trains and inserters

[britblad]

my question is how can i set up my inserters so that if i'm off loading 1 product and loading another for example i have 1000 plastics and 500 iron plates i want the insertes that are loading the plates to stop at 500 instead of continuing to load till the train leaves at 0 plastics is this possible at the moment? if so how?

[ratchetfreak]

in lieu of being able to read train contents you'll need a bit of trickery.

use the circuit network to only put 500 iron into the input buffer chest and then use a SR-latch to force the inserters feeding them to turn off and at the same time turn on the inserters that will put the items on the train.

detect the presence of a train with the rail signals and when one leaves you re-enable the inserters feeding the buffer chest and disable the ones inserting into the train.

[Bushdoctor]

i want the insertes that are loading the plates to stop at 500 instead of continuing to load till the train leaves at 0 plastics

I got a feeling you mixed up loading and unloading, and perhaps also metal plates and plastic in your question. So, let's try to answer ALL of it.
If you want to load a certain amount of items onto a train, you can set the squares inside the wagon to accept only specific items.
To do that, you click one of the squares with your middle-mouse button (usually the scroll wheel) and you pick the item you want in that square.
You can now copy that setting to other squares with the regular in-game copy function. (shift + right click, and shift + left click).
This will allow you to set an exact amount of items, based on the stack amount of those items.

If you want to unload a certain amount of items from a train, you can do that by connecting a filter-inserter and a chest with a colored wire.
Once you connected them, you can set the inserter to only take out items from the train when the chest has less than X.
For instance, only take out plastics if the chest has less than 500. Which would look like this: [plastics] < 500
Perhaps this is not exactly what you want, because you can not literally control the items that are taken out, but instead you control
the amount that should be stored in the chest...

I hope that helps.

[SyncViews]

If you want just 1000 plastic and 500 iron regardless of where you load and unload, since the total is less than the wagons capacity, you can just filter the wagon slots (middle mouse button) so that you only have 10 plastic slots and 5 iron slots (and block the spares like with chests), since inerters will never insert into the wrong filtered slot or a "red" slot (even when stack inserter research allows them to sometimes pickup too many items, it will only drop those allows and carry on holding the spare).

To unload a specific item, a filtered inserter works for a single item (since cant filter chests and even if you could or come up with a clever circuit, stack inserter bonus problems...). If you are not too concerned about unloading an exact amount each time, no circuit is needed. e.g. a simple solution is to just unload into a passive provider chest with limited slots for the "buffer", if the logistic bots immediately take some so you unload a little extra, well then there was demand so likely not a problem.

[britblad]

Thank you for all the great answers I am going to try a couple of them see which ones work best for me but I think using that middle button and filtering the squares maybe the best way to do it thank you very much

[deepdriller]

Hold on, I thought you could connect the train station to the circuit network to read train contents. From there, limiting item loads is trivial.

[torne]

You can't yet, but I think it's being added in 0.15.

[reallyLost]

use a SR-latch to force the inserters feeding them to turn off and at the same time turn on the inserters that will put the items on the train.

A latch isn't actually needed here. In this situation it is easier to use rail signals. You can force an entry signal red to prevent the train from entering the station until the chest is full. Then use a second rail signal, located immediately after that first signal and just before the station entrance, to detect when the train is at the station. When that signal is red (the train is in the station) then turn off the inserters loading the chest.