LED Taillights, Custom Made for the 914 Options

[CptTripps]

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.

[palmer_md]

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.

[stugray]

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

[Spoke]

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. (IMG:style_emoticons/default/smoke.gif)

[stugray]

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...

[SirAndy]

(IMG:style_emoticons/default/smilie_pokal.gif)


So, how much for a complete kit?
(IMG:style_emoticons/default/idea.gif)

[McMark]

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...

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. (IMG:style_emoticons/default/wink.gif)

[mikesmith]

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)

[Spoke]

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...

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.

[Spoke]

(IMG:style_emoticons/default/smilie_pokal.gif)


So, how much for a complete kit?
(IMG:style_emoticons/default/idea.gif)

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.

[Spoke]

I think that's a little too bright for running lights.

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.

[mikesmith]

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

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...

[Speedmster]

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

[Spoke]

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.

[CptTripps]

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

[ClayPerrine]

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

<insert rimshot here>

[AE354803]

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...

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.

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

Andy

[JmuRiz]

Off topic: Lehigh, good wrestling team!

[Spoke]

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.



Blinded by the light.



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

[Spoke]

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. (IMG:style_emoticons/default/dry.gif)

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