LED tails for B5

[Steve in Chicago]

I'm trying to modify my B5 tail lights to have the LED look of some of the newer cars out there. I've yet to see something aftermarket that I like. One of my bosses has a Cadillac Deville with factory LED tails. These tails create a solid panel of light with no bright spot in the center. The entire panel goes on/off, simply appearing and disappearing as one uniform block of light. There are two sections of panel on the Cadi tail so it can indicate running, brake, turn lighting. If you get an opportunity, notice how the Cadi tails look next time you're behind one of them.





I'm going for a similar effect, with solid, uniform blocks of light flicking on/off without the glow-on/glow-off of incandescent lights and no "hot spot" in the center. I've tried upgrading the bulbs to LED plug-in bulbs and that gives a nice digital on/off. But they still have a hot spot and aren't a uniform panel of light.

I saw a Deville with a smashed tail and looked at how GM gets the "panel effect". They have a layer of refractors between the bulbs and the outer shell of the tail light.

[Steve in Chicago]

So, I cut open a B5 tail light and installed two layers of refractors over the various sections of tail light.

This is the outer shell of the tail.


In the reverse light section, there is a blue filter I removed.
I want my reverse lights as bright as possible.
In the turn signal section, there is an amber filter I removed.
This part is why the OEM bulbs are clear. The amber color comes from the filter.
The LED bulbs I'm experimenting with for the turn signal section use amber colored LED's.


Two layers of refractors cut to fit the various sections of the tail light housing.
The bottom layer is clear prismatic pattern.
The top layer is clear cracked ice pattern.


Opened up fixture and panels ready to go in.


Panels tacked in place with hot glue for testing.


Modified fixture tacked back together for testing.



The results looked good, but not good enough. There was much less of a hot spot in the center but it still had some. The results weren't worth the effort.
I think the only way to get the same effect as the Cadi is to do what GM did and switch from one bulb in the center to multiple LED's spread evenly across a panel behind the refractors.

Cadi tail refractor panel. Looks like fresnel lenses.


Cadi tail LED panel.

[Steve in Chicago]

So the next question is quantity and type of LED's. I looked around a little bit for flexible PCB and didn't find anything practical. I'm thinking a flexible PCB bristling with LED's to lay in the arc of each reflector section.
Since I'm going for a solid block of light effect, I'm thinking MANY led's that don't need to be significantly bright per bulb.

Keith, if and when I come up with a final design, I can ship you my "research & experiment" fixtures so you can explore your style mod options on B5 tails.

[Steve in Chicago]

Keith's answer from the other "LED Tails" thread.

Led tails for b5.5., but are they for sale?

You are correct that you will need multiple small LEDs in arrays. The arrays will likely have to be comprised of several balanced sub-arrays or you will have uneven light production.

The LED studio designers have some SMDs and clear (not chrome) reflectors that would work well in parallel rows, perhaps three or four deep with each B5 tail segment. The same design I was noodling for B5 tails using chrome reflectors may produce the effect you are seeking by using clear reflectors with a diffuser lens over them.

I'll order some samples this week of both. Then we can mockup the B5 tail arrays with the clear and the chrome to test each. But they will have to be mounted on flat PCBs. Don't think we can spec curved or flexible PCBs.

[Steve in Chicago]

I ordered some prototyping PCB's and some LED's to do some mock-ups with.

PAD3U BusBoard Prototype Systems | Mouser

5mm Red High Flux LED | Component LEDs | Super Bright LEDs

5mm Yellow High Flux LED | Component LEDs | Super Bright LEDs

I'm hoping I can use these in the reverse light section if they don't produce too much heat.
5 Watt MR16 LED bulb - Multifaceted Lens with High Power Epistar COB LED | Boat/RV/Other Bi-pin Bulbs | Boat/RV/Other LED Replacement Bulbs | Boat, RV, and Other Lighting | Super Bright LEDs

[CotySinz]

Nice job so far Steve, interested in the outcome. Subscribed to say the least.

[gostivar]

GO STEVE

[dtgrdn]

x2 on the subscribe

[the_abuse]

why dont you buy the litek led taillights they look like the golf R ones

[keithwbloom]

I don't know how much time to want to spend with project PCBs, but I was thinking your effect would be attainable with arrays made from these:



You can buy them at the LEDStudio DIY site.

Each array row can be up to 37cm or 14.5" long and is 13mm or 1/2" wide. To get your effect, I would suggest not using the pictured reflectors, but rather some overall diffuser type cover like you have already been experimenting with. Stack 3 or 4 rows of these arrays, and stagger them on a 1/4" shift and you will have a tidy light panel to back light your diffusers.

These are the style of arrays I was projecting to use with B5 tails design in my thread, but I was planning to use the reflectors and ultimately have custom PCBs printed so the rows were all on one flat within each tail cell.

These arrays also support 3-chip SMDs, which allows for you to design with two colors on the same reflector. With a little Arduino processor, I am betting you could put on some fancy, shmancy light shows to entertain your victims as you leave them behind.

With all those LEDs in series, you are going to have arrange them within rows in sub-arrays with in-line resistors to to balance light output. I didn't see them in your parts buy. I can't remember where I came across an R value calculator, but was very handy. It could calculate the sub-arrays and Rs needed for each if power specs and total LEDs in array were input. I might have some reference data in my project folder for the B5.5 rounds, which were tricky to do sub-array design on because of the requirements to have the outer and inner rings on the separate circuits so they could be progressive. If I can dig up the calculator URL, I will post it here.

Glad you are taking a stab at this, I have been noodling it for some time, and actually the B5 tails are much easier to design for than the B5.5s, so I was going to have a go at this exercise first. Looking forward to your progress. Let me know if I can help. I have several pairs of B5 and B5.5 tails here to mess with.

[JayTheSnork]

why dont you buy the litek led taillights they look like the golf R ones

[keithwbloom]

why dont you buy the litek led taillights they look like the golf R ones

Because the B5 is nothing like the Golf R perhaps? It is amazing that aftermarket tail light designers think that everyone wants their 10+ year-old cars to look like they just came off the set of Furious Five. The B5 tails need freshening, that's a given. But the B5 and the B5.5 for that matter do not have the lines of a Lexus, Scion or Hyundai, and there is no design element of the B5 chassis that makes an angular, Klingon glyph graphic complimentary.

My 2¢.

On a side note, for those must have the Golf R Spec look for your B5, please consider stealth bulbs for the amber turn signals. That yolk look is hideous-er.

[Steve in Chicago]

Why don't you buy the Litec led taillights? They look like the golf R ones.

I can see how those might appeal to some, but they aren't my cup of tea.

[keithwbloom]

I can see how those might appeal to some, but they aren't my cup of tea.

What office are you running for? Have you kissed any babies today?


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[Steve in Chicago]

Keith...

I like those linear PCBs a lot. With 3 chip LEDs and a controller, something as fancy as the Bugatti Veyron tails could be done.

I'm planing on sub arrays wired series-parallel. 5 to 7 LED's make up a sub array. The actual number will depend on how the parts I ordered behave. I'll make a series and measure voltage drop across one component to see if I need to add more or remove to get me close to the components "typical voltage" and below its "max voltage". Sub arrays will be wired parallel to each other.

As for layout, staggered rows. The physical rows and the series strings don't necessarily need to match. The series break can happen anywhere. Lets say I decide on 6 LEDs per sub array. I can make 3 physical rows of 8 as long as they are wired into 4 sub arrays. The lower brake section is smaller then the upper brake section (5-brake light mod). I'll need to experiment and see what works best to get both sections to illuminate with the same intensity. Maybe 3 sub arrays in the small section and 4 in the larger.

If that doesn't go as planned, I'll turn to resistors.

[Steve in Chicago]

What office are you running for? Have you kissed any babies today?

Haaaaaaaa!

In that case, I'll second Jay's opinion.


I've got to check out that LEDStudio website. It'll probably spark some good ideas.

[Steve in Chicago]

With 3 chip LEDs and a controller, something as fancy as the Bugatti Veyron tails could be done.

This is the best I could find showing Veyron tails in action. The frame rate of the camera is messing up the effect so it looks all wonky in the video.
I'm not going for this effect but I wanted to post an example so people would know what I was talking about.

[Bdubskii]

Not so much better quality, but found this, it shows the left tail lights LEDS circling the light, pretty nifty.

[Steve in Chicago]

The LED bulbs arrived today but the circuit boards won't come till Monday. I test fitted the LED spot lights in the reverse light section and they fit with room to spare. I closed up the fixture and powered it at 12.4v for 10 minutes to check the heat output. Afterward, the bulb was only slightly warm. The plastic fixture was very slightly warm. Much cooler than what I would expect to see from the stock incandescent bulb run through the same test.



Was it bright? Were you born on the SUN?!!! Yes, it was bright.

I did a brief test with some of the component LEDs and it looks like a series of 6 will probably work well. That will put each bulb at the "typical voltage" spec if powered at 13.2v and not hit the "max voltage" spec unless that circuit jumped to 15v. More testing needed.

I haven't yet decided how I'm going to do the running lights vs brake lights In the uppermost section. I can have separate arrays for the separate functions. Or I can have the same array run at two voltages. The second one is probably simpler.

[Steve in Chicago]

Calling on electronics geeks!

Should I head up each array circuit with a linear voltage regulator like an LM7812? A Current Regulating Diode? Or is there a better way to do this? Or is this unnecessary?

[vwb5t]

since im not paying attention to the LED's you are using got a specs sheet on them? mostly looking for the voltage range

also keep in mind the LM78 regulators need higher input voltage than the output to work, so to put out 12 volts it needs a min of 14 volts to work. all fine and dandy when the car is running, assuming alternator is actually putting out 14.4 volts, but the second the engine shuts off you will have no rear lights at all

my mom would be so proud of me, all that money on my electronics degree and i actually remembered something from it.

[Steve in Chicago]

5mm Yellow High Flux LED | Component LEDs | Super Bright LEDs

5mm Red High Flux LED | Component LEDs | Super Bright LEDs

These are what I'm working with. Typical forward voltage of 2.2v and max forward voltage of 2.5v. Six in series should be able to handle up to 15v?

[euroblood]

hey if the b5 tails are made of acrylic, you can use a solvent to melt scraps into a paste useful for reassembling the body of the light. i did this a while back while attempting to make a custom set for my 89 golf... the paste worked so well that the lights were as strong or stronger than the originals. the only problem was that the paste formed bubbles that could be seen through the clear part since the solvent i used boils at room temp. of course if you are using it in a place where it cant be seen, then its perfect for the application! the other problem is that the paste dries very fast and so needs to be applied quickly. it also shrinks so if you use a lot of it you can melt surrounding acrylic and make the whole assembly very tight.

[Steve in Chicago]

euroblood... Good to know. I may try putting some shavings in acetone (or another solvent) to see if this type of plastic will do that. I'm not yet sure how I'll be attaching parts and sealing the fixture closed. Tricks like that might come in handy.

vwb5t... so should I use an LM7809 and make all the sub-arrays run at 9V? (4 in series would want 8.8V normal with a 10V max) Or is this entirely unnecessary and I should just set up the sub-arrays up to run at battery/charging voltage with no voltage limiter? (6 in series) The reason I thought I might need a limiter is to protect the LEDs from voltage spikes or over-volting. Also to make sure they are the same brightness no matter what the buss voltage is (car voltage fluctuates depending on what's going on). Maybe this is an added complication I don't even need to worry about. I definitely don't want the tails to go off during cranking.

[vwb5t]

The lm7809 would work just fine, you are looking for a minimum of 8.8 volts to run the LEDs at there voltage.

The 7809 puts out 9 volts at 1amp so it would work pretty good, each led is looking for 100 milliamps. You could use a current limit resistor if you are worried about spike or frying the LEDs. But, and I don't feel like doing the math out so estimate would be around a 5 ohm resistor as a current limiter without reducing the voltage too much.


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[vwb5t]

As for tails going out during cranking, I don't recall how the passat deals with it now I know it shuts off a few circuits when cranking so max power goes to the starter. I don't remember if the tails or cut or stay on during that cause I've never had a reason to check


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[vwb5t]

The power of the Internet, there are now calculators online for everything including current limit led resistors. Calculator says you want a 2 ohm as a current limiter. I was pretty close


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[Steve in Chicago]

I'm pretty sure the load reduction relay does not cut power to the tails during cranking. That could get you killed if you were trying to restart a stalled car in the middle of the road in the dark. What I was wondering about was your comment about the voltage regulator cutting off power below the voltage limit. If the voltage dropped under 12 during cranking (likely), the lights would go out. That's what I want to avoid.

Unless there is a good reason to include a limiter, I'm now thinking I should just wire everything to run at battery/charging voltage (6 in series) and leave it at that.

[vwb5t]

Steve, I completely forgot about that part about the cranking and stalled.

Throw a volt meter in the tail light and crank the car are what the voltage is


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[Steve in Chicago]

I picked up one of these today because old people like me can't see to solder small stuff like they used to. (and this stuff isn't even all that small)



Going to do the turn signal sections first. Pix tonight.