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Discussion Starter #1
I am testing a LED Tail Light for the K1200S for Kevin and Francis of www.homebody-design.com of Victoria, BC. They make Brake! LED Tail Lights for most of the BMW bikes.

Kevin and Francis are great guys and deserve our business. They are focused on making LED taillight conversions for BMW bikes. Both are experienced in electronics but Kevin is the a trained engineer. Francis trained in robotics and is the marketer. And both are motorcyclists. Kevin rides a Honda CBR 600 Fi, and Francis had a BMW R Bike. They workout of modest premises in a converted two-car garage.

And you will be impressed with the brightness and quality of their new LED for the K1200S.

Kevin expects the final version will be ready for my testing within days. And the product will ready for sale soon- possibly within one-month.



Did you know that the same LED light is used for the running and brake light? I erroniously thought that there were two sets of LEDs similar to two filaments in a bulb. I thought the running light was a standard LED equivalent to a 5W filament. And I thought the brake light was a brilliant LED equivalent to a 21w filament. Wrong.

The same LED is used for both. A processor creates the illusion of a lower intensity filament by flicking the LED on and off so the LED is on only 10% of the time. Like a video monitor or fluoresant bulb, it flickers over 60 times per second, and the eye interpretates the LED as being continuously on albiet at a low light intensity.

When the brake light circuit is activated, the processor creates a pulsing effect and then full intensity light by increasing the interval the LED is on vs flicked off, until it is completely on.

And unlike a bulb, the brake light circuit does not power the LED. Rather, the LED takes its power completely from the running light circuit. The brake light circuit only triggers the processor to put the LED completely on. So current draw remains low.

Another interesting fact is that LEDs are now available in 1w and 3w intensities. Unlike older LEDs that required 15 to 20 LEDs on a single circuit board, now only two will do! Just one 3w LED is so bright that it will blind you if you look directly into it.

Very cool.
 

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I am waiting impatiently. I have one on my K1200RS, and it is the indispensable addition, in my opinion. I will put one on my KS as soon as it is available.
 

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Discussion Starter #4
Its amazing how much more visible the LED makes the bike.

The LED helps on days like today when its grey, overcast and raining - typical fall weather in Vancouver BC. The tail light has a distinctive brighter colour in normal running mode. And the bike stands out when the brake is applied. The tail light is brilliant when the brake is applied and the LED pulses and then goes full-on.

And for something Completely different: The LED is so brilliant that I'm thinking... I may use it as a "Happy Light" for the upcoming dark and dreary days of winter.
 

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KPower said:
Its amazing how much more visible the LED makes the bike.

The LED helps on days like today when its grey, overcast and raining - typical fall weather in Vancouver BC. The tail light has a distinctive brighter colour in normal running mode. And the bike stands out when the brake is applied. The tail light is brilliant when the brake is applied and the LED pulses and then goes full-on.

And for something Completely different: The LED is so brilliant that I'm thinking... I may use it as a "Happy Light" for the upcoming dark and dreary days of winter.
How does it supply the amperage load the brake ckt requires for the integral abs...or...does it replace the bulb or not?
 

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cjack said:
How does it supply the amperage load the brake ckt requires for the integral abs...or...does it replace the bulb or not?
Yes, it replaces the bulb.
 

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Discussion Starter #7
Kevin at homebody-design.com can answer this better than me.

But as I understand it, pressing the brake lever triggers the ZFE to activate the ABS/ brake system. And apparently activating the ABS/ brake system triggers the ZFE to flow current to the brake light. The brake light and the ABS/ brake are apparently separate circuits both controlled by the ZFE.

Unlike my old R1100S, the K1200S does not require the special circuitry for the ABS system. In all my testing, there has been no ABS faults.

Its interesting that the ZFE does report burned out bulbs - ie too high resistance in the running or brake light circuits. Kevin and Francis had to experiment with different resistors so as not to generate too much heat and trigger a fault. Ideally the resistor should be minimal - just enough to avoid a short circuit. But if the resistor is too low, the resistor will get too hot and trigger a ZFE fault - just like a burned out filament. So the trick is to find just the right resistor value - not too low or high.
 

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cjack
I have the one made for the k12RS in my s and had to adapt it, but the light came with a resister pack to mimic the bulb draw. The taillight worked fine but the brake light would trip the bulb warning while on. The resisters fixed it. The resisters cause the LEDs to draw as much as the bulbs, so no savings on draw. They are VERY bright, just what I wanted.
H
 

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Discussion Starter #9
This is Francis logged on as KPower for the purpose of answering the question of how the unit handles amperage draw.

The way that the Brake! unit handles the need to work with the BMW computer system is not exactly simple... ...but I will try to sum it up. The computer on the bike is looking for a certain current draw during running like mode and a different current draw during braking. The unit itself satisfies the computer's need for current draw while, at the same time, it changes this current draw on the taillight and brake lines to satisfy the computer's different needs for current draw during braking. Basically there are resistors built into the unit that will draw enough current on the various lines at the right times and the unit switches their function dynamically during running mode and braking mode.
 

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Is this kit available for the K1200S yet? I've been wanting to get a LED braking light setup! There won't be issues with the computer telling me that the brake lights are out will there? Is there a resistor built into the unit that compensates for this issue?

Thanks!
 

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No, the kit is not shippinig yet.

As far as the technical side, read Post #9, the one you replied to. It discusses the resistors.

Randy
 

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Discussion Starter #12
Kevin hopes to have a final version in less than three-weeks.

Currently they are programing/ finalizing the unit's processor.

Regards
 

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KPower said:
Did you know that the same LED light is used for the running and brake light? I erroniously thought that there were two sets of LEDs similar to two filaments in a bulb. I thought the running light was a standard LED equivalent to a 5W filament. And I thought the brake light was a brilliant LED equivalent to a 21w filament. Wrong.

The same LED is used for both. A processor creates the illusion of a lower intensity filament by flicking the LED on and off so the LED is on only 10% of the time. Like a video monitor or fluoresant bulb, it flickers over 60 times per second, and the eye interpretates the LED as being continuously on albiet at a low light intensity.

When the brake light circuit is activated, the processor creates a pulsing effect and then full intensity light by increasing the interval the LED is on vs flicked off, until it is completely on.
Give me a break! You don't need a "processor" to do this! The correct term is Pulse Width Modulation (PWM) and it is done by a trivially simple circuit that switches the LED on and off at a rate faster than the eye can perceive. This is ancient "science"!
Another interesting fact is that LEDs are now available in 1w and 3w intensities. Unlike older LEDs that required 15 to 20 LEDs on a single circuit board, now only two will do! Just one 3w LED is so bright that it will blind you if you look directly into it.

Very cool.
And rather pointless. LED brake and tail lights have no significant advantages over incandescent lamps, other than they have a longer life, and they seem to impress the technically ignorant. If you do the math, their faster turnon time equates to only a couple of feet of additional safety at city speeds. Not even close to a bike length.

The 1 and 3 (and 5) Watt LEDs you refer to can NOT be installed as replacements to regular LEDs. THEY GET HOT ENOUGH TO SELF-DESTRUCT very quickly, and require a heat sink to dissipate their heat as well as a special (and expensive) metal-core circuit board (Check out the details on the Lumileds website). LEDs of any kind may be a little more efficient than regular lamps, but they are still very inefficient, and almost 80% of their input power is dissipated as heat. In fact, contrary to what people seem to believe, high power LEDs are not even close to being as efficient as (for example) fluorescent lamps. Hence the heat buildup problem with higher power LEDs.

Besides, 1 to 5 Watt LEDs cannot be used as brakelights anyway. Their light eminates from a tiny point, and is so intense that it is literally blinding. We use a lot of these high power LEDs at work, and the first time we tried one, we had serious vision problems for a half hour later!

Bob.
 

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KPower said:
Its amazing how much more visible the LED makes the bike.

The LED helps on days like today when its grey, overcast and raining - typical fall weather in Vancouver BC. The tail light has a distinctive brighter colour in normal running mode. And the bike stands out when the brake is applied. The tail light is brilliant when the brake is applied and the LED pulses and then goes full-on.

And for something Completely different: The LED is so brilliant that I'm thinking... I may use it as a "Happy Light" for the upcoming dark and dreary days of winter.
Nothing much amazing about it. If you put a larger-than-legal standard light in there, IT will be brighter too.

I made an LED brakelight for a friend here in Vancouver last year. It had 6, 1-Watt Lumileds Red LEDs. I made a simple circuit that caused them to come on full power (BLINDING!!) each time you hit the brake for only 250 milliseconds (to get people's attention RIGHT NOW!), then they "throttle back" to a much lower level to stop drilling holes in people's eyes.

The results were pretty effective, although it was nothing you couldn;t do with regular light bulbs. Personlly, as an engineer who works wit these things, I am really amused by how fixated people get on such old, mundain technology. The "gee whiz factor" I guess.

Bob.
 

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Discussion Starter #15
Hi Bob,

I noticed you are from Vancouver - I assume BC as well.

We likely have met.

I often can be found at John Valk BMW. I traded in my '01 R1100S for Lawny A.'s "old" grey K1200S with the titanium full exhaust system in August 2005.

As to your post, well ... Us Canucks are a very polite bunch EH.

In response to the PWM, trivially simple, ancient science, no significant advantages, can NOT, very inefficient, technically ignorant, and serious vision problems .... Did I say I am a Canuck? EH.

And I can only report to you what my experience is, albeit obviously very trivial, simple, ancient, of no significance, inefficient, technically ignorant and that of someone who is having serious vision problems, ... THAT my bike has the prototype LED with two 1 watt LEDs lights. And it works great. It generates a brilliant light without generating any perceivable heat or causing anyone to go blind.

Let Rusty at John Valk BMW know when you might be in, and I will bring the bike by for you to look at the unit. I can come by on Sunday, Monday or likely this Wednesday.

Regards,

Bruce
 

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Bob,

I think you are being a little hard on Bruce. OK, it isn't rocket science, but not much is or should be. He has seen the product work and is happy with it and I can respect that.

The bottom line is that to me, the BRAKE! LED that they make is one of the best investments I have made to my bike (K1200RS). It is FAR brighter both as a tail light and a brake light than the standard bulb. We have done side-by-side comparisons and the difference is night and day.

Simplistic or not, the flashing really gets others attention; I have had comments from other bikers and cages. In fact, I have been directly responsible for 5 sales simply because they were so impressed with its performance.

I also chose the LEDs for their reliability. I have never had an LED bulb in my bikes, cars or boats go out from a sharp jolt....you can't say that about bulbs. The positive about SOME bulbs is that if they do fail, you can replace them at a local store!

I am glad that you are capable of making your own; many on here are not. Rather than belittle other members for trying to be more visible, why not just make your point that it Isn't "magic" and leave it at that?

Randy
 

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KPower said:
Hi Bob,

I noticed you are from Vancouver - I assume BC as well.

We likely have met.

I often can be found at John Valk BMW. I traded in my '01 R1100S for Lawny A.'s "old" grey K1200S with the titanium full exhaust system in August 2005.

As to your post, well ... Us Canucks are a very polite bunch EH.

In response to the PWM, trivially simple, ancient science, no significant advantages, can NOT, very inefficient, technically ignorant, and serious vision problems .... Did I say I am a Canuck? EH.

And I can only report to you what my experience is, albeit obviously very trivial, simple, ancient, of no significance, inefficient, technically ignorant and that of someone who is having serious vision problems, ... THAT my bike has the prototype LED with two 1 watt LEDs lights. And it works great. It generates a brilliant light without generating any perceivable heat or causing anyone to go blind.

Let Rusty at John Valk BMW know when you might be in, and I will bring the bike by for you to look at the unit. I can come by on Sunday, Monday or likely this Wednesday.

Regards,

Bruce
Yup, Vancouver BC. I live just to the west of Valk's shop. Good that the tail light works for you.

But with a fair bit of experience in LED lighting, I can assure you that a 1 Watt LED can't possibly operate at the 1 Watt level "without generating any perceivable heat or causing anyone to go blind"! A 1-Watt LED generates about 800 mWatts of heat, and that is enough to raise its temperature above its rated maximum, in a few seconds of operation without adequate heat sinking. Also, with 1 Watt of input power, an LED is blindingly bright at close range. You literally see serious spots for many minutes aferwards. The 5 Watt ones are killers!

I suspect you may have a 1Watt LED, but it is "throttled down" somewhat (as I had to do with the one I mentioned I made last year that had 6 Lumileds "Luxeon" 1-Watt LEDs in it). Easy to check, though. A high power red LED will have a voltage drop of about 3 Volts across the LED itself (not including the power wasted in its current limiting resistor). So to get 1 Watt into an LED it needs to draw about 350 mAmps.

Anyway, glad you like the setup.

Bob.
 

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BRAKE! LED Fails

I like the concept behind the BRAKE! LED light. I own four BMWs and I installed their lights on three of them--was waiting on the light to come out for the K1200S. Now I'm not so sure about the lights. The light that I installed on my 2004 R1150GS Adventure has failed to operate. Suddenly without any warning, with only three months of service, I'm without tail or brake lights! I thought the LEDs were supposed to last longer than regular bulbs.

I guess I'm going to find out about their warranty...
 

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htheater said:
Bob,

I think you are being a little hard on Bruce. OK, it isn't rocket science, but not much is or should be. He has seen the product work and is happy with it and I can respect that.Randy
You're probably right. It wasn't meant personally at all.

It's just that as someone with years of design experience in this and related fields, I sometimes get a sort-of "Oh give me a break" feeling when I hear how simple concepts are sometimes grossly overcomplicated by cost-ineffective design.

I run across this constantly in my work, where more and more, electronics guys coming out of school have lost the ability to design simple, effective, and cheap analog designs, and instead eveything has to have a processor to do the most absurdly simple function. We seem to be loosing the art of ELECTRONICS, and substituting it with higher cost, higher complexity processors and programming skills. I get frustrated with new engineers who often lack even the most basic useful electronic design skills, and instead seem to have been taught that everything revolves around the computer.

A case in point is the LED brakelight I designed for a friend that I mentioned, that had 2 brightness levels it automatically switched between. The circuit had a grand total of 2, 10 cent transistors and about 30 cents worth of other parts. No "processor", no programming, or any other silliness. Just a matter of professionalism, from my (somewhat distorted) perspective.

My apologies!

Bob.
 

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Hey Bob since you've got so much experience in this field why not help out the Brake! folks with getting a bright, and well designed unit made?? I'm not trying to be sarcastic I just want a bright led brake/tail light.
 
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