The feedback on the dim level, the lights on the side go up/down depending on the dim rate. Little things. Other than that not much.
This is an old topic, but I was considering the same question of being able to use standard (existing) ‘dumb’ light switches and have the possibility to turn on/off from Home Assistant as well. I came across below information on orientating for this question.
Solution #1 - with latching relays
This solution is applicable if you have an existing house with less options to pull new wires trough walls. I came across below description:
He describes the different methods of operating lights from different points.
What he does is using the finder 26.2.8.230.0000, which is a latching relay. A latching relay is a relay that switches when it receives a high pulse (caused by clicking the switch), and then keeps its position, even if the signalling pulse is back down.
The “2” in the Finder type no. indicates that it switches two relays on and off parallel.
See below table:
Source: https://cdn.findernet.com/app/uploads/S26EN.pdf
What the article suggests is to use one switched load for the light(s) and the other for an input of a Microcontroller unit. The author uses a Modbus module, but also GPIO pins can be used.
See below picture:
You can place several hubs in your house and detect the status of the relay by adding the latching relay to a circuit in which a GPIO pin is set to high signal when light is on.
I am a proponent of all wired design and prefer Ethernet connections. As a hub for instance you can use the Olimex POE which can be flashed with ESPHome
As in this solution both a high voltage and a low voltage (to the GPIO) are being switched within the relay, it is important to make sure that you seperate both. Or consider using an optocoupler in the wiring, so that your low voltage circuit won’t be nuked by High voltage and dangerous situations can occur.
Similar:
A similar design is discussed in this topic on the Openhab forum.
From that topic is this schematic:
I also came across this Github repo: GitHub - crgarcia12/electronics-homeassistant-lightscontroll
In which someone describes a complete designed PCB board for use in combination with a latching relay:
Solution #2 - Using a High voltage detector and a two way switch circuit
There are high voltage detector modules, that don’t need contact with the High voltage circuit to detect wether there is a current running.
Available here: Aliexpress
With these you could set a two-way switch circuit. With one switch your wall switch and the other being a relay. Based on the readout from the voltage detector, you can then determine whether you need to open or close your relay contact in order to turn on/off the light.
Do consider using a different DC source then your MCU board for your relay module in this situation. Like a buck converter. So that High and low voltage circuits are seperated. Something discussed in this youtube video:
A similar solution with a buck converter instead of a High Voltage detector is described here: https://myhomethings.eu/en/smart-alternative-switch-with-esp8266-for-iobroker-via-mqtt/
From that page:
Solution #3 - Shelly 4pm pro, applicable on new home build
If the house isn’t wired yet, then I think using these would be an option: Shelly pro 4pm (shop)
More info on these:
Shelly pro 4pm information
They are very welll priced, I think. Using these you do have to wire every light all the way back to the place in the home where the Shelly Pro 4 PM. The Shelly pro 4pm can be connected via ethernet cable.
I stumbled across this video:
(links directly to point, where he demonstrates).
In this video he shows that you can see the light status from the shelly Pro and that after turning it down, he still is able to use the physical light switch. I personally never used this, so you do have to verify whether I am correct here.
I think in this situation it would be best if you use momentary wall switches. These are switches in which you press a button and it reverts back to the position, like a button instead of on/off position. This is easier for a user, so he doesn’t get confused by on/off position of the switch
Googling led me to this document Shelly pro 4 (not PM):
It had some information about being able to set button type in the software.
Not sure whether this means that you need to set this in combination with momentary to work with toggling light from HA, but you can check that out.
Solution #4 using a Shelly 1 or Sonoff
I personally have a preference for an all wired solution. For reliability reasons and because I don’t want too many wifi devices in the house (EMF radiation). However the Shelly 1 seems to be a solution for both wireless and wired.
The shelly can be controlled by both the wall switch and via wifi or via the GPIO as stated in above image.
However, if using GPIO for controls do insert an optocoupler in the circuit, so that a connected MCU won’t get accidentally nuked by a High Voltage.