Need help with Train stop and Circuits

[0swaald]

Thanks in advance for sticking through this wall of text.

Ive spent 8 hrs trying to figure out circuits today. i even built a special test rail area to speed up the process. This issue is why.

So I have a main coal depot. This is where most of my coal gets dropped, its then split between the Ore Bus, and the Steam Array 'Bus'. I have a second coal depot call "chemical coal depot". & Currently I have two trains which delivering coal.

Previously I had my 4 car trains drop all but 1k of their coal at the "main depot", and then drop the last K at the "chemical coal depot". However more coal was being delivered to the "chemical coal depot" than needed causing my trains to wait around without due cause. Which is why I resigned myself to figuring out the circuit system in game.

So what Ive done is wired the boxs at "chemical coal depot" , counted the coal, then I transmit the amount of coal signal to the "chemical coal depot" train station to enable when coal falls to 3k or less, I also transmit the signal to the "main coal depot" which tells any train there to go to "chemical coal depot", I dont this as a condition in the trains route plan. So this system works mostly.

---NB---
However If there is a train at the "main coal depot", with a second train queuing to off load, what can happen is that both trains end up trying to go to "chemical coal depot" to offload, as the second train will arrive in "main coal depot" and get the same signal as the first before the first has arrived at the "chemical coal depot". When the first train does get there, thanks to stack inserters the station is quickly disabled. However the 2nd is out of place and will return all the long ass way to the coal mine before returning to the "main coal depot" to off load.

How can I arrange it so only one train will be summoned in a situation like this.

I have attached some images for clarity. Note I have a light array which indicates coal levels, green for more than 6K, Red for less than 3k, and Blue for in-between.



Chemical coal depot:



Train Schedule:

[Zavian]

Personally I prefer solutions that aren't fragile. (ie solutions that aren't going to break if I change something/something unplanned for happens. Maybe I'll switch to solid fuel for power or nuclear/solar, or move the refinery and plastic production to an outpost).

So, personally I would have separate trains feeding each station, and probably add a low coal alarm to the power station. (I don't need an alarm for the main bus, but power about to shut down because of no coal is a big enough issue that it is worth an alarm).

Another way to do it is to name both stations the same, and to have them share a common stacker. That way you can have trains unloading in both stations simultaneously. (If supply exceeds demand, then both stations will get as many trains coal as they want, but if demand exceeds supply, then the station closest to the stacker will tend to get more trains. I haven't looked at your map carefully enough to see whether a common stacker is practical without a major rearrangement).

[0swaald]

What is a stacker? This isnt a concept im familiar with??

[wobbycarly]

What is a stacker? This isnt a concept im familiar with??

From a google search:
https://factorioprints.com/view/-KkOMhxwVGemt2uQNpXe


Basically it's parking lot that you feed trains into before their stations. It needs to be set up so that they all park without blocking other trains from entering the station. They also "work better" if the distance that each train needs to take is the same (as in this example, they all come on from the bottom left and leave top right - if they come in bottom left and leave top left, the inner lanes will get priority.)