This repository contains ESPHOME exterenal component for 4 channer i2c dimmer.

https://lectronz.com/products/i2c-4ch-ac-led-dimmer-module

There is four pin header having VCC, SDA, SCL and GND for the i2c connection.

For the AC connection there is two screw terminals for the AC INPUT, and the device automatically detects whether the input is 50 Hz or 60 Hz. Then there are four AC outputs for 4 channels.

The A2, A1, A0 switches can be used to select the i2c address, by default all of them are low meaning address 0x3F is used. Turning switches on will pull the specified address line down and will select different addresses from 0x38-0x3F.

There is two pull up dip switchies pulling SDA and SCL up using pull up resistors. Those are off by default.

The register map for the device can be considered to have 4 registers as follows:

In the configuration file the channel is not really a channel, it is the register number associated with the channel, so the channel: 128 means the first channel.

For each register writing value 0 means channel is fully open, i.e., full brightness, and writing 100 makes it fully closed, i.e., turned off.

The Arduino example in the link above sends two bytes in one transaction, where the first byte is channel and second is dimming level, but for the i2c protocol this is exactly same as writing dimming level as one byte to register associated with the channel.

This example contains code that will allow controlling dimmer by just using one button. This button will work as follows:

This example uses two buttons to control the dimmer. Buttons are configured as follows:

The dimmer configuration depends on the actual light bulbs you are using. If you are using LED lights there is minimum brightness level required for them to still light up, so you first need to find that. Start with configuration where you have gamma_correction set to 1.0, and then set max_value to 100. The max_value tells you the maximum value the dimmer will turn the brighness down, i.e., 100 means it will completely turn off power. Set the debug level to verbose and start system.

The configuration will be something like:

logger:
  level: VERBOSE
...
light:
  - platform: i2c_dimmer_4ch
...
    gamma_correct: 1.0
    max_value: 100
    min_value: 0
...

Then use home assistant to turn the brightness down until the led light still lights up. Make sure it keeps working even if you turn it off and on at that brightness level. Then go to the esphome logs and find a line saying:

[13:25:15.707][V][i2c_dimmer_4ch:053]: Brightness to ch 131 update: 84 (raw: 0.011765)

You find that at that brightness level (raw 0.011765) the dimmer is configured to value 85. If that value goes up any more, the led light I used in my testing shuts down.

Now configure that value you find to max_value setting, and then adjust the the gamma depending on your light. For incandescent lights gamma 1.0 is ok, for led lights you most likely need something like 2.8 (you can also comment out the debugging level VERBOSE at this time too):

logger:
#  level: VERBOSE
...
light:
  - platform: i2c_dimmer_4ch
...
    gamma_correct: 2.8
    max_value: 85
    min_value: 0
...

To adjust gamma_correct you just need to try different values and adjust the brightness in home assisntant and see which value gives you the brightness response you like. If you use gamma_correct: 1.0 for led lights the brightness stays about the same between 35-100%, and only drops significantly when you go to the 5-15% range. This makes using dim light settings difficult. For incandescent bulb the gamma_correct: 1.0 is much more usable as there is significant difference between 50% and 100%. But even for them using bigger gamma correction might be better.