Protecting external turnout decoders


25 May 2021
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This layout was started before I came along so I am in discovery mode, yesterday I found couple of motors which had been modified to include the decoder inside the box.

The decoder is at the opposite end to the terminal block, it requires small holes drilled to pass the motor wires through the slots under the unit and then connected to the existing terminal block. Another small hole drilled to allow the two wires to the track.

Im not sure if this is better or worse, it's an alternative, it does require additional water proofing.


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Semi-Retired; more time for trains.
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Usually some small "weep holes" drilled in each corner will expel any condensed moisture. It's actually impossible to fully waterproof the enclosure, i.e. a hermetic seal.
Arggg, I have to agree (again ;)) Fully sealing is almost impossible, so either cover to prevent water reaching i.e. a small building or allow any moisture that does get in an outlet :)


Phil S
11 Sep 2015
Ann Arbor, Michigan
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The idea of using a small decoder such as the Zimo in the space vacated by the terminal block is inspired....
Agree! While you've got the soldering iron out you'll still probably want a couple of more robust leads to connect to the track though.

Greg Elmassian

8 Mar 2014
San Diego
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Thanks Jimmy! ;)

I learned many a time that a true "hermetic" seal is very difficult, and any tiny leak usually works against you, as a box cools in the evening, it pulls in moist air, which then, since the outside of the enclosure is cooler than the inside, the moisture condenses inside.

The weep hole idea is that the condensed moisture will be pushed out when it heats the next day, and any accumulated moisture will go out the weep holes.

We did extensive testing with some DCC turnout controllers with the us firm Train-Li, and found that the trick is a small weep hole in EACH corner of a rectangular housing, that means that there is at least one weep hole in the lowest corner, i.e. any moisture that accumulates will be by the weep hole. 1/16" seems to be enough.