Power -> Zigbee Light Switch -> Zigbee Dimmer -> Lights
I want to be able to control the lights with the dimmer only. When the switch is already on that's not a problem. However when the switch is off I'd like to be able to do the following:
If switch on the dimmer (via on command or setting brightness >0) the switch to be turned on, wait a bit for the dimmer to become online and set desired dimmer brightness (as initially instructed). This one I am not sure if possible and how to go about it.
When dimmer is being turned off i'd like the switch to be turned on as well. This one seems to be straight forward.
Update: I do have neutral wire going to the switch and all the lights.
Your location would help with this answer as different electrical systems in different parts of the world would have different answers here.
Generally speaking, in the USA at least, we don't wire switches like that. If you have two switches, they are called 3-way and 4-way switches and they have multiple inputs and outputs to direct the power to various wires, they aren't simple switches.
The larger issue is that I doubt the dimmer would be happy being turned off like you want to do. Most smart devices like being online all the time.
Why the two switches? Why would you want to turn the dimmer off with another switch ike that?
You can wire the light (load) to the dimmer and power the switch with no load. Then use RM for whatever rules you want.
I wouldn't use the switch to control the power of the switch. Bad for the dimmer and will likely mess up your Zigbee mesh.
At that point, why not use a much cheaper Pico remote, or something like a RGBGenie Zigbee remote? No need for a mains powered switch, although this would work like you describe.
To give a bit more context. I'm in New Zealand. I have 9 dump ceiling lights in a living room, controlled by a single dump light switch. I want to split the 9 lights into 3 dimmable groups be injecting 3 Zigbee dimmers (wiring in ceiling allows to do that). However there's only a single wire going to the switch.
So the actual wiring diagram will be i though will be something like:
I would not daisy chain the dimmers behind another switch, unless you plan to always leave the switch ON, and only use it in an emergency to turn off the lights. In that case, it would be simpler to use a “dumb switch” instead of a smart switch, to just kill power in the event that the Smart Controller (i.e. Hubitat Hub) is not working for some reason.
To manually control the three dimmers, I would add some Button Controller devices. These would communicate to the HE hub, which would then adjust the three dimmers.
If you only have a "single" wire to the switch (I assume you mean one wire into and one wire out of the switchbox ), then you do not have a neutral wire available at the switch. This means that you, most likely, will not be able to install a smart switch in place of the normal switch, as most modern smart switches (and smart dimmers) require a neutral to operate. (The Lutron Caseta dimmer (not the pro model) is one of the few exceptions)
As mentioned, daisy chaining smart switches/dimmers is not a good idea.
To clarify: i do have 3 wire cable coming to the switch and to all lights (live, neutral, earth).
I understand that it's recommended to switch of the dimmers and ideally they should be always on.
I might be going with this approach, as it's most simple and cost effective.
However, before i give up on the initial idea, I'd like to learn more about what Hubitat would do with a Zigbee dimmer if it's offline for a long period of time.
Is it going to remove it eventually?
Is it going to prevent any attempts to send commands it (e.g. from device page for instance)? (of course those commands will never arrive)
Is it going to prevent rules from triggering based on those dimmer commands (e.g. setBrightness)?
If that answer is no for all 3 questions then I'd like to run this experiment to see how it will work in practice:
When switching on the dimmer (via on command or setting brightness >0) the switch to be turned on, wait a bit for the dimmer to become online and set desired dimmer brightness (as initially instructed).
I acknowledge the concerns that this is not ideal nor recommended, but i'm a tinkerer and like to experiment
Most smart switches work without the hub, (they still have a way to physically operate) so I don't think there is a reason to even use a master "kill switch". Smart relays and things of the sort don't have an easily accessible switch (if any at all) so you possibly want a kill switch in that situation.
If you kill the Zigbee devices, you may get weird things happening like other devices may stop working because you screwed up the Zigbee mesh. You might not be able to control anything or may have to re-pair certain devices every time you go to use them. Some battery operated things seem pretty sensitive to having a stable Zigbee mesh.
If any rules rely on these now dead devices or you have automations like motion lights that run through the dead devices, at the very least the automation won't work, and you get lots of errors in the logs.
As mentioned by @neonturbo, the biggest issue is screwing up your Zigbee mesh network by powering off three repeater devices.
Have you considered simply using all Sengled smart Zigbee bulbs instead of the 3 dimmers? They are actually designed to be powered off/on by a physical switch without negatively impacting the Zigbee mesh. You can create Hubitat Groups of these bulbs, and enable the Zigbee Group Messaging feature to eliminate any “popcorn effect”.
If it is a battery powered Zigbee device, then it is not a repeater. In the Hubitat vernacular, a battery powered device that turn on/off/dim another device would be called a Button Controller.
If the bulbs act as repeaters, then they will need to have power applied to them 100% of the time. Otherwise, when they lose power, any devices that were routing through them will be messed up until they can find a new repeater.
You need to think of how big of a deal it will be WHEN the hub is not available. Because there will come a time that it true - upgrades, hub crashes, something.
If it is just a minor inconvenience then go for it. If you can't live with the functionality sans hub at all / major inconvenience, then I wouldn't recommend doing it.
So when I switch off the light switch it switches itself back on (after about 0.5s) and toggles RGB LED after 1s delay. The delay is needed so that the RGB controller switches back on after power loss.
This results in the light switch working as a scene switch.
So this might be a viable "best of both worlds" solution with RGB controller being kept always on (sort of) and being able to switch off the light if Hubitat is down.
It's worth noting that when I reduced brightness of the LED to 50% the power left in capacitors inside the power supply (I assume) during the short switch off was enough to keep the RGB controller powered. This means with smaller load the 1 second delay could be removed from the rule. Perhaps if I get a more powerful power supply it could handle the full brightness for 0.5s without power?
It works pretty well, however when switching the light off it blinks. Not a major, however I need to test it over a longer period of time in a real setting to see if it becomes annoying.
Here are some short videos demonstrating this (with 3 different light bulbs):
