This ESPHome external component allows control of a Hauslane UC-PS18 range hood by manipulating its front panel buttons and by reading the communications from the front panel to the main control board.

Setup

Hardware

You will need the following hardware to wire up the range hood:

1x ESP device such as ESP32-C3 Super Mini
5x optocouplers such as 4N35*
5x resistors 1 k\Omega
1x PNP transistor such as 2N3906
1x 2cm \times 8cm perforated prototype board

*I used 4N35 optocouplers in my build because that is what I had on hand, but they are overkill for this application since they are only used to "press" the front panel buttons, which uses very slow switching speeds of >250 ms. If I were patient, I would have waited for the much cheaper PC817 which should be more than sufficient for this task. That said, I do not guarantee that it wlll work with PC817 optocouplers. I suggest doing a test on one of the buttons using a breadboard before making a more permanent installation.

YouTube video

For safety, unplug the range hood from the AC power source before taking it apart. Remove the drip tray and the washable baffle filters. Use a screwdriver to remove the 8 screws from the fan cover assembly and remove the cover. You can then remove the 2 screws from the light assembly to detach the lights. Be careful to support the light assembly as you remove the screws as each bulb is attached to a cable. Detach the cables to remove the light assembly and put it aside. This should expose two more screws on the bottom by the front panel. Remove the screws and unclip the 3-wire harness connecting it to the main conrol board, and you can gently pull the front panel assembly out. The front panel is screwed into a plastic box with two smaller screws. Remove the small screws to remove the front panel control board from the assembly.

On the front of the panel find where the 3-wire harness connects to the board. Flip the board to the back and identify the solder points on the back. From left to right, these are GND, TX, and 5V. To power the ESP32-C3 (or the variant of ESP board you are using) from the panel, connect GND on the panel to GND on the ESP32-C3 and 5V on the panel to 5V on the ESP32-C3. To read the state of the fans and lights, connect the transistor's emitter (on the 2N3906 this is the leftmost leg with the flat side facing you) to RX on GPIO 6 of the ESP32-C3. The transistor's base (middle leg) connects to the TX point on the front panel board, and the collector (rightmost leg) attaches to GND either at the front panel board or on the ESP32-C3.

Each buttton is a capacitive spring with a single connection point to the front panel control board at the spring's base. Shorting this point to ground discharges the spring and acts as a press -- or more accurately a touch -- of the button. In theory, a transistor can do the job here too, but the leakage from the transistor will influence the capacitive spring and will not register presses reliably. Instead, wire the output side of the optocoupler by connecting the spring to the optocoupler collector and ground to the optocoupler emitter. On the input side, connect GPIO pin->resistor->optocoupler anode in series and the optocoupler cathode to ground. These can be done using GPIO 0, 1, and 3-5 on the ESP32-C3. Avoid pin 2 if using the ESP32-C3 as it is a strapping pin and will cause issues with detecting button presses. The sample configuration YAML assumes the timer button is on GPIO 0, up botton on GPIO 1, down button on GPIO 3, light button on GPIO 4, and power button on GPIO 5, but these can be configured in YAML.

Since a lot of new connections will need to be made to ground, I recommend using something like a perforated prototype board and make a single connection to ground from the prototype board to the front panel control board, then connect all other grounds needed for the circuiti to each other using the prototype board. A 2cm$\times$8cm board fits perfectly in the empty space below the front panel in the front panel assemple. I also made all connections to the back of the front panel control board with wires with female Dupont connectors, then used male headers on the prototype board so that the additional circuitry can easily be removed.

Once you have everything connected, reassemble the range hood.

Software

Use the uc-ps18.yaml sample configuration and change any options such as Wi-FI and API settings to match your preferences. If you are using different pins or a different model of ESP board, make sure to change those blocks in the YAML file. Flash the ESP32-C3 using ESPHome. The command API can be used to control the device, or you can interface the device with something like Home Assistant for a graphical user interface. Each button on the board can be pressed by using command X, where X is one of timer, up, down, light, or power.

Licensing

The ESPHome component code is distributed under the GNU General Public License version 3.