> During the process of researching DCC options, it became clear to
> me that most decent DCC systems have far more power output than
[quoted text clipped - 7 lines]
>
> -Tom
I have used 12 volt tail light bulbs to provide protection to separate power
districts.
IIRC, the 1156 bulb works fine with single engines (HO) and glows slightly
with two units pulling a long train. It glows brightly when a switch gets
overrun or a short happens on the track - and doesn't appear to trip the
overload on the booster.
A side benefit is that you can identify which district has the short.

Signature
73 de KT0T
Bob Schwartz
Modeling Waseca, MN in the '50s
Bob May - 29 Apr 2005 19:59 GMT
The light bulb idea is a very good one as it allows the booster to not trip
on an overload. Bulbs can be paralleled to the point where the booster can
supply them, thus with a 4 amp output of a booster, you can put 4 1156 bulbs
(they draw 1 amp at 12V) in parallel on the booster without any real
problems if you have the need for that much power although you may
occcasionally get glitches when the short occurs due to the inrush current
of the light bulbs.
FWIW, I once worked on a telephone system that used light bulbs at the
outputs of the power supplies to insure that when a particular switching
card went bad, the whole system didn't go down. The light bulbs were
labeled with the card slot that they fed.
--
Why isn't there an Ozone Hole at the NORTH Pole?
Froggy@ the pond.com - 29 Apr 2005 21:19 GMT
>FWIW, I once worked on a telephone system that used light bulbs at the
>outputs of the power supplies to insure that when a particular switching
>card went bad, the whole system didn't go down. The light bulbs were
>labeled with the card slot that they fed.
Sort of a "poor man's" crowbar.
Froggy,
froggy@thepond.com
If you don't want to go the PM42 route, build the electrical system as if
you were going to use one (that is, each "district" gets a double-gap with
insulating joiners). Each of those will have a pair of bus wires. Install a
fuse or circuit breaker (3 amp, fast blow) and a toggle switch for each one.
Note that in general, circuit breakers or fuses are not as fast as the PM42,
but by selecting 3 amps or less, the booster short detection shouldn't kick
in first).
So for each district, you get circuit protection from shorts, and a switch
to just run it off. If you would rather rely on the booster short protection
and still save money, don't put the circuit breakers in, but do put in the
toggles. When you have a booster shut down, just start turning the districts
off one by one until the booster resets to find the problem.
For me, given the overall cost of a layout with track, benchwork, loco's,
rolling stock, etc., the price of a couple of PM42s was lost in the noise.
If you need all 4 circuits in a PM42, it works out to $16 per district.
See all the wiring for DCC web site noted in my sig.
Ed
> During the process of researching DCC options, it became clear to
> me that most decent DCC systems have far more power output than
[quoted text clipped - 7 lines]
>
> -Tom

Signature
Ed Oates
http://homepage.mac.com/edoates
DCC wiring information is at http://www.wiringfordcc.com
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If you want units from other DCC manufactures NCE offers a similar unit
to a PM4 but with 3 outputs. Tony's Trains offers units in multiple units
1, 2, or 4.