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3: Bridge rectifier module vs. discrete diodes.
about ⅛ amp being drawn through the rectifier, so a 1-amp
unit will be fine.
There are two capacitors in this circuit.
The filter capacitor (C1) is an electrolytic (polarized) unit. Its
function is to store the pulses passed by the rectifier. It makes
DC out of the pulses of DCC that have been directed by the
bridge rectifier. 10 µF is enough to smooth out the pulses. A
25-volt rating will work with all DCC track voltages up to 20
volts. If you are in garden railroading or using track voltages
up to the 27-volt DCC maximum, use a 35-volt capacitor for
safe operation.
The other capacitor (C2) is there to remove any spikes left due
to asymmetry in the DCC signal. This should be a small mica or
ceramic capacitor. The electrolytic capacitor doesn’t filter these
small spikes, so the addition of a spike suppressor capacitor in
parallel will help you have clean DC for sensitive electronics like
the camera. A frequent value is 0.1 µF at 50 volts. This could be
anywhere from 0.01 µF to 0.5 µF, as long as the rated voltage is
above 35 volts.
Figure 5 shows the oscilloscope display reading the DCC signal
being applied to the power supply whose circuit is in figure 2.
3
