Ken, Would it be possible to install two (2) all around white LED 'bulbs' into a Perko 200 series anchor light fixture? I would gladly expend the power to have a very bright anchor light.
Eric Thompson S/V Procrastinator South San Francisco [EMAIL PROTECTED] ----- Original Message ----- From: "Ken James" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Sunday, October 19, 2008 4:37 AM Subject: Re: [Liveaboard] color mixing in led marine nav lights >I am seeing more and more led navigation lights > designed with no optics or shielding to prevent > the colors mixing between sectors. This is an > issue that is often overlooked by hobbyists, > DIY'ers, and those who do not fully understand > what is required of such a light. > > If you think this is an unimportant or trivial > problem where such lights are concerned, take a > look at a led nav light with and without a method > applied to correct this problem here; > > scroll down on > > http://www.firststarled.com/products.html > > A normal nav light that uses an incandescent bulb > solves the problem of color sector overlap by > using colored filters, and placing the bulbs > filament, which is thin long and vertical in such > a light, behind the filters in such a manner that > if you take a horizontal plane 'slice' through the > fixture, all the rays going through the filter > between the edges from one color and the next will > be coming from what seems to be a single 'point > source' at the center of the fixture in such a way > that any two rays that are next to each other will > diverge at all times and not mix, so if one goes > through the red filter and one right next to it > goes through the green filter, they cannot mix. > In the real world, some mixing does occur but it > is relatively slight with a good design. > > And BTW with a good led nav light design there > will be even less overlap than with a 'normal' light! > > Now if you imagine an led which emits a cone of > light, but a cone that does not have a perfectly > sharply defined edge or boundary, you can start to > see what the problem is regarding color sector > overlap with led nav light design. > The cone has a 'fuzzy' edge. If you make the cone > smaller it will have a more sharply defined edge > but then you will soon get to a point where it > will not have enough beam spread to be useful as > it will need too many leds to make the required > horizontal and vertical coverage required with no > 'nulls' or dark areas between cones, and that > point will come before the beam is sharp enough to > prevent color sector overlap between sectors and > still maintain sufficient brightness all the way > up to the edge. > > Again, when you put the narrow beam leds conical > emission patterns next to each other, to avoid > 'nulls' or dark areas you must overlap the beams > more as such a beam falls off sharply on the edges > and would result in incomplete filling of the > sector space, and with a beam that has > insufficient vertical spread you will need overlap > there also. > > For a light that uses colored leds and shines > through a clear fixture, on the edges where the > colors meet you will have a problem, if the colors > overlap and mix you will get a dangerous confusing > display. > > You must use some form of shielding or optics to > prevent this. > > Considering a led light that uses either colored > light or white light leds and shines through a > colored lens fixture, because the multiple leds > are emitting a pattern of light that does NOT > posses the property of the incandescent bulb > filament in the above example, that is the leds > make a pattern that is not a 'point source' in a > horizontal plane 'slice' originating in the center > of the fixture, the result is you can have an led > that shines through the edge of a color sector > behind the fixtures lens but then the rays will go > on to converge with another leds rays further from > the light. If you had an led aimed from behind the > lens, through a colored filter, but aimed so that > the rays it emitted crossed from one side of the > color filter to the other after they left the > fixture, that would result in color sector overlap. > It would make no difference if it was a colored > led behind a colored lens or a white led behind a > colored lens, you would get overlap, as with the > white led it would change color then converge. > > If you aim the leds that are directly behind the > edges of sectors such that the edges of their > conical emission pattern is straight toward the > sector edges you then must insure the cone is not > too 'fuzzy' at least not where the sector edge is > supposed to be, otherwise it will not maintain > sufficient intensity all the way to the edge, or > it will overlap as in the above examples. > > Colored filters alone will NOT solve the problem > of color sector overlap with an led nav light! > > Once again, the solution is shielding or optics. > > Companies like Perko and Orca Green (and me) go to > a lot of trouble to see that this problem of color > sector overlap cannot happen, if you look at their > led combination navigation lights such as their > tricolor models you will see that they have part > of the fixture providing shielding for Perko, Orca > Green uses the leds aluminum heat sink as > shielding, and I use shielding on the leds and > also the leds copper heat sink to prevent internal > reflection. > > But be warned, there are now many manufactures > offering led lights that use no optics or > shielding to address this potentiality deadly > problem! -Ken > > > > _______________________________________________ > Liveaboard mailing list > [email protected] > To adjust your membership settings over the web > http://www.liveaboardnow.org/mailman/listinfo/liveaboard > To subscribe send an email to [EMAIL PROTECTED] > > To unsubscribe send an email to [EMAIL PROTECTED] > The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ > > To search the archives > http://www.mail-archive.com/[email protected] > > The Mailman Users Guide can be found here > http://www.gnu.org/software/mailman/mailman-member/index.html _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [EMAIL PROTECTED] To unsubscribe send an email to [EMAIL PROTECTED] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
