Each one wakes every fifteen minutes, reads a paper strip, and goes back to sleep drawing a few microamps. When water crosses the strip the reading jumps about fivefold. That is the moment it writes down, with a timestamp, and it keeps counting until the surface dries.
Coming soonThe same board and sensors go in all of them. Drag any one to turn it. Weights and times are for a 0.4 mm nozzle at 0.2 mm layers.
A cottontail is thirty-eight millimetres tall. A bench wand is three hundred. The board is the same micro:bit in every one, so what changes from one instrument to the next is the shape around it and where you are able to put it.
Every event is written to a microSD card inside the unit, and pulling that card is the only route that exists today. The board is a micro:bit V2.2. Its radio can do two things: Bluetooth Low Energy, which is how it would talk to a phone, and a separate 2.4 GHz micro:bit broadcast, which is how it would talk to a second board acting as a base station.
Neither the phone app nor the base station exists yet, so neither is something you will be able to buy on the first day. Both are short-range links meant for walking out to the unit, not for watching a garden from indoors.