Chasing Car Tail Light Using 1 watt LEDs

The post discusses the construction chasing car tail light circuit using high bright 1 watt amber LEDs. The idea was requested by Mr. Brian Walton.

Technical Specifications

I've been giving the project some further thought. I am wondering what changes might be needed to use single, higher power leds instead of the advised 5mm ganged in threes? So there would be 6 LED's rather than 6*3 5mm

The reason is that I have combined LED DRL & indicators on the front of my car, so I would like to retain the OEM look & feel at the rear - where I propose to use your excellent circuit design.
I'm thinking along the lines of the LEDS in the link below.

They are Osram Opto Diamond DRAGON Series GW Amber LED. They are designed for automotive use in DRL's and indicators.
They are 2.9v forward voltage and appear to take about 1.4A at typical lumens.

The LEDs above are not definitive but a suggestion in terms of output and style for my construction needs.

So my question is can the circuit take or how do I need to modify the circuit to take the extra power these LED's may take.
For info; from a practicalities point of view, I intend to have a separate driver circuit for each side of the vehicle - it makes installation simpler given i'm going to attach the pulse form the existing indicator
relay as discussed previously with you.

I hope you can advise me (again!) and many thanks for your devotion to the electronics hobbyist on the web.
Best wishes

Solving the Circuit Query

Thanks Brian!

Incorporating higher wattage LEDs will need individual transistor buffers across the 6 outputs from the IC, it's actually very easy to implement.

I'll try to explain the connections verbally, although I am also thinking of updating a suitable diagram for this particular application, I may do it within a couple of the meantime you could try doing the following mods in the above circuit:

Use TIP122 for the buffer transistors.

Connect the bases of the 6 transistors to the respective outputs of the IC 4017 via the indicated diodes. Make sure the base have individual series 1k resistors

The LEDs will need to be attached across the transistor collectors and the positive, the LEDs too must have their own series limiting resistor

The LED resistors could be calculated using the following formula:

R = (Us - LEDfwd)/I

where Us is the supply voltage,

LEDfwd is the optimum glow voltage of the LED or the forward voltage drop spec.

I is the optimum current for the LED as specified in its datasheet.

That's all..... now your circuit is ready and would be capable of handling any type of high watt LEd in the range....

Circuit Diagram

Need Help? Please send your queries through Comments for quick replies!


  1. Thanks for the reference link Swagatam!
    Great work - as always :-)


  2. You are most welcome Brian, I hope now you have understood how the transistors and the LEDs need to be wired:-)

  3. what do you mean by left flasher and right flasher there are 4 diodes?

  4. the arrow points will become common and go to indicated flasher outputs that may be present inside the relevant lamp sockets

  5. I have been reading your posts on your site all day. I enjoy your work on here. I am wondering if you have any time could you help me with a project I want to do with my jeep wrangler.
    I am new to electronics but will have help setting things up. I am trying to come up with a design of a circle ring of about 15 leds that I could have seperated out to do the chasing effect when the turn signals is used. I also would like to use the same LEDs for the running lights and brake lights/ Hazard lights also.

    I would like the chasing effect to start from the middle on both the top and bottom of the circle/ring and go either left or right. I do know that can be achieved by placement of the leds.
    Is it possible to tell me where I would have to connect the wires(left/right turn signales, brake lights, running lights) from my vehicle

    If any of this doesn't make sense please let me know or if you have any diagrams that can achieve this effect could you point me in the right direction.

    I really appreciate your work on here

  6. Thank you Kaleb,

    I think I already have one ready circuit design in this site which you can customize as per your design:

    Here is the circuit that I am talking about:

    please feel free to ask you have further doubts

  7. Hello, Sir Swagatam. First i want to thank You for Your efforts in building this site and sharing knowledge with everyone.

    I've build this circuit and it's working fine, only had to change C1 value, because clock pulses were very very very slow. I've used bc337 for driving outputs from 4017 and i'm driving 10 channels of 8 white leds (4 in series and 2x4 in parallel). Main ground for all bc337 is switched by one tip122.

    But i'm wondering, is there any way to make a latching effect to outputs to have a bar graph not a dot run without using SCR's in place of my bc 337?

    I hope You understood my question. Sorry for my english and have a nice day, thank You in advance.

  8. Thank you unknown,

    yes C1 can be changed as per individual preference.

    for latching feature, you may have to add SCRs across the outputs of the 4017 as shown in the following article:

  9. ...without scrs it's not possible with may be possible using by using IC 74LS164 shown here:

  10. Thank You for quick reply, Swagatam.

    One more question: when 4017 receives clock pulses, it always starts to count from same output? Or somewhat randomly?
    I want to use pulsing power supply from cars flasher circuit and time the clock pulses so all leds light up in one ON pulse from flasher relay, then turn off for OFF pulse from flasher relay. Is this possible?

  11. Hi Paulius

    Yes that's possible but only if pin15 of IC 4017 is reset automatically at every switch-ON pulse.

    if you are using the above circuit then the pin15 will need to be connected with pin5 through a high value resistor such as a 100k....and pin15 further connected to the positive supply via a 0.22uF capacitor.....this will take care of the issue and enable the 4017 outputs to always start from the start that is from pin#3 onwards


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