Thanks for taking the time!
Where is the power coming from? Don't see an power input. And depending on the source you might want to add a capacitor on the board just to have a local buffer. Place it near the Arduino.
Power is coming from the USB port. I checked my power requirements and I will come out at (max. rating):
50 mA Relais
8 mA OLED
5 mA LED Relay
~10 mA button/encoder/etc.
So I'm using the Nano's voltage regulator and power everthing through +5V. As a capacitor I looked around and found recommendations of 1-100uF. So I selected a 22uF electrolytic cap, which should do the job.
For the potmeter, swap the 5V and the wiper pins on the connector. That way if you reverse the plug nothing breaks (only inverts the scale) whereas now you put the voltage between the wiper and GND when you reverse it which might burn the pot if it's set pretty low.
VCC and GND are actually on opposite sides, the 5V label is just a bit to the left.
If you place the buttons between GND and a pin you don't need external pull down resistors. Just turn on the internal pull up resistors. Yes, the logic of a button is inverted but that's not a big deal, just flip it in software as well
Will do so for my next project, for now it is just easier to solder three resistors than go through the code again.
I do like it very much you put GND low and the 5V symbols up
A lot of I2C devices already have a pull up resistor on the data lines so maybe they are redundant.
On the super cheap ones which I ordered I couldn't find any, so I decided to include some for the printed PCB.
Be sure to grab a mains rated (no fuse so at least X2) for C_SNUBBER.
It's an MKP-X2 305 V~
It's more common to let the software number the components instead of names.
I wanted to make ita biteasier forme on the PCB
The relay symbol is a bit weird and I can't see a type name. But if 11 is the common then 12 looks like to be the NC contact. Do you want the AC to be on if the relay is off?
It's a Finder 43.41.7 5V 250VAC 10A Relais. Eagle doesn't have this specific model so I got it externally. However, contact 11 is the common, and the switch occurs between 12 and 14.
If I am not mistaken, the connection between 11-12 is the off-state and 11-14 is the on-state. In the datasheet 11-12 are also connected in the symbol. Or am I making a mistake in reading it? datasheet
A 1N4148 would suffice for the flyback diode and I would even prefer it over the 1N4007 becasue it's faster (and cheaper).
Thanks for the tip!
And not because it's wrong but why not use I2C for the BME280 as well? And I assume both the display and the sensor are both close to the board? I2C and SPI are both not designed to length.
I've tried for several hours to get my BME280 working alongside the OLED but didn't succeed. as soon as the BME library was loaded the display would only show white noise. Maybe it was partly because a levelconverter was used with the BME, but since it has also SPI interface and I had enough pins to spare I used that instead.