Multi RH/T Sensors w/ Same I2C Address

by <a href="http://community.silabs.com/t5/Welcome-and-Announcements/Community-Ranking-System-and-Recognition-Program/m-p/140490#U140490"><font color="#000000"><font size="2">Genius Employee</font></font> </a> Daniel_H on ‎09-28-2016 05:31 PM

Question

More than one RHT sensor is needed on a single I2C bus, however the I2C addresses are the same. How can two or more RHT sensors be used on the same I2C bus?

Answer

The RHT sensors do not have a programmable I2C address. Using a multiplexer and a device select line, multiple RHT sensors can use the same I2C bus. A single NMOS is placed on the SDA line with the drain on the host side and the source on the slave side. 10k pull-up resistors should be placed on both side of the NMOS. The MCU can control the SDA line by the device select.

Comments
by <a href="http://community.silabs.com/t5/Welcome-and-Announcements/Community-Ranking-System-and-Recognition-Program/m-p/140490#U140490"><font color="#000000"><font size="2">Legend</font></font> </a> erikm
on ‎09-29-2016 10:22 AM

the above would, probably, work if the sensors are close; however having humidity sensors close does not seem likely.

I'd use the NXP I²C bus drivers/expanders such as PCA9507 - PCA9511 which improves the drive