Sunday, January 1, 2012

How to Make Car LED Chasing Tail Light, Brake Light Circuit

The circuit explained here is presented in response to a request sent by one of the avid readers of this blog. The proposed circuit is of a sequential LED light driver, especially designed to suit the application of a multipurpose car tail light indicator.
The circuit is integrated to the brake switch and works as a brake light, it’s also connected to the turn signal switches for indicating the turning of the vehicle with chasing light patterns, and the circuit can also be used just as an ordinary tail light warning indicator.

In order to successfully make the proposed car LED chasing tail light, brake light circuit, it will be important to first  understand the circuit functioning in details with the following points:

The CIRCUIT DIAGRAM can be divided into two sections, the first consists of the LED driver stage, where the IC 4017 forms the main LED sequencer and is configured in its usual counter/divider mode.

Only six channels of the IC 4017 have been used to avoid lengthy sequencing patterns and crowding of the LEDs.

Two arrays of LED are taken from the above outputs such that they “run” in opposite directions when switched ON, however both the channels are never run together since they are used for the LEFT, RIGHT turn indicator purpose and therefore only the relevant side is switched ON depending upon the vehicles turning side.

The IC 4060 is configured in its standard mode, as an oscillator and is used for driving the IC 4017 with its clock signals. With every rising peak of the clocks, the outputs of the IC 4017 shift from one pin out to the next in the shown order, making the connected LED illuminate sequentially.

The pot associated with the IC 4060 may be used for adjusting the sequencing speed as desired.

The LED stage consists of the LEDs arranged in a definite sequencing pattern as discussed in above explanation. The LEDs are connected to the IC 4017 outputs so that they are able to perform the intended sequencing or chasing function.

The LEDs are also discretely wired up to the different vehicle controls like the brake switch, the turn signal switches and an optional DIM tail light switch.

When the brake switch is applied, the LEDs light up all together brightly, indiacting the application of the brakes.

When one of the turn signal switches is switched ON, say for example the LEFT turn signal is applied, the LED array positioned on the LEFT portion starts sequencing from center, toward LEFT, indicating the intended moving direction of the vehicle.  

The above function is repeated toward the RIGHT side by the right portion LED array when the right signaling is made with the relevant switch.

A couple of optional switches (S1) may also be included and wired up with the LEDs as shown in the diagram. This provides a feature of operating the LEDs as a dim tail light indicator which stays switched all the time with a relatively lower brightness, however when the brakes are applied the LEDs light up brightly.

The driver circuit is powered through the IC 7812 which is a voltage regulator and provides safe operating stabilized voltage to the circuit, irrespective of the input fluctuations.
In the above position, the turn signals will also work, but is not recommended as the DIM light at the background may affect the signaling. 


  1. This is AMAZING! Thank you so much! I can't believe you did it so quickly, too!

    Just a few questions if I may:
    1: Is there a set limit of how many led's can be safely used with this?
    2: If the brakes are on, will the turn signals still operate or would the brakes being on override that function, keeping all of the led's lit constantly?
    3: Are the brake light switch and signal indicator switches providing the ground? Also why is "to brake light switch" on there in two different places?
    4: lastly - is there a particular type of LED you'd recommend. There are so many different types out there now, it's overwhelming for a laymen like myself.

    I apologize for what probably seem like stupid questions, but I want to make sure I have a good grasp of everything that's going on here before I even think about attempting this.

    Thank you, again, for the phenomenal work you did on this!

  2. Thanks very much B!

    Here are the answers to your questions:

    1)3 nos. per channel is the recommended quantity for any type or color of LEDs for optimum brightness.
    2) Applying brakes will override the chasing feature and the LEDs will remain lit as long as the brakes are ON.
    3)All the vehicle switches bring positive supply to the shown inputs, all the "brake switch" marked inputs can be made into a common terminal and connected to the brake switch.
    4) 5mm RED LEDs will be most suitable here, since we are using the circuit as a warning indicator.

    Your questions are all valid and I very much appreciate them.

    Thanks and Best Regards, keep in touch!

  3. Thank you for replying so quickly, Swagatam. You are extremely helpful!

    I have one last question for you. I now know that 3 per channel is the recommended quantity of LED's, but is that the TOTAL number of LED's per channel, or just the number that should be run in series? Would you get the same brightness out of the LED's if you had four "clusters" (a "cluster" being 3 LED's run in series) of lights run in parallel per channel? Does what I'm saying make sense?

    The only reason I ask is my tail lights are rather large by today's standards and I think I might need to use more LED's to fill them properly.


  4. Hi B,

    I am not exactly sure regarding what will be the LED brightness if more numbers are added, however you can try connecting a couple of more strings in parallel to the existing string in each channel, don't forget to connect a series resistor with each string.
    You may reduce the series resistor value to 680 Ohms for getting more brightness.
    If you are using RED LEDs, make the series into 4 LEDs, that would add an extra LED to the string and help to increase the over all number of LEDs.


  5. OK I lied... haha. I have one more quick question on this. Would you mind, terribly, providing a parts list as you have in other posts I've seen. I'd rather not have to ask, but I'm not entirely sure what all of these symbols mean. Also is there a specific pot which should be used in conjunction with IC 4060?

    Thank you again! I'll have to send you a video of this thing in action when it get's done!

  6. Hi B,
    The orange boxes are the resistors, the black arrow like symbols are the diodes, the BC547s are the transistors and the the three large squares are the ICs 4060, 4017 and 7812.
    All the diodes are 1N4007 or, 1N4148 will also do.
    The resistors values are printed over or near the orange boxes, you can find them easily, most of them are designated with the letter "K"
    The resistors are all 1/4 watt rated.
    The pot can be any standard type with three pins and a spindle, having the shown value.
    The parts dealer will know everything, you can take his help.
    The switches are two pin type, any make and size will do the job.
    It seems you are pretty new in the field, are you sure you can build this???
    Let's hope positively.... I'll wait for the video, wish you all the best.
    Thanks for posting!

  7. Yes I am new to circuits like this, but I am positive that I can build this. If I have any trouble with anything during the build, my dad has experience with building circuits and he can lend a hand if the need should arise. I am excited to get started on it! I've always been a self taught and hands-on guy and this will be a great experience!

  8. Nice...go ahead and make it :-)

  9. Hi again Swagatam. I tried to get a friend of mine to help me out with this as I didn't want to bother you any more about it, but it turns out he is out of the country for the next two months. I don't want to ask you to design another circuit since I already got more than I had hoped for with this one. But if you wouldn't mind, could you possibly take a look at the linked picture below and tell me if this idea would be do-able by modifying this circuit or if this would require a whole new setup. I would be most appreciative of any help you can give.

    I laid it out in such a way that the dim/bright switched lights would operate independently of the turn signals. I figured this would make the implementation of all the functions together easier. But as you see, there are over one hundred LED's which would make up this light. I did make it so the number of led's used is a multiple of four (as in 4 led's connected in series). The top three rows of led's would be strictly dim/bright. As in running/brake lights / hazard flasher. The bottom two rows are separated into 7 "banks" of led's and used strictly for the sequential turn signals. Lastly - I'm wondering if there is any way to use pots to independently control the brightness of the dim and bright settings? Anyways... If there's anything you can do to assist in this, I would very much appreciate it.

    I know this is a lot and if it's not something you would prefer to take on, I would certainly understand!

    Thank you so much either way! Oh - and here's the picture:

  10. Hi B,

    If the dim/bright LED section is kept entirely aloof from the sequencing LED section and operated independently then definitely your idea will work.
    The dim level of the LEDs can be controlled by making the 220 Ohm resistor variable or by replacing it by a pot.


    1. I think I understand how this is working all the way up to the switch (S1) for dim control of the LEDs. I would definitely us a pot for this. I do need to use the (S1) for my application. The brake light and turn signal wire are the same wire at the tail light and the brake light is canceled in the turn signal switch. If I put the pot on the positive side and eliminated the brake light switch lead in that area of your schematic. Would this work? It appears that the LEDs would sequence one time for the brake and stay lit until the brake is released.

    2. I could not understand your exact need..... but yes a pot would work with the positive also for the. dimming purpose

  11. I’ve been looking for this for a few weeks and it looks great but I have a few ques
    1: what type (trimpot, cermet or rotary) and size pots ton replace ic 7818 and the 220 ohms r
    2: what switch should I use for the two at the bottom of the second image(push on/off, toggle threw, pushbutton (by the way what is the purpose for them?)
    3: can I replace the 1uF/25v with a 1uF/35v
    4: will the flashers from the turn signal bother the design or is it better to go striaght from the turn signal switch
    Thanks for the post and for any help given

    1. 1. A trimpot will do
      2. any ordinary DPDT toggle switch
      3. 1uF/35V will do.
      4. Straight from turn signal switch and not from the flasher unit.

      Thanks and Regards.

  12. dealing with the leds is kinda tricky due to the fact of the sodering in series, the diodes and resisters.
    but when dealing with the led max voltage, max continuos forward current and max peak forward current what do i go by to get to the resister i'm confused.....
    if the led is 3.6v max cont current is 30mA and the max peak current is 75mA and its 3 leds in series will 1k r work or 680ohm r to get the brightes glow
    cuase on line calculator recomends 18ohm or 47ohm r when doing the math
    sorry for being a pain just want to get the right resisters for the job


  13. Hi

    Does this work with ordinary tail light bulbs or does it have to be LED's? Thanks in advance for your help

    1. I am sorry no, this circuit will work only with LEDs and not with incand. bulbs

  14. Hello, I came across this via Google search. I am in the process of building a custom chopper and the shop that has my bike would like to run a set-up like this. I am not a circuit builder, where do I purchase the parts you used for this setup? I appreciate any input you can share.

    1. Hello,

      You can ask any local electronic retailer in your area, he would be able to suggest you better from where to get the parts.


  15. I am currently bulding a setup like this for my car and found your circuit to be very helpful. my question is how can you configure it so that the sequential overrides the brake function?

    1. You mean when the side signals are ON, the braking should not affect the sequencing?

      In that case you will have to do following mods:

      Introduce a TIP122 transistor in the circuit with its emitter connected to the common termination of all the 1N4007 diodes, connect the collector to supply positive, connect its base via a 1K resistor to the brake switch (to the cathode of the existing 1N4007 brake switch diode).

      Also connect its base directly to the collectors of the BC547 transistors via two individual 1N4007 diodes, the common anode of the two diodes will connect to the base of TIP122 and the cathodes will go separately to the collectors of the two BC547 transistors;)

  16. I am interested in building this set up but I have one question. When your driving lights are on will the tail lights be dim and brighten when brakes are applied? Or is that what the dim switch is for?

    1. I think there's a slight mistake with the brake switch connection, there's no ground available to the LEDs when brakes are applied. I'll correct it and update the article soon....

    2. I am sorry, the circuit has no mistakes..... yes, if S1 is kept switched ON then while driving the LEDs will be dimly lit and will brighten up when brakes are applied.

  17. Thank you so much for the great posting and diagrams. I am looking to create this circuit for my car. I think your response of Nov 29, 2012 defines what I want to accomplish, in that I want the turn signal indication to remain in an active sequencing mode even when the brakes are applied. The modifications you detail in your Nov 29 29 posting allows this to happen, true? If so, can you provide a diagram that shows the placement of these added components. Again, thank you.

    1. Thanks so much! appreciate your kind words.

      Actually the present work load is not allowing me to concentrate here, I wish I could do it immediately, yet I'll try to update the required diagram asap.

      Bets Regards.

  18. Hi Swagatam,

    Merry Christmas to you and to all your followers.

    i make this circuit but i got a problem. when im turning on the signal left or right the LED is not sequencing? what could be the problem?


    1. Hi Mike,

      Merry Christmas to you too!

      Did you check the circuit on table before installing?

      You will need to check it manually through a 12 power supply before installing it.

      Connect the LED resistor common ends directly to ground and confirm whether the circuit is sequencing or not.


    2. Hi Swagatam,

      i already test it connecting the resistor to the ground without the transistor. still the the same no sequence movement for the LED, all in light mode only like a break light.
      i check it also connecting the LED direct to IC 4017, the sequence mode is working.
      what would be the problem? is it something is missing?


    3. Hi Mike,

      Disconnect the diode common anode wire entirely from wherever you have connected it, then check.

      The LEDs are always ON means it's getting positive supply from the diode common anode, there cannot be any other reason for its continuous illumination.


    4. Happy New Year Swagatam...

      Thanks, it is working now. i thought the diode going to the battery is for the park light. it was my mistake.
      i have a little problem, how can i make the signal much brighter?


    5. Happy New Year to you too Mike!

      You may reduce the LED series resistor value to 470 Ohms for increasing the light intensity.


    6. Could you be more specific on the components. I tried to purchase the 4060, 4017, 7812 and BC547 components; however, some of these components have multiple suffixes. I would appreciate a specific listing of components and a possible source.

    7. I have provided the core numbers which are universally recognized, the suffixes are not important and can be ignored....the concerned dealer should know about all these, if he is unable to recognize them then it would be difficult for you.

  19. Hi Swagatam,

    I just recently started to put this circut together and was wondering why a 555 wasnt used instead of the 4060 as it is somewhat of a simpler chip(less pins)? I also had a question as i seem to not be able to get it to sequence, i've tried all Things i could possibly think it could be and have tried the solutions on here as well with no luck any idea would be great.

    ps. i have a background in electronics and i'm about to say that the chips i have bought are defective(hopefully not).

    1. Hi Jack,

      IC 555 can also be used, no issues..... in fact any design that is able to generate the required clocks is perfect.

      IC 4060 has 10 outputs and we want to use only one out of them, so eliminate the remaining 9 pins from the the total 16 pins, becomes 7, means it's even simpler than a 555 which has 8 pins. Moreover it's highly accurate compared to 555.

      You could probably check the stages separately, first check whether pin14 of IC 4017 is getting the required clocks from IC4060.

      Then check the LED, diode polarity etc etc.

      The design is pretty straightforward and their shouldn't be much problems making it work.

  20. Hello Swagatam,
    I found this circuit and it is very helpfull in designing a set of custom tail/turn/brake lights for my '86 Monte Carlo SS.

    One question: do you think it is difficult to make the turn signal a bit different, I want my turn signal not as chasing led's (only one on at a time) but they have to switch on after eachother and stay on until the last one lights up. Then all switch off and repeat the sequence.

    One remark: to control the brightness difference between the tail light function and the turn/brake function, I'm going to use a led dimmer based on a 555 (basically by varying the duty cycle) instead of changing the current through the led's by changing the resistor.

    1. Helo Toontje,


      I think you would love reading the following article, it's probably what you are looking for:

  21. Great write up! I'm going to do this within the next couple of weekends.

    2 questions...

    Do both sides need separate drivers, or is it one driver to run both sides?

    Also, looking at the LED portion of the circuit we'll take the left side for example, I'm confused as to why the right turn signal power is connected to the left turn signal.

    Thank you

    1. Thanks Chris,

      You won't require two drivers, the first circuit works for both the sides.

      The arrow heads from the LEDs which are assigned with identical numbers will need to be joined together and connected to the relevant diode termination from the IC4017.

      yes you are right, it looks like a drawing mistake, please ignore it, the right/left power must obviously join with the corresponding sections:)

  22. hi
    i am new to this.... i just want to know if 1uf 25v is non-polarize or polarize?

    thank you

    1. Swagatam,

      I have read this thread and some of the links. I understand what I want to do is entirely possible but I need some clarification and/or a specific diagram for my challenge.

      I would like the sequential turn signals like Toontje and Chris requested with the turn signals priority over the brake signal AND functioning (dimmer) tail lights when stop or turn signals are NOT in use.

      A link to a corrected, specific diagram would be fine.


      Also I want to use 10 outputs with 3 LEDs on each x2 for each side.
      (30 LEDs + 30LEDs for left and 30LEDs + 30LEDs on the right)

    2. Hello Bill,

      Please check out the first circuit given in this article. It should suit your application.

      Since you are interested to use all the 10 outputs, T1 disappears from the circuit and all the 10 outputs of the 4017 IC get configured with the SCR/LED network as shown.

      For each three LED string you will need a 150 ohms series resistor for limiting current.

  23. Hi , i wanna use this for turn lights
    1 this circuit is secvential , first led is on until last in on , or only one at 1 time ,
    2 you sad in one comment that max 3 led / 1out , connected in paralel?
    3 what happen if i conect from the flasher unit Taillight

    1. 1) it's sequential but one led at a time, not like a bar graph, rather it's like a dot sequence.
      2)yes three LEDs in series for 12V supply, a couple of more can be added with 16V supply.
      3) sorry, did not get your question??

  24. Hi Swagatam
    How could i use this circuit using a feed direct from the flasher unit? I was wondering if it could be modified in the same manner as the sequential bar graph circuit that has the time delay circuit addition to hold the current.
    I want to use the above for the rear indicators only and obviously the feed from the flasher is readily available - Rather than having to run a specific signal wires from the front of the vehicle to the rear just to supply the signals.
    Thanks in advance of any assistance


    1. Hi Brian,

      you can achieve the same by doing the following quick modifications.

      Increase the base resistor values of the BC547 transistors to around 10K, and connect a 470uF/25V capacitor between the resistor's outer ends (diode junctions) and ground.

      Do this for both rthe BC547 transistors.

      finally you may simply integrate the Right/left diode ends to the readily available outputs from the flasher circuit over the relevant turn signal lamp sockets.

  25. Hi Swagatam
    Many thanks for the swift reply to an old thread!
    I will follow up on your suggestion and maybe others will find the mod useful too!
    You've got a fantastic site here for the hobbyist and done some great work and provided a fabulous service for the less able
    Thanks again

    1. Thank you Brian! The pleasure is all mine!

  26. Hi (again) Swagatam :-)

    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

    1. Thanks Brian, I appreciate your interest very much:-)

      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....

      Best Regards.

  27. Hi Swagatam
    I really appreciate your assistance and the fast replies are a treat too!
    I have seen your piece about limiting resistors on another page and thanks for reiterating it.

    I really pleased I've given you some food for thought in enhancing your original design!!
    Im looking forward to seeing the revised diagram ....if and when you have the time that is! I'm on a steep learning curve and think I get your explanation but the proof will be a bonus.

    1. Thank you Brian,

      I'll draw the schematic and try to post it soon in a new article, for your reference.

    2. Thankyou again Swagatam!
      As a child I used to pull apart old radios to see how they worked. That was a long time ago ( hint pre transistor) Since then I've always been fascinated by the world of PC's and now, with your site, I've had my interest in electronics reignited!

    3. You are right Brian, I too started in the same manner, and I think most of the hobbyists usually begin by breaking and mending old junks.
      Be assured with my association your electronics passion will not just ignite but light up fiercely:)


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