Model Railway Electrics - Lights
There are two types of lights,
Filament Lights and Light Emitting Diodes (LED's)
lights produce their light as a result of passing electricity
through a thin piece of wire (filament). The electricity passes
through the wire heating it up until it produces light.
The glass bulb stops oxygen from reaching the filament which
would result in the wire burning out.
The most common filament lights used
on model railway layouts are "Grain of Wheat" and "Grain of Rice
Bulbs" due to their small size. Filament lights can come in many
colours although the colour comes form the colour of the
bulb/lens rather than being produced by the filament.
Because filament lights produce light by heating wire it is not
surprising that the bulb itself also becomes hot. This can pose
a fire risk in some circumstances. This heat is a waste product
and accounts for approximately 90% of the power consumed meaning
filament lamps are very energy inefficient.
lamps do however produce a more natural light. As filament bulbs
have in the past been the main source of light in homes it is
not surprising that they still produce the most realistic light
when lighting model railway buildings. LED's tend to produce a
light that is more akin to that produced by modern energy saving
light bulbs than the incandescent bulb. The time period you are
modelling may affect your decision on lighting.
Grain of Wheat and Grain of Rice
bulbs often come pre fitted with wires to allow for easy
connection to a power source.
Street lights and Building lights.
Produces a more natural white light. Light is not restricted to
the direction of current they are connected to.
Disadvantages: Become hot when in use, less reliable
than LED's, more
power hungry than LED's, and
are more fragile than LED's (glass bulb).
is important to remember when using LED's that they can only be
connected one way round and for this reason you should use a
Directional Current (DC) power supply. You should connect the
positive (+) wire to the anode (a) and the negative (-) wire to
the cathode. You can identify the cathode and anode by the
length of the lead coming from the LED. The shortest lead is the
Cathode (you may also notice that the cathode side has a flatten
surface.) and the longest lead is the anode. If you are unsure
because for example you are using salvaged / second hand LED's
you can look inside the LED. The side with the largest wedge
shaped electrode is the cathode. Of course you can simply use
trial and error.
You can connect LED's to an Alternating
Current (AC +/-) power supply but the led will only light when
the current is the correct way round resulting in the LED
turning on and off at the frequency of the AC power supply.
LED's require a very small amount of current.
Standard LED's usually require a resistor to be placed in the
circuit to reduce the current. Failure to do so will result in
the LED burning out and becoming unusable. A 1k resistor should
be enough to connect an LED to a 12V (volt) or less power
are available in a range of colours although you will pay a
premium for Blue and White. LED's are also available in a wide
range of shapes (round, square, rectangular, and triangular) and
various sizes. Personally I tend to use 3mm (millimetre) LED's
when the LED is to be on show as they are closer to scale
without becoming too fiddly to wire. I have used them to build
railway crossing lights, and railway signals but they would also
be perfect for streetlights.
1.8mm rectangular LED' s are perfect to be
converted into railway lamps by simply painting them and using
one of the leads as the handle. I have also seen them widely
used for locomotive directional lighting.
In general round LED's are easier to fit as
they only require a hole drilled or you can use LED panel clips.
LED holders provide a quick and effective way of connecting your
LED to a power source without the need to solder wires onto
Tri-colour LED's - LED's also come in
Tri-Colour combination of which the most useful version is the
Green / Yellow / Red.
The LED comes with 3 leads one of which is
the common feed, one for the Red and one for Green. The yellow
is produced by supplying power to both the red and green LED.
The mixing of red and green produces yellow.
If using batteries, Where heat is a problem (fire risk), When
requiring large numbers of lights.
Advantages: Low power consumption, Very reliable
when correctly powered, Does not get hot.
Can only be connected one way round when using Directional