Computer Control with Dead Rail, Part 1 – Locomotive Control

Disclaimers – I have very little knowledge of electronics. Despite what my local club members might think, I am an entry-level tinkerer at best. But like most model railroaders I’m very dedicated and can figure most things out given enough time surfing YouTube. That said, I know what I want, and I don’t like being told it can’t be done.

Also, I’m not in business with Darrell Lamm – I’m just a very happy customer and I want to trumpet the usefulness of his creation to advance the hobby.

NOW –

Premise – The Quest for Automation

One of my highest aspirations for the LESRR is automation. I want to be able to run a train manually, make stops and setouts and pick ups, all the while having other traffic on the road to contend with. Of course, this is the goal of operating sessions with multiple human crews and a dispatcher. But what if, as usual, its just me? Or maybe me and one or two other operators? Enter computer control.

Modern software such as Train Controller ($) or JMRI (free) can be used for just that sort of thing. With a little setup to establish your inputs and outputs, the computer can be made to act on its own, with very little human interaction. It uses sensors positioned around the layout to detect the location of trains, and the computer runs its own throttle for each train it controls, executing protocols to regulate speed, make station stops, activate sound functions, and more. This technology has been used on conventional hard-wired (track powered) railroads for some time, where it forms the basis for most automated signaling systems.

Now move to the world of dead rail, and capabilities for computer interface evaporate pretty quickly. Most dead rail control systems connect one locomotive to one throttle, and that’s usually enough to get most people moving. But while some systems do have capability to add consisting (more than one locomotive per throttle), I have had a hell of a time finding one that will allow software like JMRI to operate a throttle in place of a human user, like on a hard-wired layout. It took more than a year of web browsing to find a solution.

First Steps in Basic Control

Before I get to the finish line, I want to share a little about what I did while searching. After all, at the end of the day we all just want to run trains. To get myself off the ground and running I found Steve Shrimpton’s excellent WifiTrax chip, controlling my locomotive with my phone via Wifi. It’s a great example of the technology that’s out there at reasonable cost. Simply plug your battery wires into one side of the chip, and your DCC feeder wires to the other, and off you go!

Now, the same effect can be had with DIY. Tinkering around with Arduino, I built a DCC++EX base station that actually fit inside my locomotive tender. For about $30 in parts on Amazon, I was able to duplicate most of the WifiTrax functionality in this way. The components were cheaper than a WifiTrax board, but still did not enable computer control – only control of a single locomotive.

A Complete Solution

The “ProMini Air” created by Darrell Lamm takes a signal from a DCC base station and broadcasts it over the air using radio waves, much like a Wifi network. A receiver in the locomotive then picks up the signal and converts it back into DCC using battery power, the kind you would receive from the rails in a conventional track-powered layout. In this way, Lamm’s ProMini Air system works in a similar manner to the old Tam Valley DRS1 system. The biggest difference, so far as I can tell, are that the ProMini Air is compatible with other loco receivers like CVP Airwire, NCE/QSI Gwire, and Stanton Cab – while the others are more or less strictly proprietary systems that don’t play well together. To that end, another very significant difference is that the ProMini Air is open source – if you’re up for the minutiae of building a circuit board and coding it yourself, Darrell gives you the information to do it. But best of all, and probably the biggest selling point for me – it’s one of the most economical options on the market today. I bought one transmitter unit and one receiver unit from Darrell for $50 each ($100 total) plus the actual cost of shipping.

Installation

The units arrive fully assembled and ready to go. I connected the ProMini Air transmitter to my DCC++EX base station output wires – the same that would go to powering the track in a conventional layout. Those are the only connections necessary on the transmitter. I then found space in the tender for the ProMini Air receiver, which I connected to the battery leads and DCC feeders to the locomotive. The chips have velcro on the backs, which not only makes mounting easy but also protects against shorts caused by resting them on metallic surfaces while energized.

My test locomotive (indeed, the LESRRs only operational loco so far) is ACL 326, a Bachmann Big Hauler ‘Annie’ Anniversary Edition, to which I’ve made some minor modifications.
I’ve managed to fit a 4″ Kenwood Speaker and a 6800 mAh CVP battery, and still have plenty of room for the ProMini Air into the tender of my Bachmann Big Hauler “Annie”. The original opening has been enlarged and some material removed to place the speaker and make the battery removable.
ACL 326 during a recent shopping – showing her TCS WOW 501 Steam DCC decoder mounted in the boiler and the wiring harnesses I built for the locomotive.

Testing

The system operated flawlessly right out of the gate. Testing was accomplished first with the Engine Driver app on a cell phone, and then, for the first time, directly from the JMRI computer. Both worked great, confirming that the computer could control a throttle to support automation.

One of my biggest concerns for radio systems on the LESRR is range – the layout is spread out over a roughly 210 ft by 60 ft area. As I approached the extremities of the layout, I did encounter some range issues. I was still rather impressed that the stock transmitter antenna was able to reach my test locomotive reliably for more than twenty feet into the basement staging area (‘Old Town’) – the nearest part of which is about 50 feet away from the antenna. At the other extreme, the locomotive received good signals except in the long tunnel, and up until it passed behind the ‘shadow’ of the mountain. Darrell’s programming of the chip to keep the locomotive running in the event of an outage gets her through the tunnel reliably every time. The problem is that the railroad is much larger than these limits.

To answer the range issue, Darrell recommended two possible solutions. First, a repeater unit consisting of a separate receiver and transmitter, and Darrell already has plans for this. Second, an amplifier and larger antenna. The amplifier solution was cheaper and so I decided to give it a try. Thankfully that gave me the boost I needed, and I stuck with it. The amplifier and larger antenna communicated very easily with the locomotive at the furthest extent of the basement (84 feet from the antenna and behind two masonry walls) as well as the extreme west end of the lot (tested further, from neighbors yard 170 feet from the transmitter), even in the shadow of the mountain and buildings. My shopping list to make the amplifier and antenna setup is given at the end of this entry.

Feedback

This system is the only real solution for my needs that I’ve yet encountered. I would recommend it to anyone seeking to automate their dead-rail outdoor layout as I do. The only criticism I have thus far is Darrell’s marketing of the system. His blog offers lots of great technical information, but isn’t terribly convincing of its chief advantages, which are significant, unless you are familiar with the finer points of how the electronics actually work. And I think the technical approach may be scary for other electronics noobs like me. I also think the name ProMini Air sounds like some kind of tablet or phone, and not a train control system. That said, Darrell himself will tell you – he isn’t building these for profit as a business in any real sense, he’s building them to help advance the hobby. In that, I call the ProMini Air a tremendous success.

Next Steps

Now that I’ve found a solution for computer control of dead rail locomotives, I’m turning my search to a system for my ‘stations’. These will be small computers spread around the layout (probably in the station buildings) that will allow turnout and signal control as well as track sensor feedback. Like the locomotives, I’d like them to communicate with the JMRI computer wirelessly.

I’ve been following the progress over at MQTrains with some excitement. The principle is sound, and exactly what I need, but it still isn’t as smooth and easy to build as it probably needs to be. I’m hoping to see it get there in the next year. The creator has a video explaining his concept here.

Further Reading & Resources

Darrell Lamm’s ProMini Air information pages

Email Darrell with questions or to order: darrelllamm@me.com

My shopping list to add a signal amplifier and larger antenna for extending range

Inexpensive DCC Command Station – DCC++EX

Engine Driver App – use any smart phone to control DCC locos

JMRI – open source free Computer Control software for Model Railroads

I’m going to put all of this into a YouTube video, soon to follow.

2 thoughts on “Computer Control with Dead Rail, Part 1 – Locomotive Control

  1. I just purchased a transmitter and receiver from Darrell. He sent you info. I am in Portsmouth today, any chance of stopping by to see your set-up?

    Like

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