The theory was to use the isolated pieces of rail that existed at each end of the station on the old layout - the signal changed to green on entry and then back to red as the train passed over the points at the other end. With the new layout I decided against overly complicating things and now that the points on the station approach on the outer loop have been removed, I need a better solution.
Of course you can buy signal aspect controllers but I'm
The relays mounted on the PCB in this picture were originally controlling the track isolators in the station, now that this has been simplified this PCB is redundant so I carefully removed one of the relays.
The diodes were bought as a job-lot for various other signalling control ideas and the resistors were supplied with the LEDs I bought to make the control panel. I also have a few capacitors left over from the points control PCBs and several transistors...
And this is the first attempt at making a time-delay signal aspect control.
There are two 1K resistors here, due to the size of the capacitor and even with the briefest of supply pulses, the circuit took nearly a minute to discharge the capacitor fully and release the relay so the second resistor is bypassed, which gives a time of around 20-25 seconds. That should allow even the goods train to pass through the signal and clear completely before the signal reverts to green.
An extremely cheap and seemingly quite effective method of basic signal control, which I can hopefully integrate into the layout without too much grief!
Video of the circuit being tested:
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