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The PM42 has four separate track power circuit breakers, each
with its own input and output. Multiple PM42s may be connected to
one booster. All four inputs of each PM42 may be connected to the
same booster, or divided between two or more boosters, and each output
may be programmed for auto reversing. But, when set for auto-reversing,
that output is no longer a circuit breaker. You may, however, use
one output as a circuit breaker, then run its output to the input
of another for auto-reversing - thus taking two outputs for the auto-reverse
section with circuit breaker protection. You may connect more than
one auto-reversing output to one circuit breaker output, but a short-circuit
in one auto-reverse section will stop the other auto-reverse outputs
from working until that short-circuit is relieved.
While the two main uses for this device are stated
as being able to protect from derailment short-circuits and auto-reversing,
I think an important use is providing a second (more sensitive) level
of short-circuit protection. Since these devices come set for three
amps max, they will more likely shut down for a "resistive"
short circuit than a five-amp booster will.
What is not widely known, simply because it doesn't
happen very often, is that not all derailments are dead shorts. And
if it isn't a dead short, it may not make the booster shut down. But,
if there's still three amps of current coursing through the short
circuit, it can melt plastic parts next to the metal parts that are
causing the short - especially with N scale where the parts are so
much more delicate.
In addition to this major advantage, it allows HO
and N scale users to opt for higher-amperage slave boosters. For example,
the DB200+ eight-amp booster
is only $16 more than the DB150 five-amp
booster. The power supply for the eight-amp booster is only $16 more
than the power supply for the five-amp booster. So, for only $32 more
(17% overall), you get 60% more current - to run 60% more trains without
having to have yet another slave booster. The PM42 will add $64 to
the overall cost, but it not only provides additional Short-Circuit
Protection, it also adds operating versatility by not having the entire
layout shut down due to a typical derailment.
While some HO users are using the higher-amperage
boosters without additional circuit breaker protection, we do not
recommend it.
PM42 units are set at the factory for three amps,
which is ideal for N and most HO scale operation. But this doesn't
mean that S, O and G scalers can't use them. PM42 units may be set
for any amperage needed, from three to 12 amps, in increments of 1.5 amps.
Note: when connecting the PM42 to any booster, just
because you have four outputs set for three amps each doesn't mean
that you now have 12 amps of current. You still have only the amount
of current the booster can provide. It's just that not more than three
amps will be used by any one output.
Since each output has its own input, it needs four
connections for each bus wire going in. This may be from one booster,
from two boosters, or however many power sources you want (up to four).
Two examples are shown below. |
