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Author Topic: ProMini 3.3V and 5V - which one is which?  (Read 534 times)
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I have two Arduino Pro Mini 5V and two 3.3V. Now I soldered one 3.3V to a board and a 5V, but I forgot which one is which and I can't see below to see which of the boxes is checked. I have two reference ProMinis, but couldn't detect a difference so far.

How can I distinguish which one is which?


Massachusetts, USA
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The 3.3v model will have a 3.3v regulator and 8 MHz crystal/resonator.
The 5v model will have a 5v regulator and 16 MHz crystal/resonator.

The regulator appears to have 5 pins and is between the processor and the end with the serial port connections.
The crystal/resonator is near Pin 2.

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Since there is an on-board regulator, apply a voltage to the RAW pin and measure VCC.

Ideally you should apply >6V.  Even if you only have 5V source available you can probably still tell the difference between the 3.3 and 5 boards.  (The 3.3V board will be 3.3V with 5V on RAW while a 5V board will be something less, probably around 4).

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