LED taillights

Discussion in 'The Projects Forum' started by Picksl1, Jan 4, 2009.

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  1. Picksl1

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    Jan 4, 2009
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    I am an auto DIYer with minimal knowledge on electronics, but am determined to make LED lights for my car because nobody makes aftermarket taillights for my car. One problem I am running into is that my 2057 bulb is dual filament and I can't figure out how to make the LEDs appear brighter when the brakes are applied. I haven't decided on which LEDs to use because I am also at a standpoint where im not sure if a higher MCD will be better or too bright for taillights on a 1995 Saturn SL1 that has a red lens with ridges to difract the light. If you guys had any ideas for MCD brightness please pitch in ideas. My tails board where I will mount the LEDs measures 6"x2 3/8". I plan on using 72 LEDs per tail. At first I was thinking use 4 rows for brakes and 4 for tails, but then I realized that when the brakes are applied the LEDs would be the same brightness.

    Most of the LEDs I've looked up range from 3.2-3.8 volts, so I figured wire them by connecting pos to neg of each row of 4 LEDs then the pos of each row to the taillight socket and neg of each row to the neg side of the socket. This way I wouldn't have to use any resistors. I was looking at some LEDs in 5 MM:
    http://cgi.ebay.com/100-5mm-13000mc...06987QQcmdZViewItemQQ_trksidZp1713.m153.l1262

    http://stores.ebay.com/Light-of-Victory-Led-Store-lvehk_W0QQfrsrcZ1QQfsubZ3103116QQtZkm



    I have also tried the 2057 bulb from the auto parts store and they just aren't bright enough. The incadescent bulb spraed the light over a wider area of the lens as opposed to the LED bulb just having the light in a small circle of the lens.
     
  2. Picksl1

    Thread Starter Member

    Jan 4, 2009
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    It probably would have helped if I added my question. DUH!!!! What would be the best way to make the LEDs appear brighter when the brakes were applied? Or would I be able to achieve that by tapping into the socket and not using any extra components? I've heard of people using PWM's, but that was for more "dancing" of the brake or turn signal function, which is one thing I could care less about since I have small taillights in my opinion.
     
  3. Wendy

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    Mar 24, 2008
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    There are lots of ways to do this. It really depends on the wiring in your car though. As I understand it most tail lights are dual filiment, actually 2 lights in one. It would seem that you could do something similar with the LEDs, use two LEDs, one designed to be dimmer than the other.

    PWM (Pulse Width Modulation) has nothing to do with light chasers (aka "dancing"). It has everything to do with brightness of the LED.
     
  4. mik3

    Senior Member

    Feb 4, 2008
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    I am not sure about what value of brightness you have to choose but have in mind that LEDs brightness decreases with as the viewing angle increases.
    You can use half of the LEDs for the tail and half fr the brakes. When the brakes are pushed it will be brighter because all the LEDs will light (at night because the tails will be already on) and not only half. During the day half of the LEDs will light for the brakes.
     
  5. Wendy

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    Assuming there is a defusion filter or red tape it will take care of the LED tight beam problem, I would think.
     
  6. mik3

    Senior Member

    Feb 4, 2008
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    Another think I forgot to mention is that you have to use resistors in series with the LEDs to limit the current. Because the voltage across the LEDs varies with temperature and they have low internal resistance you may burn them. A resistor will make the design safer.
     
  7. Picksl1

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    Jan 4, 2009
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    Based off the links of the LEDs I posted in the first box, which size resistor do you recommend and how many? Also both links are 20+/-5 degree viewing angle. If I get the 55k MCD ones do you guys think they would be too bright? I found a link to measure lumens if you have the viewing angle and MCD. When I put in 55K MCD and 25 degree angle I get 8.192 Lumens. The 2057 bulb puts out 402 Lumens.


    So if I am thinking correctly then.....
    a single 2057 bulb= 402 Lumens
    a 55K MCD LED with a 25 degree angle= 8.192 Lumens


    If I use 72 of those LEDs would I get a rating of 589.824 Lumens?
    This would be brighter than the stock bulb then? <--sounds like a stupid question, but I ask therefore I learn :)
     
  8. Wendy

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    Mar 24, 2008
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    Truth, before we start with electronics you need to figure the mechanical arrangement. This is because it will determine how many LEDs you will use. You also need to figure out the basic configuration of the lights, in other words, you have two lights, the tail lights and the brake lights. They are separate circuits. Then you have the turn signals. Are they a separate circuit? This is a combination of the electrical and mechanical layout. Are you going to use plywood and press fit these LEDs into it, screwed into your car somehow?

    Basically you have some experiments to get all three of these lights to work they way you want them too. The actual electrical implementation is pretty easy.

    The lights you were looking at on eBay were white. Wouldn't red LEDs be better? They are definately cheaper. If you haven't bought them yet we can refer you to better sources.

    I haven't actually gone through your math, but from what I see it appears sound. The mechanical arrangement is the hard part. The resistors are easy (cheap too!).
     
  9. Bear_2759

    Active Member

    May 23, 2008
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    after learning allot myself with a project I am working on, I would suggest using a PWM to controll the brightness, my guess is you are in the states? I'm not exactly sure what the laws are about the taillights/indicators etc are in the states but know they are different from here in Aus... the part I'm not sure about is here in Aus, the indicators need to be seperate from the tail lights, but I don't think that's the case in the US...

    FYI when PWM is used for brightness, the lights do flicker, but faster than the human eye can see. for example if the duty cycle is 50% then the brightness of the LED's is 50%, if the duty cycle is 75% then the brightness is 75% and so on.

    lets say the circuit is all finished and wired into the car.
    headlights on, duty cycle = 50%
    Brakes applied, duty cycle = 80%

    if the indicator is part of the same fitting as the brake/tail lights, then you could have the PWM increase the duty cycle by 20%. how to do this I don't know, haven't really thought about it but sure its possible.:rolleyes:

    I may be overestimating my knowledge here as I too am a bit of a noob but I think PWM is the best way to go. I would suggest asking one of the many experts on this site first though...

    and I agree with Bill, you need to work out what LED's your using and the physical layout which will determine how many LED's you end up using in total then it's easy to work out the total current required, then the circuit required to controll them. I would suggest (if you havn't done so already) get a spare pair of tail lights from a wreckers to experiment with then when you're done do a straight swap. or if you can't afford that then a piece of ply or something to work out the physical layout on.
     
    Last edited: Jan 4, 2009
  10. Picksl1

    Thread Starter Member

    Jan 4, 2009
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    http://s420.photobucket.com/albums/pp283/picksl1/LED tails/

    There is a link to what I have planned out so far. Those were the only LEDS I had from a previous project.

    These are the boards I plan on using:
    http://www.radioshack.com/product/index.jsp?productId=2103804
    I would need to trim this one down a bit to the size of 2 3/8" by 6 for the taillights/brake lights. I will also use the remainder of the board for the turnsignals

    http://www.radioshack.com/product/index.jsp?productId=2102844
    This one is just 2cm shy of being perfect. So after a little sanding, this one will be perfect for the reverse lights, which I plan on using blue LEDs for. Yes they are illegal, but how often does a cop see you in reverse. The inspection stations in North Carolina don't check reverse light anyways. I've passed in my car with blue reverse lights 3 years in a row and my Jeep passed and the reverse lights don't even light up. LOL.
     
  11. Wendy

    Moderator

    Mar 24, 2008
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    Your photobucket account is password protected. You could use the albums here on AAC. Until then, your photobucket link is busted.

    Think patterns of LEDs and what they are going to do. Here is a layout I made for someone else...

    [​IMG]

    You can also display images directly, like I did above, if you know the http address. Put it between {img}{/img}, but substitute brackets "[" and "]" for the { }.

    Check this thread out...

    http://forum.allaboutcircuits.com/showthread.php?t=14451
     
    Last edited: Jan 4, 2009
  12. Picksl1

    Thread Starter Member

    Jan 4, 2009
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    [​IMG]


    THIS PIC SHOWS THE TAILLIGHT LAYOUT WITH PAPER DRAWINGS


    [​IMG]


    TURN SIGNAL AREA. THE SMALL HOLE ON THE RIGHT WILL HAE A DOWEL PLACED IN IT TO HOLD THE PCB OF LEDS


    [​IMG]


    THIS IS A PAPER DRAWING OF THE SIGNAL. THE LEDS WILL GO IN THE MIDDLE OF THE SQUARES


    [​IMG]


    HERE IS THE REVERSE SECTION. YOU CAN SEE THE DOWEL ALREADY IN PLACE TO SECURE THE PCB OF LEDS. I PLAN ON USING BLUE LEDS FOR HERE AS I ALREADY HAVE BLUE REVERSE LIGHTS. I KNOW ITS NOT LEGAL, BUT THE INSPECTION STATIONS DON'T CHECK FOR THE REVERSE LIGHTS AND WHEN WOULD AN OFFICER SEE YOU WITH BLUE REVERSE LIGHTS?


    [​IMG]


    HERE YOU CAN SEE THE 5mm LEDS WITH THE TAILLIGHT LENS ON. THEY TOUCH THE LENS SO I THINK I MIGHT HAVE TO GO WITH 3mm LEDS SO THEY WON'T TOUCH


    [​IMG]


    ANOTHER SHOT OF THE LEDS TOUCHING

     
    Last edited: Jan 5, 2009
  13. Picksl1

    Thread Starter Member

    Jan 4, 2009
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    [​IMG]

    HERE YOU CAN SEE THE TAILLIGHT LENS INSTALLED AND THE SHADOW OF THE PCB THROUGH IT.

    [​IMG]

    LENS OFF AND YOU CAN SEE THE 2 DOWELS THAT WILL SUPPORT THE PCB. ONE ON THE TOP LEFT AND THE OTHER ON THE BOTTOM MIDDLE. THE DOWELS WILL NOT INTERFERE WITH THE LEDS BEING MOUNTED AT ALL.


    [​IMG]

    THIS PICS HERE SHOWS THE LEDS MOUNTED 9 WIDE. I DIDN'T HAVE ENOUGH LEDS, BUT THEY WILL BE 8 DOWN FOR A TOTAL OF 72 LEDS PER TAIL/BRAKE CIRCUIT. 4 ROWS WILL BE USED FOR THE BRAKES AND THE TOP 4 ROWS WILL BE USED FOR THE TAILLIGHTS. TOMORROW I WILL TAKE A LOOK AND TRY TO FIGURE OUT HOW TO ACTUALLY SOLDER THEM INTO THE SOCKETS.


    ALTOGETHER EACH TAILLIGHT ASSEMBLY WILL HAVE 140 LEDS :)
     
    Last edited: Jan 5, 2009
  14. Picksl1

    Thread Starter Member

    Jan 4, 2009
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    In the last pic I just put the LEDs I had through the paper I was using to design where I wanted the LEDs to go and put them on the PCB
     
  15. Wendy

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    Mar 24, 2008
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    Cool. I wouldn't worry too much about the LEDs touching, if it really bothers you you can take a dremel and cut the lense down.

    You could use a variable current scheme (which PWM is a subset), or have two sets of LEDs on the board, one being the brake, the other being the turn signal. When both are on it is twice as bright, and you can figure out which you want brighter.

    With blue and white leds, you can connect three in series, with red, green, or yellow you can 4 in series, each group requires its own resistor. The exact type of LED will require a different resistor, though they can loosely be grouped according to colors.

    Assuming you have two groups intermingled, how many LEDs per function? If not this scheme how are you planning on doing it?

    To make it a bit clearer I'll draw quick schematic to show what I'm talking about and post it in a bit.

    [​IMG]

    This particular scheme has some problems with a car. At this point I wouldn't worry about it, but lack of regulation for the auto's voltage is a problem, as they can vary between 12VDC to 13.7DC (or more). If this turns out to be a major issue there are a lot of ways around that are pretty simple, one transistor, one resistor, one zener per bank of LEDs (above is 2 banks).
     
    Last edited: Jan 5, 2009
  16. SgtWookie

    Expert

    Jul 17, 2007
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    You'd really be better off using something like Phillip's Superflux LumiLEDs.
    HPWT-xH00-, where "x" = M (100°), D (70°), or B (50°).
    Typical Vf is 2.5v @ 70mA.

    See the attached datasheet. [eta] In particular, look at
    HPWT-RH00-x400 where x=D thru H - these are 25°x68° focused LEDs; use the 25° in the vertical, 68° in horizontal. See page 8, 2nd graph on left.

    The HPWT-xH00- series are red-orange, which are compliant with the US D.O.T. color specifications for taillights. This means that your taillight lens will have minimal impact on the brightness of the lights whether it's on or off.

    White LEDs emit a broad color spectrum of light, where the red-orange LEDs emit light only in the proper color spectrum (about 620nm). Your red-orange taillight lens will block all of the off-spectrum light; with the white LEDs, most of the light will be off-spectrum.

    These LEDs are much lower profile than the LEDs you are considering, and are VERY bright. You will need fewer of them than the 3mm/5mm that you're considering.

    Don't let the lumens rating on a narrow-focus LED fool you. Your taillamp lens will scatter the light widely. You might as well get some honest numbers; this datasheet will give you that.

    When will the police see your blue back-up lights?
    When you shift from Drive to Park after they've pulled you over for some other infraction. :eek:

    Using any kind of blue lights that are visible outside of your vehicle is not only illegal, it's a very bad idea.
     
    Last edited: Jan 5, 2009
  17. Wendy

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    Mar 24, 2008
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    What do you think the cost is for those, and how many per light?

    Would the scheme I've been suggesting work? I suspect a regulator will be needed, but it may have been a good idea in any case.
     
  18. SgtWookie

    Expert

    Jul 17, 2007
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    Gee, I guess Philips isn't making them anymore; I can't find them in stock at my favorite suppliers; or anywhere else for that matter.

    However, here's a close substitute:
    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=160-1511-ND
    typ Vf 2.15 @ 70mA , 70° view, 2 lumens typical. 10 for $3.65 + shipping.
    Datasheet: http://optodatabook.liteon.com/DataBookFiles/7197/LTL91xVxKSA.pdf

    As far as how many per light, that'll be a bit of a problem to calculate. I don't know what percentage of a tungsten-filament bulb's light spectrum is filtered out when it passes through the taillamp lens assembly - but it'll be a LOT of it. As I mentioned before, these LEDs will generate light only in the correct spectrum (618nm-625nm) so comparing these LEDs to a tungsten filament incandescent bulb is sort of like comparing a sniper to a large bomb.

    Keeping the parts count low (and from a reputable source like Digikey) will be good for reliability and speed of assembly.

    Using brighter and fewer LEDs will allow our OP to use a smaller board, pulling it further inside the reflector assembly, which will make for better diffusion.
     
    Last edited: Jan 5, 2009
  19. Wendy

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    Now we find out if the OP already has a pile of parts, or is willing to spend more money.
     
  20. Picksl1

    Thread Starter Member

    Jan 4, 2009
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    Ahh the joy of a stick shift:)


    Right now I don't have any LEDs but the ones in the picture above so I am willing to buy. I didn't buy anything yet, as I was unsure of which MCD to get or degree of beam. However from this 2 days I have learned ALOT!!! You guys are genius's compared to me.

    Since the superflux LEDs have 4 pins, how would you connect them? From seeing the data sheet I see there are 2 + and 2 -. Would that mean I could connect only 1 + and neg connection for the tails and then use the other anode and cathode for a separate brake circuit making the tail light be twice as bright?

    I was also thinking about using SMD LEDs being as they are small in size, but I've never used them before and didn't want to buy so many and have them not work out correctly. However, after getting advice from here, I can feel confident that I can buy enough of ANY kind of LED to light up a landing strip at an airport.
     
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