Model Forum / General / Railroads / December 2004

I like to use the white LEDs and mount them in the clerestory (if the car has one
obviously) or along the top of the ceiling.
Two brass rods anchored at the end bulkheads and connected to the trucks serve as the
buss to which I can attach any number of LEDs that I consider necessary.
I use DCC and build a very small rectifier and voltage regulator to hold the voltage
at the proper value for the LEDs. Not all of them use the same voltage so you will
need to try to standardize on one type that is relatively inexpensive. LEDs have the
highly desirable feature of not generating measurable heat in plastic cars, something
that was always a major concern previously.

........F>

   First we have to pick up power from the track.  Best for this is
metal trucks and metal wheels which let the metal wheels transfer the
juice to the truck thru a low friction rolling joint.  Second best is
axle wipers in plastic trucks. Axle wipers are superior to wheel wipers
because the drag of axle wipers is less than wheel wipers.  Wiper drag
can be a real problem.  I did a lighted caboose with wheel wipers once.
When coupled onto a coal train, the extra drag of the wipers was so bad
that the locomotive (a heavy Bowser I-1 "hippo") could not pull the
train up the hill.  Plastic wheeled cars can be re equipped with metal
wheels with some checking around to obtain a metal wheel that fits the
trucks.
  Phosphor bronze is springy and makes a good wiper.  Shim brass is not
springy enough.  Hardware stores sell phosphor bronze weatherstrip that
makes good wipers.
  Walthers makes a nice light kit for their new passenger cars.  The
kit is a plastic bar that fits into the car ceilings.  It carries three
bulbs and some constant brightness electronics and sells for something
like $8.  I have been able to fit the Walther's light kit into IHC
streamliners with little trouble.  It gives a nice even light over a
wide variation of track voltage.
  The white LED's are bright, but the color of the light is very blue
and does not look much like an incandescent lamp. LEDs are polarized,
and need the same polarity to work.  Incandescent lamps don't care about
polarity and the color of the light is right, so for a simple car light
rig I would go with 12 volt bulbs.  For a fancier constant brightness
circuit I would go with a standard voltage regulator chip fed from a
full wave bridge rectifier.
  There are some humongous capacitors out there, like 1 FARAD.  These
will hold enough juice to keep the car lights on for 20 seconds after
track power is removed.  They completely solve the flicker problem.  The
caps are electrically fussy.  They are polarized and good for only 5
volts. So you need a full wave bridge and a 5 volt regulator to to
charge them, and a 1.5 volt regulator to drive 1.5 volt lamps.  LEDs
need a 330 ohm current limiting resistor.

David Starr