DCC Impulses Column - 6
don’t fit in an 1930s vintage passenger car. So, I tinted them
with Tamiya acrylic X-26 clear orange paint
. The variation
between LEDs obtained by hand painting the LEDs helped the
overall look. The light is not evenly distributed throughout the
car, as it would be with factory tinted LEDs.
The two brass rods running the length of the car have
rectified DCC on them. The LED modules connect between
the rods. Alternatively, individual LEDs with droppingresistors,
or 12 volt LEDs, could have been used. I just happened to
have the modules in stock when I did this car, so I used them.
I have also obtained some LEDs that flicker like candles or
other flames
. I’m going to experiment with
adding some of them to this car to create an effect based like
oil lamps.
Power Storage
What hasn’t been mentioned so far, is that all of these
concepts rely on sliding or rotating power pickup from the track
and frequently have only one or two contact points per rail.
The result is flickering lights. If one is modeling an era before
electric lights, flickering lights can be fun, as I mentioned
before. The entire car shouldn’t flicker at once.
Eliminate the flicker with onboard energy storage. Since LEDs
draw relatively little current, large elecrolytic capacitors can fill
the need. There is no need to revert to super caps or the large
energy storage modules necessary to keep a motor turning.
Figure 9 shows closer detail of the power supply I built into the
car. The brown wires bring track voltage from the truck (4). The
green module is a bridge rectifier assembly. I don’t remember
what the ratings for this one were, but 50 volts and 1 amp units
are easy to find and inexpensive. Higher voltage or current
ratings are okay, but not necessary.
The bridge rectifier puts DC on the two brass rods: positive
on the far rod and negative on the near one. The LEDs can be
hooked to these rods with a bridge rectifier connecting to the
track. I did that originally and the LEDs flickered constantly.
Time for energy storage.
I went back to my stock and found a 4700 uF 35 volt capacitor.
This is the lowest standard voltage that is totally compatible
with DCC standards (track voltage as high as 27 volts).
However, if you promise not to use track voltages over 20
volts, you could use a 25 volt unit. Note that it is connected
to the power rods correctly, with the negative lead connected
to the one closest to the camera. This keeps the LEDs running
for about 4 or 5 seconds with no power applied. If you want
9: Detailed look at power supply in lighted passenger
car from figure 1.
9
MRH-Sep 2013
