> Is there a "standard" for headlights? IE led XXX with resister YYY?
A standard resistor size for all lights on a DCC-powered layout is somewhat
difficult because there are so many variables. For one, the track voltage can
be different from one layout to another since it is user adjustable with the
better DCC systems. N scale likes 9 volts and G scale likes 20+ volts. Other
scales like all things in between. My track voltage is 15-1/2 volts. Another
variable is the rating of the bulb: 1-1/2 volts, 5 volts, 12 volts and 16 volts
are all fairly common. Then, of course, the LEDs add another variable to the
situation. Not to mention that white LEDs want something different from red
LEDs. And constant lighting units like something different from individual
components. Different brands of decoders have a different amount of voltage
"consumption" which then leaves differing amounts of voltage remaining for the
bulb/LED. As you can see, the optimum resistor value is different for each of
these situations.
It is certainly possible to standardize for your own personal layout if all the
various variables are also standardized. But if you then take a loco to a
different layout, the optimum conditions might be violated. When that
happens, bulb life could be shortened, brightness can be dimmed, LEDs can burn
out and so forth. These problems may not occur immediately, but will be slowly
damaging over time. Since the effects are not promptly apparent, many folks
will be unaware of them.
So what to do? One solution is to install a resistor that causes the bulb or
LED to operate at 10-15% less than its rated voltage or current. It will be
dimmer, but last longer and be somewhat protected as a result. If you do not
like dim lights, install a miniature voltage regulator which will precisely
maintain the set voltage at all times regardless of track voltage. Some of the
better decoders already have voltage regulators built in.
If all this is overly complex, there are online web sites that teach how to
make the calculations for each specific installation. This way, the computer
does all the work. Having an assortment of resistors on hand really makes the
job easier. Costing about 3 cents each, it is not financially burdensome to
have many resistors in the parts box for a wide variety of situations.
Good luck...Ed Loizeaux
www.sscale.org
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