Arduino Mini confusion

I’m hoping someone can clear this up for me

I have an Arduino Pro Mini and I am unsure on the voltages!

As I think I understand it, I can put anything up to 12V on the RAW pin. Does that mean that a regulated voltage of 3.3V or 5V will be available on the VCC pin depending on what board it is?

I need to supply 5V - 5.7V to the board but the sensor needs 3.3V!

I was hoping that I could connect the 5-5.7V to the RAW pin and connect the sensor to the VCC pin.

The reason for the confusion is that one of the Arduino Pro Mini boards spec. says 3.3V input.

The Arduino pro mini is not an official arduino.
It does not have a voltage regulator, so it does not provide the 3.3 V similar to
other Arduino models.
There are mini models for 3.3V, but they only work with a clock speed of 8Mhz.
See the schematic of the Arduino pro mini at:

RV mineirin

I looked at the link and it says that the Arduino Pro Mini does have a voltage regulator! The schematic gives a voltage of 3.3V or 5V on the VCC pin so I think it will do for my project!



What voltage do you aim to put on Vraw?
How much current do you need from the 5V and 3V3 pins for peripherals?

Tom… :grinning: :+1: :coffee: :australia:

Hi Tom,

Vraw would be between 5 & 6 volts, the sensor only takes 1.1mA, then it is a data send cable to relay sensor readings. Nothing else connected.


See that this U2 regulator, does not provide + 3.3V, but transforms the RAW input (from +6 to + 12V) in + 5V VCC, in the arduinos to 5V
And that should be different on arduinos for + 3.3 V.

RV mineirin


Might just have to set it up and measure the stability of the voltage, after I determine which version I have as there is no indication on it.



You need to look at what the lowest value of Vraw can be.
The regulators on the ProMini are low dropout linear type, but you will not get a regulated 5V output if you only put 5V in.
There has to be some headroom, so you need to seroiusly consider what your power supply is going to be?

Tom… :grinning: :+1: :coffee: :australia:

Vraw should be no lower than 5V, which is why I was considering a 3.3V Arduino board and a 3.3V sensor.

You can buy 3.3V versions of the Pro Mini, which output 3.3V on the Vcc pin. The “official” one designed by Sparkfun has the MIC5205 low dropout, 150 mA output regulator.

A Pro-mini will normally have ONE voltage regulator, designed to go from Vraw to whichever voltage the board is set for. Vreg appears on the Vcc pin(s), and you can also feed in an already-regulated voltage at Vcc instead of an unregulated voltage at Vraw.
The regulator is tiny and lacks much in the way of heat-sinking, so you can’t get a lot of power out of it, especially at input voltages that are substantially above the output voltage.

What the Pro-mini LACKS is a SECOND regulator. Uno-like boards will have one regulator to provide 5V from the DC power jack, and a regulator that provides a 3.3V power source as well.

Thanks for the info, the sensor I am using only draws 1.1mA so hopefully a generic 3.3 board will suffice! I will try it and if it does not work, I will look at feeding a regulating voltage onto the Vcc pin.

Thanks for that, more expensive of course but if they work, fine! Had a quick look, not always easy to spot the genuine article!