How to connect BMP180 and SHT21 sensors together

Hi,

I'm pretty new to this so forgive me if i ask a dumb question..

I'm trying to build some kind of weather station. I need to get the temperature, barometric pressure and relative humidity.

In order to do so i bought a BMP180 sensor - for pressure, and a SHT21 sensor for temperature and humidity. The plan was to connect them to an arduino mega.

Both sensors use I2C so how can I connect them together and read the results from both of them? The acquisition doesn't have to be simoultanious for my purposes.

Thanks!!

Alon

I2C is a bus so multiple devices can be connected to the SDA and SCL pins, just daisy chain them ...

The Arduino Mega 2560 is the only Arduino board with 10k pullup resistors on the I2C bus. That means it has a 5V I2C bus, and I think those sensors are 3.3V. So you need a I2C level shifter between the Mega board and the sensors.

Do you have a Arduino Uno, to do some tests with the sensors ?

Did you find libraries for both sensors ?

Thanks for the fast reply!!

robtillaart - By saying daisy chain you mean connect them in series?... :roll_eyes:

Peter_n - I don't have an UNO to use but I already connected them (one a time) to the SDA and they seemed to work OK (although as you said they are 3.3V). This means that it will continue working or should I connect an I2C level shifter anyway? I managed to find libraries for both sensors.

Another thing i didn't understand is how to approach each sensor while they are connected together... If they get different addresses it means I have to approach somehow to a specific address to get the readings of each sensor?

Thanks, Alon

yes, so the share the SDA and SCL line - see the tutorial link.