I thought I would share this project that I have been working on for about six years, on and off. It is a controller for four aspect model railway signalling.
Functionality of four aspect signals
When most people drive these signals on a layout, the will use a rotary switch to change the signal, but when you have a layout with multiple of these signals, the control board becomes very cumber sum and hard to maintain.
When I first designed the controller I designed it for use on a Picaxe MCU, as at the time the only MCU I had looked into. The basic Functionality of the system was to take tow inputs, a binary number and to then drive the LED's on the signal, as the majority of manufactures of the model signals use 3mm leds with a common cathode, this requires four outputs. The driver for the LED's would also include a small RC Circuit to have them fade as a incandescent bulb would.
| Input | Signal Output | Pin Output |
|---|---|---|
| 00 | Green (Go) | 0010 |
| 01 | Yellow (Next Block Red) | 0100 |
| 10 | Double Yellow (Red Two Blocks Away) | 0101 |
| 11 | Red (Stop) | 1000 |
The second design, again on the picaxe had more complex functionality, in an attempt to make the system more autonomous. It included functionality for a TOTI (Train on Track Indicator) which would set the signal to Red, and the ability to chain the systems together, bu adding one onto the input and passing it out.Along with the functionality to include a feather, which is used to indicate which way a point is going, and a second input which it would use when the track was switched. I use input as the system is moving in the opposite direction to the train.
The second design came rather far, but i wanted to focus on a more generic system which would be near fully automated. and so i designed it using logic gates (sorry as don't have an image of the Logic). I then started thinking about making the design more user accessible, ie making a kit, posting PCB layouts and schematics. So i am now looking at what would be the best way for me to implement this design so that I can share the whole System.
My main Goal for doing this would be small form factor (I working in 4mm:1ft scale and the signals are small), low cost, ease of self assembly and although not necessary low power consumption.
The other options i would like to be able to add; are a control board, basically a mimic layout device (a device with a sketch of the layout on it) to change the signal to Red, or even other states,
Having thought about how to implement it I have considered a couple of options;
1. Generic Logic Gates
2. Field Programmable Gate Array, or other programmable logic device
3. Arduino programmable Micro controller
4. Micro controller, such as pic or avr.
I would like to hear any suggestions or advice the community have on how i should implement the system, and hopefully i may be able to share files about it with you when it is finished.
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