What is the real difference between a 5v and a 3.3v pro mini?

Projects General Guidance
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Hello i was wondering what is the difference between a 5v and a 3.3v arduino pro mini? The both look the same i can not tell the difference only by what it says in the writing. Unless I'm missing something?

Joseph

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Oh okay so does that mean it is using the internal crystal and program differently? Can i do the same with my 5v one or do i need to buy a 3.3v one? Reason why I'm asking my project all parts are running at 3.3v besides the pro mini it's self.

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josephchrzempiec:
Oh okay so does that mean it is using the internal crystal and program differently? Can i do the same with my 5v one or do i need to buy a 3.3v one? Reason why I'm asking my project all parts are running at 3.3v besides the pro mini it's self.

There is no internal crystal.

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josephchrzempiec:
Oh okay so does that mean it is using the internal crystal and program differently?

It has an internal oscillator, not a crystal. I don't know which one the 3.3V Pro Mini uses.

Can i do the same with my 5v one or do i need to buy a 3.3v one? Reason why I'm asking my project all parts are running at 3.3v besides the pro mini it's self.

The 5V version runs at double the clock speed so is twice as fast. For many projects 8 MHz will be plenty fast enough; for other projects I've been selecting my ATtiny on the ability to do 20 MHz .

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The 3.3 V Pro Mini has an external 8 MHz ceramic resonator. It doesn't use the internal oscillator. Of course you can set it to do so by just changing the fuses.

The 3.3 V Pro Mini has a 3.3 V voltage regulator connected to the RAW pin. The 5 V Pro Mini has a 5 V voltage regulator.

You could power your 5 V Pro Mini at 3.3 V via the Vcc pin but that's out of spec for running at 16 MHz. You might be able to get away with it or you can run it at 8 MHz to obey the rating specified in the datasheet (Fig 32-1).

This hardware core makes it easy enough to switch to using the 8 MHz internal oscillator:

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The reason they use an external resonator on the 3.3v one is probably becuase the internal oscillator is not factory calibrated well enough to guarantee UART (ie Serial - used for uploads and Serial.print/etc) will work.