Railroader:
Does Your calendar say april the first already?
Just saw a 6 light railroad signal at home. 1 white, 3 green and one green was blinking. How to interpret that?
Well, it's not North American, for sure. White is usually a "restricting" indication in many countries. It means it's okay to enter the block at reduced speed, prepared to stop for another train in the same block (hence slow enough to stop halfway since another train at the other end will also see a "restricting". But there would usually be a red light with that. It's rare here because it can be represented as a red over yellow, or red-red over yellow.
Blinking green means different things depending on the position on the mast relative to the other signal lights.
bears0:
The board is going to have a maximum amount of current it can supply that will limit the number of LED's you can light up at a time. If they're signals you would just count the most number of LED's on at a time and multiply by the current consumption of one LED. (Assuming they are all basically the same)
200mA is the cumulative maximum for the Mega (because it's the supply pin maximum).
Another weird thing - in North American protocol, an interlocking has no exit signals, only entry signals. So an interlocking controller (which I am working on...) generally doesn't have to drive any lights - only send modified occupancy and speed indications to the entry signal control modules that drive the LEDs.
Railway enthusiast here. How many lights are on a single mast, for subways?
Block signals usually have 3 lights: Green, Yellow, Red.
Interlocking signals usually have 6 lights: Green, Yellow, Red / Green, Yellow, Red.
There are instances for additional lights such as Lunar White or Home signals. However, I will choose to only use the 3 light combinations with several instances where only 2 lights are present.
Also, are these lights low power LEDs? The board is going to have a maximum amount of current it can supply that will limit the number of LEDs you can light up at a time. If they're signals you would just count the most number of LED's on at a time and multiply by the current consumption of one LED. (Assuming they are all basically the same)
This project will only light up 4 LEDs at once. The 1.8K Ohm resistor will limit the current draw to under 2mA per LED.
As far as block occupancy is concerned, I have built and tested 125 current detectors using bridge rectifiers.