6
6: BD-4 detector board from Digitrax – photo courtesy
Digitrax, Inc.
advantage is that, with some detectors, the remote diode mod-
ules can be located where the wiring to them is easy and the
detector board can be located in a more convenient location.
The disadvantage is that the diodes suck up some of your DCC
voltage and power.
The BD-4 is Digitrax’ simplest detector board, detecting up to 4
districts. The detection diodes are the two black components
on the left of the board. This detector does not support remote
sensor diodes.
The NCE BD-20 uses a ferrite toroid (doughnut) as a signal
transformer to sense the current flow. Okay, what does that
mean? There is a little ring on the board. You wrap one of the
wires between the booster bus and the detection district bus
through the ring a few times (see the manual for how many).
The advantage of this design is that it doesn’t drop any of the
voltage going to your track. The disadvantage is that you need
to locate the detector where you can conveniently wrap the
wire through it.
The BD-20 board from NCE will detect one district. You can see
the toroid in the photo (7).
Other manufacturers use these two basic themes. Once you
see the photo of each, you should be able to recognize which
design is being used, based on a photo of the board.
What resistor value?
Ideally, you want the highest resistance possible for your resis-
tive wheel sets, to keep the current draw to a minimum.
Digitrax says that it needs 10,000 ohms or less for positive
detection. So I’d recommend that value for all your wheel sets.
7
7: BD-20 detector board from NCE – photo courtesy NCE
Corporation.
DCC Impulses - 6
MRH-Aug 2013
