Sequential LED Taillights

MisterBill2

Joined Jan 23, 2018
18,167
I'm pretty sure that all the automotive red LED tail-lights use red LEDs.
It would be more costly and inefficient to use white LEDs.
That was the point that I was hoping to be making. It seems that I am misunderstood a lot these days. But I don't know what the forward voltage is on those super bright RED LEDs. My point has been that the series string drop should be around ten volts. The idea being to have the resistor dropping less than one LEDs forward drop. And the current set to be just a bit below the max operating current at the absolute top DC system voltage, probably maximum charging.
Then for normal operation the current should be comfortably below that level. It is not a good idea to run LEDs at the max value, just like it is not wise to run your car's engine at the rated horsepower just short of red-line RPM for extended times.
 

Thread Starter

bwilliams60

Joined Nov 18, 2012
1,442
@bwilliams60 Look at how the OEMs are doing it, your a car guy right? Go to the local car dealer or parts store and ask to look at some replacement lights.
I may have to go that route. Although I spend a lot of time on automotive /Truck and Coach electrical/electronics, I haven't spent much time tearing things apart like I used to. I think a trip to the yard is in order but here is what I do know from the past components I have taken apart. Most lighting units are wired in groups with resistors as mentioned, and then the current is controlled by the BCM so that is why I am looking so hard at current control for my setup. This car does not have a BCM. I do a lot of cluster work and same thing only SMD. They are current controlled through BCM.
One thing I haven't floated out there is zener diodes. Anyone?
BTW, a lot of the ones I have taken apart have white LEDs and colored lenses. Interesting thought. Maybe I should collect a few lenses and use all the parts from them :)
 

MisterBill2

Joined Jan 23, 2018
18,167
At the start of this thread you gave some fairly small dimensions, which I had presumed were the lens sizes. So it seems like you are going to have quite a few LEDs in a fairly small space. That should help decide how big the rest of the circuit package is going to be.
And it has hit me that on some cars the turn signals were yellow so that stupid folks could tell the difference between stop lights and turn signals. They are all red on my cars so perhaps that fad has passed.
 

Thread Starter

bwilliams60

Joined Nov 18, 2012
1,442
Nothing has changed since the start of the thread. I am still in a small space and trying to calculate how many LEDs I will need. Maybe only two rows of ?? I am guessing multiples of three. I am playing with size/spacing/lumens/heat. There is a lot to consider to do it right. Maybe I am overthinking it but I want to make sure it is correct.
As for the stop and taillamps, they are all red, no yellow here. And that will be the next adventure. As soon as I get the reverse lights sorted to my satisfaction.
 

Wendy

Joined Mar 24, 2008
23,415
@Wendy, I think we are thinking along the same lines so far. I was thinking of an LM317 as you mentioned. The lens is a stock lens that comes with the vehicle so I will experiment with LEDs in a dark room with a photocell or LDR to measure resistance values according to light.
1W Super LEDs seems to be the way to go but I want to make sure they are not too bright.
There will be three circuits in total. 1) reverse lighting 2) taillamps 3) brake/turn lights
Do you think I will need an LM317 for each circuit or will one do all three? I am not sure on the limitations. I guess I should grab a datasheet and do some experimenting to see what it can handle.
One quick question about the LM317. If I use this, do I not drop a couple of volts across it before it hits my circuit?
The reason I mentioned going with a LDO 3 terminal regulator is to eliminate the voltage drop associated with the LM317, I don't have the new generation of part numbers memorized yet, but it will happen with time. The difference in voltage drops is worth switching over to the new part. You will still need to heat sink it. Just because an LED is rated for 0.3A (1 W) doesn't mean you have to drive it to the max. It will last longer too.

Experimentation is always the fun part for me.
 

Wolframore

Joined Jan 21, 2019
2,609
Just a couple points to add

although the amount of photons are generated linearly with increasing current, our eyes see brightness logarithmically, brightness at max and half power is not that noticeable.

another important fact. White led is not actually white it’s blue. LED light has very narrow bands and does not include full spectrum. You will be disappointed to put a red lens on most white led unless it was produced using an RGB led.

the amount of light generated by led is far superior to filament bulbs. so 1 watt LED can be extremely bright. My 60 watt filament bulb was replaced with 6 watt LED. 10:1 ratio is a good rule of thumb. So if your 1157 are about 3-5 watts. You need 1/2 watt of LED per bulb. You can still use the 1 watt LED but no need to run them all full current.

the power issue is not that critical for tail light. Headlight is another story.

5mm LED usually have a 60 degree viewing angle you can get ones with wider angle. I believe the straw hat tops are wider. Personally I would use SMD but that’s just me.

resistors are fine If you’re doing series 10 mA. Even with a 3v drop that’s only 30mW.

You can always add a regulator if this is too simple... or PWM... I would just work on the logic or microcontrollers for the sequencing instead. Actually PWM with fading sequencers would look cool
 

MisterBill2

Joined Jan 23, 2018
18,167
If the vehicle is going to actually be used as a car, and not being just a show car to enter in competitions, then the space taken by all of the support electronics will matter. And I would never ever consider using a consumer-grade microcontroller in a car. Between transients and electrical noise they would not live long. And they are certainly mechanically fragile.
There are standards available that describe how much light and in what directions it must show, and really, rear lighting is quite important, and especially the stop and turn signals. So a simpler system is a better choice, and once again, running near the max power will not gain you enough to be worth the pain of replacing the LEDs. And if you can get the super bright red ones in a surface mount package that will be the way to go.
 

shortbus

Joined Sep 30, 2009
10,045
Why not use colored LEDs? It would be a whole lot more efficient. Of course the white ones have been developed because that is where the market is. But using a red lens wastes all of the light that is not red. There is no color conversion going on, only color filtering.
I'm pretty sure that all the automotive red LED tail-lights use red LEDs.
It would be more costly and inefficient to use white LEDs.
And from my experience with car repairs you would be wrong. Not that there aren't some that use a clear lens and red LEDs but most cars, if you look while driving, have a red tail light lens. Some of it is due to regulations controlling the actual color to qualify as a tail and brake light. The ones that have a clear lens have a red LED that isn't like your everyday red LED.

Any LED bulb replacement for an incandescent bulb is a white LED.
 
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shortbus

Joined Sep 30, 2009
10,045
And it has hit me that on some cars the turn signals were yellow so that stupid folks could tell the difference between stop lights and turn signals. They are all red on my cars so perhaps that fad has passed.
That is not the reason for the yellow turn signal lenses. It was because they took out the original style turn signal switches, to make room for the more modern stalk switches, that controlled more and more things. The old style turn signal switch mechanically separated the brake and turn signal in the switch it's self. They then found a way to put the brake and TS int the body control ECU, and make the yellow turn signals able to be phased out.
 

MisterBill2

Joined Jan 23, 2018
18,167
And from my experience with car repairs you would be wrong. Not that there aren't some that use a clear lens and red LEDs but most cars, if you look while driving, have a red tail light lens. Some of it is due to regulations controlling the actual color to qualify as a tail and brake light. The ones that have a clear lens have a red LED that isn't like your everyday red LED.

Any LED bulb replacement for an incandescent bulb is a white LED.
Certainly correct. Of course the super LEDs are none of them like the everyday 5mm leaded LEDs we learned to love. My friend had LED high beams on his car, and they had cooling fans that came on when he used them. LOTS of light indeed. Even in the 96 LED outdoor lights, surface mount and nothing like I ever saw before. And now there are all sorts of ceramic based and metal mounted LEDs that put out far more light than a 100 watt spotlight. And it all comes from a small point.
For rear lights on a car it does seem like red LEDs will be the best choice since all of the light is the desired color, so that none would be absorbed and converted to heat. And if the lens is ever damaged then the light will still be the right color.
 

MisterBill2

Joined Jan 23, 2018
18,167
That is not the reason for the yellow turn signal lenses. It was because they took out the original style turn signal switches, to make room for the more modern stalk switches, that controlled more and more things. The old style turn signal switch mechanically separated the brake and turn signal in the switch it's self. They then found a way to put the brake and TS int the body control ECU, and make the yellow turn signals able to be phased out.
And the big advantage of that BCU (body control unit) is that if any part fails then it is $300+ for a replacement to get it working again. That includes the horn and the inside lights. CHANGE is certainly often NOT an improvement. That stupid BCM switches off my parking lights after just a few minutes when I leave them on. The whole purpose of parking lights is to make a car parked in a dark place visible. And LED lights could be left on for days without draining the battery. WHAT were those fools thinking when they changed that?
 

Thread Starter

bwilliams60

Joined Nov 18, 2012
1,442
And the big advantage of that BCU (body control unit) is that if any part fails then it is $300+ for a replacement to get it working again. That includes the horn and the inside lights. CHANGE is certainly often NOT an improvement. That stupid BCM switches off my parking lights after just a few minutes when I leave them on. The whole purpose of parking lights is to make a car parked in a dark place visible. And LED lights could be left on for days without draining the battery. WHAT were those fools thinking when they changed that?
A BCM will cost far more than $300 by the time it is diagnosed, replaced, programmed etc. If you can get one that cheap let me know where you are getting them and I will place an order for a large quantity. BCMs are programmable so leaving your lights on longer is probably an option depending on your OEM. Multiplexing is here to stay, like it or not. I am sitting on the fence as I find it is creating more parts replacers than anything else. Down side of technology.
Well I am going to order a bunch of LEDs and maybe some drivers and do some playing around. This conversation has done nothing than create more questions but that is good, right? :)
HAPPY NEW YEAR! to all the regulars and to all the newbs, stick around, there is lots to learn here on AAC. Hope you guys have a good one and thanks for all the help in the past year. Cheers!
 

Audioguru again

Joined Oct 21, 2019
6,672
It is illegal to tamper with vehicle lighting. Usually tampering results in lights that are too dim or too narrow angle or wrong color.
Factory lighting is certified to be standard and safe. Can you certify your tampering?
 

Thread Starter

bwilliams60

Joined Nov 18, 2012
1,442
It is illegal to tamper with vehicle lighting. Usually tampering results in lights that are too dim or too narrow angle or wrong color.
Factory lighting is certified to be standard and safe. Can you certify your tampering?
First of all, not sure what this line of questioning has to do with anything, but Happy New Year to you too.
If you have been reading this thread at all, you would have figured out that I am in the automotive/truck industry and know the laws that govern lighting on our vehicles very well but thank you for pointing out the obvious. As for what I am doing, I am working on a historic vehicle which belongs to a friend of mine and it only goes to shows so that is one thing. The other thing is that I am on here trying to improve my knowledge of LEDs, drivers etc so that when I do this build, it will put out relatively the same amount of light as the stock unit, thereby changing nothing. I have been blinded by many new vehicles with lighting much more powerful than what I am building so again, not sure what your point is, but I am not a newb on AAC. And why would I certify that I am tampering?
Again, Happy New Year!
 

MisterBill2

Joined Jan 23, 2018
18,167
It is illegal to tamper with vehicle lighting. Usually tampering results in lights that are too dim or too narrow angle or wrong color.
Factory lighting is certified to be standard and safe. Can you certify your tampering?
Only in a police state is servicing or repairing vehicle lighting illegal. If the performance of the system is adequate and within specifications then who cares who modified it or worked on it. I "tampered with" my rear lighting system by adding a trailer lighting connection that is totally NOT OEM, and nobody has complained at all. And I have made recisions to the lighting on a few previous vehicles and even in a cracker state they passed the mandatory inspections. So where is it that A.G. lives that has such laws? I once visited a place like that, and I left as fast as I could, never looked back, and will never return. And that is their loss not mine.
 

Wolframore

Joined Jan 21, 2019
2,609
I'm all about roll your own... there are a few "rules" to follow... such as no blue lights (they are for police use only)... other than that as long as you're not designing for sale do what you want. If someone gets into an accident it's possible lawsuit. If you get into an accident it's on you...

Antique cars had such crap lights to begin with anything that produces more light and draws less power will be a huge improvement.
 

Audioguru again

Joined Oct 21, 2019
6,672
I mentioned the illegal lighting so that others who see part of this thread do not do it.

Kids are modifying their car lighting illegally with junk from ebay and it is obviously too dim. Here in Canada a car with obvious modified lighting is impounded.

What is the certified viewing angle for LEDs used on a vehicle? It is much less of an all-around angle produced by an old incandescent light bulb. Many LEDs are focussed into a bright narrow beam that cannot be seen from the side.
 

Audioguru again

Joined Oct 21, 2019
6,672
All the expensive cars have blinding blue headlights, and snowploughs also have blue lights.
All the old Jeeps and Chryslers used blinding high beams for daytime running lights. Kias and VWs are copying them now.
 

Reloadron

Joined Jan 15, 2015
7,501
While I can appreciate making your own board I would consider using 12 volt off the shelf automotive LEDs. Also look at some of the LEDs designed around use on motorcycles.
I'm pretty sure that all the automotive red LED tail-lights use red LEDs.
I can tell you that the replacement LED tail light fixture for my motorcycle uses red LEDs.

Ron
 
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