LED,s for Interior Lights

[DLT]

Moe,

Yes, I understand that. But, with those commercial "DOT-it" units, I've assumed that they already addressed that issue.

So, the resulting problem, using the "DOT-it" is to supply 3.5v, independent of current, which would normally be supplied by 3 batteries. They must have internally resolved the current limiting issues.

My suggestion of a voltage regulator and two diodes should result in real close to 3.5v, thereby replacing the batteries.

Obviously, you could just say the heck with all that confusion and use 3 batteries. But, personally, I'd rather not have to bother...

[Moe]

I strongly suspect the Dot-Its are 3 LEDs paralleled under one resistor, which drops the remaining 1 volt or so out of the 4.5 volts three alkaline AAA batteries would supply. If you want to supply regulated voltage for a Dot-It, I'd shoot for 4.4 volts, or one diode's drop after the 5V regulator.

[DLT]

I'm sorry, you're right... Bad math moment there...

Yeah, you probably only need one diode to drop the 5v regulated supply down. But, hull you probably don't even need that... You can problably get away with just the regulator, since a 1.5 volt battery, brand new actually produces a bit more than 1.5 volts. Therefore, their unit can probably withstand up to 5 volts...

[Moe]

That could be true, although I think I'd want to measure the current being drawn by the Dot-It at 5 volts.

[baldbaby2000]

The current-voltage (I-V) curve on an LED (or any diode) is very non-linear and not even the same for different devices even with the same part number. This is why they should not be directly paralleled. There needs to be some current limiting (a series resitor is easiest) or they can be driven by a current source but a directly connected voltage source will not guarantee the correct current even if the voltage is regulated. The I-V curve is also a function of temperature making current limiting even more important.

The disadvantage of a series resistor is that there is wasted heat but the overall efficiency is still better than incandescent lamps. Some efficiency might be gained by using a switching voltage regulator (not a linear drop out regulator; they heat up just like a resistor) to reduce it to a lower voltage first. A current limiting resistor would still be needed but there would be less wasted power in heat.

BB

[DLT]

Ok, how's this (yes I'm still convinced the voltage regulator is the way to go):

1 - Use the commercially available DOT-It lights, as is. this means replacing batteries on occasion. Maybe not an issue for you. This is the easiest, up front anyway, solution.

2 - Use the commercially available DOT-It lights. But, replace their batteries with a 5v voltage regulator supplied by ship's power. Here you may need/want another diode to make sure you stay at or under 4.5v. Personally, I wouldn't use another diode, because I'm comfortable with accepting that 3 AA batteries can supply 5v, and therefore accept any risk that 5v will be too much. Here, you just have to trust that they have worked out the current limiting problems.

3 - Rework your existing fixtures to use LEDs.

3a - You can do it John Defino's way. I certainly have no problem with that. It works fine. The only problem, as noted, is brightness being a function of battery voltage.

3b - Use a voltage regulator to give you a steady 5v. Then, use a ~75ohm (assuming you want 3.5 v accross the LED) resistive element (likley a combination of resistors) in series with each LED. Doesn't this solve all the outstanding problems? This removes the brightness/voltage dependence. It also give you current limiting for each LED. Of course, you might have a mess of resistors to deal with...

4 - Do nothing and quit your b*tching about how power hungry your stock lamps are.

Yes, the voltage regulator I'm suggesting is not very effiecient and does create heat. But, so do the larger resistors that are being used to drop the voltage from ~12v. I'll admit that these voltage regulators, in combination with a current limiting resistor, may be less efficient than the bigger single resistor alone, but then you have the brightness being dependent on battery voltage. I'm just trying to present a way around that bightness/voltage problem...

Sure, you can make a timing circuit and a capacitor to 'create' your own more efficient switching voltage regulation scheme, or buy a commercially availble unit, but why? Isn't that just adding complexity/cost?

[Moe]

I think a 100-hour battery-powered stick-on Dot-It would be a good solution to the X's missing light in the head. The batteries would last at least all season even with occasionally forgetting to turn the light off.

I have mixed feelings on converting the two existing lights. Their 1.44A 1141 bulbs use a lot of power, and even when one is on, the 21 spherical candlepower brightness is glaring to say the least. But that being said, it's nice to have that much light, especially with both on at times. I've considered what it would take to convert them to LED and still have that handy, but intense brightness all around, and I've come to the conclusion it would require one or two Luxeon emitters each. I bought two extra Bargeman fixtures for the purpose of trying that, but never got around to it. For those who can live with less brightness for about a 33% savings, a GE 93 bulb draws 1.04A and produces 15 CP.

Frankly, we didn't use the factory lights much and really only needed about 1 candle power (pun intended) in the evenings.

[DLT]

Wow, is that something good that can be said about the M? Just kidding you Moe...

The M does indeed have a light in the head... Of course, it would be rather unsafe to burn a candle in such a confined space


As far as LEDs, right now, I plan to follow option #4. Yes, they are power hogs. But, I have more storage capacity than most anyone on this board. I have the biggest alternator, with 25amps dedicated to charging. I will be keeping her in a slip next season, with electricity, and just bought 120W worth of flexible solar cells to secure to the top of my bimini. So, I have way too many other things to spend my time worrying about.

If I were looking to go out for more than a night or two on the hook, I might reasses. But, that's just not an issue for me any time soon...

[Paul S]

Guess I never thought about how much power the stock lights used. But with all the other power hungry stuff we have on board (no idea HOW the boat still floats), the lights are the least of my worries..lol

Even after 4 pots of coffee (on household maker through inverter) we still have enough power to run everything else (12v pressure water, lights, vhf, etc)

I just keep water topped off in the batteries (probably the only owner using wet cells here; I still think they are the best choice IMO), and them charged up between uses

Changing the lights to LED is probably the furthest thing down on my to-do list.

Paul

[Zoran]

I found in local store here in Vancouver, and I am somehow sure they are available all around 12V LED bulbs and you just replace the existing light bulb without any modifications. However, they are giving much less light and are not good for reading. My plan this winter is to install additional socket and switch on each light fixture with addition of LED light in the head. This will give me option to go on energy saving mode and have a cabin fairly lit with LED to reading mode with the convencional bulb without any major work. If I succeed in this I will post the mod, but do not expect it for a few months.

Zoran

[Moe]

The LEDs that replace automotive light bulbs are very directional off the end, like a flashlight. I won't use them in a motorcycle tail light because they're MUCH dimmer off-axis. Some have a few LEDs shining to the side into the reflector, but they're still too dim. In the Bargemann fixtures in the Mac, that put the bulb horizontal, they'll mainly shine a spotlight on the cabin wall.

[baldbaby2000]

I'd sure like to save some power on my interior lights but I just don't like the light provided by LEDs. Usually the incandescent lights in my boat are brighter than I need so I'm thinking of making an adjustable electronic light dimmer that would allow for full off to full bright and anything in between. The principle is pretty easy and cheap. Build a potentiometer controlled variable pulse width circuit that switches a transistor on and off. Little heat is wasted because the transistor is either completely on or completely off. The thing I wonder about is interference to my AM radio in the same way that a household 120VAC light dimmer can interfere. The hardware store variety 120VAC dimmers have a choke filter but still can interfere. FM and marine frequencies are probably high enough not to be affected. Of course when it's full on there's no power savings but when it's dimmed for a mood effect there would be. Has anyone tried this?

BB

[Hamin' X]

With all the talk about LED's, a word of caution is due here. Candle power ratings are way overblown and are similar to paper horsepower. That's how you get 1,000,000+ candlepower out of a hand-held spotlight using the same 55 watt H-3 bulb found in many fog/driving lights rated at 10 times less candlepower. It is a matter of focus. What you really need to look at is the lumens output.

I'm not convinced that LED's are the best option for general lighting. One would have to do some serious apples-to-apples comparison to get an accurate answer, but I believe that I would go for fluorescent for general cabin lighting.

[ronacarme]

1. I have read that incandescent lamps are essentially electric heaters that given current greater than a threshold amount will begin to emit light, whereafter adding more current gives more light., up to the rated current maximum of the lamp.
Thus, reducing current enuf dims the light output to zero whereupon the lamp simply continues to draw current and generate heat, until all current is switched off.
The point? Is that dimming the incandescent lamp will reduce light output but may not reduce current consumption all that much.
In contrast, the LEDs I have played with continue to emit light roughly proportional to current therethru, dimming as current drops, and go dark only when current drops to near zero, e.g. < 100 microamps, which I would gues to be less than the self discharge rate of my boat battery.
2. Also, I have read that, in general, that a 6 watt incandescent lamp gives fewer lumens/ watt than a 60 watt one (say 7 l/w vs. 15 l/w). Thus, substituting a lower wattage incandescent for the one supplied by Macgregor in the dinette overhead fixture may not proportionally reduce current draw.
3. A fluorescent lamp would give much higher l/w than incandescents or LEDs, but the smallest I have seen are 7 w, may create radio receiver interference, give unfocussed (OK for general cabin lighting but not bright task lighting) light , and more to the point are disliked by my wife.
4. Thus, I use 50 mA (0.6w) LED swivel spots in the cabin, which give good task lighting and enuf peripheral/reflected light to enable moving about the cabin, with little draw on the house battery.

[baldbaby2000]

Thus, reducing current enuf dims the light output to zero whereupon the lamp simply continues to draw current and generate heat, until all current is switched off.
The point? Is that dimming the incandescent lamp will reduce light output but may not reduce current consumption all that

You're right in that the efficiency of the lamp isn't as good at a lower voltage or current, but reducing the voltage will always reduce the current unless you're dealing with something with a negative resistance or a current sink.

Reducing the voltage (pulsing the voltage has the same effect) will cause the lamp to put out more of it's output where you don't need it, in the infrared whereas an LED puts out at about the same wavelength so from that point of view the former is less efficient. But you'll still save power in the first case just like a light dimmer for 120VAC saves energy. Pulsing the current and varying the duty cycle for DC is essentially what an AC light dimmer does. I might go with fluorescent (still a hassle to control with a dimmer), but I don't like the LEDs for general lighting.

BB