It turns out that could use some help using a transistor to switch the sensor on and off... I am using this schematic:
... and I can't get readings from the sensor. If I replace the sensor with a led + 220ohms resistor the circuit works as expected, my control pin lights the led on and off.
If I measure the voltage between Vcc and the transistor's collector (that feeds the GND side of the sensor), I get a stable 3.3V when the control pin (4) is high, but readings between 1 and 3V when the control pin is down. I have tried adding a 220ohm resistor in series with the sensor, same result.
The transistor is a pn2222a, the sensor is the htu21d module mentioned above in the thread... any hint appreciated!
Thanks,
Franck