One of the nice things about DCC
is that you not only have individual control of each loco irrespective
of where it is on the layout, but you also have independent control
of other electrical devices on each loco or train. How many things
you can control depends on how many functions the decoder has and
how it is wired.
With DCC, track voltage is constant
all the time. This allows lighting functions that can be controlled
regardless of whether the train is running or not. So, if you want
the headlight on, you turn it on - at any time. If you want it off,
you turn it off - at any time. Further, other lights can be controlled
while providing special lighting effects such as Mars lights, Blinking
Ditch Lights, and more. A loco could have front and rear light, Mars
light, Blinking Ditch Lights, number board lights, truck lights, and
running board lights -all independently controlled. On top of all
that, smoke units, coupler control, passenger car doors, and literally
anything electrical on the train can also be controlled. Literally
anything you can model or modify to be controlled electrically can
be controlled with DCC - not only on the train, but anywhere on the
layout. All these things can be controlled from a hand-held throttle
that's plugged in anywhere around the layout, from a Radio, from an
Infrared control throttle, or from a computer.
Control of the loco's speed and direction
is not considered to be a function. When a decoder is advertised to
have four functions, that implies that you will be able to control
the train's speed and direction, plus four more things - such as headlight,
rear light, Rotary Beacon, etc.
Typically, a decoder has a function
wire that controls the flow of electricity from a blue common power
wire. This function wire is connected to the electrical device you
want to control, along with the blue common. When you have that loco
selected and operating on the layout, all you have to do to turn that
electrical device on is to press the function button that controls
the function wire your device is connected to. Pressing the function
button again will turn it off.
Functions are numbered from 0 through
12 - for a total of 13 functions. Currently, decoders come with anywhere
from 1 to 9 functions. I don't know of any decoder that doesn't at
least have Function 0 for the headlight, with most having front and
rear directional lighting. As far as I know, the only decoder that
uses up to Function 8 is SoundTraxx sound decoders. In the near future,
there will be decoders that will allow some or all of their functions
to be remapped to the higher functions.
Function wires are colored so you
can tell which to use for which function button. The NMRA has set
some wire color standards to help make this easier. Power pickup from
the track is red and black, motor control is orange and gray, and
the common (power lead) for all functions is blue. Following is the
list of functions the NMRA has set a color standard for:
Function 0 forward - White (for front
light)
Function 0 reverse - Yellow (for rear light)
Function 1 - green (usually the bell when sound is used, but otherwise
can be for anything)
Function 2 - violet (usually the horn/whistle when sound is used,
but otherwise can be for anything)
Function 3 - brown (isn't actually an NMRA standard, but is used by
Digitrax as their standard)
Function numbers greater than 2 are
not designated by the NMRA, so refer to the manufacturer's decoder
documentation for wire colors of these functions.
Most functions simply provide voltage
on/voltage off control. But there are other ways a function can work.
The rest of this page will be about that and some of the things that
can be done with functions.
As noted above, Function 0 can have
two wires - one for the front light and one for the rear. The way
this normally works is, when Function 0 is turned on the front light
will be on when the loco is going forward and the rear light will
be on when the loco is going in reverse. This is called Directional
Lighting. Many decoders provide a way to separate the control
of the white and yellow wires into two different functions. This provides
two non-directional, independently-controlled functions. With Digitrax
decoders, for example, programming a "01" into CV 61 provides
non-direction on/off control of the white wire with Function 0 and
non-directional on/off control of the yellow wire with Function 4.
Other manufacturers may do it in other ways, so you'll have to check
their documentation.
Most function buttons work the same
way - pressing them one time turns them on, and pressing again turns
them off. This is called a toggle function button. This is useful
for most lighting and other applications - press Function 0 once to
turn the headlight on, press again to turn it off. Function 2 is different
(at least with Digitrax's systems). Function 2 is designed to control
the horn/whistle - press it to blow the horn/whistle, release to stop
it. This is called a momentary function button. Having a momentary
function button for the horn/whistle allows you to easily play the
grade crossing or other railroad control/informational tunes. However,
if you want to use Function 2 as a toggle, there are ways to "lock"
it on when the button is released. Pressing it again "unlocks"
it and turns it off when you release the button - just like a standard
toggle function button.
[Some manufacturers provide what
many call FX Lighting. This term was
coined by Digitrax when they came out with their FX Lighting in 1995.
Actually, Throttle Up! (SoundTraxx) had these features in stand-alone
products called HyperLights, long before
DCC came along. While the HyperLights products have been discontinued,
they still provide HyperLights in their sound decoders today. Some
manufacturers use the FX term for special lighting effects, while
others use variations of it.
Most people only use Function Control
for lighting. We've got one customer that lights up everything - to
a point of sometimes needing more than one decoder to handle it all.
For the most part this is fairly easy to do. If you want Blinking
Ditch Lights, for example, simply purchase a ditch-light kit (or scratch
build the brackets to mount regular Grain-of-Rice bulbs up front),
connect them to two functions of a decoder that offers the Ditch Light
FX feature, and program it to do ditch lights. It's the same for the
Mars light, rotary beacon, FRED, etc.
Some people go all out in their modeling.
We have customers who control their smoke units with Function Control.
Another has built a mechanism to control the coupler on the back of
his tender, and one has made operating doors in his passenger cars
that open when the train pulls up to the station. The station master
then reads off the list of towns the train is heading to before hollering
"boooooaard!" - all controlled with DCC from their hand-held
throttles. |
