Model Train-related Notes Blog -- these are personal notes and musings on the subject of model train control, automation, electronics, or whatever I find interesting. I also have more posts in a blog dedicated to the maintenance of the Randall Museum Model Railroad.

2022-03-15 - Dead Spot Detection Car for DCC

Category Train

Here’s my latest DIY experiment: a homemade “dead spot detection car”.

Here’s a schematic and a rough explanation of how it works:

This is designed to work exclusively on DCC track.

The goal is to help operators detect dead spots on the track, either by rolling the car manually or by pushing it with an engine as seen above. They need to move it till the front green LED turns off. That will allow us to determine where the break in the track continuity is located. Then using the yellow LEDs, we can determine if the break is in only one rail or both rails.

This isn’t just about breakage in the rails, either. The original motivation was to help me find issues with unpowered frogs on the layout’s turnouts. In this case by moving the car manually over a turnout, we should be able to see a green LED go off when the frog or the closure rails are not powered correctly.

When building this, LEDs polarity does matter as shown in the following electrical schematic:

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2021-07-04 - How do the Electroluminescent (EL) Displays Work?

Category Train

We’re in the process of adding a Miller Engineering animated sign on the layout, and later I want to revive the 2 broken ones (the theater one and the motel one). So naturally I wonder how they do work… What's the tech behind it?

Looking at the Miller Engineering site, they have an “experimental” section, which partially replies to that question:

So these are listed as “electroluminescent” (a.k.a. EL) displays. The Miller ones come with a little control board, and they are typically powered by a 4.5 V DC power supply or 3 x AAA batteries. They call the board an “inverted”, and it features an obvious transformer, so that gives us a fairly good clue on what it does (i.e. that’s a voltage booster).

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2021-07-03 - Motion Sensor LED Light for the Train Back Room

Category Train

Today we’re modifying this cheap “Motion Sensor LED closet/night light”:

So here’s the situation: the back room at Randall where we have the workbench presents some challenges. The switch to turn the room light is in one corner of the room, and we enter the opposite side of the room. And in between we have the Bridgeport yard, the Napa yard, and the workbench. Thus when we enter the room we need to carefully navigate around all these things mostly in the dark till we can turn on the light. Not ideal. Most of us use our phones as a flashlight to avoid tripping into something. Can we do better?

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2021-04-24 - DCC++ EX support in Android Cab Engineer app

Category Jmri

Today on the bench, we have two things going on:

On the left side, we have a “Wifi Kit 32” ESP32 running a fork of the latest DCC++ EX firmware.
On the right side, we have my
Cab Engineer DCC Throttle app for Android communicating with the DC++ EX command station.

A few clarifications and explanations are needed here.

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2020-03-15 - Dwarf Signal for Turnout, Continued

Category DCC

Here’s a concrete example that shows how to wire LEDs directly to a turnout frog, as explained here, and makes it obvious how trivial this is:

Resistance used here is 1 kΩ, that gives good brightness for both the green and red LEDs.
A 2.2 kΩ resistance also worked well enough for the red LED yet made the green one too dim.
In this example, the frog polarity is switched between rail A and B by a microswitch using the EZ-Track coil mechanism.

Another variation of this that I plan to use on the Randall Model Train layout is to only have the red LED, to make it clear when a turnout is left thrown/divergent. Especially for mainline turnouts, it acts as a “warning” signal. There is no need for the green LED in that case. I will likely embed the LED directly next to the turnout in the ballast. These LEDs are small enough that they could even be placed between the ties. The LED and the resistance can be wired to the existing terminal connected to the auxiliary contracts of the Tortoises.

2020-03-08 - Dwarf Signal for Turnout

Category DCC

Here’s an idealized turnout, showing the polarity of the frog based on whether the turnout is normal or reverse:

The frog is directly connected to rails A or B via the switch points of a slow-motion turnout motor, be it a Tortoise or a Fulgurex (in the case of the Randall layout). This works for any turnout which has a metal frog which polarity changes based on the turnout position. Examples are turnouts powered by a Tortoise or Fulgurex where the auxiliary contacts from the slow-motion motor are used to change the frog polarity. Another example are the EZ-Track turnouts with a metal frog.

We can directly wire two LEDs, green and red, with a resistance, to the frog and the A / B rails to get them illuminated to indicate the position of the turnout, as follows:

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2019-09-29 - NCE AIU and NCE EB1 Circuit Breakers

Category NCE

One issue I have on the Randall layout is that operators or automation sometimes short the layout. Then the NCE EB1 circuit breakers take over and of course shut down their corresponding power district. Then operators or staff ask me why things do not work, yet a lot of them fail to check the circuit breakers to see if they are shorting.

One idea I had a while ago was to use an NCE AIU01 to monitor the NCE EB1 circuit breakers. Then I could feed that into my automation software and get reporting of actual shorts right on my status web page.

The proposed solution is to use dual-channel optocouplers to connect the EB1 LED output to the AIU inputs.

Here are the details, as updated on 2020-02-04:

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2019-09-21 - Searchlight Car conversion to LED

Category Train

I’ve just finished this project:

The car itself is a Model Power HO Scale “Safety First #624 Searchlight”. It’s a depressed flat car with a nice & sturdy die cast metal construction. It’s really well done.

Jim got it for Randall and when we tried to use it, somehow trains started crawling when pulling the car.

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2019-06-15 - Cotton Belt 9389

Category Train

Jim gave me this engine, with the sole purpose of changing the horn. How hard can it be?

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2019-06-03 - Jupiter Steam 4-4-0 Engine

Category Train

Jim got this engine for Randall in commemoration of the 150th Anniversary of the Transcontinental Railroad.

My first attempts at doing that video were miserable as the engine would stop constantly at slow speed and I tried a few things to see if I could improve the power pickup.

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