> I'm not sure what voltage spikes
> Ed is referring to, but voltage
> regulators don't do much to filter
> out quick spikes. I think inrush
> current into a cold filament is the
> main culprit here.
> -Michael Eldridge
On my layout, the Aristo-Craft system is used to provide DC power. It has a
wireless throttle which I like very much. It also manages to start the locos
really nice and slowly without a startup jerk. As I found out (years after
buying it), the Aristo-Craft system uses high-voltage spikes when first
starting to increase the voltage from zero. These spikes budge the motor and
break loose the friction (called "sticktion" by some). Once the motor gets
moving, the spikes dissipate away and things return to normal DC. This is
similar to pulse power except that the spikes are much higher than 12 volts and
are of shorter duration than true pulse power. If they are really "spikes" or
"short pulses" I cannot say.
Other DC power packs do have higher-than-normal voltage "occurances" from time
to time. Especially the cheap power packs. DCC systems are also known to have
higher-than-normal voltage "occurances" from time to time. Most of these are
of very short duration and there are no immediate obvious effects resulting
from them.
As Michael points out, the initial inrush current to a cold bulb filament is
the main culprit. A cold filament appears to be a direct short circuit to the
power source. Thus, a whole bunch of current is set loose at the beginning.
Once the filament warms up, it has much more resistance and the current draw
returns to a more normal level. This is why even normal household light bulbs
always FLASH as you first turn them on instead of burning out after they have
been on for a while.
With voltage spikes, pulses or occurances, the initial inrush current is even
more than usual. While there might not be any noticeable effects at first,
this repeated activity will shorten bulb life. The best protection is some
sort of filtering/regulating circuit to make sure the bulb is exposed ONLY to
the desired voltage levels without any instance of excessive spiking.
Rusty Brassbasher has had some good experiences with the Dallee unit.
Personally, I think LEDs are the best solution to the entire matter. But each
to his own. We all are different.
Cheers....Ed L.
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