Add wifi relay to Gorenje Wave Active washing machine

We have a Gorenje Wave Active washing machine that has no WIFI and no timer function. Program start is done by two buttons: the power button and program start button. Program selection is done with a rotary dial. I opened the machine and found that all electronics are on one board and the button connectors are available on the board. Did not do any measurements yet, but an educated guess is that there should be a 5 volt bus on the card.
My idea is to use a tasmotized 5 volt WIFI relay with two outputs to control the washing machine with OpenHAB. The key benefit would be to make the machine start when electricity price is low.
Has anyone here done a similar modification to a washing machine? Any lessons learned, that I could benefit from?

This is how to add WIFI to a Gorenje Wave Active washing machine that has no WIFI to connect it to OpenHAB.

The washing machine has only two buttons: one for Power on the left and the other one for starting the selected program on the right:

I opened the washing machine to find a single control board behind the buttons.

The buttons are microswitches that are accessible from the other side of the board after removing 4 screws. I found that the main bus that connects the board to the the rest of the machine has a constant 5V DC supply even when the machine is off.

I connected two WIFI relays in parallel to the buttons and tapped into the board constant 5VDC supply to power the relays.

After testing I secured the soldering to the main board with some hot glue and insulated the relays with a lot of electricians tape and attached them to the washing machine so they do not move during machine operation.

The relays are tasmotazied and are controlled over MQTT. I use the waterheater script from Control a water heater and ground source heat pump based on cheap hours of spot priced electricity - #13 by masipila to find the cheapest consecutive hours of the day. I found out that the button has to be pressed 2 seconds for the washing machine to wake up from its standby state. Ended up with this script to run the washer. The script also sends me a telegram message when the buttons are “pressed”, i.e. the relays pull:

// Control of Gorenje washer with two WIFI relys connected parallel to the buttons
power = items.getItem("washerPowerRelay");
program = items.getItem("washerProgramRelay");
control = items.getItem("washerControl");
var telegramAction = actions.get("telegram","telegram:telegramBot:*********");

if (control.state == "1.0") {
// Power on the washer
  telegramAction.sendTelegram("Washer Power button was pressed fore 2 s.");
// Start the selected program
  telegramAction.sendTelegram("Washer Program button was pressed for 2 s.");
  console.log('Washer: Started.');
else {
  console.log('Washer: No washing today.');

After the modification the washer works like it used to if one wants to use it during the day: load and start program. If one wants to save money, the washer is loaded with the laundry and detergents, program is selected and washer turned off. The scripts will power up the machine and start the program when the cheapest price period starts. WAF is quite good, the washer run last night loaded by my better half without any intervention by me. Great success :wink: !