Following project describes my very basic isolation shield for the arduino platform. It is based on optocouplers and thus only digital. The current version offers 8 inputs and 4 outputs plus I2C, which can be set to either 3.3V or 5V compatible level. The minimal HIGH level for the input is approx. 1.5V and should not exceed 10V.
U1/U2 are the corresponding optocouplers for the outputs and U3 for the inputs. U4 and U6 are analog switches which set the digital output voltage level. The maximum current is limited by either on of the fuses F1/F2 or the resistor R21.
U6 is a I2C voltage level-translator, which gives some sort of isolation/protection. It also (which is it’s main usage) lowers the level to 3.3V on the microcontroller side.
Schematics, PCB and BOM
are available on the project page!