • VR1 = 100K linear pot.
  • All LED resistors are = 470 Ohms,
  • All diodes are = 1N4148,
  • All LEDs = RED, 5mm or as per choice,
  • T1 = 2N2907, or 8550 or 187,
  • C1 = 10uF/25V
  • C2 = 0.1uF,
  • IC1 = 4017,
  • N1, N2 = IC4049


Guys, so these were 6 best looking LED chaser circuits for you all that could be built and applied as a decorative piece of lighting with a dazzling eye catching effect. You can use them anywhere you like, in your home, in your vehicles, garden, hall room, for parties, on caps/hats, apparels, during festivals etc.

Think have more such ideas, please share them here for the pleasure of the entire homemade circuit community.


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

84 thoughts on “LED Chaser Circuits – Knight Rider, Scanner, Predator, Slow Fade”

  1. Dear sir
    i want to make 12 bulb circuit, but my bulbs are much higher amperes about 30A. so,
    IRFZ-14 is suitable for it? or any other one?
    what is the gate opening voltage and current of BT136 and IRFZ14?

  2. sir this transformerless cct is it possible to construct it and without connecting load is it possible to measure voltage on that zener diode without spoiling the zener?

  3. Sir I new and I am intreste to make circuit as per diagram 2. But sir the capacitor 1uf as shown in diagram connected near ic 555 the voltage of capacitor is not given. Please provide what is the volt of 1uf capacitor.

  4. Dear Swagatam,

    Thank you for your reply.
    I have tried all your solutions but unfortunately with the same result.
    I think it is weird because as you said the ICs are rated up to 15V.


    Is it possible to build a small circuit without the use of a microprocessor for flickering some LEDs?
    The flickering must simulate an arc welder, camp fire, candle light etc.?

    Best regards,

  5. Dear Swagatam,

    I have built the first circuit but without the high voltage part and the Zener diode.
    It works fine at max. 5V

    If I raise the voltage to above 5V the flashing of the LEDs becomes uncontrollable.

    What do I need to change to use the circuit at 12V?

    Thank you in advance,

    • Hi Henrik, that shouldn't happen, because IC 555 and IC 4017 both are designed to work from 5V to 15V safely. THis can happen if the power supply has some issues, or if the power supply pot is not good.

      try with a fixed 12V and see if the problem still persists.

      or alternatively you can also try readjusting the IC 555 pot after increasing the voltage to the desired higher level

  6. sir I made 2nd circuit led sequence working properly but triac doesn't switching all bulb are continuously ON. please help me to solve this problem.

  7. sir I made 2nd circuit all 6 nos led chasing properly but triac doesn't switching output bulb continuously on condition. please help me to solve the problem.

    • Rahul, change all the 1K resistors with 220 ohm or 330 resistors and additionally connect 1K resistors between gate and ground of all the triacs and check the response

    • …the bulbs cannot be continuously ON, make sure the triacs are connected correctly…A1 must go towards the bulb side…

  8. Dear sir आपके दिये हुवे second circuit image में main power supply का जो circuit है उसके जरिये MOC3021 drive करने के लिय कितने value के resistance की जरुरत पड़ेगी
    और इस supply के जरिये हम एक साथ maximum कितने MOC3021 का use कर सकते है

  9. Dear sir मैं आपसे कुछ इस तरह से Triac (BTA41) को Drive कर ने के लिए कह रहा था
    मैंने आपके mail id पर दोबारा से image send किया है
    क्रप्या इस image को देखे
    Please Sir मुझे इसका हल बताइए

  10. मतलब आपके कहने का अर्थ है 1N4007 के output से 0.33uf/400v को जोड़ना है और फिर 0.33uf/400v के एक छोर से 1k जोड़ना है और फिर 1k से Triac gate को जोड़ना है ok sir

    • No, that's incorrect

      …120V to 1N4007 (band side), then other end of 1N4007 to 1K, then 1K to SCR gate.

      after this solder the 0.33uF/400V leads directly on the 1N4007 leads (1N4007 and 0.33uF are in parallel).

    • Dear Rakesh, I have sent the image, i forgot to put 1K with the gate of the triac, so please put 1K in series with the gate

  11. Dear sir 240V AC में, मैं अगर सिर्फ एक 1N4007 diode का use न्यूटल या फेस कर तो मुझे output voltage कितना मिलेगा ?
    Please tell me sir

    • Dear sir आपने जो output बताया है मुझे इसी voltage से BTA41 को ऑपरेट करना है कैसे करूँ कोई ऐसा हल बताइए जो circuit के लिए सेफ हो
      Please sir

    • connect a 1k resistor to triac gate and then connect a 0.33uF/400V capacitor and connect this capacitor end with the 120V input….also connect a diode 1N4007 parallel with the capacitor….cathode will be towards the 120V source.

    • It's very simple…connect 120V input with the band side of a 1N4007 diode, connect the other side of the diode with 1K resistor, connect the other end of the 1K with the SCR gate.

      after this connect a 0.33uF/400V capacitor right on the leads of the 1N4007

    • Dear sir मेरे other circuit का कहने का मतलब है के दुसरे circuit द्वारा प्राप्त output voltage 0 से 0.8 DCV 200uA dimmer के लिए कम जादा कर सकते है जो की Triac को Triac Dimmer बनाने के लिए पर्याप्त नहीं है
      तो मैं आपसे ये जानना चाहता हूँ triac को dimmer बनाने के लिए अभी कौन कौन से components की जरुरत पड़ेगी ?

    • Dear Rakesh.

      0.8V will need to be amplified first with a 12V amplifier circuit or an optocoupler circuit….the output from this optocoupler can be used for driving the triac.

      MOC3063 can be used for this.

  12. sir मैं इस प्रोजेक्ट से हट कर एक सवाल पूछ रहा हूँ क्या मैं BTA41,BT139 और BT136 को Thyristor (SCR) की तरह use कर सकता हूँ

  13. सर जी क्या मैं C 0.47uf/400V की जगह पर कोई और C use कर सकता हूँ सर जी अगर कोई और C हो तो बता दो पर circuit के लिए सुरक्षी हो 🙂

  14. triac is fitted in the way your circuit but do not get that way for the entire supply triac and because of which fully AC supply cannot send. so will need to use transistors

    now you make your circuit and used
    and then some comment

  15. i am telling you after check and i can prove it
    and i am telling you that please check in circuit

    capacitor, diode and Zener diode put in the wrong direction in your second picture circuit

    • Hello Sandeep,

      see the last circuit, you can replace the bulbs with the LEDs with a series resistor.

      The mosfets can be replaced with a TIP 122 transistor as an alternative.

      You can connect 3nos of 1 watt LEDs with a resistor on each transistor

  16. Great article, thank you.
    My question is can you reverse it, have the LEDs on all the time and the circuit shut them off in sequence.

    • thanks, that would be possible with a normal IC 4017/555 chaser circuit without the forward reverse facility….there you can achieve it by simply reversing the LED polarity….I am not sure how it could be done in the above circuits….may be by reversing all the diodes an LED polarity, but I am not very sure.

    • basit, divide the supply voltage with the LED forward voltage this will give you the number of LEDs that can be connected in series on each channel.

  17. thanks sir
    circuit sahi se kam ker rahahe.1k ke badle mene 220E resrstor triac gate se connect ki ya aur apke bataye huye,1k resistor gate aur circuit GND se connect kerne par led sequence sahi a rahahe.aur triac proper kam ker rahahe.sab chanel 100w lamp se try kiya lumin sahi a raha he.
    sir mene triac pin 1-A1 aur pin 2-A2 hisab se lagaya. thanks sir guide karne ke liye.
    you r great……..

  18. sir
    mene 12v 2amp adapter use kiya.led sequence sehi aarahahe.lekin triac kam nehi kerrahahe.no.1 chanel kam ker rahahe100w bulb lagane par lumin kam ho rahahe.baki ke 5 chanel off he.

    • connect a LED with 1k resistor from pin3 of IC555 to ground, it should flash, if it doesn't then the fault could be assumed to be in the 555 circuit, other wise the fault could be in your 4017 circuit….make sure all the LEDs at the gate of the triacs are connected correctly and illuminate for enabling the triacs to conduct.

  19. sir,
    triac ke gate aur GND par 1k connact kene par sequence sahi arahahe thanks. lekin triac 100w bulb flash nehi ker rahaye. No.1 chanel se sirf flash ho raha he, lekin lumin kam ho raha he.
    me ne 1k ke jaga 220E resistance se triac ke gate connect kiye,lekin No.1 chanel chor ke baki sab off he.lumin thora sa change huya lekin baki kam nehi ker raha he.
    sir triac pin-1-T1.pin-2/tab-T2
    pin-3-G.circuit me to is hisab se nehi he….sir plz help me…..

  20. sorry sir,
    apne samay nikal kar mere prashna ka jabab diya,lekin kam ke bajese me try nehi kar saka.
    aj mene try kiya led negetive se 1k lagaker GND se connect kiye.lekin 12v 2amp smps se sequence tut raha he. plz sir help me.

  21. sir
    mene apka 2 no. circuit try kiya.lekin jo 12 v hai o kam nehi ker raha he.12 v adopter use kerne par sequence proper nehi a raha hey. plz help me sir…

  22. how many 5w 230v bulbs can be put in single triac in parrel? is there any triac for large watt handling?

    • 100nos if the triac (BT136 etc) is mounted on a heatsink, for more bulbs you can try other higher rated triacs.

  23. I've made the 12V car version. I've only left out the leds before the mosfets. But it's not working. When I don't connect the positive wire going to the 22k resistor, port 8 and 4 of ic555 and to port 16 of ic4017. All the light are burning, but when i connect this positive wire nothing is working at all. Have you any idea what could be wrong and how i can check it?

    • that's weird, because without the positive supply connected the LEDs would never light up.
      I think there's something terribly wrong with your connections or the components.

      Separate the 555 and the 4017 stages….build and test them separately, once the results are confirmed you can try integrating them as per the diagram.

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