Guts. Time to talk about guts. Electronics guts of course…
Which microcontroller should we use for this project? The first requirement is it hast to have WiFi, since it will be the way its way of sending notifications to my phone. About number of general purpose input/outputs (GPIO), two would be enough (one for detecting the door lock state and another one for actuating the cycle start button remotely). I could use a classic Arduino UNO, with a WiFi shield:
The classic 
Its WiFi shield
This one is known by most makers out there. It supports thousands of libraries, which you can make tons of things with, but… It has like 20 pins between digital and analog, and even though the WiFi shield uses some of them, I still think it’s overkill for my project. Two pins would be enough.
What other choices do we have? A lot more I know of, but the one I found and ended using is the ESP-01 board:
This miniature board (1.4 x 2.5 cm) has an ESP8266 microcontroller, with even better specs than arduino, and it is also cheap, being found for about 2 euros (2.3 dollars at this time) from China. It’s main feature is it comes with WiFi on-board, so it is very good for domotics/IoT. If you’re new to this board, you can check this link for getting started. It was very useful for me 🙂.
Okay, we have chosen the microcontroller to use. What’s next? I will need power. Not terribly interesting. Time to reuse one of the dozen power adapters I have laying around. In my case, the one from an old Samsung phone:
I will also need something to detect if the door lock is active or not. Since it works with 230v, I will nedd something that, being totally isolated from that voltage, can tell me if there is current or not in its wire. I could use a relay, a small circuit with an optocoupler, or… why not a pilot light (that I’m not really sure which machine it came from but I have had it for quite a while now) and a photoresistor?
Mistery pilot light 
Photoresistor
The plan is to mount the pilot facing the photoresistor, and encapsulate it in some material that keep them isolated. I could print something in 3D, but… why not the case of an old and dry marker? 😊
Is there something else? Yes, a relay to bridge the wash cycle start button. I did not check, but I think the button probably works at 230v too, so this way the 230v would be isolated from the microcontroller’s 3.3v.
We will also need a box to put everything into, to isolate it from the rest of the washing machine guts. How about a cheap junction box from the local shop?
And not much more. Next time, we will start mounting hardware.
See you in the next post!
