12 volt LED

[John Doe]

I've been looking for a source on the net for 12 volt LED's. I was hoping to
find the bright LED's that operate on 12V DC so that I could add some accent
lighting to my boat. My question is: Are 12 v LED's available (I haven't
found any)? If so, where. If not, what other options do I have.

[Dan Hollands]

I've never heard of 12V LEDs most LED drop 2 to 3 volts. To run them on 12V
each LED would have a resistor in series to control the current thru the
LED.

--
Dan Hollands
1104 State Road
Webster NY 14580
585-703-2963
Quick...@USSailing.net
www.QuickScoreRace.com
"John Doe" <joh...@yahoo.com> wrote in message
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[HC]

FWIW, I've done a DSM (Mitsubishi) logo for a friend of mine, comprised of
LED's running on a 12v DC system and I found through trial and error that
exactly what Dan is saying is right; run one resistor for each LED, and run
each LED/resistor pairing in parallel with the others (if you're running
more than one LED). That is:

(+)---^^^R^^^-----LED---(-) for one and

--^^^R1^^^----LED1---(-)
|
|-^^^R2^^^----LED2---(-)
(+)---|
|-^^^R3^^^----LED3---(-)
|
|-^^^Rn^^^----LEDn---(-)
.
.
.

I found that 670 (roughly, I don't remember the exact value of the resistors
I used was) worked great, but that 1k and 1.5k ohm resistors caused the
LED's to be a bit dimmer than I wanted.

HTH

--HC

"Dan Hollands" <dhol...@rochester.rr.com> wrote in message
news:PpSda.74114$_7....@twister.nyroc.rr.com...

[rw]

google for "led bulbs". these are led assemblys to replace
existing light bulbs on cars etc.
rw

[Dan Barlow]

HC wrote:
> FWIW, I've done a DSM (Mitsubishi) logo for a friend of mine, comprised of
> LED's running on a 12v DC system and I found through trial and error that
> exactly what Dan is saying is right; run one resistor for each LED, and run
> each LED/resistor pairing in parallel with the others (if you're running
> more than one LED). That is:
>
> (+)---^^^R^^^-----LED---(-) for one and
>
> --^^^R1^^^----LED1---(-)
> |
> |-^^^R2^^^----LED2---(-)
> (+)---|
> |-^^^R3^^^----LED3---(-)
> |
> |-^^^Rn^^^----LEDn---(-)
> .
> .
> .
>
> I found that 670 (roughly, I don't remember the exact value of the resistors
> I used was) worked great, but that 1k and 1.5k ohm resistors caused the
> LED's to be a bit dimmer than I wanted.

You can calculate the resistor by subtracting the LED drop from the
supply voltage and dividing by 20 mA to get the resistance.

12V - 2.5V = 9.5V
9.5V/0.020A = 475 Ohms

That gives you the maximum safe brightness for that LED.
A higher resistor will be dimmer, adjust for your taste.

If you string several LEDs in series you can add their voltages
and use one resistor for the string:
2.5V * 4 LEDs = 10V
12V - 10V = 2V
2V/0.02A = 100 Ohms

This might save you some money on resistors... and is more efficient.
-Dan Barlow

[CoyoteBoy]

> If you string several LEDs in series you can add their voltages
> and use one resistor for the string:
> 2.5V * 4 LEDs = 10V
> 12V - 10V = 2V
> 2V/0.02A = 100 Ohms
>
> This might save you some money on resistors... and is more efficient.
> -Dan Barlow

Though I never believed it before, I found the problem a lot of people talk
about with this - I strung 3 sets of 4 together with 1 resistor for each 4.
LEDs started blowing left right and centre. I'd go with the one for each
approach if I were to do it again.

JB

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[HC]

When I ran multiple LEDs to one resistor the power dissipation on the
resistor got high enough that it started to get warm or even hot (1/4 watt
resistors). I get resistors at a local electronics store (Tanner
Electronics in Dallas/Farmers Branch) for 3 cents a piece so the cost of the
resistors was negligable. I bought a hundred of each of the 670 or so, the
1k and the 1.5k and didn't spend much for 'em.

To each his own, but I found through playing with it that the one resistor
to one LED seemed to work better, run cooler, and in my mind was the best
solution.

Anyway, none of that is meant to be antagonistic or hateful, so I appologize
if it reads that way; I'm just trying to relate my experiences and thought
processes in the matter.

Thanks for the equation for the resistance value, that's handy.

--HC

"Dan Barlow" <danb...@radix.net> wrote in message
news:3e78b500$1...@vienna7.his.com...

[Rob Paisley]

The real advantage of placing LEDs in series with one resistor per
group is the reduction in current required.

For example; if one l LED uses 20 milliamps then 4 LEDs in parallel
will use 80 millamps. If however there is sufficient supply voltage
that the 4 LEDs can be connected in series then the 20 milliamps
required by one LED can drive all 4 in the string.

This can be a considerable advantage for a battery powered system.

However in a circuit where the LEDs are not located near each other
the extra wiring needed for a series circuit could be a major
disadvantage.

Here is a calculator that can be used to determine resistor values
and there wattages.

http://home.cogeco.ca/~rpaisley4/LEDcalc.html

You will find that with LEDs in series the power rating of the
resistor decreases as the voltage drop across the resistor decreases
as the voltage drop across the LEDs increases.

(There's too many "as the's" in that statement)

Rob.

P.S. Another point to remember is that automotive and marine systems
do not operate at the nominal 12 volts stated but at close to 14 volts
when the engines are running.

"HC" <hboo...@gtespam.net> wrote in message news:<H49ea.59260$iq1....@nwrddc02.gnilink.net>...

[rm]

try here

http://www.alliedelec.com/

[Jimmy]

Auto stores sell led replacement bulbs that run on 12volts. THey are meant
to replace incandesent bulbs, They are a little pricey.
"rm" <rme...@attbi.com> wrote in message
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