LED Lighting

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Airborne473

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Hi, am starting to work out a new electrical system and have decided to reduce battery loading by using LED lights.
I understand there have been some articles on making your own lights in one of the magazines.
Does anyone have any information on constructing LED lights for cabin and masthead.
Any info most gratefully received.
 
I have just seen some LED lights in IKEA. Theya are sold in a pack of four with a transformer and are meant to go under cupboards. About 2 inch in diameter and very thin. Attach using double sided tape. I think you could discard the transformer and use lights individually (12 V). From memory about £20 for four. Considering trying them. Regards Chris
 
The guys at www.ultraleds.co.uk are really helpful. I just switched my bulbs and kept existing lights, really cheap. The light produced by their 'warm' versions is just as good as conventional bulbs - I think they mix some orange leds in with the white to make the light less harsh - highly recommended.

I used these:

warm ultra bright
 
we also used ultra leds and found them very friendly and helpful- initially we took some digi photos of our existing bulbs and emailed them and they told us what led equivalents were avaiilable - bought several and those we were unhappy with (found some in spot light installations not bright enough) they willingly took bag- the others now had for a season and are excellent- strongly recommend the warm colours compared to the standard cold colours,

good luck
 
There are readymade LED "bulbs" that will fit almost any existing lamp. My boat had BA15D sockets and I found some really cheap 9-led lamps in a hobby store and modified those, fitting sockets from old BA15d incandescent lamps. Used them this summer for reading lights. They are "cold-white" and have a very narrow beam but work well for reading and uses one tenth of the power of the old.

Got one of these for my daughter's bunk, but have not fitted it yet.

http://www.mitron.se/jpg/Lite-W.jpg
 
All that glitters...

12 volt leds 'made' to work with a transformer may blow on a boat 12v system when charging voltage rises. "Proper" marine applications like ULTRALEDS have built in protection up to 16 volts.
 
Re: All that glitters...

OK to answer the question.... An LED often comes as a small bulb 3/16 inch diameter with 2 wires. The longer being positive. These LED have a lens built in to give a light angle of about 30 degrees. If you buy them from a catalogue they come in different colours and light intensity. Make sure you get high intensity like 10000mCd.
Electrically a LED requires a constant current and exhibits a volt drop usually about 1.5 volts. Some are higher so get the electrical data which will also specify the current. Typically 50 ma (.05 amp)
Note however ohms law does not apply to LED and if you put a 1.5 volt LED across a 1.5 volt battery it would melt. It does not in itself limit its current. They must have a series resistor.
LEDs can be driven by various elecronic circuits which pulse and control current.

The simplest way is to use a series resistor. So for a single LED dropping 1.5 volt used on a 12 volt supply you need to drop 10.5volts at 50 ma so a resistor of (R=Current divided by amps) 10.5 divided by .05 =210 ohms. The power dissipated in the resistor is amps X volts = .05X 10.5= .525watts. So get a resistor rated at least 1 watt.

Now it is more efficient, to rather than waste about 8 times as much power in the resistor as the LED, to put more LEDs in series if you have a 12v supply.

So 5 LEDs in series drop 7.5 volts which leaves 4.5 volts dropped in the resistor. R=E/I so R = 4.5/ .05 is 90 ohms dissipating .225 watts so a 1/2 watt resistor will serve.

Note here that unlike light bulbs the watt rating of a resistor is the max it can disipate. because we specify resistance. So a 10 watt resistor is simply more rugged but does the same job as a 1/4 watt resistor.
In a light bulb we specify voltage and wattage and that wattage is what it actually dissipates in light when connected to the specified voltage.

Back to LEDs if we put 8 LEDs (of 1.5 v drop) in series by calculation we need no resistor. Wrong because the current would not be limtied the LEDs would melt. We need some resistance to limit the current. So 7 LEDs leaves 1.5 volts to drop in a 30 ohm resistor. That would be OK however............

On a boat or car the voltage of the supply varies a lot . from 11volts to 14 volts. With 7 LEDs 30 ohm resistor we get .05 amp at 12 volts. But at 14 volts the resistor drop is (14-10.5= 3.5 volts) 3.5 volts across a 30 ohm resistor allows .11 amps to flow. This is twice the max permitted for the LED example so LEDs melt.

The only thing to do is set the resistor value for max volts to be encountered 14 v. ie R= 3.5/.05=70 ohms resistor. But if the battery volts fall to 12 volts then we get only .02 amps throught the lights so pretty dim. (40%). If the voltage falls to 11 volts then current is only .007 amp or about 12% of normal brightness.

If however you compromise and have a larger resistor chosen for 14 volt supply and have less LEDs in series the problem becomes much less. So 5 LEDs reqires 6.5 volts to be dropped at 14v. R = 6.5/ .05 is 130 ohm resistor. Now at 12 volts the lights will draw 4.5 /130 ohms = .035 amps or 66% brightness and at 11 volts .026 amps or 50% brightness.
Less LEDs = more resistance equals less concern about low supply voltage. Typically 5 LEDs is a good compromise. But less number of LEDs if they are higher voltage drop types. Or use an electronic regulator circuit.
If you take your battery home for recharge or never charge the battery with lights on then you can safely calculate on 12v supply.

If you have a head lining and can get behind the lining you can make beaut cabin lights by drilling 3/16 inch holes and pushing the LED through the linign and have them shine straight down. Reds or whites or a mix. For a separate fittiing use a smal,square of thin plastic.
Some LEDs however are made in surface mount technology a tiny flat shape with metal area at each side. These are used in commercial LED lights for Nav and cabin but are extremely difficult to solder and have varying types of lenses.

I would suggest buying a LED Nav light fitting rather than try to use individual LEDs for Nav lights. The LEDs have to be aligned to give the required coverage angle. For a sail boat both in the up and down as well as azimuth angles.

So get some resistors and LEDs from Maplins or similar and have a fiddle. For the cost in pennies of the resistors and LEDs you will have some fun even if you don't fit them to your boat.

I have 3 LEDs set in the front hatch cover shining up onto the jib and they give a usefull light onto the sail and tell tales for night racing. They virtually can't be seen from the sides of the boat such is the narrow beam angle. They barely emerge from the F/G so can be trodden on without problem. .... olewill
 
Re: All that glitters...

Hi, thought you might like to know of another supplier - specialising in boat lighting www.bedazzled.uk.com They include a wide range of 'marine' rated bulbs as well as light strips set into carved wood up to 6 feet long and end stackable - ideal for ceiling and gunwale lighting!
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