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| Non-Directional
with Directional Lighting • Dimming with
Directional Lighting Dimming While Going Forward • Equipment Requirements |
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Directional lighting means that the front light will be on when the loco is going forward and the rear light will be on when the loco is going backwards. They will never be on at the same time. With traditional DC Analog control, directional lighting can be achieved by using a pair of diodes. Since diodes allow voltage to flow in only one direction, the diode controlling the front light would allow electricity to flow only when the polarity was correct to make the loco go forward. Same for the rear light, only for going backwards. Also with traditional DC Analog, lights typically get brighter as the train goes faster. That's because the voltage on the track is higher to make the motor go faster. Constant brightness lighting can be achieved with the use of more diodes. When running the motor power through a couple of diode pairs, there will be 1.4 more volts on one side of the diodes than the other. This voltage differential can be used to light 1.5-volt bulbs. But still, if the loco is stopped the lights are off. With DCC, track power is on at a constant voltage all the time. This means you have constant brightness lighting without special motor diodes. It also means you can have lighting whenever you want it - even when the loco is stopped. In fact, you have full control of lighting at all times - even to a point of having special lighting effects. When you turn the lights on, they are on at a constant brightness - even when the loco is completely stopped. Further, they can be programmed or wired to be directional, non-directional, even dimming. And with the right decoder, you can also have many other special lighting effects such as Mars lights, strobes, Blinking Ditch Lights, and more. In fact, with the right decoder(s), you can have head and tail light, Mars light, ditch lights, running board lights, truck lights, cab lights, and number board lights - all individually-controllable if desired. When you turn the lights on with a decoder that has directional lighting, the front light comes on when the loco is going forward. When you reverse the direction the front light goes off and the rear light comes on, and vice versa, even when the loco is stopped. Most decoder manufacturers provide directional lighting on their decoders. The companies that do not provide directional lighting say that it is not prototypical so they don't provide it. Having that kind of attitude is very short-sighted. There are, in fact, some roads that do have directional lighting. And with directional lighting you can wire it for non-directional lighting, even prototypical dimming if desired. This is something that can't be done without either directional lighting or a special effect to do so. First and foremost, many people want directional lighting simply because they want the front light on when going forward and the rear light on when going in reverse - and they don't want to have to change it manually. They want this not just for the lighting, but also for visual feedback so they will know which direction the loco will go when they give it throttle. While there is an indicator on the hand-held throttle as to which direction the train will go, many people don't look at their throttle when running trains. Instead, they've learned which buttons on the throttle does what and can run the train without having to look at the throttle. By having the lights on the loco change automatically with the change of loco direction, this gives them the feedback they need to assure them that the train will go in the direction they want - without taking their eyes off the train to look at the throttle. This gives them more time to watch the trains run - which is what DCC is all about. It's as simple as that. They don't care that it's not prototypical. They're having fun running and watching their trains - it's a major convenience. |
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| Non-Directional with Directional Lighting |
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Most current decoders offer a programming
way to separate the white and yellow wires to make them non-directional.
However, some older and/or low cost decoders do not have this option.
The following illustration shows how to get non-directional lighting
from a directional lighting decoder that doesn't have a programmable
non-directional option. |
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Both white and yellow use the same
resistor. When going forward,
the white wire turns the light on. When going in reverse, the yellow
wire keeps the light on. |
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| Dimming with Directional Lighting |
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Some roads have rules
that require a loco to dim the headlight when stopped and/or when
going in reverse. This can be accomplished in two ways: with a Digitrax
or Train Control Systems FX Lighting feature
or by tricky wiring of directional lighting. Since some low-cost decoders
do not have FX Lighting features, you're left with doing it with tricky
wiring. Here's how to do that: |
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Most bulbs require a resistor in
line to reduce the voltage. The resistor on the yellow wire has a
higher resistance than the one on the white wire. The white and yellow
wires are tied together after the resistors. When going forward, the
front bulb gets full brightness |
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voltage from the white wire.
When going in reverse, the front bulb gets less voltage (for a dim
bulb) from the yellow wire. If your road's rule is to dim when stopped,
put your loco in reverse while sitting still. Wires can also come
off the blue and yellow (before the resistor) for a directional rear
lamp if desired, or from all three (with their own set of resistors)
for dimming on the rear lamp. |
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| Dimming While Going Forward |
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Some roads dim the
headlights when two trains are approaching each other on parallel
tracks. The above scheme doesn't allow for dimming the headlight while
continuing to go forward. There are two basic methods to achieve this.
Both methods require the use of a separate dimming function. The first
way is the safest to wire. |
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This
is similar to automatic dimming above, but works differently. While
it will automatically dim when going in reverse, it has to be operated
manually to dim the light while going forward. The resistor on the
green (function |
#1) wire needs to
be a value that will provide dim lighting. The resistor on the white
wire needs to provide enough additional current to make the light
bright. To operate it, you turn both function 0 and 1 on. When the
loco is in reverse, the white wire will turn off, leaving all current
to go through the "dim" resistor. To dim the light when
going forward, simply turn Function 0 off, again leaving all current
to go through the "dim" resistor. |
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There
are several variations of this. If you don't want anything to be automatic
(you have full control of when the light will be on or dim), you'll
have to program the decoder for non-directional operation or wire
it for non-directional operation using the white, yellow, and green
wires to the front light. For totally manual operation, some people
might prefer the next example: |
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The resistor on the blue wire
is the correct resistor to make the bulb at the correct full brightness.
The resistor on the green wire is enough to draw enough current to
make the bulb dim. To operate it, turn Function 0 on for |
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normal
directional lighting. Turn Function 1 on to dim the headlight. This
scheme does not provide for automatic dimming, only manual dimming
when going forward. This means that if you leave directional lighting
in effect, the headlight will be off when in reverse. |
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To have
automatic dimming with this scheme requires you to connect the yellow
wire and resistor as shown below. This scheme provides full brightness
when going forward, and dimming when going in reverse or when Function
1 is turned on. If Function 1 is turned on when going in reverse,
the light will be much dimmer if not off all together. |
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With three resistors
and its complexity, it's easy to see why this is not a popular solution
for automatic/manual dimming. |
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There
are many more variations, both in dimming needs and how to implement
them. These three options should provide you with enough information
for you to devise your own variations for automatic/manual directional/non-directional
dimming for front and rear lights in any combination. Various decoders
provide various options for lighting. Sometimes it's possible to use
one of these features and then provide additional wiring and resistors
to achieve what you want. |
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| Equipment Requirements for Directional Lighting: |
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Directional lighting is a decoder feature that does not require anything special from the system. To have directional lighting, the decoder MUST have that feature. All decoders carried by Loy's Toys have directional lighting (except for decoders that don't have lighting at all, such as Throttle Up! DSX and Digitrax's TD1). Most have a directional/non-directional programming option. Directional lighting is enabled as it comes from the factory. If you want non-directional lighting, you must either program or wire the decoder in for it. With Digitrax decoders, CV61 is used to program for non-directional lighting. With Train Control Systems and Throttle Up! SoundTraxx decoders, non-directional lighting can be achieved via FX Lighting and/or function output programming. With Lenz decoders, directional/non-directional programming is done in CV51. With NEC decoders, non-directional operation can be attained via function-output programming. All of Digitrax's current systems can program any value into these CVs. |
