Anybody know if its ok to run an arduino on 5.1 volts. I am using an arduino with the ATmega328 chip. I tried to find the specs on the ATmega328 data sheet, but I must be blind.
Thanks
rr
Certainly you can run a 328 at 5.1vdc. Heck the USB voltage coming from a PC has a wider range of variation then that.
One USB reference I googled said:
When operating at a full unit load, a minimum VBUS of 4.75 V is specified with a maximum of 5.25V.
Lefty
Thanks for the info... I have a ton of 5.1v power supplies and I wanted to use them in a project.
Wait, though, what kind of 5.1V power supplies are these? Are they regulated or "wall-warts" that, despite what is printed on them (e.g., 9V/500mA) do NOT put out exactly the voltage they say. A 9V wall-wart can easily put out 13V under no load. If your "5.1V supply" puts out 8V at low currents, you will easily damage your 328.
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do NOT put out exactly the voltage they say. A 9V wall-wart can easily put out 13V under no load. If your "5.1V supply" puts out 8V at low currents, you will easily damage your 328.
As one who has always shopped for my wall wart supplies at thrift and second hand stores I have seen a large up swing in different kinds of wall warts avalible these days as so many seem to upgrade their cell phones etc. It's been my experiance that any DC wall wart that labels their voltage with includes a fractional number of .1 or .2 volts will be a regulated supply. Makes sense, what would be the reason to have a small fractional voltage specification for a unregulated DC wall wart. 
However common sense would have one always first measure the output unloaded to see if it matches the labled voltage or not.
PS: Keep an eye out for laptop DC power modules in thrift stores, they come in many voltages and most have pretty nice current capacities and all seem to be of light weight/small size switcher types. I found a nice HP 3amp 13 volt regulated one for $2 awhile back, that's what like 5 cents a watt.
Lefty
If it's a bit too high, one quick hack would just be to solder a few diodes together to drop the voltage.
I've read that 5V AVRs will run at 6V without releasing the magic smoke, but I wouldn't recommend it..........