Power Pins:

• Vin - this is the power pin. The sensor chip uses 3 to 5 VDC, so you can use it with just about any microcontroller. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V
• GND - common ground for power and logic

I2C Pins

• SCL - I2C clock pin, connect to your microcontrollers I2C clock line. This pin can be used with 3V or 5V logic, and there's a 10K pullup on this pin.
• SDA - I2C data pin, connect to your microcontrollers I2C data line. This pin can be used with 3V or 5V logic, and there's a 10K pullup on this pin.

Other

• ACK Pin - This is the interrupt/alert output. You can set up the sensor to warn you on overly high or low UV signal. Logic level is the same as whatever you set Vin