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So, I ran into a strange thing when setting up basic excess recycling on Fulgora. I believe it is a bug and will report it if confirmed, but I'm also not entirely confident with circuits past simple comparisions and RS latch, so I would appreciate if someone smarter could go over my setup and either tell me what I did wrong or confirm it is a weird behaviour.

The setup



The basic structure flows like this:

1, Selector combinator gets input from a logistic network with all the items in it and outputs a stack size for each item.
2, Data gets passed into Arithmetic combinator which multiplies the the stack size by 40 to get the amount of stuff I want to keep (40 stacks.

3, Decider combinator receive both green input from logistic network and red input from the arithmetic combinator. Compares "each - green - items I have" > "each - red - maximum I want to keep" - outputs each signal that passes the test with the value of 1, basicaly outputting.

4, That feeds into selectorcombinator which again outputs the stack size into a requester chest which uses it to set the logistic network request for items to be recycled / voided (the chest on picture is disabled on purpose since I found out it requests and recycles stuff it shouldn't, so I turned it off to investigate).


All in all it seemed like a good way of automating cleanup on Fulgora, since in theory the recycling for a given item should automaticaly start once its storage exceeds 40 stacks.

The issue

However, what I realised was that in addition to the stuff I expected to be recycled, other low profile things get pulled in. F.e. concrete, which is bacialy nonexistent in the system, since I am starting out Fulgora and all concrete goes towards crafting or rail supports, which just began crafting, both got pulled into the recycler requester chest and I'm bloody not sure why. Any ideas if there's an issue with my setup I am not seeing or is this a genuine bug?

one thing i can imagine is you've daisy chained the signal along a chest of some kind like an active provider, and it has its read contents (the default), this will lead to, say if its one of the ones from your scrap recycling array will lead to occasionally their existing the concrete signal, and if that wire you daisy chained is the one that contains the set request for your overfill recycling you will get pulses of random things you dont want to recycle as they appear in the scrap recycler output.

At the decider that decides to keep or trash an item, the signal with the 40*stack size information is probably 2 ticks late in comparison to the original signal from the content network. The content signal is fed into a selector combinator (1 tick latency), then multiplied by 40 (1 tick latency).

So some new item not present before gets into the inventory has 0*40 allowed content for 2 ticks, so it gets identified as surplus, so it will be requested by the trash requester chest. The request will vanish after 2 ticks and the signals stabilized, but any item that got assigned for pickup by some logistic bot in these 2 ticks will be carried to the requester for voiding.
This could be repeated: it's possible a new item being just slowly added gets completely removed from the signals within the 2 ticks (reservation by bots is enough, it doesn't need to be physically picked up yet), so the stack size will also vanish, and so it will be compared to 0 again when some additional item is being stored, and it will be carried away again.

2 Solutions:
1. delay the item input at the decide for these 2 ticks with 2 combinators that just pass through any signal (EACH+0 = EACH).
2. don't use this stack size * 40 calculation. Personally, I configured every possible item with an individual threshold. Some threshold is just a few stacks, some other threshold is multiple chests. It's a bit tedious to configure each item, but it's also more flexible. With "every possible item" I didn't really entered every existing item from the Factorio game. I added the most obvious items, then just observed the logistic network inventory and if there was some item showing up with excessive surplus, I added it to the list.