Multisim Design Project Help

[multisimislife]

I was wondering if anyone could help with a design I'm working on. It is on NI Multisim 13.0 and I am planning to use the design for a breadboard, also. So here are the basics of the design:

• It is a railroad crossing.
• There's a traffic light located at the railroad crossing.
• The track's used by both east and west heading trains.
• There are three sesnsors along the railroad track: one's at the crossing and one on either side of it (both are each 1/2 mile from the crossing.
• At all times, each sesnor indicates whether some portion of the train is at that location.
• Trains may be up to 1 1/4 miles long, so that at any moments 0, 1, 2, or 3 of the sensors may be active.
• Normally, the traffic light is green. However, when a train aprroaches within 1/2 of a mile of the crossing, the traffic light must go yellow for ~2 seconds, and then stay red until the train is completely past the crossing.
• Trains do not reverse directions while in the vicinity of the crossing.
• The input summary: 3 (the sensors at the crossing and at either side of the crossing, 1/2 a mile from it).
• The output summary: 3 LEDs (traffic light; can be colored, like red, yellow, and green).
• There's also a sensor in the road at the crossing, which at all times indicates whether there's a car crossing the tracks. On either side of the crossing, 1/4 of a mile from it along the track, there are two warning lights (which warn trains if there's a car on the crossing).
• The additional input summary: 1 switch (the car sensor at the crossing).
• The additional output summary: 2 LEDs (Warning Lights).

I am having trouble getting a grip on what the project is asking to do. If you could explain possibly the logic on multisim used and a general outline of what the design would look like on the multisim and on the breadboard. All helpful answers are good. Thank you all for any helpful answers that are good.

[Buechsenschuetz]

There are many possible approaches to this project, and I think there is not a problem with Multisim but rather with designing an electronic control system in general. 

Of course this problem can be solved using your own circuitry which would consist of sensor interface, control logic and output interface. This can be done hard-wired by logic circuits. Another approach would be using a simple microprocessor and programming it. You can also use pre-fabricated devices which exist as PLC (programmable logic controllers). There are quite simple PLCs consisting of a single device and limited number of inputs and outputs (sometimes expandable), and more sophisticated ones with CPU modules, input and output modules. Most manufacturers offer a development software, and pretty often this allows for designing with (virtual) logic components such as AND gates and OR gates. 

Whatever approach you take, you should be familar with designing logic circuitry and (if necessary) designing interfaces for the necessary sensors. When using a PLC, there are many sensors available with PLC compatible outputs which can be wired directly to the PLC inputs.