1.16.5 -- I created a pickup system with a minecart traveling a loop around all my farms and machines, as it passes under a hopper (collection site) it picks up a few items which in most cases is perfect. I have the need in some instances to pick up a lot of drops from certain hoppers. For those, I have placed a comparator looking at the collection point (hopper) which when items are present, a sticky piston extends halting the cart until the hopper is empty. If the cart fills, I need to allow the cart to continue on.
I have an activator rail at the collection site which checks how full the cart is, if it is x full it sends a redstone signal which I want to use to cancel the active signal by the collection hopper which is powering the piston. This would allow the piston to contract and allow the cart to continue on. I cannot seem to figure this out.
Well, getting a little farther.... The minecart will still not "stay put" until all the items in the hopper are gone -- it grabs like 16 or 17 and the piston retracts. Attached screenshots show overview, what is in the minecart and the chest that should measure minecart capacity but now seems to be based on slots used.
I'm struggling to understand your redstone, I'm thinking the signal from the detector rail must be going through a tunnel somewhere?
Also I don't understand the purpose of the two repeaters and the comparator just to the right of the chest, it seems like the signal on the side of the comparator would always be weaker than the signal on the main input so I wouldn't think it would do anything, I'll have to test it.
But I'm not sure that this is a redstone problem.
One thing about the capacity measurement is that the chest has a lot more slots than the hopper minecart, so it takes a lot more items for the chest to reach the same level of "fullness" as the hopper, it might be easier to compare if you used a hopper instead of the chest.
Also the slot thing sounds like you might not be understanding that your chest contains 5 stacks? Since a "stack" of swords is only one sword.
So if you switch out the chest for a hopper and use stackable items the comparison should be more direct.
You original design had just 1 piece of redstone dust between the comparator at the detector rail and the next comparator, your current design has a distance of about 7 blocks so I'd really want to know what is in between.
It seems like if it was just redstone dust that it would take a lot more than 4 stone blocks to make the signal go that far?