LED headlightinggreenspun.com : LUSENET : Wiring for DCC : One Thread
Some basic education in LED application for locos please. Not hard to find sources but the tech data encountered on the net for selection by this amateur is wanting so far.
What is required with a LED labeled 12 volt for installation as a loco headlight in DCC operation? And same question with a second light facing aft on the same loco? Are LEDs not labeled 12 volt also usable?
Any suggestions for preferred manufacturerof LEDs? Any experience in choosing between three grades of brightness offered for 12 volt LEDs for loco installs?
-- Bob Tappan (email@example.com), July 18, 2002
There are no LED's designed for 12V, all are diode junctions that operate from .7 to 1.2V. I assume you are interested in white Led's. These devices are actually Blue Led's illuminating a phosphor target. It's the phosphor that emits the white light you see.
To the best of my knowledage, there are three manufacturers of White Led's. The ones I am most familiar with are made by Lumex. They are available in both T-1 (3mm) and T1 3/4 (5mm) sizes. I use the 3mm Led's for locomotive headlamps. The part number is SSL-LX3054UWC. DigiKey has these as part number 67-1606-ND.
These and most other Led's want to operate at about 20ma so if you are driving them from a DCC decoder output a resistor of about 680 ohms is just right. If you are running them from DC then 470 ohms is a good choice.
I hope this helps.
-- Ken Brantley (firstname.lastname@example.org), August 05, 2002.
The Nichia "white" LED needs about 3.6 volts to turn it on. Red, green and yellow LEDs usually run about 1.6 volts. See http://www.trainweb.org/girr/tips/tips7/white_led_tips.html for more info.
-- George Schreyer (email@example.com), August 10, 2002.
There are led's with resistors built in so they can take 12 volts.
-- scott herman (firstname.lastname@example.org), November 25, 2002.
I am not in the train biz but if you wan't the brightest white 5mm LED out there go to
6.99 CDN = 4.50 USD. Good deal for the brightness because you can always use a resistor to lower once it is installed.
-- Mike Yannotti (email@example.com), December 02, 2002.
I use golden white led's from TTX and amber coloured led's from DCC concepts. Both get a 1K or 1,2K - 0,5watt resistor and draw 15mA. This way they'll last even longer and stay cooler. And you can dim them too. In the same way I give 1,5V light bulbs a 820 Ohm resistor to drop the working voltage to 1,4V.
-- Jean Marie (firstname.lastname@example.org), September 12, 2004.