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Old 04-12-2013, 19:17   #136
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Re: LED Anchor Light

Got my SDR cranking and ran a random wire and connected it to the ham coax to the back stay. Below is the photo of the screen. The spike to the right of 161.9716 mhz is actually my camera processor when I turned the camera on. Did not expect that. I turned it off and back on, which is the gap mid screen down on the water fall. The two spikes to the right of the screen is noaa weather.

Turning my anchor led light on and off made no difference at that frequency. There was no signal visible. The LED is an inch from the back stay, so should have seen something.
As noted yesterday there is a quieting of the background hiss at 28.2 ish mhz with the led on, but nothing heard or seen at standard VHF. I don't have a down converter, so can't check frequencies below 30 mhz



I'll do more experimenting tomorrow, when its warm outside again
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Old 04-12-2013, 20:06   #137
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Re: LED Anchor Light

The chipmakers are aware of RFI issues with drivers, btw. Some of the new LED drivers (regulators) are designed for the automotive industry, where keeping RFI down within the auto itself has become an issue. I don't know that any of those special "RFI quiet" chips are being used or considered in masthead LED lighting, but apparently the issue is known, and being addressed, by the chipmakers.
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Old 05-12-2013, 07:46   #138
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Re: LED Anchor Light

Anything other than a pure sine wave or DC voltage, generates noise all over the signal spectrum.

PWM circuits used to regulate LED forward currents are inherently susceptible to generating EMI/RFI by their very nature, with every wire and or trace in the circuit acting as a mini antenna. Effects may be reduced by using new (read expensive) low EMI ICs and appropriate circuit design.

LED driver circuits using Linear Regulators or plain resistance to regulate forward currents generate little or no EMI other than a possible single spike when the circuit is energized or de-energized.

The arguments of PWM vs Linear vs restistance regulated circuits is another can of worms, but if RFI is a concern, due to the proximity of a device to a VHF/SW antenna, a PWM driven light is probably not the best choice.
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Old 05-12-2013, 12:40   #139
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Re: LED Anchor Light

" a PWM driven light is probably not the best choice. "
Unless your criteria include minimal power draw. A number of folks have said that by going to a fast 50% duty cycle (of various types) they can get 100% "effective" perceived brightness, while using half the power. How far you push that in terms of short sparse pulses, etc. is a whole other question, but PWM does allow for a lot of power conservation.
While under way (nav light) the power conservation might be less important than RFI quiet. But while anchored, power conservation might be more important. (Or not.)

Then of course there's some sales value to be had if you can market a device as "low power drain with NO RFI".

On a whole other note, it is nice to see how LED prices have dropped, with wider beam spreads and good brightness, at last.
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Old 05-12-2013, 12:49   #140
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Re: LED Anchor Light

What do you think about carrying something like this solar powered LED from Carmanah as a backup to a wired masthead anchor light? I've got one in my inventory, but haven't used it for anything yet. I thought it might work as a back-up anchor light if I hoisted it up a flag line or perhaps mounted it on a pole or somewhere else. It's also able to be operated via remote control, so potentially it could be mounted on the mast too.
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Old 05-12-2013, 13:12   #141
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Re: LED Anchor Light

LED navigation lights need to be current regulated due to half life brightness considerations inherent of LEDs. IE: as an LED ages, it's brightness goes down when driven at the same current levels. To accommodate this, PWM controllers are used and controlled where hours on are counted and as the hours go up, so does the duty cycle and therefore the RMS current. This keeps the LED at a relatively constant brightness over its life. Note that this also means that the average current draw of the fixture will go up as the unit ages. The life is counted in 10's of thousands of hours. Temperature also may or may not be considered in the duty cycle. PWM is far more efficient than linear regulation in this application. It is not difficult to design a quiet PWM controller, only more expensive. There are additional and more expensive components in both the magnetics and capacitive filtering. I'm sure that there will ultimately be a shakeout of LED nav light manufacturers, and ultimately low EMI will be a contributing factor to that shakeout.
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Old 05-12-2013, 13:15   #142
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Re: LED Anchor Light

"hours on are counted and as the hours go up, so does the duty cycle"
nice theory, but I'd expect it would be simpler and cheaper to just use LEDs that are rated bright enough to still be in spec at the designed life cycle. 50,000 hours or whatever is chosen.

Are you saying that you know for a fact of any manufacturers who are counting hours and actually adjust drive current to compensate for this?
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Old 05-12-2013, 13:40   #143
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Re: LED Anchor Light

You guys are way to technical for me! All I can say is my Optolamp has never caused any noticeable interference to anything I know of, including VHF, SSB, and AIS. This is an interesting discussion though, and as an Optolamp reseller, I have passed some of this info on to them for comment. I still think they are great value, but I do understand some people can make one for less $$$. Probably lower quality, or no labour charge! I have not seen one I believe to be similar in quality for anything near the same price. IMO
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Old 05-12-2013, 16:00   #144
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Quote:
Originally Posted by hellosailor View Post

Are you saying that you know for a fact of any manufacturers who are counting hours and actually adjust drive current to compensate for this?
Lopolight say they do, but to counteract degradation of the epoxy.

http://www.lopolight.com/design/design.html
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Old 05-12-2013, 16:24   #145
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Re: LED Anchor Light

Lopolight, ROFL.

They're selling smart systems that notify the bridge when a light is due for replacement, and 300-1000 euros are common prices on their list. Although, the price list doesn't specify which lights have the brains onboard.

And, their lights are not sold for the US market in any case.

Nice exercise in how to make something simple (a light bulb) into something way more complex, and arguably frail.
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Old 05-12-2013, 17:26   #146
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Re: LED Anchor Light

[later]

From the journal Nature :
The Visibility of Ships' Lights : Abstract : Nature

"The Visibility of Ships' Lights
...IT may be remembered that in 1890, the German Marine Observatory tested some three thousand running lights in use on board ships, and found two-thirds of them defective. Further tests of the visibility of lights of known candle-power were made by the German Committee last year, and some of the results obtained are noted in a leaflet just distributed to seamen by the U.S. Weather Bureau. The law of emission for a white light is that its visibility is proportional to the square root of its. candle-power, and the results of the experiments by the Com mittee closely follow the law, the departures being no greater than the estimated errors of position of the vessel. The mean, of a large number of observations gave as the distance at which a white light of one candle-power became visible 1˙40 miles for a dark clear night, and 1˙00 mile for a rainy one. Experiments undertaken in America, after the International Maritime Congress in 1889, gave the following results in very clear weather: A light of I candle-power was plainly visible at 1 nautical mile, and one of 3 candle-power at 2 miles. A 10 candle-power light was visible with an ordinary binocular at 4 miles; one of 29 candles faintly at 5, and one of 33 candles visible without difficulty at the same distance. On a second evening, exceptionally clear, a white light of 3˙2 candle-power could readily be distinguished at 3, one of 5˙6 at 4, and one of 17˙2 at 5 miles." (there's lots more article at that link)

Point being that "visibility" ranges, which are the crux of COLREGS, have been tested and found to be variable. And, also long and well tested so they can be rather simply met by choosing the brightness of the light source and lamp. The only rocket science needed here, was already done in Jules Verne's day.
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Old 05-12-2013, 18:06   #147
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Re: LED Anchor Light

COLREGS Inland Rules

CFR Title 33 > Chapter I > Part 84 - Annex I: Positioning and technical details of lights and shapes

33 CFR 84.15 - Intensity of lights

84.15 Intensity of lights
(a) The minimum luminous intensity of lights shall be calculated by using the formula:
l = 3.43 x 106 x T x D2 x K-D
where:
I is luminous intensity in candelas under service conditions, T is threshold factor 2 x 10-7 lux, D is range of visibility (luminous range) of the light in nautical miles, K is atmospheric transmissivity. For prescribed lights the value of K shall be 0.8, corresponding to a meteorological visibility of approximately 13 nautical miles.
(b) A selection of figures derived from the formula is given in Table 84.15(b).

Table 84.15(b)

Range of visibility (luminous Minimum
range) of light in nautical luminous intensity of light
miles in candelas tor K = 0.8
D I
1nm 0.9
2nm 4.3
3nm 12
4nm 27
5nm 52
6nm 94

(No interpretation required....Just the facts ma'am)
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Old 05-12-2013, 20:48   #148
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Re: LED Anchor Light

Quote:
Originally Posted by hellosailor View Post
"hours on are counted and as the hours go up, so does the duty cycle"
nice theory, but I'd expect it would be simpler and cheaper to just use LEDs that are rated bright enough to still be in spec at the designed life cycle. 50,000 hours or whatever is chosen.

Are you saying that you know for a fact of any manufacturers who are counting hours and actually adjust drive current to compensate for this?
As mentioned, Lopolight does. From their website:
-
during the very long life of the navigation light the LED will become less bright due to degradation of
the epoxy surrounding the individual LED, even the high quality silicon expoxy we use will degrade.
To compensate for this we adjust the current over time, in the beginning the current each LED sees
is very low and during the 50.000 hours we increase the current 25% to ensure that a Lopolight has
the same high brightness over the full 50000 hours.
Here is a technical summation discussing the problems.
I would not trust an LED navigation light to be within specification over time if there is not some allowance made for brightness half life. And you're certainly welcome to stay with incandescent bulbs, with all of their shortcomings. Everything is a trade off.
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Old 05-12-2013, 20:59   #149
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Quote:
Originally Posted by hellosailor View Post
Lopolight, ROFL.

They're selling smart systems that notify the bridge when a light is due for replacement, and 300-1000 euros are common prices on their list. Although, the price list doesn't specify which lights have the brains onboard.

And, their lights are not sold for the US market in any case.

Nice exercise in how to make something simple (a light bulb) into something way more complex, and arguably frail.
The alarm is an add on, as far as I know all of their lights have the circuitry built in to give a visual warning when getting close to and past 50,000 hours.
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Old 05-12-2013, 21:07   #150
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Re: LED Anchor Light

Quote:
Originally Posted by hellosailor View Post
Lopolight, ROFL.

They're selling smart systems that notify the bridge when a light is due for replacement, and 300-1000 euros are common prices on their list. Although, the price list doesn't specify which lights have the brains onboard.

And, their lights are not sold for the US market in any case.

Nice exercise in how to make something simple (a light bulb) into something way more complex, and arguably frail.
Not sure where you got that. I think Jamestown sells to the US market.
They're pricey, but very well made, the design has had several improvements/evolutions, and Lopolight stands behind their products. The masthead is a pretty harsh environment for electronics.
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