Running chip w/o external oscillator question

I wanted to keep my project as small as possible, and I read it can be used w/o external crystal. Since it will be on 5v source, the guides I found for reprogramming to make it run on 3.3v with internal oscilator seems wrong or can I ignore the voltage issue? Or would arduino run fine as is on 5v without external crystal?

I just need to know what is involved to make 328 usable w/o external oscillator on existing 5v source. I have access to ISP programmer shield and I have few spare ATMega 328 to play with.


you can run slow with 5 volts but you cant run fast with 3.3


When you boot load the chip chose the lillypad option and the internal fuses will be set for 8mhz using the internal oscillator.

Cheers, Geoff

You can certainly use the internal oscillator with 5V power. You can run at 8 MHz with 2.4V power.

Ok thanks for the response, so I’d have to change the boot to use internal oscillator then.

I am currently using 328p @3V3 and 7.37MHz internal oscillator (set with OSCCAL) and 115k2 upload works fine. You may set the internal oscillator from 5-15MHz with OSCCAL, afaik..