Originally my Kovarex arrangement was based on timing a yellow grabber snagging exactly 1 U-235 off of a belt out of the back of a centrifuge with blue belts:
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This obviously had problems where a centrifuge would not get enough U-235 or get clogged when the ultimate output bin was full, forcing me to go over the entire array of 40 or whatever of them and manually fix each one.
I upgraded to using circuitry to count the U-235s, and that prevented under feeding, but it had the problem of getting clogged still, where the count would get off somehow and it would stop operating because the grabber had only counted to 26 or something but hadn't filled the centrifuge.
I wanted a way to count up to 40 exactly, but then dump extra U-235 in to the output bin if something went wrong and the belt was clogged again. I think I've done that with these timer sets.
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I don't know if anyone has documented the wire connections like I have here though - the posts I have seen just have blueprint links, and loading them up in an online blueprint viewer is better than nothing, but I found I couldn't click in to see the settings on each Decider Combinator.
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In the image, I'm using red and green lines to indicate red or green wires.
Round ends are input side.
Diamond ends are output side.
A Text Explanation
All of the circuitry is decision making to manipulate the "Out Gate" on the belt.
There are two timers:
1. Group 1 counts to 40 U-235, and opens the Out Gate for 500 ticks.
- The inserter is stopped while this timer is running
- It resets at the end of 500 ticks
2. Group 2 checks to see if there is U-235 present in the In Gate, if there is, it starts a 400 tick timer.
- If the timer is greater than 100 but less than 400, it opens the Out Gate
- If U-235 leaves the presence of In Gate at any time, the timer resets
Honestly it seems so simple written out like that, but it was a lot of trial and error to put together and actually implement. Factorio circuits / combinators are really unintuitive. I might make a post about how I feel like they could be improved at some point.