I have some LEDs that I would like to use on my boat. They currently
operate on 3 AAA batteries or 4 1/2 volts.

Question: What would happen if I wire them in direct to 12 v? My
understanding is that LEDs have a fairly wide operating voltage range.

Please advise. Thanks.

Joe

On Sun, 25 Mar 2007 23:04:29 -0400, Joe Bleau
wrote:

I have some LEDs that I would like to use on my boat. They currently
operate on 3 AAA batteries or 4 1/2 volts.

Question: What would happen if I wire them in direct to 12 v? My
understanding is that LEDs have a fairly wide operating voltage range.

Please advise. Thanks.

Joe


They'd die. Google LED.

LED's are restricted as to the amount of current they can stand so a
higher voltage = more current = death. To use with a higher voltage
you will have to (1) use a resister to drop the amperage, or (2)
install a voltage regulator of some sort.

Bruce in Bangkok
(brucepaigeatgmaildotcom)

--
Posted via a free Usenet account from http://www.teranews.com

"Joe Bleau" wrote in message
...
I have some LEDs that I would like to use on my boat. They currently
operate on 3 AAA batteries or 4 1/2 volts.

Question: What would happen if I wire them in direct to 12 v? My
understanding is that LEDs have a fairly wide operating voltage range.

They don't, it is in fact the opposite. LED's have a very steep U/I curve
just like any diode. They might not draw any current at 1.5V (red LED) and
fry on 2V. LED's operate on current, not voltage. You need to calculate a
series resistor to limit the current to 30mA which is the maximum for normal
LED's.

To do that, take the maximum voltage that you need to apply, i.e. 14.4V for
a 12V system and calculate the resistor as follows: R = (14.4 - Vled) /
0.03. Vled depends on the color, red LEDs are 1.6 to 1.8 and yellow and
green LEDs around 2.1V. Blue leds are around 3V but might depend on the
technology used, the same goes for white LEDs.

You should not parallel LEDs and use one resistor since LEDs might vary a
bit in voltage, resulting in uneven currents through the different LEDs. You
can connect them in series, and add the voltages. So 5 red LEDs would need a
total voltage of 5 x 1.6V = 8V. The added benefit is that there is less
voltage drop across the resistor and the overall efficiency increases.

Meindert

"Meindert Sprang" skrev i en meddelelse
news:460767a8$0$22762 You should not parallel LEDs and use one resistor
since LEDs might vary a
bit in voltage, resulting in uneven currents through the different LEDs.
You
can connect them in series, and add the voltages. So 5 red LEDs would need
a
total voltage of 5 x 1.6V = 8V. The added benefit is that there is less
voltage drop across the resistor and the overall efficiency increases.

Meindert
Excellent post, I`ve filed it away, and now I`m an instant expert on
LED`s ;-)
Thanks.
Bob

There are a number of cool on-line calculators, Google "LED Resistance
Calculator:.

I'm partial to this one: http://metku.net/index.html?sect=vie...calc/index_eng

MW

wrote in message
oups.com...
There are a number of cool on-line calculators, Google "LED Resistance
Calculator:.

I'm partial to this one:
http://metku.net/index.html?sect=vie...calc/index_eng

Just remember Ohm's law (V = I x R) and you don't need a funky website to do
this. Besides, this one is a bad example, with the parelleled LEDs on the
3rd diagram.

Meindert

On Tue, 27 Mar 2007 01:13:03 -0800, ray lunder wrote:

SNIP

I like the white xenon lights I found at WestMarine for $27 with a
high/low setting which pulls .7 - 1 amp per.
Hurry on spring!

Wow! $27.00 at Waste Marine! That means we could probably get them
for $5.00 almost anywhere else.

On Tue, 27 Mar 2007 08:30:09 -0400, wrote:

On Tue, 27 Mar 2007 01:13:03 -0800, ray lunder wrote:

SNIP

I like the white xenon lights I found at WestMarine for $27 with a
high/low setting which pulls .7 - 1 amp per.
Hurry on spring!

Wow! $27.00 at Waste Marine! That means we could probably get them
for $5.00 almost anywhere else.

Or just get some xenon festoon bulbs and fit them to standard lights,
eg:

http://www.buylighting.com/Xenon-Festoon-s/196.htm

What would be handy is a modified fitting for both a 10W and 5W bulb,
and 3 way switch for 5, 10 and 15W

cheers,
Pete.