Simple signal control for modular layouts?

Model Railroader General Discussion (Model Railroader)
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I was thinking of a way to add very simple signal control to an HO modular railroad. Because it is modular, with each module owned individually, it is very unlikely that there would ever be one standard signal system to hook up to thus creating normal blocks. But it’s often annoying to see the same signal color all the time, especially when set up for shows, etc…

So I started looking around online and found an interesting product by Circuitron, called SA-1. This is a selected quote from Circuitron’s catalog:

“Complete, simple, signal detection with timed 3-Color signal animation. Signal turns red as train passes. After last car clears signal, adjustable time delay starts (0 - 30 seconds). After time delay completes, the signal turns yellow, after another adjustable time delay, the signal goes back to green.”

It uses light sensitive sensors mounted in the track. So no need for resistive wheels like you need for current detection systems.

So this sounds great. Especially when most modular display layouts run trains in the same direction and in plenty of light so the sensors should work fine.

However I have an extra requirement. In addition to the 3 colors, Red, Yellow, and Green. I would also like to have Flashing Yellow. So it goes, Red, Yellow, Flashing Yellow, Green.

But so far I haven’t found any systems that can handle this without using a large interconnected block signal system. Obviously something that is not practical for a multi-modular layout.

I even emailed Circuitron asking about Flashing Yellow, but have yet to receive any response.

So does anyone here know of such a system? Where it doesn’t depend on blocks to change a signal, but also includes Flashing Yellow?

I plan to use the new

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flashing yellow is a little more advanced circuit needing a looping timer to control a voltage on/off.

Not impossible but adds more circuitry. And maybe cost. Flashing yellow may be more road specific rules. Multi-head displays are often used for more aspects.

I would be happy with just G/Y/R.

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Thanks.

I should have added that I’d like to simulate Santa Fe ABS signaling. So that’s why flashing yellow is needed. But I agree it does add to the complexity. Adding the electronics for this aspect probably were not worth it when many roads likely do not even use this aspect.

This pretty good website further explains the basic Santa Fe signal aspects:

Santa Fe Signaling

Now these mainline signals are all (or being converted) to approach lit CTC signals. “Approach lit” meaning they go dark when no trains are in the block. This is done to increase bulb life. Although I always wondered if constantly powering on and off ends up being worse for bulb life.

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Free-mo adopted a signal bus standard that allows for and ABS type signaling on a modular layout. Check out there yahoo group for Free-mo at http://groups.yahoo.com/group/Free-mo/. It uses some basic parts for detection and a since you can use a few different driving boards you can integrate whatever signals you want to use.

Chris

Lancaster, CA

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Actually, light detection for signalling has been around for at least a couple of decades. As you say, It works well if you have the same light intensity at the spot you have the sensor. However if the light changes, like if you like to operate at night using layout lights, the signals may not function correctly because the sensor may assume the darkness indicates a train is overhead and turn all the signals to red. In these situations using infrared might work better.

I believe the Atlas signal system has a similar set up, one option is as you describe where the train tripping the sensor turns the signal to red, then a timer moves it to yellow and then green. Again I think you’re right in saying that it would work great on say a double-track mainline where trains are only going one way on a particular track. It wouldn’t work so good on say a single-track main where trains are going both directions. That’s because when a train is coming from the other direction and clears the block, the signal should really turn straight to green not yellow then green.

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