Why my bedroom lights come on one at a time
I spent this evening doing the least glamorous home-automation chore there is: tidying groups. The porch, the hallway, the bedroom - each a fixture with several bulbs that had drifted onto the dashboard as several identical-looking entities. One control per fixture is the goal. So I grouped them, hid the individual bulbs, and moved on.
Except one of those groups isn’t like the others, and I couldn’t stop thinking about it.
Two of them are real groups. Those bulbs joined a group out in the radio network itself, so when I say “turn on,” the command goes out once, as a single multicast addressed to the group, and every bulb acts on it at the same instant. It’s quiet and it’s immediate.
The third is a group the way a shopping list is a meal. Those bulbs share no identity in the network. The software just keeps a list of them and, when I flip the switch, sends the same command down the line - first bulb, then the next, then the next. Stand in the room and you can watch it: a small wave of light rolling across the ceiling. People call it the popcorn effect, and once you’ve seen it you can’t unsee it.
Here’s the part that nags at me: it isn’t supposed to be this way. The underlying standard has supported group messaging for years - group IDs, shared keys, one multicast to reach them all - and a recent revision made it more official still. The hardware can do it. The spec says so. But no major controller, mine included, actually implements it yet. So those bulbs sit in a group that exists only in software, and the software takes the slow road.
The tidy dashboard, in other words, told me nothing about which kind of group I was looking at. Both draw the same icon and the same name. One keeps the promise of “all at once”; the other hopes you won’t notice.
The groupcast support is coming - it just isn’t here. What I have is a better question to ask of any tidy-looking group: is this real, or is it a list? A group can be a promise the hardware keeps, or a polite fiction the software maintains one device at a time. I’ll still take the tidy dashboard. But now I know which bulbs to watch.