this is a newbie question I'm sure but i'd prefer to ask than release magic smoke from my project
i currently have a nice little weather station in principle up and running. Using an arduino uno , DHt11, bmp 085 and an anemometer
it works and will display data on lcd screen
i'd like to switch the uno for a nano 33 iot board because i'd like to display my data on the cloud dashboard
my questions stem from the fact that the nano 33 iot is a 3.3 v logic board and i don't understand the implications of this.
so 1) if i have sensors that are currently working on the 5 v logic of my arduino , do i need to do anything (code or component wise) to get them working on 3.3 v
i've read that you shoudl make sure you never attempt to send more than 5v to a pin on a nano 33iot, how do i tell if a sensor will do that? i know what input voiltage they need but my limited knowledge of putput is that they give me an anolgue number between 0 and 1023
if the nano 33iot is a 3.3v board , why does it have a 5v pin? can i just use that as the VCC for my sensors.
i'm sorry if my questions don't make sense. i'm trying to understand the fundamental difference between a 5v and a 3.3 v board.
There shouldn't be any code issues. Component wise, there may be issues. The DHT11 spec says it will work from 3V to 5.5V (so should work with both 3.3 & 5V systems). The BMP085 datasheet says that it is good for up to 3.6V. As you are using an UNO, then I assume that the BMP085 board has additional electronics on it to correctly translate the logic levels between the BMP085 and 5V as well as provide the lower voltage the BMP085 operates from.
Generally the sensor won't output a higher voltage than the voltage it is being supplied with. A 3.3V sensor won't output 5V.
To make things easy and avoid level shifters, your sensors should be powered with the same voltage that you system operates at. For the Nano33, use 3.3V.
You need to connect them to the 3V3 line if they will work that low. Look at the data sheet for each sensor to see if they do. If they don't then a lot depends on the sensor's output, it might be possible to condition the signal.
The nano Iot uses a Arm® Cortex®-M0 32-bit SAMD21 processor, this is a 3V3 only processor, never connect anything that produces a voltage greater than 3V3 to that device. This normally means using 3V3 to power your sensors.
To allow you to power it from a regulated 5V supply, using the onboard regulator. So that pin is from the USB if you plug one in, otherwise it is an input.
Thank you all, that has helped greatly . especially knowing that if i power from 3.3v then i won't output more than that ( which of course makes total sense now i think about it)
because you might use 5v peripherals and because it is standard nano form factor that has 5v pin. on the other hand mkr boards also have 5v pin but when powered from battery it is 3.3v, go figure. If you have 5v peripherals use level converter, it has both 3.3 and 5 v sides and allows safe data transfer
The Vusb on the schematic is shown to be connected to the 5V pin via a series solder link pad.
I still don't see why this can't be used as an external input to power the board, in the absence of a USB lead connecting to it.
just in case anyone is interested. I just wanted to let you know that i have sucessfully transitioned my project onto the nano 33iot board without releasing any magic smoke and as a bonus am actually getting sensible readings from my sensors.