Powering Arduino Uno with 3.3V

Projects General Guidance
1

Hi everyone,
I am working on a project that will have the Arduino connected to my home Intercom, I have a SIM800 shield on top of my Arduino which would let it call my cellphone when someone calls my Intercom.

I want the Arduino to be standalone and be powered by something permanent, so not a battery.

When I take apart my Intercom I can see that it has some pins which output 3.3V, that is what I can use to power my Arduino.

The question is, is there a way to power the Arduino from that 3.3V output? I am a newbie when it comes to electricity and I did see some converters from 3.3v to 5v online, but I am not sure if those are safe to use. Additionally, it seems like Arduino is powered by 5V only when connected via USB, otherwise it has to be powered by 7-12v.

Could anyone give me some advice on how to accomplish this? Remember, the only power source I have is 3.3V.

Thank you!

2

The Uno requires 7-12vdc. A boost circuit that will accept 3v and output 7v should work.

3

adwsystems:
The Uno requires 7-12vdc. A boost circuit that will accept 3v and output 7v should work.

It would be more accurate to say that an Uno runs on 5v which can be supplied to the 5v pin or it can be powered by 7-12v supplied via the barrel-jack.

An Uno runs at 16MHz and an Atmega 328 will not run at that speed on 3.3v. However an 8MHz Atmega 328 on a breadboard or on stripboard will work very happily on 3.3v. I think it is possible to buy a 3.3v version of some of the smaller Arduino boards.

...R

4

If you run an ATMega328 at 16MHz powered by 3.3 Volts, this is out of specification and you are effectively overclocking it.
However, it is likely to work. Some Uno clones even have a switch to switch between 3.3volt and 5volt mode. To do this, simply power it via the Vin pin.

Here is an example from a forum member's shop:

720×600 115 KB

5

adwsystems:
The Uno requires 7-12vdc. A boost circuit that will accept 3v and output 7v should work.

I think that's the route I'm going to take. Thanks for the pointer in the right direction :slight_smile:

6

Or Boost 3V to 5V, and power the board via the 5V pin, bypassing the regulator.
Pololu carries a bunch that can work as low as 0.5V!

7

lastxtemplar:
When I take apart my Intercom I can see that it has some pins which output 3.3V, that is what I can use to power my Arduino.

I doubt that. :astonished:

8

What about the SIM800 shield, that might need 5volt/2Amp.
Leo..

9

Robin2:
However an 8MHz Atmega 328 on a breadboard or on stripboard will work very happily on 3.3v. I think it is possible to buy a 3.3v version of some of the smaller Arduino boards.

Indeed: there's a 3.3V, 8 MHz version of the Pro Mini at least. That'd do great for this application. It's nice and small, too.

The Uno, with its plug-in headers, isn't a good choice for a permanent project. That's what the Nano and Pro Mini boards are for, those you can solder directly on a piece of perfboard.

Wawa:
What about the SIM800 shield, that might need 5volt/2Amp.

As far as I know these SIM800 parts don't need that high voltage - they do indeed need a 2A burst when registering to the network.