Replacing Arduino 5V regulator with 3V regulator

Hi all

I was thinking about replacing the 5V regulator on my Uno with a 3.3V one because of all the issues I’ve had logic level shifting.

Something similar to this:

I was wondering if anyone has actually done it and if there are any issues to consider?

Will you replace the resonator also with an 8 MHz part? The '328P will be out of spec running at 16 MHz at 3.3V, you may see odd performance with no explanation. It needs ~3.8V to be in compliance at 16 MHz.
2.7V + (6/10 of the difference between 2.7 & 4.5V) is needed for 16MHz = 3.78V

CrossRoads:
Will you replace the resonator also with an 8 MHz part?

Interesting. I could do if it's necessary. I mainly just wanted to gauge the feasibility of replacing the regulators.

I could just buy a 3.3V Pro mini but I would also need to get something for FTDI.

Some time ago (on Youtube) I saw an Arduino which had a switch to toggle between operating at 5V and 3.3V. Does anyone know what that might be? I'm sure I saw it, just cant find any like that ..

a8rakadabra:
Some time ago (on Youtube) I saw an Arduino which had a switch to toggle between operating at 5V and 3.3V. Does anyone know what that might be? I'm sure I saw it, just cant find any like that ..

a8rakadabra:
Hi all

I was thinking about replacing the 5V regulator on my Uno with a 3.3V one because of all the issues I've had logic level shifting.

Something similar to this:
3.3V Conversion | Arduino Tips, Tricks, and Techniques | Adafruit Learning System

I was wondering if anyone has actually done it and if there are any issues to consider?

I wonder why you want to do that? Is it to be able to plug in 3.3v-only shields?

At 3.3v, you may run into problems with the brown out detector tripping. Also, your clock oscillator will be weak. The Arduino UNO uses a ceramic resonator and the default fuse setting for the oscillator is "low power" (as opposed to "full swing") - your oscillator may not start, it may be slow to start (like literally a second or more) or it may be flaky.

You MAY be able to get away with it if you change your brownout detector settings and also change to "full swing" on the oscillator.

All in all, I think you're opening yourself up to a lot of grief... do you REALLY need a 3.3 volt Vdd?

I can confirm all my 328p and 1284p chips work fine with 3.3V and 16MHz oscillator (full swing set with 1284p).
The atmega32(L) does not like 16MHz at 3.3V, so I use 12MHz or something like that.
I’ve never ever heard about somebody w/ problems when powering these chips 3.3V…
I am not using Uno however, but diy boards.

a8rakadabra:
I was thinking about replacing the 5V regulator on my Uno with a 3.3V one because of all the issues I've had logic level shifting.

I was wondering if anyone has actually done it and if there are any issues to consider?

I can confirm this worked for me on a genuine UNO and I did not need to change the resonator.

cr0sh:
http://www.seeedstudio.com/depot/Seeeduino-V30-Atmega-328P-p-669.html

That's something like what I saw a while back, thanks.

pito:
I can confirm all my 328p and 1284p chips work fine with 3.3V and 16MHz oscillator (full swing set with 1284p).
The atmega32(L) does not like 16MHz at 3.3V, so I use 12MHz or something like that.
I've never ever heard about somebody w/ problems when powering these chips 3.3V..
I am not using Uno however, but diy boards.

Thanks that's really useful. So I've found some cheap clone for £4 and I'm planning on replacing the 5V regulator with a 3.3V one, and also replacing the 16MHz crystal with a 12 or 8MHz one. You think I'll be alright?

a8rakadabra:
Thanks that's really useful. So I've found some cheap clone for £4 and I'm planning on replacing the 5V regulator with a 3.3V one, and also replacing the 16MHz crystal with a 12 or 8MHz one. You think I'll be alright?

12MHz is not so good as the Arduino core is better suited to 8/16MHz. You don't need to replace the 16MHz resonator as simple fuse setting changes will allow the use of the MCU's internal 8MHz oscillator. If you do change the MCU's default speed of 16MHz then you will either need to burn a new bootloader or program using external programmer.

Riva:
12MHz is not so good as the Arduino core is better suited to 8/16MHz. You don't need to replace the 16MHz resonator as simple fuse setting changes will allow the use of the MCU's internal 8MHz oscillator. If you do change the MCU's default speed of 16MHz then you will either need to burn a new bootloader or program using external programmer.

How would I go about doing that fuse setting change?
I found this thing: http://www.engbedded.com/fusecalc

..but I don't really know what I would do.
I'm pretty set on changing this regulator on the Uno so if I don't need to replace the 16MHz crystal that's even better.

To change the fuses you either need a programmer like a tinyusb or another uno loaded with arduinoisp. If you change the fuses then you will also need to burn a suitable bootloader to upload sketches or upload them using a programmer.
Sorry no links as on a tablet and it's to much of an arse to do on this.

Thanks that's really useful. So I've found some cheap clone for £4 and I'm planning on replacing the 5V regulator with a 3.3V one, and also replacing the 16MHz crystal with a 12 or 8MHz one. You think I'll be alright?

Just replace the regulator to 3.3V. You must not change the 16MHz crystal.