LED Lights ?????

[Cobra Dude]

Hey folks,

I've not been reading this thread, until now when Tony brought it to my attention. Here's my take on the incandescent vs. LED subject...
First, Cobrajeff -- nice artwork!


Incandescent (1157) bulbs...
============================
These bulbs generate light by heating up a small tungsten filament, super hot, that they glow, and glow white. But a lot of heat needs to be generated, and most of the power consumed is wasted as heat. Sealing them in glass and removing the oxygen keeps them from just buring up instantly.


Halogen (1157-equiv) bulbs...
=============================
Pretty similar to incandescent, but there is halogen (or similar) gas inside the glass housing. This lets the tungsten filament be heated more without burning up. The extra heat means brighter light, also that they will consume even more power.


LED lights (for taillights and similar)...
==========================================
LEDs are actually semiconductors that produce light primarily. Yes there is some minor heating, but most of the power consumed is output as light, and not heat.


Pros of using LEDs...
=====================
1. Comparing equivalent light-output between incandescent and LED lights, the incandescent can draw as much as 10x or 50x the power of the LED lights.
2. Regular taillights were not designed for halogens, so I'm not surprised if it melts the plastic. I'd be surprised if you notice the heating of LEDs. Personally, in a (fiberglass) Cobra, I'll avoid *any* sources of heat, for my own sanity.
3. Speed -- LED's switch on MUCH faster, and in a braking situatiion, this is very good. I've heard that the faster turn-on time of LED's actually makes a noticeable difference in the stopping time/distance of the car behind, but I cannot find any documentation to prove this.


Cons of using LEDs...
=====================
1. Directional light output.
2. Higher cost still (prices are still dropping fast though).
3. Requires some circuitry.
4. The usual (thermal) automotive flashers will not work


Solving the LED issues...
=========================
1. The red translucent plastic taillight housings have a textured surface on the inside, so that widely scattered light on the inside (from an incandescent bulb) will collect and emit evenly outside of the filter. Yes, the intention is to make them narrow and directional. The already-directional nature of LED's means that they will actually be hindered by the textured surface. Not a major problem though, as I'm thinking the plastic surface can be ground/sanded down and flame-polished to get a clean smooth translucent surface.

2. The slightly higher price is a small consequence of getting the other benefits of LED's. Deal with it .
Actually, the cost of wire is often overlooked, but is significant in any system, especially automobiles. The much lower current of LED taillights means much smaller wires are required (running from the front to the back), so that the higher price of LED taillights is not as significant anymore. If your car is already wired up, then this is not a benefit to you.

3. Although you can theoretically just string LED's together and using a current-limiting resistor to get the proper current for the LED's, there is a way to get more light out of LEDs with the same average power consumption. The trick is to overdrive the LED's (most can be overdriven with at least 4 to 5 times higher current, and many mfgrs actually specify the higher peak current) but pulse them on and off rapidly. Controlling the duty-cycle is the key here. But a small bit of circuitry is required. Personally, I'd do this with a small microcontroller. A separate switch input could be provided to reduce the duty-cycle significantly lower to get the park vs. brake intensities.

4. The thermal flashers in most cars work by an heating an internal element (like a bimetallic strip or equiv). The much lower current from LED taillights will cause these flashers not to work. However with a microcontroller already in the system, its just a simple matter of adding one more input and some microcontroller-code to flash the LED's. Did you know that some companies actually make a resistive-load device to draw as much power as incandescent bulbs when using LED lights (so that the flashers will work)? Personally I think the concept is odd. See here... http://www.superbrightleds.com/1157.htm .

BTW, if anyone wants ready-made 1157-replacement LED bulbs already at a right-angle, this is the place to get them... https://www.netdisty.net/ds/aut1157ri/default.asp . Beware, these folks are expensive though.


I've got Tony's Cobra taillights here, and will be experimenting with converting them to LED's. (If any of you have an old or broken taillight (even from any other vehicle), I'd love to have it to experiment with removing the textured surface inside of it.) After that, I'll make a small PCBoard designed specifically for the shape of the Cobra taillamp, then play with some electronics to put it all together. I'll post results.

Cheers,
-Neil.

[zimmy]

Neil and others:

You may have missed my post on this subject, but the work of the led circuit board has already been done. See the link to Lambert engineering. He has a 1"x4" Led strip that is a tail light brake light design that is easily fit into the Lucas rectangular housing we are all familiar with. They are very bright (even in direct sun) and they work great. If your flasher doesn't work, you just need to replace the flasher with a newer electronic flasher. I can give you the number if you need. Worse case, he sells the small device to bring the load up to make the old flashers work.

Let me know if you need more info on the conversion process or the flashers.

Call or check Lambert - you won't be sorry.

[Cobra Dude]

Zimmy,

I did see your post, but I could not find images on Lambert's website that would indicate how a 1"x4" board of LED's would fit into a 1-5/8" high, by 1-1/2" to 1-3/4" wide (non-rectangular) shape. My intention was to fill up the irregular shape as much as possible with LEDs, and also to gain more light output by pulsing the LED's.

What I missed was the part about the electronic flashers ... who makes/sells these?

Cheers,
-Neil.

[cobrajeff]

Neil -

Both "Murray's Auto Parts" and "Auto Zone" (here in Michigan, at least) carry the "Variable Load" flasher units. They had both a mechanical version (about $4.00) and an electronic version (about $12.00). These were on the shelves with their standard flashers, fuses, fuse links, etc. You should be able to find them at any auto parts chain.

I bought one of each, but after my experiment with my cheap LED's (which turned out to be dimmer than an incandescent 1157), I took the LED bulbs AND all the flashers back for a refund.

regards,

Jeff

[zimmy]

Neil:

I must have misunderstood what tail lights you have. The ones that I modified with the 1x4 strip is the standard rectangular Lucas tail light as used by ERA, Superformance, and my Contmporary. I'm not sue what you would use.

[Jack21]

Sounds like you and Petek (another digital electronics guru, pretty sure he's an EE) ought to collaborate on this, then find a marketing avenue for this amittedly niche, but necessary device could prove to be a profitable sideline.

I'm perhaps the worst example of retaining originality when more contemporary technology makes for a better, safer car. (17" wheels, power steering that works, factory power brakes, and heatshields on the sidepipes.)

I have the '66 twin round Healy lights. Red for tail and stop, and amber for turn. The Ron Francis "Bright Lites" make a substantial difference in the visibility of the car at night. If the lenses were glass, I'd try halogen bulbs, but the heat output of the halogens would quickly melt the plastic lenses. The Ron Francis lights have one drawback, and only on the brake lights. Short lifespan in high traffic density areas where the brakes are on most of the time in stop/go and rush hour traffic. I carry a pair of spares for the brakelights in the car, and find I'm replacing them about every 3 - 4 months. The front park/turn, and rear turn are the originals from Sept '01 when the car was first put on the street.

If you guys come up with an LED substitute for the '66 Healy style lamps in red, and amber; that function in dim mode (park - tail), and bright mode (turn - brake), I'll buy a set.