Sonoff Si7021 Teardown

Here are the photos of the Sonoff Si7021 temperature and humidity sensor which uses the Silicon Labs Si7021 sensor attached to the Silicon Labs EFM8BB10F2G-QFN20 microcontroller. The other side of the PCB is completely blank.

Teardown of the Sonoff Si7021 temperature and humidity sensor
PCB of the Sonoff Si7021 using the Silicon Labs si7021 temperature and humidity sensor and the EFM8BB10F2G microcontroller.

The sensor is actually pretty large due to the size of the PCB (note the size of the 2.5mm jack). Here it is compared to a simple thermometer with an LCD display:

Sonoff Si7021 temperature and humidity sensor next to Welleman PMHYGRO sensor
Sonoff Si7021 temperature and humidity sensor next to a Welleman PMHYGRO sensor for size comparison.

The I2C signal from the sensor is passed through the EFM8BB10F2G microcontroller and converted into a 1-Wire signal described here which is similar to the AM2301 (DHT21) sensor output.

Here is the most comprehensive comparison of various temperature and humidity sensors by Robert J. Smith.

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