Possibly Stupid Question about Zigbee Bulbs and Power Cuts

Hi folks, I had a thought last night that’s been bothering me.

I’m just getting into all this and have invested in a starting set of Zigbee bulbs, outlets, and switches from Ikea (Tradfri) in order to bootstrap a robust network. I also have a few sensors from Xiaomi but I think those were a mistake considering their terrible Zigbee network behaviour. Anyways…

The Ikea bulbs, at least, have a nice behaviour pattern when it comes to regular power switches such as most houses already have: whatever the bulb had most recently been set to, if you turn it off at the power switch and back on again, it comes on. This is good when you’re living with people who are smart-thing-sceptics, because it means they can carry on turning things on and off in the way they’re accustomed to, at least at first until they see the light.

However, this suddenly made me rethink my plan of installing the bulbs in the bedrooms, too: what happens when there’s a blackout? When power is restored, do all of the bulbs go straight to 100%, as if the wall switch had been flicked to ‘on’? So, in the middle of the night sometimes, we’ll all suddenly get woken by blinding brightness as power is lost and restored? That’s not something we can consider here, there are members of my family with heart conditions that would be put at risk. :confused:

Hoping to learn more about this, perhaps there are brands of bulb that don’t do this that are more suited to bedroom use, or perhaps there is a way to configure the Tradfri bulbs not to do this.

If it’s relevant, I’m not using the Tradfri bridge, I’m using zigbee2mqtt for everything.

Yes. The bulbs have no way to know the difference between a power outage and loss of power because the switch was flipped off.

It is for this reason and others that I always recommend smart switches or devices that turn “dumb” switches into smart switches (e.g. Shelly1) over smart bulbs unless being able to control color is really important to you. In that case I recommend smart switches and smart bulbs be used so you can still turn on the light automatically even when the switch is powered off. Smart switches will usually remember the last state of the switch when power is lost and then restored unlike bulbs which do not.

Thank you @rlkoshak - further reading after this has given me an approximate way forward:

  • Hue bulbs appear to now support a ‘power state memory’ function which is supported by zigbee2mqtt, so I can set them up to remember their prior state and restore that on power cycling.
  • For other bulbs, I could then perhaps go with a ‘canary’ approach where a low-wattage bulb is set up somewhere dark with the power constantly ‘on’ but the bulb set to ‘off’, with a light sensor triggering a global shutdown of the house lights. So that on power-cycling the house, the ‘canary’ would trigger the other lights to disable. Although, I could go one better and have an MQTT topic for ‘most recent states’ with a sticky message that they are all restored from.

That way, the bedroom lights and perhaps the hall lights would be ‘power-cycling sane’ but the rest of the house could be the more affordable Tradfri bulbs with a hacky solution that would permit a very brief ‘on’ period after a power cycle.

It’s just a pity that the Zigbee Hue bulbs are still so expensive, even second hand. :confused:

I am open to a wall-switch solution BTW, but it would have to be a zigbee device that fit the following criteria, and it seems very difficult to answer these questions from online research:

  • Device has no blinkenlights or constant ‘heartbeat’ lights. I love darkness at night, I hate devices that interrupt it.
  • Device has a switch or button that toggles power supply to the lights in a way that does not require Zigbee to work.
  • When directed by zigbee, this power supply toggles exactly as if the button had been pushed.
  • It can know the ‘state’ and therefore if directed to ‘on’ while already ‘on’, nothing happens.
  • In either case, the device remembers its state when power is lost or disabled.
  • Device needs to be suitable for an Irish power/standards situation, which I believe to be the same as the UK but it seems like they have more legacy issues with lack-of-neutral-wires over there… I’m pretty sure we have a live/neutral/ground sitch over here for light switches.
  • Device needs to be zigbee2mqtt compatible.

This behaviour would be perfect and I would happily install these things and then use Tradfri bulbs. But I have no idea how to answer some of these questions let alone all of them. I think the Hue bulbs, despite the silly pricetag, are the only viable answer in this case, right now.

Why Zigbee only? WiFi would be a problem?

For the switches that I’ve used (Zwave mostly) the status light can be controlled with a configuration parameter. For the devices like Shelly, they go inside the switch box behind the existing switch so even if they have status lights, you’d never see it.

ALL “smart” switches and even those devices that go behind the light switches also work as a dumb switch. That’s kind of the whole point.

Again, that’s kind of the whole point. The only caveat is with devices like Shelly, they can’t physically toggle the “dumb” switch it’s wired to so you might need to treat that switch as a toggle (i.e. flipping the switch changes the current state instead of up always means on and down always means off).

Again, it’s not a smart switch if you don’t know what state it is in. And I’m not aware of any sort of device that has a problem with receiving an ON command when it’s already ON.

You will have to look into specific devices but all the ones I’ve used thus far remember. Or at a minimum revert to off when power is restored.

Again, you will have to search but I know of many UK users on this forum who use smart switches.

Why? The whole point of OH is that you are not limited to just one technology.

Not sure if this should be a new topic, but it seems to kinda fit here:

What happens when zigbee bulbs are dimmed by a conventional dimmer (or even a smart one, like the shelly dimmer 2, which would look just like a dumb dimmer from the perspective of the bulbs, I guess)?

So what I learned in this topic is go how for example the IKEA smart bulbs behave when being turned on (though I’m still wondering whether there is any delay between receiving power and lighting up) so my question is not about power on/off but “a little bit on” as it were.

My IKEA Tradfri bulb, when powered on by a dumb wall switch, has no noticeable delay. However, when switched on it quickly fades to full brightness, rather than immediately switching on to full brightness, which may be perceived as a delay. IKEA publishes the Warm-up time to 60% of the full light output, which should help you.

I don’t know what happens when attached to a normal dumb dimmer switch, though I presume it just returns to the brightness set by the switch - that’s controlling the power to the bulb, after all. Be careful though: not all IKEA Tradfri bulbs can be used with a dumb dimmer switch: check the Technical Information for the bulb you’re interested in, and look for the Dimmable specification (as opposed to Wirelessly Dimmable) - not all are Dimmable.

The electronics will shutoff and bulb won’t function. Smart bulbs won’t dim unless you use their micro controller.

As you note, the in-wall dimmer works by reducing the power available to the lightbulb. So, a smart bulb will just stay on and functional until you dim the in-wall switch to the point where there’s not enough power to sustain operation. And then it’ll be off. :wink:

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Apparently not true, according to IKEAs specifications for some of their bulbs…

And depending on the type of smart bulb (as mentioned in the very next sentence), on and functional may even mean that the bulb dims as you would expect when using a dumb wall dimmer.

Can you post a link? Love to see it…

Real question why do you want to do this? Smart bulbs intended to be left on…

I am asking what is the use case for cycling power? They also make dimming remotes.

I would just extend this question (with a statement :wink: )… It’s possibly a bad idea to power cycle these devices.

If you turn off the bulbs, then your network will not work well… If you had 2 or 3 wifi routers in your house, would you turn them off and still expect to get Wifi coverage? It’s just worth noting that the same is true for ZigBee. The system will build up routes through the network - battery devices MUST have a parent (which are these routers) and if you turn the routers off, then at best this will take time to reconfigure and re-route traffic, and at worst you will likely make some devices in your network uncontactable.

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One which is not dimmable.

One which is dimmable.

As mentioned, scroll to Technical Information, and you will see they distinguish between Dimmable and Wirelessly dimmable. Both are Wirelessly dimmable, but only the second is Dimmable.

Note: it’s not me who asked the original question…!

@hafniumzinc from ikea tradfri page:

I would not power down the zigbee network on purpose as @chris

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See my post just above yours. Your link is to one which is not dimmable.

When they say dimmable in the technical details they mean with their dimmer. I say this because In the link you posted under product details it states not to be used with wired dimmer.

Buy one and have a go! Then you will know for sure. Best way to find out.

What is reason you want to use a wired dimmer? I am trying to understand. Their could be an alternate solution.

I didn’t click Read more! I wonder why they differentiate between Dimmable and Wirelessly dimmable then? Anyway…

Not me.

BEcause some tradfri bulbs may be on off only no dimming.

@tophee ?

They’re all Wirelessly dimmable. At least, the ones available in the UK: https://www.ikea.com/gb/en/cat/wireless-led-bulbs-36813/

Anyway, this is a side show to the main topic. I’ll edit my previous posts.

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