This sensor works quite nicely out-of-the-box on a 5V Arduino, and the specs suggest that it should also be compatible with 3.3v systems. The only problem I have with it is that the humidity sensor is quite laggy. When moving it from high (~99%RH) humidity test chamber to a low (~38%RH) humidity area it takes close to 30 seconds for the reported humidity value to start decreasing, and several minutes for it to stabilize at the lower value. Moving from low to high humidify it updates much more quickly, taking 5-10 seconds for the output to stabalize. This is a lovely little sensor for anyone who doesn't need to measure rapid RH changes, it should be ideal for a 3D printer enclosure or greenhouse.