Problem with sensor when battery connected

#1

Hello

I have a problem with my cebucell board,
When connected via usb it measure me temperature and humidity ( SHT30) SHT 30 is connected to VIN,GND,SCL,SDA
When switch to battery, value temperature is -45 and humidity 0 that mean device dont see my sensor :frowning:
What could be the issue ?

#2

I think you’ll find there’s nothing on VIN (0V) when you’re running from battery. You need to use Vext:

pinMode(Vext,OUTPUT);
digitalWrite(Vext,LOW); // Turn the external power supply ON

#3

Thank you @UniquePete