I installed two Z-wave switches into my house that i wanted to be synchronized, turn on one light switch, have the other turn on too, and vice versa. I first created a home assistant automation that worked using Z-Wave JS to MQTT, this worked but had a lag of a few seconds. I was hoping to find a way to have less latency to make everything work, so in comes Z-Wave Group Associations.
Z-Wave groups enable multiple devices to be controlled from one single button on a remote control, just as if they were one single device. A single command makes all devices in the groups switch On/Off at the same time. Since all devices in a group receive the same commands, it’s useful to group similar devices into one group. If different devices are mixed, you may get confusing results.
Similar to associations, most remote controls only use the BASIC command class to control groups. This allows different devices to be mixed, but only to a certain extent. Mixing a dimmer and a switch will result in the dimmer acting as a switch.
Most remote control instructions describe the switching of groups but don’t refer to the switching of a single device. To switch a single device just place this device into a group and switch the group. It‘s also possible to assign one device to different groups.Vesternet
Home Assistant Automation
I started out with a basic pair of automations in home assistant. These work and are reliable, but they have a bit more latency between the first and second light switch turning on than I was hoping for. So I decided to try out z-wave groups to see if I could significantly reduce that latency.
The group looks like it is working, and its more consistent in its latency than the home assistant automation, but its not much different in overall latency, which was my main goal, so I’ll go to keeping all my automations in home assistant to keep control of them in one place
I know the advantage of using a z-wave group would be that it would work if my home assistant instance went down, but since it is self hosted and not in the cloud, if my home assistant instance is down, either I’m working on it, or the power has been out longer than my UPS can cover. We’ll take this one as a loss.