I think that's a little too bright for running lights. For brake lights, they could be as bright as the sun! Little cars + weak brake lights = disaster.

Keep at it. Those are awesome.

I agree this project is awesome. Keep at it. The key in my view is the difference between the driving light and the brake light. I've seen a few cars with led lights that the driving light is so bright that the brakes are not as noticeable. Need to have a toned down driving light and a bright brake light.

They make adjustable "buckpuck" drivers so you could just turn them down to where you want them.

The Buckpuck was one of my design wins at my last job. The MP2483 is the buck converter in many of the Buckpuck modules. LEDdynamics manufactures these in Vermont. Great little company in a beautiful part of New England.

I've been thinking about using a buck converter for this application; either a module like the Buckpuck or roll my own.

Spoke - Cool that you worked on that.
Are you an EE and do you still do desgin/layout work?

I have also always wanted to make a brake light module with a MEMs G-force sensor in it.

If you press the brakes lightly (low G-force) the light comes on like normal.
If you stomp on the brakes (high G-force), the Brakes lights Blink furiously...

So, how much for a complete kit?

Hey, I thought the same thing! Only, I would do it with two of the stock brake lights switches set to operate at different distances from the pedal. Not quite as fancy as a G-force sensor, but would be much easier to set up.

I've worked a bit with the MEMS sensors; they're a bit annoying, but I think probably more repeatable in terms of measuring deceleration than any sort of correlation with pedal travel...

BMW call their system "brake force display"; the BFD2 behaviour is pretty neat, even ties into the ABS:

http://www.e90post.com/forums/showthread.php?t=500751

Blinking brake lights -> "I am braking too hard" 8)

Yep, EE with Masters from Lehigh U. I design, lay out, and assemble circuit boards. Most we have completely assembled but others we do by hand.

I laid out and assembled the 5mm LED PCB here. If you want to build something we should talk. I've already done a PCB for another member.

The MEMs sounds cool but I've been concerned lately with complexity with brake circuits with digital logic.

I want to do about 3 sets for folks of this 5mm brake light to get some out there to see that they work ok. Component cost is always an issue with low volume and with paying myself below minimum wage to assemble these will mean these first sets of 2 boards will be $95 for a pair including shipping CONUS.

I've cut the current down about 50% for the running lights. I'm running a burn-in test tonight as I plan to power the running light level overnight at 13.5V.

I over-estimated the voltage drop of these diodes based on the datasheet parameters. Instead of 2.5V per LED I'm seeing about 2.0V per LED.

This is the line of thinking that's led to the current ECM + peripherals architecture in most modern vehicles; most of the complex logic and sensing is concentrated in a small number of high-cost components centrally located in the vehicle, and then things like lights are just as smart as necessary and no smarter.

I've been tinkering with the idea of a 'body' computer to host this sort of thing, plus a pair of LIN busses to hang stuff like lights and switches off. It's probably more complexity than most folks would put up with, but when you look at the pile of stuff that some people add (the entire Dakota Digital catalog, just for starters) it starts to look attractive.

A fairly 'dumb' LIN node with a handful of in/out ports could be done with a BoM in the sub-$10 range using one of the integrated system basis + micro SoCs...

Spoke, How did your test go back on the 24 Dec?

The overnight test of the taillights went well. No issues.

I now have both brake lights on my 914 converted to the low power LED design with 63 5mm LEDs running about 5mA each for tail lights and about 45mA each for brakes.

Taillights are a bit brighter than the bulb and are much more focused behind the car. I need to take a few more videos of the tail and brake lights for comparison.

Been working on the high power design with 20 Cree XBD LEDs. These things are very bright. I've already cut the brake current from 300mA each to 250mA each and I think I need to go lower.

The high power design runs cooler than the low power LED board since I'm using a switching converter to do constant current. Pretty neat how the circuit draws less current at higher voltages since it's putting out constant power.

I want to get this one mounted in my 914 and see how it looks.

Those look brilliant. Can't wait till a full set is available for purchase.

<insert rimshot here>

No way! I'm an ME w/ masters from Lehigh. Looks like a nice winter project.

Andy

Off topic: Lehigh, good wrestling team!

These Cree's are super bright. I'm off by a factor of greater than 5 in current.

This is the shadow of the brake setting. It's way way too bright. It's dangerously bright. At 15 feet, one cannot look at this light and its already in the 914 taillight.

Click to view attachment

Blinded by the light.

Click to view attachment

This is the shadow by the taillight setting. It's probably as bright as the brake light should be.

Click to view attachment

OK, I think I have some good levels now. I need to check the relative brightness with the other 5mm LED unit as well as the standard 1157 bulb.

For the taillights shown below, I'm running the LEDs at 2.5mA. For the brakes, I'm running the LEDs at 35mA. I started at 300mA.

The Cree brake unit is now running at 1.4W. This is compared with the standard 1157 bulb at 21W.

Looks good. I'm inclined to believe that they can't be bright enough. Our tail lamps are lower than most cars and if those following us are indeed one car length per 10 MPH then the brightness should not be a problem. IMO

Thanks for the great work! I can't wait to get a set.

DAvid

David: That may be true, but there comes a point where you can flash peoples eyes and cause spots where they CAN'T see. That's REAL bad when they're driving behind you. ;-)

I thought the same thing when I started this design. High power LEDs nowadays can put out ridiculous amounts of light.

To compare output levels, I have one board with 63 of the standard 5mm LEDs running about 50mA in each LED. This board with 20 Cree's running 35mA puts out more light than the 63 5mm LEDs.

The test I did today with 200mA produced so much light that was painful to look at. I stood 20 feet away from the board installed in a 914 housing and I couldn't look at it. The shadow produced on the wall looked like a powerful red spotlight.

I will adjust these to be as bright or brighter than any vehicle brake lights I see. The main idea as you point out is to make our 914's be seen under braking.

Obviously you have first hand experience with how bright these are and therefore trust your judgment. Looking forward to having this upgrade in my car.

Thanks again

David

Could you do a few milliseconds of bright flash and then step down to a safe level?

Are you doing something for the 911?
Having pulled up behind a few I am concerned the taillights are far to dim

Neat idea. Yes, this would be easy to do. How long of brighter flash would be good? 1/10 sec? 2/10 sec?

I plan to do one for the 911. They have really small brake lights.

Here's the latest 914 brake light. I stretched the board vertically to fill the brake light cavity and moved the LEDs to the edges of the board to get a larger light footprint. LEDs shine in the direction you point them. The lenses don't have a very wide dispersion so these will look larger especially at night.

I added the leading edge bright flash when the brakes are applied like Mark suggested.

The circuitry on the back really shrunk since I didn't need all the current the first circuit was designed for. I still use a big ass DPAK FET where I think I could have used a converter with a built-in FET.

Plus I changed from a boost converter to a buck converter. Buck converters are more suitable to handle transients on the brake/taillight wires than a boost converter.

Looking good

I really like the idea of a brighter flash for a couple milliseconds and then stepping it down to just bright.

There are legal limits on the light output from both brake and running lights, something in the range of 100-300 candela for brake lights in the US.

Jim

I'm not seeing a maximum limit. I see a minimum limit. I'm looking a NHTSA Table IV-a—Effective Projected Luminous Lens Area Requirements. Then again I'm not even near expert on reading regulations. Anybody know how to read this stuff?

Easier version:
http://books.google.com/books?id=K7OqEdViZ...nts&f=false

NHTSA version:
http://www.fmcsa.dot.gov/rules-regulations...spx?reg=571.108

Maybe that's why the "NOT FOR ROAD USE" printed on the board.

Been contemplating a way to secure the board to the housing with minimal effort.

Mikesmith suggested a clip that would be held in place by the taillight lens and would just clip onto the divider on the housing and the board and thus hold the board in place.

So I used some sheet brass to mock up such a connection.

Here are the pieces. Looks like it will work just fine. I will look into getting these made in plastic or metal.

Click to view attachment

Just insert the clips into the holes in the board.

Click to view attachment

And slide the clips onto the plastic dividers.

Click to view attachment

Great work man. That's a seriously great project...expertly executed.

Beautiful!

Here's a comparison of the Cree LED board and the 1157 bulb. The first two flashes are the taillights and the last 3 are brake lights. Quite an improvement over the 1157 bulb.

For braking, the 1157 bulb is burning 21W while the Cree LED board is burning only 1.4W. One can also see the immediate light of the LED vs the 1157 when the brakes are pressed.

I had put in a circuit to flash the brake lights 4 times the intensity for about 1/4 second but it's not working in the car. Worked nicely in the lab with short wires to the power supply. The longer wiring of the vehicle must be slowing the rising edge of the voltage to the lights.


https://www.youtube.com/watch?v=qyFzq9C1hxM

This set of LED brake lights is now for sale. This is the only set available with these 5mm LEDs.

I wanted to try these out before I had the Cree LED board going. I've been running these in my car for the last several weeks.

These work well and put out a lot of light. See posts 186 through 196 for the light results.

This is the only set. Just looking to cover my cost at $55 + shipping. Includes 2 boards with pigtails and light bulb bases as shown, and 6 clips.

Real simple installation: pull bulb, insert bulb base, insert clips into boards, clip onto existing enclosure frame.

Respond to this thread if interested in purchase.

I am in for a set!

Spoke, is there a chance you could shoot a video or take a photo in broad daylight about 20-30 feet behind the car? Interested in how the LEDs preform in the daytime also. Similar to the photo in post #196 that was at night from the rear of your car.

Wow- this project is moving forward very nicely. That is looking nice. I too would like to see some video from behind during the daytime. Thanks for the hard work and dedication.

Here's some daylight vids.

This one is the Cree LED vs 1157


https://www.youtube.com/watch?v=Ca_TNjqifBw


This one has the Cree LEDs and the 5mm LED board.


https://www.youtube.com/watch?v=1HQjAIiWPz0

Are the Cree LED's red?

Spoke, those look good man! Both Cree and 5mm show pretty good.

I would like to purchase the 5mm LED Lights. PM sent.

Yes. The p/n is XBDRED-00-0000-000000701.

Just toying around with a different LED pattern. Instead of a grid of 5 x 4 LEDs, what about a box pattern. More like connected lines outlining the brake light.

I mixed the box and fill when I was playing with the smart LEDs; at distance it's hard to make the box out - would have worked better with clear tails and double-wide.

I'm in for a pair of 5mm when they're available.

How about running lights as the "box" perimeter and the whole thing for brakes? I think that would look cool.

Finally got the costs figured out for the 5mm board.

$90 + shipping.

This will include:
2 PCBs with 64 LEDs each.
Pigtail with 1157 base to plug directly into existing bulb socket.
6 clips to mount the boards to existing light housing.

New PCB is larger than the prototype as the LED grid grows by 1 to 64 LEDs in an 8x8 pattern instead of the 7x9 with the LEDs spread out a bit more to provide a larger lighting footprint.

Click to view attachment

Prototype 5mm PCB shown with pigtail, bulb socket and 6 clips.

Click to view attachment

I am in for a set. Will ordering info be coming soon?

Great looking product, thanks!