hello,i want to use a 9v battery to power both my 5v pro mini and mpu 9150…so i used voltage divider to get 3.3v for the mpu-9150.But the mpu-9150 uses 12c communication and it keeps saying connection failed even tho sda and scl are properly connected to the pro mini
You cannot use a voltage divider to power circuitry.
You need a 3.3V regulator to power 3.3V circuitry (some Arduinos have a 3.3V output, which can be used), and for communication between 5V and 3.3V circuitry, you generally should use a level shifter. Some sensor modules have built-in level shifters, but check to make sure.
Finally, a 9V PP3 battery won’t last long. They are intended for smoke alarms.