ATmega328P board schematic

Hello, I would like to make my own board for a project. I've already made a schematic, but this is my first experience with designing and I'm not sure if everything is wired correctly.

If your not sure its wired correctly, perhaps try the circuit out on a breadboard ?

If your using 3.3V sensors then you would normally need logic level conversion between the 5V ATMega328P and the 3.3V sensors.

I know, but the components haven't arrived yet.

But for example on the arduino UNO board there is no converter and the sensors work fine. Am I wrong?

Yes. If you directly connect a 5V Arduino to 3.3V sensors, you will eventually destroy the Arduino, the sensors or both.

Do you also think it might be OK to plug 110VAC light bulbs into a 220VAC socket?

Okay, thanks. But how is it possible that some sensors are 3,3 - 5V and don't have only one logic level?

Those sensors have logic level shifters built in.

However, you cannot trust what sellers say on sites like Amazon, eBay and Alibaba.

You can trust the product descriptions for reputable sellers like Adafruit, Sparkfun, Pololu, etc. and on those sites, you can always look at the sensor schematic, which will clearly show the level shifters.

For example, the Adafruit MPU6050 breakout shows the logic level shifters
on the upper right of the schematic (labeled I2C pullups and shift)

5V logic will soon be a thing of the past. Get on board.

Well, I found on the internet that there are two basic level transfer options. Which would be better for me, to use IC or MOSFET with resistors? What happens if there is a logic level shifter on the sensor but also on the board? I assume I have to use the IC or MOSFET on the SPI NRF24 as well (but then there will be too many components), am I right? Where on the arduino UNO board (this is a clone) is the logic level shifter?

Why do you think there is one?

Which would be better for me, to use IC or MOSFET with resistors

Learn how they work, how they are constructed, weigh the pros and cons, then make an informed decision.

Because I used BMP280, what is 3.3V sensor and it worked.

You got lucky, but the luck will probably end soon.

Have fun with your project!

Hm, now I'm confused, it's even written in the guides online. For example BMP280 guide.

There are two versions of the board\modules for the BMP280 and BME280 sensors sold. One is for 3.3V logic circuits the other for 5V logic circuits. There are good reasons why there are two versions.

Just because you might get away (for a while) using a 3.3V sensor on a 5V logic circuit, that does not make it the correct way to do it.

Have fun.

You can also plug a 110VAC light bulb into a 220VAC socket, sometimes with pretty interesting and fun results.

I used it for about 14 days in my home temperature app and it still works now.

I can imagine :slight_smile:

And its still not the coreect way to do it.

The Titanic was unsinkable.

Concorde was the safest aeroplane ever, after all it had never crashed.

Okay, thanks for your time and advice. I'll use them.

Impressive! Let us know when it stops working, and which parts failed.

Perhaps contact Bosch and ask them to correct the error you seem to think they have made in the 'absolute maximum' voltages quoted in the datasheet for the BMP280, to increase the limit to allow for 5V on the logic pins ..........

There are other significant errors in your schematic, but maybe it will work.

I came here to fix them. So can you please tell me what else is wrong?