How to daisy chain solenoids

MikeMl said:

The triac or SCR is the "latch". You have to come up with a way of triggering it on (the n-1 tank water level became "full"), and then you have turn it off (the nth tank just became "full").

A ring counter made this way has a lot of hazards. For example, what happens if more than one triac/scr comes on when power is first applied. Will it sort itself out and settle into "only one on at a time" cadence? Not easily.

A ring-counter made from four "latches" is a state-machine with 16 states, only four of which are useful to you, specifically 1000, 0100, 0010, and 0001. It needs an Arduino (or lots of discrete steering logic) to detect the 12 illegal states so as to put it into the legal sequence. This gets more complex than letting the Arduino sort it out...

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