How can you group devices so one command turns on multiple lights at the same time without a popcorn effect?

Coming from the X10 world where I had switches that could subscribe to one event and they would set their level/on/off all concurrently. That way one wouldn’t see the lights pop on or off individually and setup time for the scene was almost instantaneous. worked great for the basement where I had 8 independent lights that turned on concurrency in one room.

For SmartThings does the Z-wave or Zigbee protocol and device managers support a subscription type model where a multiple devices respond to a single command? I have purchased 8 Sengled bulbs which are Zigbee but all sources tell me that these bulbs when setup via SmartThings scenes pop on one at a time. What are the options?


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My understanding is that at the present time the SmartThings platform does not support zigbee Groupcasting. ( @tpmanley might have more to add. )

If you are using bulbs which work with the hue bridge, the hue bridge itself does do groupcasting so you can often reduce the “popcorn effect” that way, although you might need to use the Hue “scenes” feature (not the smartthings scenes) to see improvement.

I used a simulated switch and WebCoRE to make everything turn on at once. Although since @JDRoberts didn’t mention that (or the lighting smartapp), I assume that I must be missing something.

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Thanks I sort of deduced that SmartThings doesn’t support that capability. Looks like I may have to re-wire that section of the basement to use a z-wave wall switch to those 8 lights.

If it works for you, that’s great, but in most cases SmartThings actually will issue an individual command for each of the devices included in your group. It’s sufficient for many situations, but when there are multiple lights in the same space, such as the OP describes, it can still create the “popcorn effect” where there is a slight pause between the first light coming on and then the second light and then the third. If it’s very brief, That may not bother people, but sometimes it’s pretty obvious and can be annoying.

Zigbee does offer groupcasting as a way around this, where a single command is sent to multiple devices at once, but last time I checked, which was several months ago, this was not supported in SmartThings.

You’re absolutely right that you can definitely group lights together with the method you mentioned so that pressing a single switch turns on multiple lights, it’s just that you can’t force smartthings to issue a single command to the group. That’s probably just fine if you’re turning on, say, lights in several rooms at the same time. You likely won’t even notice if they are slightly out of sync. But when there are multiple lighting zones in one large room, it does tend to be more noticeable.

For those who are just looking for how to group lights in SmartThings, There’s a how to article in the community – created wiki that explains the various methods.

But it sounded like the OP was looking for something more specific to groupcasting.

Previous community discussion which includes a video showing the popcorn effect in action for those who’ve never seen it:

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@RonV42 Try the community developed app by @Kriskit called Trend Setter, it provides the capability to group individual lights into groups which may match your requirements [RELEASE] Trend Setter

It’s worth a try, but my SmartApp doesn’t get around the way that ST issues commands to devices. Sometimes you can’t see a delay, sometimes you can. I believe that ST basically does a loop over the devices it is told to issue a command to and sends them in turn rather than in parallel - I may be wrong though and the “popcorn effect” is attributed to some other quirk like latency.

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It’s just as you say. I couldn’t see it most of the time with two Sengled Element Plus bulbs, but sometimes it was very noticeable. My Wink v1 hub, oldly did not show the issue at all, and it certainly does not support Groupcasting. Wink would drop one of the bulbs every few weeks, so that ended that. Now those bulbs are on Hubitat, and I still slightly notice the issue, but I don’t know if that’s anything to do with Hubitat, which is super fast at controlling them, and about as smooth as those bulbs will get. They’re odd-balls in the Zigbee light category, since they’re doing a trick (conventional dimmer compatibility) that no other Zigbee bulbs do (one other I think, but can’t remember who). So I blame no one if they can’t control those bulbs perfectly. Maybe Sengled can with their bridge.