LOCOMOTIVE LIGHTING
USING SURFACE MOUNT
LEDs
Jim Hinds
RICHMOND CONTROLS
INTRODUCTION
There are many ways to use surface mount
LEDs to provide lighting functions in model
railroad locomotives.
This discussion
covers illuminating headlights, signal
lights, and ditch lights using the “603” size
of surface mount LED, which measures
approximately 0.060” x 0.030”.
WIRING CONFIGURATIONS
TERMINOLOGY
In this discussion, the non-illuminated side
of the LED where its contacts are located
will be referred to as the “bottom”. The
large light emitting surface on the opposite
side will be referred to as the “face” or
“top”. The term “mounting hole” is used to
refer to any hole in the locomotive body
shell or detail part meant to represent an
empty light fixture, where an LED will be
installed.
TERMINOLOGY
INTRODUCTION
Installation generally requires a clear
pliable adhesive and sealer, several drill
bits, and highly opaque black paint. The
mechanical LED mounting techniques are
the same regardless of the type of power
system and drive electronics used for the
locomotive and its lights.
INTRODUCTION
Several clear and pliable adhesives that
also serve as sealers are available and
recommended for this activity, including
Pacer’s Formula 560 Canopy Glue and
Micro-Scale Krystal Klear. Pactra Racing
Finish black paint is a very effective and
opaque black paint.
INTRODUCTION
The user must insure that an appropriate
current limiting resistor and any other
appropriate protective components are
used, PARTICULARLY if the LED is
“white”. (“White” LEDs tend to be
damaged more easily by voltage issues
than non-white LEDs.)
INTRODUCTION
Recommendations for electronic
components for use with the LEDs can be
found at www.richmondcontrols.com in the
LED section. (All Richmond Controls
modules have these components.
Decoders generally have all necessary
protective components.)
INTRODUCTION
The selection of mounting arrangement for
the LED is primarily determined by the
geometry of the existing light opening and
the ease with which factory-installed
lighting components can be removed or
modified. The installation approaches
discussed are:
INTRODUCTION
• Mounting the LED’s face over an open
light hole not containing a lens,
• Mounting the LED to the surface of a lens,
• Inserting the LED end-first into a hole,
• Inserting the LED face-first into a hole,
• Inserting the LED into a bezel and
mounting this lighted bezel into a hole.
MOUNTING AN LED OVER AN
OPEN LIGHT HOLE
This approach is useful when the headlight holes
are small and it is undesirable to modify them.
Examples are the headlight holes in brass Z
Scale and N Scale hood diesels. Simply glue
the LED in position with the LED face over the
hole.
Example: AZL Z Scale C44-9W
MOUNTING AN LED OVER AN
OPEN LIGHT HOLE
MOUNTING AN LED ON THE
INSIDE SURFACE OF A LENS
In some cases, the locomotive’s clear
plastic lens cannot be removed gracefully,
or it may be desirable to retain the lens.
The LED’s face can be bonded to the
inside surface of the lens.
Example: Kato N Scale GS4
MOUNTING AN LED ON THE
INSIDE SURFACE OF A LENS
MOUNTING AN LED ON THE
INSIDE SURFACE OF A LENS
A similar technique is to remove the
backing from an MV lens that is somewhat
larger than the headlight hole, insert the
LED through the hole, glue the LED to the
back of the lens, and then glue the lens to
the front of the hole.
Example: Kato HO Scale GP35
MOUNTING AN LED ON THE
INSIDE SURFACE OF A LENS
INSERTING AN LED END-FIRST
INTO A LIGHT HOLE
An appreciable amount of light comes out
of the LED’s ends. The LED will fit endfirst into a #56 (0.046”) hole if its wires are
configured to exit from one end of the
LED, tucked against its bottom and
insulated with a thin application of clear
pliable adhesive.
Example: Model Power N Scale RSD15
INSERTING AN LED END-FIRST
INTO A LIGHT HOLE
INSERTING AN LED END-FIRST
INTO A LIGHT HOLE
Assuming the mounting hole is smaller
than 0.046” after removing the stock lens
assembly, use a #56 drill (0.046”) to drill
from inside the shell to countersink the
mounting holes. DO NOT LET THE DRILL
BIT BREAK THROUGH TO THE FRONT
SURFACE OF THE LOCOMOTIVE.
Example: Intermountain N Scale SD45T-2
INSERTING AN LED END-FIRST
INTO A LIGHT HOLE
INSERTING AN LED FACE-FIRST
INTO A LIGHT HOLE
This operation is the same as when
inserting the LED end-first, except a #47
drill (0.078”) is used to countersink the
light hole if space is available. This larger
hole allows the entire LED to fit into the
hole face-first.
Example: Athearn HO Scale FP45
INSERTING AN LED FACE-FIRST
INTO A LIGHT HOLE
INSERTING AN LED FACE-FIRST
INTO A LIGHT HOLE
If a #55 drill (0.052”) is used, the light
emitting part of the LED will fit snugly into
the hole, with the larger base outside the
hole.
Example: Athearn HO Scale C44-9W
INSERTING AN LED FACE-FIRST
INTO A LIGHT HOLE
INSERTING THE LED INTO A
BEZEL AND MOUNTING THIS
LIGHTED BEZEL INTO A
HEADLIGHT HOLE
This technique is ideal for cab type
locomotives in all scales, and hood type
locomotives in the larger scales, where the
headlight hole diameter is larger than
about 0.075”.
Example: Athearn HO Scale F7
USING A LIGHTED BEZEL
USING A LIGHTED BEZEL
Another option is to countersink the back
of the bezel as in technique #4. The LED
can be permanently bonded inside the
bezel, creating a “lighted bezel”, and then
the lighted bezel can be installed in the
locomotive’s mounting hole.
Example: Kato N Scale F7
INSERTING AN LED END-FIRST
INTO A BEZEL
FINAL STEPS
Note that for each of these mounting
methods, it is generally recommended that
a clear pliable sealer should be applied
over all exposed portions of the LED
visible inside the locomotive. PACER’S
FORMULA 560 CANOPY GLUE is ideal
and strongly recommended.
FINAL STEPS
The sealer should also be applied where it
will wick between the LED and the inside
surface of its mounting hole, to prevent the
black paint applied later from being able to
wick around to the front surface of the
LED. After the sealer cures, an opaque
black paint can be applied to control stray
light, like Pactra BLACK Racing Finish.