21/9/2017 · If you prefer a portable light meter project, then you can enclose the finished project in a suitable, ready-made/3D-printed enclosure, of course, with a compact power supply. Because the Arduino Nano expects a 6- to 20-V unregulated power supply through its VIN terminal (pin 30), a safer solution would be to use a 2S Li-ion/LiPo battery (~7.4 V), which would be plenty to run the whole system.