As someone who has been away from the hobby for a number of years, but is
just getting back into it now, can someone please explain to me what on
earth DCC is? I have seen it mentioned often on this group, but have no idea
what it is!
The simple answer is Digital Command Control (DCC). Traditionally, model
trains have been controlled with 12 volt variable DC current (depending on
scale) to control the movement of trains. This has meant that a train fitted
with lights brighten and dim with the varied current used to control train
speed. Double heading or running in multiple has also been awkward due to
different motors having varied current consumption at the same notch on the
controller. If you wanted to move only a particular loco amongst many on a
portion of track, they would all move at once unless you had lots of
isolating sections and switches.
With DCC it is a completely radical. First, the track is energised with a
constant 15 volts DC with a square wave ( a vague kind of AC). Each
locomotive is equipped with a decoder that monitors digital signals on the
track. When you tap in the number on your controller it will now respond to
your commands. This in cludes, direction, speed and functions (e.g. lights).
So appart from moving a loco when and where you fancy, you can have trains
approaching each other on the same line, constant lighting in trains and
loco lights will stay at a constant brightness. You can vary the
accelleration and braking rates with some decoders and some have back EMF to
create a uniform speed up hill and down dale. Ideal for double heading and
DCC can also be driven from a computer with the right software and hardware.
Block detection is available and points and signals are easilly controlled
The DCC standard was created (with the help of Lenz) by the National Model
Railroad Assosciation of America (NMRA).
It means if DCC equipment is compliant to these standards then decoders and
control equipment will work with each other. Equipment is also forwardly and
backwardly compatible, so you will not get left with an obsolete system on
Wiring a DCC layout is much more simple and straightforward. However,
locomotives require a different approach especially the British outline
ones. A few are now 'DCC ready' this means you take the body off, remove a
plug and insert a decoder. The decoder has a plug and flying lead with a
sticky pad. The only challenge is identifying pin 1. Some loco manufacturers
stamp this on the circuit board while others do not. It is not a problem to
identify the wires and orientate the pins.
Unfortuneatly, most UK outline locos do not come 'DCC ready'. In this case
you must isolate the pick ups from the motor circuits as the current flows
from the track to the motor via the decoder. In most installations the RF
suppressors are removed and the decoder takes care of the TV interference
(this does not apply to ZTC manufacture decoders where supprerssors are left
in for operational reasons).
Whilst this sounds all a bit dauting, there are now DCC user groups on the
net who are ready to help plus the manufacturers and distributors.
At first glance DCC appears expensive, but considering all the facilities
you get it is an absolute bargain. My Lenz set 100 can control 256
locomotives from 31 controllers plus 1024 points with a 5 amp transformer
for under £300 and that is a top of the range set. DC only locomotives can
still be used, but all lights will light up (the AC nature of the curent
will overcome directional diodes) and you get a strange noise from the
motor. Lima pancake motors cannot be used like this for a long time.
Decoder fitted locos can run on conventional DC but never with a feed back
controller or on layouts with working overhead lines (this will burn out a
decoder). Overhead electrified lines are just for show on DCC and you do not
need current from them as a seperate control circuit as was required in
years gone by.
Aplogies for the long posting.