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Author Topic: ProMini 3.3V and 5V - which one is which?  (Read 372 times)
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jbrenon
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« on: September 09, 2011, 09:40:39 am »
 Bigger Bigger Smaller Smaller Reset Reset
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?

Jenson
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johnwasser
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« Reply #1 on: September 09, 2011, 10:12:56 am »
 Bigger Bigger Smaller Smaller Reset Reset
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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James C4S
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« Reply #2 on: September 09, 2011, 01:04:15 pm »
 Bigger Bigger Smaller Smaller Reset Reset
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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