3.3: Siskiyou Line - DCC short management

26 Oct 2013

TMTV
Rating: 
4.5
Average: 4.5 (6 votes)
Summary: 
6:31 - Managing shorts on a DCC layout (2006)
Description: 

The nemesis on DCC layouts is getting a short. Learn how to permanently end the cry of 'who shorted the layout?' and to make it possible to 'shortproof' power districts so the rest of the trains in the district keep running even if another train happens to cause a short.

Foillow along as Joe Fugate explains step-by-step how to install inexpensive short management to shortproof your layout so only the train causing the short quits running, and all the other trains keep running, even in the same booster power district.

Note: This video was originally shot in older Standard Definition and then upsampled to HD for TMTV. As a result, the image is softer than is typical for TrainMasters native HD video.

Comments

This is a very risky practice.  This does indeed fool the DCC unit into not switching off when there is a short, however if a wheel is causing the short (the most common scenario), high current will be flowing through that wheel.  As there will be some low resistance around the wheel this will generate heat in the wheel, more than enough heat to start melting plastic, gears, axel insulators, axel housings etc.  I have seen this happen with poor wiring, where the resistance of the wiring was too high to trip the DCC unit when a short was put on the rail, which is exactly the same result as this video.  Put in a few more of those DCC power management units in e.g. Digitrax PM42.  It will save you money in the long run.  The DCC system are designed to stop a high current flow through a short and hence protect valuable rolling stock and possibly trackwork as well.

joef's picture

I've had this in place on my layout since 2000 and I've not yet fried a wheelset or piece of equipment. 

The 1156 bulbs actually do limit the current to 2.1 amps, which is a lot less than 5 amps, 8 amps, or 10 amps (common power supply outputs for DCC). The 2.1 amp level is just enough lower that it limits the damage by quite a bit. If you recall in the pre-DCC days, 2 amp power packs where common - but 5, 8, or 10 amp power packs were not as common, so the 2.1 amp bulbs actually make the situation with shorts a lot more like the DC days, which is quite manageable.

For about $1 per bulb, this level of protection is a lot more affordable than $40 per protected sub-block within a power district.

I have heard various objections over the years because this is not a true electronic solution. But in actual practice, it works extremely well and all the gloom-and-doom purist predictions just have never come about in well over a decade of op sessions.