LED,s for Interior Lights

ken · Post by **ken** » Mon Dec 05, 2005 6:28 pm

I found this site where you can buy LED,s for about $20 to replace your present interior light,s bulb. Has anyone used this bulb for replacement? It looks like it only draws about 10% (amps)of the standard bulbs in most boats.

http://www.superbrightleds.com/other_bulbs.htm

Ken

Moe · Post by **Moe** » Mon Dec 05, 2005 6:49 pm

Some here have tried those. Do a search first on 1141 and read that thread, then search on LED.

Post by **kmclemore** » Mon Dec 05, 2005 7:07 pm

Indeed, Moe... this has been discussed numerous times.

Ken, the search facility works very well... I used LED Lights, selected the button to search for all terms, and I got lots of good hits - here and here and here for example.

Try to use the search facility first please folks... it keeps from fragmenting threads. Thanks!

richandlori · Post by **richandlori** » Mon Dec 05, 2005 7:48 pm

I have two of these: one for the head and one for the V-berth and that is ALL I want. it works for simple light, but it does make a blue light and I wouldn't want to try and read by them. They do use little power....but they are not an all out replacment for the "old fashion" lights.

Tom Spohn · Post by **Tom Spohn** » Tue Dec 06, 2005 10:58 am

I am using the PCB ones. They are OK for all but reading. They are a bit bluer, but doesn't bother me. You will still need at least one bright light for when you really have to see--like when you drop something or are cooking or want to read. Fluorescents work well for the bright light.

Divecoz · Post by **Divecoz** » Tue Dec 06, 2005 5:45 pm

Does anyone have a working e-mail for John Delfino??
I have a couple questions for him and the e-mail address on his site comes back to me as an error..

Chip Hindes · Post by **Chip Hindes** » Tue Dec 06, 2005 7:33 pm

John Defino is [email protected]

John did some testing on some really cheap white LEDs I had gotten through eBay last year and mine had a decidedly blue cast compared to the ones he had.

Divecoz · Post by **Divecoz** » Tue Dec 06, 2005 7:45 pm

I had an L in there it went through as Chip and Moe spelled it
Thanks guys . .

Moe · Post by **Moe** » Wed Dec 07, 2005 6:59 am

In John Defino's pictures of his LED lights, you'll note he has one resistance for every 3 LEDs, yet in the text, he recommends one resistor for each LED. While using LEDs in series can share one current and make the light more efficient, it reduces the voltage dropped across the resistor, making it large relative to the change in battery voltage, and causing larger fluctuations in current and thus brightness. Here are some examples of configuring 6 5mm 3.5V white LEDs differently, with standard value resistors, where 20mA = (100%) of rated brightness. I used the number of six LEDs, not because John did, but because it's the lowest common denominator between single LEDs, and 2 or 3 in series.

One LED per resistor, six resistors

Charging: (14.5V-3.5V)/470Ω = 24mA (120%) x 6 = 144mA total

Not Charging:
Full battery charge (12.5V-3.5V)/470Ω = 19mA (95%) = 114mA total
Half battery charge (11.5V-3.5V/470Ω = 17mA (85%) = 102mA total
"Dead" battery (10.5V-3.5V)/470Ω = 15mA (75%) = 90mA total

Two LEDs per resistor, three resistors

Charging: (14.5V-(2*3.5V))/330Ω = 23mA (115%) x 3 = 69mA total
Not Charging:
Full battery charge (12.5V-(2*3.5V))/330Ω = 17mA (85%) = 51mA total
Half battery charge (11.5V-(2*3.5V))/330Ω = 14mA ((70%)= 42mA total
"Dead" battery (10.5V-(2*3.5V))/330Ω = 11mA (55%) = 33mA total

Three LEDs per resistor, two resistors

Charging: (14.5V-(3*3.5V))/180Ω = 22mA (110%) x 2 = 44mA total
Not Charging:
Full battery charge (12.5V-(3*3.5V))/180Ω = 11mA (55%) = 22mA total
Half battery charge (11.5V-(3*3.5V))/180Ω = 6mA (28%) = 12mA total
"Dead" battery (10.5V-(3*3.5V))/180Ω = 0 amps (dark)

NOTE: If a protection diode is added to the power input of the circuit, the battery voltage seen across the resistors and diodes will be reduced approximately half a volt and the current will be slightly less.

For a bit more money, you can use LED strings fed by a current regulator integrated circuit (and resistor), which will keep the current the same regardless of battery/alternator voltage. I don't know of any commercial lights that do this. Because of the 1.25 volt drop of the regulator sense resistor, the number of LEDs in each series should be limited to two, which cuts in half the current draw, compared to a resistor for each LED, but draws about 50% more total than 3 in series. A TO-92 cased National Semiconductor LM317Z adds about $0.33 to each string of two, but saves about $0.10 on one resistor (only one 1/4W 62 ohm per regulator). But it also means the same 20mA current and 100% brightness from alternator charging at 14.5 volts all the way down to starter cranking at 9 volts or just below.

DLT · Post by **DLT** » Wed Dec 07, 2005 8:12 am

It seems to me that a good bit of the voltage fluctuations could be eliminated with a voltage regulator, rather than a resistor. 5v regulators accept just about any voltage, that we'd be dealing with, and produce a clean 5v.

Then, you can use a single resistor, or resistor combination, for current limiting, for whatever number of LEDs in parallel. The problem will be finding the low resistence resistors that you will need. But, this isn't a real problem. For example, two identical resistors, in parallel, results in half their resistence value...

Assuming you have 3.5v drop LEDs that each need 20ma, you need to limit the current to 20ma using a resistor that will give you a 1.5v (5v-3.5v) drop at that current.

1 LED - 20ma - 1.5v/20ma=75ohms --- Radio shack sells 220ohm resistors at $0.99/5. Three, in parallel, will get you real close to 75ohms.

3 LED - 60ma - 1.5v/60ma=25ohms --- Radio Shack sells 100ohm resistors at $0.99/5. Four, in parallel, will get you there.

5 LED - 100ma - 1.5v/100ma=15ohms --- Radio Shack sells 15ohm resistors at $0.99/5.

7 LED - 140ma - 1.5v/140ma=10.7ohms --- Radio Shack sells 10ohm resistors at $0.99/5. They also sell 22ohm resistors at $0.99/5. Two, in parallel, will get you to 11ohms.

All of these resistors will have some variance. So, measure them and you'll likely find one, or a combination, that gets you even closer to the exact value you need...

Yeah, this increases the complexity and drives up the project cost. But, a 5v voltage regulator only costs $1.59 at Radio Shack...

On edit:
After re-reading this post, I feel compelled to make the follwing statement:
I do not work for Radio Shack, do not own stock in Radio Shack, and have absolutely no affiliation with Radio Shack... But, they should be paying me for as many times as I worked their name into this post...

jmdefino · Post by **jmdefino** » Wed Dec 07, 2005 9:08 am

In addition to the individual LEDs I have used to make my fixtures I recently came across an item called a Sylvania "Dot It". I was impressed with how white, and bright these little fixtures are.

They are battery operated but easily adapted for boat use. I bought one at Walmart and paid, I believe, $8.88. Here is a link to where you can see one online:

http://www.autobarn.net/syldotit.html

Moe · Post by **Moe** » Wed Dec 07, 2005 9:16 am

Sylvania Dot-It web page including the info that it uses 3 AAA batteries in the FAQ.

DLT · Post by **DLT** » Wed Dec 07, 2005 9:29 am

With conversion for 12vdc use in mind. Radio Shack also sells adjustible output voltage regulators (at $2.29 each) that can be configured to produce 3.5v, which is what these want (3x1.5vAA batteries). I assume these fixtures are somehow internally limiting the current...

Again, use of a voltage regulator will reduce, the battery voltage fluctuation issues... However, with an adjustible regulator, you are not going to eliminate it, since the control voltage would then be dependent on the battery voltage...

So, here, you might be better off using that 5v regulator and then two regular 0.7v drop diodes, dropping it down to 3.6v, which should be close enough...

Also, with three batteries not there, you should have plenty of space in the housing for the voltage regulator and supporting circuit. Heck, these could be relatively easy replacements for the stock lights. The only down side I can see is that the voltage regulator would always be "on", even with the light itself off. Of course that's not a big deal if you use the stock lighting circuit, since it has a 'master' breaker for all lighting...

Moe · Post by **Moe** » Wed Dec 07, 2005 9:37 am

As pointed out by one of our HAM radio members here, LEDs are current-driven devices, and that's what we should be focused on regulating. They drop what voltage they drop, and that varies even among devices from the same batch, and the variance increases as they age. For that reason, it's not good to parallel LEDs without resistance or current regulation in each leg.

MacGregorSailors.com

MacGregorSailors.com

LED,s for Interior Lights

LED,s for Interior Lights

Does anyone have

Oooooooooops my bad