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?
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.
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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