> I have been using these (ebay link - http://bit.ly/hbiCF0 ) LED
> strings as additional lighting for the front of my motorcycle for the
> past 3 years.  I was looking for something to make me more obviously
> visible to oncoming traffic in an attempt to reduce my likelihood of
> having someone in pull out in front of me because they didn't see me
> and when they do, to make sure they have absolutely no excuse.
>
> Of all the options I've found so far these seemed the best because
> they don't require any modification to be run from the 12V supply on
> the bike, they are water-resistant due to the rubber moulding, they
> are flexible so can be formed to the shape of the internal fairing
> around the front wheel where I have them mounted, and because they
> have a rectangular shape allowing them to be mounted with the lights
> pointing along the tangent of the surface where they are mounted.  The
> only similar products I have found are flatter strips with the lights
> facing normal to the mounting surface which therefore don't suit my
> application.  I want them facing forward towards the oncoming traffic
> rather than inwards to the front wheel.
>
> A holiday photo (800x600 jpg) showing what this looks like: http://bit.ly/e4L5ur
>
> The problem is that after about a year they begin to lose brightness
> and the flexible circuit seems to deteriorate so that some of the LEDs
> (usually in groups of 3) begin to fail (as those with keen eyes might
> spot in my picture).  Having replaced a set on one side of the machine
> which had failed, it was quite noticeable that the new set were
> brighter than the old set.  Perhaps the lesson to learn is to always
> replace the whole lot at once but I'd rather find an alternative that
> won't need replacing in the first place.
>
> In summary I'm looking for:
> Strings of white LEDs in a clear flexible waterproof housing
> Run directly on 12V
> LEDs are spaced approximately 1cm apart along the string
> Can be mounted to face along tangent of mounting surface
>
> Longer mtbf (mean time before failure AND before fading)
> Better durability in automotive environment - vibration, moisture,
> heat and cold.
>
> Does anyone have any suggestions?
>

> been recommended by a few people so I duly went to wikipedia the great
> source of information and mis-information to get some ideas in that
> vein. Before I ask for advice on how to implement this idea I should
> provide some more information on the set up as it is, and why I put it
> together that way.
>
> The LEDs are powered from the side-lights circuit on the bike by
> splicing the line coming in just under the headlight assembly.  This
> means they are only powered when the ignition is on and they can be
> switched on and off using the normal handlebar switch along with the
> other lights.
> There are 2 each of white and yellow LED strings each with 24LEDs,
> 24cm long mounted on the sides.  There are also 3 strings of 12 white
> LEDs mounted around the top.
> The top strings are driven directly from the light supply and the
> white and yellow side strings are driven via a pair of relays.  When
> the turning indicator is inactive, the white string is lit (normal).
> When the turning indicator is lit, the yellow string is lit and the
> white string is not.
> I set it up this way because I thought having lots of white lights
> facing forward and very little area of indicator visible from the
> front, it might be difficult for oncoming traffic to see when I'm
> indicating to turn.
> If anyone has a better idea than the relays for the indicators part
> I'd be glad to hear it, by the way.
>
> Providing a single constant-current source for the whole set up might
> be problematic when indicating as I expect my relay will have a breif
> moment of not powering either of its connected 24LED strings meaning
> the current source(tuned for normally driving 84 LEDs) would be shared
> between 60 instead.  Is this something I should be concerned by?
>  If so, perhaps I should have 3 separate constant-current sources.
> One for the top 36 LEDs and one each for the side sets with their
> relays.  The next thing I need to know is what's the correct constant
> current.  I plan to determine this by measuring the current drawn
> using a clean 12V supply prior to re-installation.
>
> I'll also need to build and weatherproof the new circuit(s) and
> preferably have them all together in as compact a package as possible
> along with the relays.  This will be tucked into the space just under
> the headlight and secured with cable-ties. This package would have 10
> connections, 2 for the incoming supply, 2 for top LEDs and 3(x2) for
> white/yellow/ground on each side. I plan to use the standard 2 and 3
> way connectors similar to those found all over the rest of the bike.

> But also note:
>
>>> The best LEDs operated correctly can have lifetime in the 50k - 100k
>>> hours range to 70% output.
>>> The worst manage under to well under 1000 hours.
>
> This is when driven properly.
>
> And
>
>> - Use LEDs from a reputable "big 5" LED maker OR one using technology
>> from a maker who knows what they are doing. There are many small LED
>> makers worldwide but I am unaware of any that have managed long LED
>> lifetimes by themselves. I'd risk saying that ANY Asian LED maker who
>> cannot show a direct technology link from "big name" LED makers does
>> not make quality product.  There is now a substantial cross linking of
>> licences. Some (not all) competent LED makers are (in no order) Cree,
>> Osram, Lumiled/Luxeon. Nichia, Avago, Sharp, Seoul semi ...
>
> ie - you can drive them as well as you want, but if they are junk they
> will still be junk.
> Essentially any LED without a traceable path to the technology of the
> big-few is Junk.
>

> If you were rolling your own then a trivially easy current source can
> be made with an LM317 + one resistor.
> BUT The LM317 requires 1.25V output drop plus about 2.5V "headroom" for the IC.
> Too much for 3 LEDs on 12V.
>
> A 4 channel current source can be made with eg an LM324, 4 x MOSFETS,
> 1 x TL431, 4 x current sense resistors and a few other r's and c's.
> Very cheap.
> LED current flows to ground via MOSFET and  sense resistor.
> Op amp section monitors resistor voltage wrt reference voltage and
> drives MOSG\FET gate to maintain V_R_sense at same voltage as Vref.
> Works well.
>
>    R
>

>
>
> A constant current supply has
>> been recommended by a few people so I duly went to wikipedia the great
>> source of information and mis-information to get some ideas in that
>> vein. Before I ask for advice on how to implement this idea I should
>> provide some more information on the set up as it is, and why I put it
>> together that way.
>>
>> The LEDs are powered from the side-lights circuit on the bike by
>> splicing the line coming in just under the headlight assembly.  This
>> means they are only powered when the ignition is on and they can be
>> switched on and off using the normal handlebar switch along with the
>> other lights.
>> There are 2 each of white and yellow LED strings each with 24LEDs,
>> 24cm long mounted on the sides.  There are also 3 strings of 12 white
>> LEDs mounted around the top.
>> The top strings are driven directly from the light supply and the
>> white and yellow side strings are driven via a pair of relays.  When
>> the turning indicator is inactive, the white string is lit (normal).
>> When the turning indicator is lit, the yellow string is lit and the
>> white string is not.
>> I set it up this way because I thought having lots of white lights
>> facing forward and very little area of indicator visible from the
>> front, it might be difficult for oncoming traffic to see when I'm
>> indicating to turn.
>> If anyone has a better idea than the relays for the indicators part
>> I'd be glad to hear it, by the way.
>>
>> Providing a single constant-current source for the whole set up might
>> be problematic when indicating as I expect my relay will have a breif
>> moment of not powering either of its connected 24LED strings meaning
>> the current source(tuned for normally driving 84 LEDs) would be shared
>> between 60 instead.  Is this something I should be concerned by?
>>  If so, perhaps I should have 3 separate constant-current sources.
>> One for the top 36 LEDs and one each for the side sets with their
>> relays.  The next thing I need to know is what's the correct constant
>> current.  I plan to determine this by measuring the current drawn
>> using a clean 12V supply prior to re-installation.
>>
>> I'll also need to build and weatherproof the new circuit(s) and
>> preferably have them all together in as compact a package as possible
>> along with the relays.  This will be tucked into the space just under
>> the headlight and secured with cable-ties. This package would have 10
>> connections, 2 for the incoming supply, 2 for top LEDs and 3(x2) for
>> white/yellow/ground on each side. I plan to use the standard 2 and 3
>> way connectors similar to those found all over the rest of the bike.