Factorio Forums

Electric mining drills have a circuit output that counts ore below the drill and ore on the entire field, but to get the number of mining drills that have ore beneath them you would need to connect every mining drill to a comparator separately and use output 1 each.

An option on the mining drills themselves to instead output 1 of each available resource (or even outputting 1 to a chosen circuit signal) would massively simplify counting how many mining drills still have ore, which would be useful for creating an alert that more outposts are needed before throughput actually drops (by collecting the counts on a central circuit line).

The only other ways to work out more outposts are needed are to check throughput (delayed notice and has to drop below consumption - can't pre-empt issues), monitor total patch ore (inaccurate), or attach a combinator to every miner (can't pack miners as tightly).

Side note: I have no idea what the below-miner-only resource output would be used for other than to see if a miner is depleted.

If you can guarantee which miner will run out last you could count active miners by taking its output on a separate wire, converting just that one to a math-only symbol, and divide the summed outputs of the whole field by it. The problem of course is that this could quite easily overflow the signal limit for a large, rich field. You could subdivide the field in the event of an overflow, though.