I'm trying to learn how to utilize circuits and having trouble figuring how to lay it out (unmodded).

I have my science assembly lines lined up to feed into my research labs but I only want to send out science for as long as they are needed. To keep things balanced, I want to keep the amount of science packs sitting on belts as low as I can and even so the belts that take the packs to the research labs ideally should be empty.

Basically like this:
enter image description here

To achieve this, I wanted to block off sections of the belts so I only let through packs until a certain amount are at the research labs.

enter image description here (ignore the wires, was trying things)

I thought I could place a wire at the end to send a pulse every time a pack goes through and count then on the input side, enable the belt for every pack the went out. Problem was that the wired belts doesn't just allow a single item through, but it's just on/off for as long as the condition is true. I guess I misunderstood how these are intended to be used and since these are slow belts, it might not be long enough to allow any through.

Maybe I'm using the wrong tools for this and should be using inserters to make it easier instead? How can I set this up to work like I want?

  • have you considered a buffer chest with filtered stack inserters to fill/empty it at the point the mixed line is put together?
    – Trish
    Commented Dec 15, 2022 at 21:15
  • You can simply connect all belts togehter, then get the total item count of red science and if that count is lower than, say 2, enable your red science facilities. Or you connect a transistor(self built) to each end of the belt and you add one to a counter at the beginning and reduce that counter by one if a item is leaving. Wiring the whole belt and reading the total number of items is way easier. Commented Dec 16, 2022 at 11:09
  • I am currently in the process of relocating the assemblers and research but will rebuild with the same idea. I guess one of my unstated goals was to not be "wasteful" if I can and not have to wire up too many things if possible. Commented Dec 16, 2022 at 17:57
  • @ChrᴉzremembersMonica yeah, I suppose I could wire up all the belts and hold the count, that'll give me a steady count of what in the belt and only allow assembly as long as that count is 0. Though in my mind, wiring up that many items seems wasteful and there could be something more efficient. Anyhow I'll update the post with some things I considered. Commented Dec 16, 2022 at 18:00
  • 1
    @Trish I'm not sure I understand what you're proposing. So at the end of the line, the chest will be there as a "gatekeeper" buffer that will is expected to hold N science for each type of assemblies I have. Then on the other end, I would wire each picker as an indication of what has been released. I think that could work. Commented Dec 16, 2022 at 18:04

1 Answer 1


I feel like this is suboptimal but seems to do the job.

I have added a chest at the end of each assembly line to hold the amount of each science it holds. The chest is connected to a wire holding the count. That count is inverted and added to a constant that equals the amount of assemblers are making that color science. Then if the sum is less than zero, the pickers for each of the assemblers are enabled.

enter image description here

This might let loose more science than I wanted due to the travel time to the chest might not be fast enough.

Ultimately I would like to:

  • reduce the number of connections needed (every picker in the assembly line has to be wired up)
  • I would prefer not needing a box and pickers to get the counts

It seems like to get it exactly how I want it, I effectively would have to wire up every single belt in the line to hold the count of science throughout the system. And only enable the assembly if there are no packs on the belts. But this would directly conflict with my first concern above with needing to connect literally everything.

I'll refine this over time I guess but this works for now.

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