So I've got some projects I'm playing with right now that involve 24VDC and also an Arduino Uno. My 24VDC supply (re-purposed from the guts of a laser printer) also provides 5VDC (maybe 5.2.)

I'd like to power the Arduino directly from that instead of using batteries or a separate power supply, but I can't find info on its power tolerances.

The regular power inputs need 7+ to regulate down from, and the 5V pin bypasses the onboard regulator.

Anyone know if 5.2V is likely to somehow upset it? I realize it will change my default Aref, but any other reason not to do it?

 

Look at the ATmel data sheet for the processor. IIRC, it can go to 5.5V.

 

So I've got some projects I'm playing with right now that involve 24VDC and also an Arduino Uno. My 24VDC supply (re-purposed from the guts of a laser printer) also provides 5VDC (maybe 5.2.)

I'd like to power the Arduino directly from that instead of using batteries or a separate power supply, but I can't find info on its power tolerances.

The regular power inputs need 7+ to regulate down from, and the 5V pin bypasses the onboard regulator.

Anyone know if 5.2V is likely to somehow upset it? I realize it will change my default Aref, but any other reason not to do it?

You will be fine using the 5V supply. You can add a properly biased 5.6 v Zener to make sure you don't damage your arduino.

 

Good news! Datasheet says 6.0V. More forgiving than I thought.

 

Now check some other things.

Can the on-board voltage regulator chip tolerate 6V on its output pin when its input is not connected?

Can the USB interface chips tolerate 6V?

What happens if you have 6V to the board and you plug-in 5V from the USB?

Can the 6V backfeed into the USB?