Optically isolator Arduino Shield has been designed to provide optically isolated I2C communication between Arduino and any other device or sensors that works with I2C protocols. I have used the ISO1540 Low-Power Bidirectional I2C Isolator IC from Texas Instruments to build this project, and the device is compatible with I2C interfaces. These devices have logic input and output buffers that are separated by Texas Instruments Capacitive Isolation technology using a silicon dioxide (SiO2) barrier. When used with isolated power supplies, these devices block high voltages, isolate grounds, and prevent noise currents from entering the local ground and interfering with or damaging the Arduino board. The ISO1540 has two isolated bidirectional channels for clock and data lines. The project is suitable for multi-master applications. For applications where clock stretching by the slave is possible. LED D1 is the power indicator for side two. This board requires two separate supplies, side one powered from Arduino UNO 5V, side 2 require separate 3.3V to 5V.
Optically Isolated Bidirectional I2C Shield For Arduino – [Link]