In this project we show how to Isolate sections of track to avoid collisions at a simple crossover. The basic idea is that the train switches on a timer after passing over a sensor, which isolates the other track for a period of time while the train goes through the crossing.
Let’s assume the train is on Track A coming from the left.
At this point in time all signals are Green and all Isolated Areas are active.
As the train passes over Sensor 1 this starts Timer A. Timer A will now isolate Track Areas 2 and 3, and switch all Signals to Red. Any Train travelling on Track B will be stopped at Area 2 or 3 depending on which direction it is travelling. The Timers are set to work for a period of time decide by how long it takes the full train to go through and clear the crossing. The Timer A will now reset, putting power back on the Tracks and changing all the Signals to Green again. The Train on Track B can now proceed forward. This will activate Timer B isolating the Track areas 1 & 4 on Track A and changing the Signals Red.
There are four sensors so that the system will work no matter which direction the Train is travelling. For example Sensor 1 and Sensor 4 are connected to the Timer in Parallel so that either sensor will activate the Timer, also Sensor 2 and 3 are connected in Parallel to activate Timer B. Depending on the physical shape of the sensor will determine the position. Remember the operating distance between sensor and the magnet on the underside of the Train is 4 to 5mm. Here are two examples of fixing the sensors.
The isolation areas should be far enough back to not allow the train to stop on a Sensor or affect the other trains. As shown the power from the track comes from point A before Isolation Area 1 into the Common on the Timer, the feed to the Isolated areas 1 & 4 is connected to the NC (Normally Closed) contact. When the timer is activated the power is disconnected to these areas. How you achieve the isolation areas is your choice, we have shown below a few examples. On a DC system we are only disconnecting one rail, preferably the positive rail.
The signals are an added extra if you require, and will be dependant on the type used. They will all start Green and change to Red irrespective of where the train is coming from and which track initiates the Timers.
The best way is to wire Track A Sensors in parallel and then two wires back to the Time A, and the same for Timer B. If using signals, again if they are wired in Parallel and then back to the Timers this will reduce the amount of wiring to and from the Timers.
The Timers require a permanent 12v DC supply from your auxiliary supply. A ON/OFF switch in the supply could be added if you want to disable the system for any reason