How do you determine if an Arduino shield uses 3.3V or 5V on their pins?

Previously, I thought all Arduino shields used 5V, since that's what most Arduinos use. However, I've been researching Arduino-compatible single-board computers like the PCDuino and Galileo, but these all seem to use 3.3V. More confusingly, they're vague about what types of Arduino shields they support. The PCDuino claims to only support 3.3V shields, but has an adapter shield to convert 5V. The Galileo has a jumper to support either 3.3V or 5V shields.

The main problem is how do you determine what voltage level Arduino shields use? I have a Seeedstudio motor shield and a Sain Smart sensor shield, and while they both take 5V power input, the docs don't mention anything about logic voltage level. How do I determine this?

  • Can you provide links to the doc's you're referring to? Maybe someone can look at those and see if the relevant info is there.
    – akellyirl
    Nov 27, 2014 at 17:08
  • A 5v shield on a 3.3v arduino could fry the arduino. A 3.3v shield on a 5v Arduino could fry the chip(s) on the shield. Could, but not necessarily.
    – Gerben
    Nov 29, 2014 at 12:54

1 Answer 1


You read the schematics and datasheets. The former will tell you what power supplies are connected and how, and the latter will tell you what voltages are acceptable to the devices.

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