are any LEDs any good?

The light fixtures on most cars are designed to work with lamps that emit light in a uniform spherical pattern. They include a reflector and refractive lens optimized for this pattern.

LED typically emit light through a narrower beam angle and, as a result, require optics designed specifically for them. Most (if not all) LED bulb replacements do not properly emulate an incandescent lamp's characteristic pattern and, as such, do not work well.

LEDs do work well in fixtures designed to use them.

I understand your point, I bought the ones I did specifically because they appeared like some thought had been given to that issue. They looked like this:

but with one fewer "stack" of radial LEDs. I don't have instrumentation to measure precisely, but based on simple visual observation their main drawback was simple overall brightness. The light actually filled out the lens very nicely so that it almost achieved the goal of having the light appear to be a uniformly glowing piece of plastic rather than being illuminated from behind. If they were brighter I would have left them in and bought more.

I guess I was expecting to be disappointed but was curious enough to give them a try, and they were almost acceptable and that's made me wonder if an actual viable product has been made yet.

It'd be really great if I could get some LEDs for the truck also, as I've got a dome light in the camper shell which is powered off the parking light circuit so until I get a wild hair up my butt and run a

+12V wire to the back of the truck (which will probably be about the same time that I run a wire for a trailer brake controller) low current draw would be a real selling feature there.

nate

I've been thinking about getting a hitch-cover brake light the next time Harbor Freight has them on sale for $4.95. They have some now that are full of seriously big LEDs. I'd mine the LEDs off the circuit board and sort of jelly-mount them in Shoe Goo or clear Polyseamseal.

My intended use for this is not taillights but the third brake light, which in most of my cars mounts the bulb transversely -- therefore I don't get much brightness. What I really want from LEDs in this position is the much faster risetime, so that the guy in the Suburban behind me with the latte in one hand and the phone in the other will realize sooner that I'm braking and won't hit me as hard. That's perhaps one reason (along with easier integration into a tricky-shaped body unit) why LEDs are often found in the factory "center high-mount stop lamp" of cars that use regular bulbs in the other positions.

The ones in trucks and buses are usually not replacement bulbs of the 1157 et al. variety, but a whole unit that is a drop-in replacement light fixture of the standard sizes and shapes used in such vehicles. (Significantly, most or all of the LED replacement "bulbs" I've seen are not DOT approved, and strictly speaking are not for street use.) As others have mentioned, the truck taillight's innards are optically optimized for use with LEDs, and you might have to do some LED position and angle tweaking to get a comparable result in your taillight housing (rather than just putting the whole circuit board in there, square on).

The extent to which it makes your butt look fat depends on the extent to which the taillight lenses are transparent rather than translucent. On a car old enough to have glass back there, you will just have to try it and see. My proposed applications are better diffused and it's harder to resolve the point source(s) of the light.

Finally, note that LEDs use less current than incandescent bulbs (and for sure run incredibly cooler than halogens) but do not use zero current as is widely assumed. Put in enough of them and you're right back where you were in current draw, though proper wiring of a tow vehicle is the "right" way to solve THAT problem.

Cheers,

--Joe

I have modified LEDs to flood rather than spot, for a small aircraft panel lighting application. The end of the LED is usually hemispherical, which focuses the light to that familiar narrow angle, Grinding that hemispherical end flat will allow the light to spread out nicely. Leaving it with the sanded surface diffuses it; I didn't try polishing it to see what it would do.

Dan

How much of difference would the rise time of a LED be compared with a tungsten bulb? Does a few tens of milliseconds make that much difference?

I remember seeing a design on the British inventions programme "Tomorrow's World" about ten years ago for a controller that flashed the brake lights a couple of times before putting them on permanently if the car braked very hard, because flashing lights tend to be more attention-grabbing than steady ones. Peugeot (and maybe othe manufacturers) have a similar device which flashes both rear indicators in this situation.

One of the factors that could make a difference is the separation of indicator and brake light bulbs on American cars. When my sister and her family lived near Boston, my parents and my sister were rear-ended by a car that failed to appreciate that her car was sitting in the middle of the road indicating to turn left into a side road and with the brake lights on. The driver said that he hadn't seen the indicator because of the brake lights and so had thought she was slowing down rather than actually stationary.

In the UK *all* vehicles have separate indicator lights, distinct from the tail and side lights rather than using the same lens/bulb. Mind you, I can remember a few British cars having the American-style combined lights in the mid sixties when I was a young child.

Why is it, though, that the modern trend is to fit clear lenses and ornage bulbs in the rear cluster, instead of orange lenses and clear bulbs? After all, you don't get clear lenses and red bulbs for the brake lights.

Some cars in the US have the seperate indicator and brake light and some have the combined system, many times even within the same make/model. For instance I have two Ford Pouruses. One a 1996 model (seperate orange indicator and red brake lights) and the other a 2000 model (the brake light and indicator combined in one red light). FWIW, both are clear bulbs and the lenses have the color.

I can't even begin to fathom why the manufacturers have to do that - seperate brake/indicator some years and combined in others or the colored bulbs and clear lens.

I think the colored bulb/clear lens thing is just a style thing. Reduces the number of colors in your light cluster from three to two and looks cleaner. I like the look, myself.

As for the rise time thing, the difference is noticeable and dramatic when you have the two side by side.

nate

I guess its a matter of personal preference. Nothing against the colored bulb/clear lens, I just think that the colored lenses look better.

But the part about combined brake/indicator in some years and seperate brake/indicator in others is what goes over my head. Personally, I wish that all the manufacturers would pick a standard (preferablly seperate indicator/brake) and stick with it. It would reduce a bit of confusion, IMO.

I've noted the difference in rise time on vehicles with the LED lights

- usually newer trucks or school busses around here. Personally, the new LED lights seem to be brighter and more notiicible compared to the incandescent bulbs. Maybe they will make replacement LED bulbs for older cars like my Porouses?

Well, ECE countries require the separate red brake/tail lights and amber turn signals. So this isn't an issue most places outside the US and Canada. I do agree that the amber function is better but so long as it's not *required* and stylists like the all-red look...

That's kind of what started this thread was a search for something like that. There already are products that claim to be just that, but for the most part they aren't very good. I was wondering if there were any exceptions.

nate

That's pretty sharp thinking. I think I'll try buzzing down this 1156 replacement that's been sitting in my desk drawer and see what happens. A pad sander should make quick work of it, as they all stick out very evenly.

(The graphical security code for this posting in Google Groups is "sperse" -- shoulda been "disperse"!)

--Joe

On Fri, 23 May 2008 21:23:58 -0400, Nate Nagel wrote:

The use of LED retro fit lamps in older vehicle applications that used the

1156/57 type lamps or their newer counterparts like 3157, etc, has certainly been scarred with bad user experiences identical to your own ever since the first LEDs were used for that application. I began constructing/modifying exterior vehicle lights before "white" LEDs had been invented and quickly learned that there were many other less obvious potential pitfalls in attempting to retrofit LEDs into older incandescent bulb applications that simply did not exist in newer designed vehicle lighting that had the use of LEDs factored into how the sockets, reflectors, switches, plugs and wiring were set up in the design of the initial vehicle. In addition, some of the issues that confronts the designer of retrofitting LEDs into older vehicles had nothing to do with LEDs but were relating to how the incandescants were initially included in the designs during that period of automotive history. HOWEVER. in spite of these potential limitations/pitfalls confronting the designer/inventor, the attraction of using LEDs to take advantage of the longer life, less vibration sensitivity, and less heat was a compelling enough motivation that the market continued to evolve and (slowly) become a viable, LED-based solution.

A good "case in point" example of LED retrofits that contain most of the possible limitations at least in my experiences thus far is the 1972-79 Ford pickup external light assemblies used for the stop, turn, hazard, backup and clearance lights. I will use this as a reference example to clarify my statements thus far, at least that is my intent anyway. Removing a light assembly from a pickup in this era, like a tail-stop-backup housing the backside is molded to accept the

1157/56 light socket with a bulb installed and be pushed in to the hole in the light assembly housing and turned clockwise a partial turn to lock in place leaving the bulb exposed into the interior cavity of the light assembly, there should be a rubber type gasket seal where the lamp socket contacts the light assembly to provide a good weather seal. The challenges/issues in using the LEDs in this situation to provide a viable (i.e., at least as relaible, at least as bright, and doesn't melt the lens assembly) are right in front of your eyes at this point some more obvious than others. First, the housing for the taillight was designed to maximize the reflection, radiation and dispertion properties of the 115x incandescent bulbs specific to it's focal length and light beam pattern which is almost omni directional, when as you mentioned, LEDs usually have a much more narrow beam dispersion, and the focal length is usually much shorter. This means that to begin with, the position of the light bulb in the housing is too far away from the lens to effectively use the pattern molded into the colored plastic to spread the available light inside the housing as the FORD designers originally intended. Initial attempts at resolving this issue were to extend the LEDs further out of the 115x socket as well as put more LEDs into the retrofit bulb assembly. This helped a little, plus LEDs were also evolving providing more luminous output per LED which helped the situation as well, but as anyone who has replaced a 115x light bulb in this or similar applications can easily see, the hole in the taillight housing is only so big and is only going top allow a retrofit bulb to be slightly larger than the diameter of the incandescent original. So, the initial 115x LED retrofit bulbs fell considerably short of being a good "plug and play" replacement option. What also must be considered in this scenario is that the taillight housing has 35 years of use on it and may have some cracks, or separations where it was originally bonded to the reflector during manufacturing. Any crack or hole allowing road contamination into the housing will make that light assembly appear to be dimmer that ones without the same flaw, this also includes the light bulb socket gasket. The most effective (and expensive) approach that has produced excellent results is to begin with a good taillight housing, cut the interface where the red lens was bonded to the back reflector with a sharp utility knife, and mount several circuit boards with at least 36 high intensity (10,000 mcd + per LED) LEDs per 115x bulb that is to be displaced, then re bonding the assembly back together with the wires for each 115x lamp exiting via the original hole made for it only being permanently sealed to the taillight housing and providing a identical wiring harness plug to that of the original socket. Reliable, can be better than original in intensity, but not cheap for sure, not top mention labor intensive. Great for restorations and collector vehicles not intended to be exactly as manufactured.

The LED components themselves continue to get brighter and more reliable in addition as less expensive, plus, the Chinese LED industry has migrated into providing the LED "array" circuit boards as well as individual LED components at very inexpensive pricing allowing quick custom LED lighting conversions without the hassle of soldering all the LEDs themselves. Not perfect, but getting much much better. I am sure there are additional points to consider but these are the ones I struggled with in the past in attempting to develop a workable solution for this LED application. I also assumed anyone taking the time to research this application would know how to configure LEDs electrically so I did not provide technical detail at that level intentionally. Good looking, packaged and guaranteed, "plug and play" lighting conversions can be provided for individuals without that knowledge via myself or others in the custom vehicle business, for a price of course. Hope this helps, best regards, Joe.

I believe that the "rise time" of even the slowest LEDs are order of magnitudes faster than the human brain's ability to detect, and signal the appropriate muscles to react to an emergency situation. Electronic vision coupled to electronic braking would certainly be able to speed things up. Could even free up additional time for increased cell phone usage for the human "driving" the vehicle.....hmmm. Joe.

Have you checked at Digi-Key? They do not carry crap, and last time I looked they did carry some LED based incandescent replacements. The LEDs I got from them to replace the incandescents for the button lighting in my truck radio are still doing wonderfully. I also have a couple 6W Luxeon LED based dive lights that are blindingly bright.

Pete C.

this is what they sell:

listed as 15.6/4.7 "cd" over a 30 degree viewing angle if I am reading this correctly. A regular 1157 bulb is rated at 32/3 MSCD and should be an effective viewing angle of over 200 degrees. This is why I'm searching to see if there's anything better out there... I guess this is definitely a niche application and the quality of "bulb replacements" is lagging LED development because manufacturers are waiting for the price of newer, brighter individual LEDs to come down before updating their "bulb" designs.

nate

The retrofits that are basically "a bunch of LEDs on a base that fits in an 1157 socket" are, uniformly, crap.

That said, there are a number of vendors of good, regulatory-angency approved on-highway LED lights now (Truck-lite.com, is one). They're made for trucks and trailers and come in standardized packages, but if you can make one fit in a vintage housing, they generally work well provided they don't wind up recessed too deep in the fixture.

What you are asking for is what companies such as LEDtronics specialized in for over 20 years. Generally this company and its few competitors will always offer the best solution technically possible. See: