If you remember my December 2012 column on Basic Electronics
, two parallel conductors separated
by an insulator make a capacitor. Well, your locomotive’s wheel
and the track, separated by insulating dirt, make a capacitor.
So, if your detector is designed to decode the signal in figure 6
and your loco runs over a dirty spot on the track, the amplitude
of the (6) signal will diminish, but the shape of the waveform
won’t change. Thus, the decoder can read the DCC signal even
through a sheet of paper. If you are detecting signal level (5)
the sheet of paper will reduce the level to zero and the decoder
won’t see any transitions.
Either detector will create a data stream for the microprocessor
to analyze and act upon.
5: Threshold Detection – looking for when the DCC sig-
nal goes through 6 volts – DCC data = 111111000011.
5
DCC Impulses Column - 4
MRH-Feb 2013
