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want to help you to If you are looking for a simple, affordable, Optical Sensor Based, Automatic Block Signal System for your Model Railroad, click here: Automatic Block Signal System Details for information about the system we have designed. You can read how our system was developed and how we put it all together. I have included pictures in the article so you can see how the system works. Click this link for the long-awaited article on building the affordable "Three-Aspect", HO Scale Signals. Experienced electronic hobbyist? Already know what you want? Go to the SALES CATEGORIES section on the left to order any Bare Circuit Boards, DIY Kits, Components or Assembled Modules you need to get started. Some Signal Basics: What is a "Block"? What is a "Block Signal System"? What do we mean by "Sensing"? Why choose Optical Sensing? A Block is a specifically defined section or segment of track in your layout. A Block Signal System is basically a series of signal lights, each devoted to a specific block, which display the occupancy status (is the train in the block?) of the block they represent, usually, by changing their color. For the Block Signal System to know the occupancy status of a block, there must be some kind of sensor that is watching for the train to arrive and leave. There are several methods of sensing a block including the more common Current Detection and Optical Detection methods. The Current Detection method senses power use while the train is in the block. Sounds easy, but in reality, you need to isolate one rail of each block from the other blocks in the layout and you need to create a "current draw" environment all along your train. The Engine, because it contains the drive motor, is already drawing current from the track, but the rest of the cars usually have no electrical impact on the track at all. While the Engine is in the block, the sensing is easy. When the engine has left the block but the cars are still in the block, you need to make at least some of the remaining cars use power from the track (Draw Current). This is usually accomplished by adding a resistance across the wheels of the trucks for all chosen cars. Adding resistance across the wheels creates a controlled short circuit between the rails and the current detection method is able to sense the current flowing through the short circuit. If you have a relatively short train, you might need to add resistance to only a few cars, but if your train is long, you need to be certain that there is always a resistance in the block until the caboose (or last car) goes completely through the block. To create a current, you need to have metal wheels and preferably removable trucks. Methods of creating a resistance include painting the axle, wheels and the wheel insulator of each truck with a resistance paint that effectively creates the short circuit. This is a high maintenance method as the paint breaks down over time and must be renewed often. The more common method is to add wheel or axle "wipers" that rub against the wheel or axle and then connect the wipers together with a physical resistor. This too is a lot of work, the wheels have to be installed so the insulated wheels are on the same side of the truck and the other truck has to be oriented the opposite way (one truck is connecting to the left rail and the other is connecting to the right rail), the wipers tend to loose their tension and stop making a good connection. Dirty tracks also makes the detection less than consistent. The Optical Detection method uses Photo (light) Detectors (or Sensors) all around the layout that "know" a train is present in the block when the light is shielded from them (they are in darkness) as the train goes over them (if installed between the ties in the track bed) or the train runs between the sensor and the light source (if using "across the track" sensing). The installation will require some work in the beginning: You need to install the Photo (infrared or natural light) Detectors (or sensors) and provide a suitable light source for them to detect or "see". Natural (room) light is usually the easiest as you rarely run your train in a dark area. For Optical Detection in a very dark location or running the train in the dark, infrared detectors are used. You will need to provide a series of Infrared emitters so the detectors have something to see. The detectors (sensors) trigger the controller when they DO NOT see any light. When the train gets between the sensor and the light source, the controller is triggered. The most labor intensive part of this method is that you need to install enough detectors (sensors) in each block so the train will be detected as long as there are any cars in the block. You need to combine the detectors (sensors) electronically so they appear to the controller as if there is only one sensor. You have to do a bit of wiring or connecting of the detectors (sensors) to the controller, but once you are finished, there is little maintenance required. An added bonus is that detectors (sensors) can be used to control more than one event. An example is using some of the detectors that control the block signals to also control grade crossing lights or gates. That cuts down on how many detectors (sensors) you end up using to control the whole layout. Read how this is done in the description for the MultiSense Board in the modules description area or directly from here. The actual Block Signal Lights are run by a Signal Light Controller. When a detector senses a train, it sends a ground signal to the Signal Light Controller by triggering an Event Controller that actually turns the ground on or off. The Signal Light Controller is connected to a Common Power loop that runs under and all around the layout. Once activated, the Signal Light controller sets the current Signal Light to Red, the prior Signal light to Yellow and the next signal light to Green. Read more about the Signal Light Controller in the modules description area or directly from here. There are also details about the Four Event Controller Module in the modules description area or directly from here. We chose the Optical Detection method because we didn't want to be responsible for any issues that might arise in the DCC system due to our segmenting sections of track. We were also concerned that the resistance that needed to be added to the cars might interfere with the commands issued by the DCC controller. The thought of having to modify hundreds of cars (the club has a large assortment in their "rolling stock" collection) to add that resistance was another factor in our decision. This web site is focused on using Optical Sensors to alert the controllers (and rest of the system) that a train is in a block. We are not limiting our products to just serving the Block Signal System, but are also working to include other devices that can be triggered the same way as the Block Signal Lights. See below for descriptions of the current projects. If you have purchased a Circuit Board or DIY Kit and want to know more about the actual Circuit Boards or how to assemble them, read our Assembly Notes. There is additional information in the Module Descriptions and Uses. If you have lost the assembly card with the component layout, drop us an email and you will be sent a link to the layout and schematic page. Current Projects:
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