DCC circuit breakers

I have many years of experience with DC, but I'm now learning the DCC
game. I've been running on our local club layout using DCC for about a
year now. I have recently purchased a Digitrax "Empire Builder" set for
my home layout. I have a question about 'power districts', or the
subdivision of the layout into several sections so if one drops out due
to some problem, the remainder of the layout can continue to operate.
My layout consists of seven sections (not modular), with electrical plug
and socket PAIRS (28 total) between each section carrying the master
power bus for throttles (4) and switch and accessory power. There is a
minimum of nine wires in each interconnect. Each section of the layout
has it's own control panel, with conventional 4-cab DC control (rotary
switches), switch machine control, lighting control, etc.
I plan on using ONE of the existing four 'cab' positions as the new DCC
'cab'. Thus I can run either DCC or conventional DC on the layout, as
desired. I do NOT plan on mixing DC and DCC on different parts of the
layout at the SAME time (possible, but too likely to cause problems with
complicated switching moves). We do this same thing on the club layout
with no problems worth mentioning.
BUT, the whole club layout is just ONE big DCC power district. As we
mostly run mainline trains for display purposes, this has not been much
of a problem.
My home layout is almost all switching operation, where the possibility
of momentary short circuits is MUCH higher (pushing against closed
turnouts, minor derailments, etc.are almost normal occurances). Thus I
wish to divide the layout into power districts so the whole thing
doesn't go 'down' when somebody does something dumb, or just has bad luck.
IDEALLY, I'd like a high speed, sensitive, circuit breaker in EACH
section. Digitrax makes such a unit, the PM42, but it has FOUR
districts, and costs about $80 list. That's a LOT of money for seven
sections, when I can only use ONE of the eight outputs on each unit.
Does anyone else make a similar SINGLE unit for less cost? Is a circuit
schematic available for building such? I could probably design one, but
why reinvent the wheel?
Will conventional non-electronic circuit breakers of suitable size trip
fast enough to keep the Digitrax unit from shutting down (I suspect not).
Alternative ideas are welcome, but my existing wiring does NOT lend
itself to a centralized multi-breaker unit like the PM42. That would
require a whole new power bus for the whole layout, with attendant
plug/socket sets (14), the complexity and cost of which would be nearly
as bad as buying seven PM42's.
Dan Mitchell
Reply to
Daniel A. Mitchell
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Dan, have you checked out Tony's PSOne Power Shield Intelligent Circuit Breaker? He sells it for $29.95 at
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Reply to
If you divide your layout into power districts as suggested, instead of using the PM42 (I use them, by the way, and like them a lot:you get a click and an indicator light when a short is detected), put a 3 amp circuit breaker in series with each district buss. The various districts are wired in parallel.
If you have a short, that breaker will open before the 5 amp (or 8 amp) booster detector. The layout will continue to run, and the breaker will give you the protection you desire.
Even with my PM42's, I have a toggle for each district so I can completely shut it off; and then their is a section of a district which has a three way toggle: running, off, programming track (I have a Chief with a DCS200 booster and my old Empire Builder DB150 as a secondary booster).
Anyway, you could arrange the circuit breakers on a panel near your DB150 booster, use LEDs to indicate that each district is ON, etc., and pretty much duplicate the PM42 circuit protection functionality.
in article snipped-for-privacy@umflint.edu, Daniel A. Mitchell at snipped-for-privacy@umflint.edu wrote on 3/10/05 8:15 AM:
Reply to
Edward A. Oates
Design is here Look for the 'Auto reverse and cutout module' it can be built as a cut out only or including the auto reverse.
Make friends in the hobby. Visit Garratt photos for the big steam lovers.
Reply to
Keith Norgrove
This looks like what I may want. I'll go over the documantation. Thanks,
Dan Mitchell ============
Reply to
Daniel A. Mitchell
Ed, this may work for a 4 amp overload but with a dead short the DCC booster protection will usually operate much faster than a normal circuit breaker, if it was this easy PM42s and the like would not be needed. Keith
Make friends in the hobby. Visit Garratt photos for the big steam lovers.
Reply to
Keith Norgrove
On my Digitrax system the trip time on the booster breaker is adjustable.
Reply to
Captain Handbrake
[ Snip ]
I think I read this in a Linn Westcott or Paul Mallery book many years ago, and used it on a power supply once.
Get a relay and wrap some additional big wire over the coil, #16 or #18 thereabouts. All of your power goes through the added coils. Adjust the number of turns so that your overload will begin to pull the armature down. The main relay coil and additional turns are in series. A NC relay contact is wired to short the main relay coil.
On on overload the heavy wire coils make enough of a magnetic field to break the NC connection and the main coil is then cut into the circuit, increasing the total resistance. So, this doesn't break the circuit, but adds resistance to keep the current level low through a short or overload. Cut the power, and it resets.
It's a simple quick acting little device. It takes a bit of trial and error to find the number of big wire turns that work the way you need. Once you get one working you should be able to make as many as you need without a lot of additional trouble.
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