led taillamps

Hi all

I would like to put together an led tail light setup and was looking for info from the people in the know. From reading the postings, i guess the best way is to have strings of 6 leds or so but how do i get them to be dimmer for park lamp and brighten up for brake without having separate strings for the brake line? I know i need to use a resistor kind of setup but what size/wattage etc.
Also, i want use 3 rows of 6 colomns of yellow LEDs in each of my 12 v motorbike turn signals. But rather than have them all just flash on and off with the flasher, i want to use a chaser circuit so that it flashes the 1st colomn then the 2nd then the 3rd etc and from the 6th, back to the 1st. Could anyone hook me up with a schematic for these projects please. Any assistance would be greatly appreciated.

Just buy ready made stop/tail or indicator LED lamps if they are legal to fit etc.
Note that you will probably have to modify your flasher can etc.

Whilst there are many options for sequencers etc, I am reluctant to help unless I am assured of legalities etc - not only for sequencers, but for the use of LEDs in your particular vehicle.
Especially for motorbikes - enough are being hit without having invisible LEDs adding to the problem.

Hi again, as you can see, im in SRILANKA where having ANY sort of light on a motor vehicle is legal!! As for led lights, brand new bikes as well as cars these days come with them as standard and as far as i can see, they are more visible! But thanks anyway.

Yes - but new vehicles are designed for LEDs etc, just like HIDs.

But more importantly in more regulated countries, they are approved with LEDs etc. Older vehicles lack such approvals.


You probably know this already, but the simplest approach is decide what LEDs you want to use (superbrights etc) and note their voltage (forward voltage drop - typically ~1.7V or ~3.2-3.6V) and their (maximum) current - typically 20mA.
Then it's a matter of having a number in series that suit the voltage of the vehicle (typically 12-14.5V) and as many in parallel as desired for overall brightness.

You might decide to have 3 or 4 ~3.4V LEDs in series (~10.2V or ~13.6V) etc with or without a series resistor, though usually a resistor is used.   

For the stop/tail, you can use separate strings, or only some LEDs, or have the stop +12V bypass some LEDs or a resistor - eg maybe 4 x 3.4 LEDs and 2 series 36 Ohm resistors for tail, and the stop bypasses one of the resistors.


For a sequencer, probably the simplest is to use a 4017 "1 of 10 counter" as a divide by N counter - a clock increments the output pin and the reset is connected to the N+1 pin so it goes 0, 1, 2, ...N (N+1 goes back to 0 = 0, 1, 2, 3... etc.

Your best option would be to go a microcontroller route.  You can kill all your birds with one stone - dimming, sequencing, etc.  Using resistors to dim the LEDs isn't the best route to go - Pulse Width Modulation is much more consistent, much more predictable, and actually easier to implement (with a microcontroller anyway). 

The only problem with it is that now instead of just needing someone to design the hardware for you you will also need someone to develop the code that makes the microcontroller work!

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Kevin Pierson

LOL!!!

I was gonna reply with a smartRs remark about not not PWMing LEDs etc as per mp3car's Changing cold cathode backlighting to LEDs as well as directing rasa to the PWM circuit partway down page 3 and an earlier thread comment about someone using PWM for their stop/tail.

Alas I now note that the dude that originally begged to differ with my writings etc has since deleted ALL of his replies.
So much for his 20-odd years of experience - it has taught him well.

Whilst I dislike "accusers" that the drift into the woodwork, most readers seem smart enough to figure why.
But as to those that continue to try to win an argument by bluffing with seemingly relevant references; transference to others.... especially when I am trying to ascertain if there is some point to their argument, else correct their thinking.
But in this case, the gutless protagonist even deleted his own posts! LOL!
And thereby the one justification for the12volt's non-ability to post-edit & delete documents - even though for the majority it would be beneficial.
Unfortunately for that mp3car woos, his posting can be reproduced in full. (Should anyone so request....)


Alas, I digressed and in doing so have touched a rule or two....

But that thread has some good PWM stuff.
I have used the 555 circuit shown to dim DC fluorescent lamps, LEDs etc etc.