LED Chaser with Slow Adjustable Fading Effect

The post 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

The Circuit Request

Dear Swagatam,

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
below,

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!!

ABU TOHA MOHAMMAD TAMAM

Circuit Schematic

 

The Circuit 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:

 

27 thoughts on “LED Chaser with Slow Adjustable Fading Effect

  1. Have questions? Please feel free to post them through comments! Comments will be moderated and solved ASAP.
    • you will have to make and install 4 of the above units on four indicator sides of your motorcycle.

      The second diagram will need to be integrated with each of the output pins of IC2 of the first diagram, the 100k pot can be eliminated if a variable feature is not required

  2. Dear Sir
    Can you advice on how to make the following circuit
    A single flashing LED circuit, in which the LED flash simulates that of beacon ie when the LED flashes, first it glows slowly, then to full intensity, and then fades. This gives the effect of a rotating beacon OR just like the lights on an aircraft tail.
    A video link to such an effect is following
    https://www.youtube.com/watch?v=zU5gJUx_8ec

    (The various types of patterns shown in this video are not needed, just the simple rotating beacon effect is required)

    The circuit is intended to be used in the car (as a flashing rear light) so the circuit may function on 12v and the LED may be bright enough to be visualized clearly so it may be 1 watt smd led.
    Kindly advise
    Thanks

    • Sourabh, A video may not be available at the moment, but you can try connecting the LED at the emitter of the transistor for getting an improved fading effect, see the last diagram in the above article.

  3. Is there any way I can fade in and out string of leds (arranged in series) connected to 4017 pinout. I am planning to make Diwali series for my home which will have the series groups attached in parallel mode to 4017 pinouts. I have googled a lot on this but could not find a concrete solution. I am banking on you for the same. The input voltage is 12V 1A

    • you can try the concept that's explained in the above article, use the second transistor driver configuration where the LED needs to be connected at the emitter of the transistors….and make sure the capacitor is connected directly across the base/emitter of the transistors and not after the diode.

      the pot can be eliminated

  4. Hello sir, the fade out effect is looking nice after connecting a 100uF(testing) 50V capacitor to the emitter and ground.

    Moving forward I have couple of things now,

    i) I have tried connecting another 100uF capacitor at the base and ground to achieve slow fade in effect, it showing up properly however I am not sure whether it is a right approach to do
    ii) How do I choose the capacitance and type of capacitor for the above effects considering total 200 leds. The connections are like total 20 leds to one pin out of 4017 arranged as 5 in parallel each with 4 leds connected in series.

    • Hello Neeraj, the fade out and fade in both can be achieved by connecting a capacitor across base and emitter between two resistors in series from 4017 to the transistor base…the capacitor can come between these two resistor and ground.

      the number of LEDs will not affect the results if the transistor is a Darlington type such as a TIP122… or alternatively a Darlington could be configured with two discrete transistors selected as per preference.

  5. Thank you sir for the quick reply, the first part regarding connecting the capacitor is not clear to me as my level of understanding is low in this context. Can it be possible for you to paste a small circuit diagram so that I can understand the connection points.

    • In the last diagram, remove only the pot without disturbing the 100uF, and replace the 1N4148 diode with another 10K resistor…that's all this will allow you to get the suggested results

  6. Hi Mr. Swagatam
    I am looking for a 11 LED Chaser and it is ruining in a circle. I know the 4017 is limited to only 10 LEDs. Do you know of any IC that can run on 11 LED in the sequence, chasing in a circle…. go on and on and it is also adjustable? kylwal@hotmail.com Thanks



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