Voila, I am a mega hardware maker. So what do we have? We can get ESP32 as a chip or a Dev Kit board (DevKit1). What do we need?

- a box so that we can mount the device either on the DIN rack or on the wall, depending on the specific situation

- in order not to look for exotic power sources, we want to feed the box from 12V - a very common non-nonsense voltage

- we need a lot of inputs and outputs to minimize the required number of devices for large-scale automation. According to my approximate calculations it seems to be: 50 buttons, 15-20 groups of sockets, 25 groups of lamps, 10-15 motor mechanisms , 50 sensors (temperature, movement, humidity, opening, lighting, etc.)

- another nuance: many relays take 5 volts for a control voltage, and esp32 gives 3.3 volts for output. If we do not address that we will have to fool arount with level converters, which is no fun. So we will need to embed the converters inside. And we never know, occasionally we might need 12v signals.

- the same’s true for the inputs - we need to think over to learn how to accept different voltages within reasonable limits. To test the hypothesis, I looked at typical mass sensors and did not find a single digital one that won’t work with 3.3v. But that is a common case for analog sensors. Therefore, it turns out that at least for analog we need to precisely take care of receiving different voltages.

- the flow of my thoughts also led me to the idea of powering the low-current sensors from the box itself, so as not to look for additional adapters. And again the supply voltage can be different, it means that we need to support a variety.

- display! in spite of the fact that the device implies autonomous operation, live updates and web interface, the human-readable output of some critical information on the body wouldn’t hurt - no blinks or Morse code to understand what went wrong

- last but not least, ESP32 has got only wifi - and although it suits myself, we think about people, so we don’t need to forget about good old and reliable ethernet (as well as the cost price of a future device when implementing these)

Now at once we will find some kind of a box, more or less satisfying the requirements. Let us understand how much space we have, and form the stated characteristics.