Can I use 5V regulated DC supply instead?

Hi,

can you power an ATMEGA168 straight from a 5V regulated DC supply rather than use say a 9V supply and 7805 5V Voltage regulator?

I can't think of a reason why not since as far as I know they both provide a 5V regulated output but thought i'd better ask before picking one up as i'm no electronics expert ! :o

In theory, yes. You just need to make sure that the regulated power supply you’re thinking of is truly regulated, as some PSUs for PC’s, for example, are not very well regulated.

I would also use a DMM to check the output of your PSU to make sure that it is at appropriate levels for the Arduino.

Thanks for the reply. Got a bit of a weird problem where the ATMega seems to reboot intermittently. At the moment the 168 is sat in a separate project box to the 7805 and I've got it wired up using a DC socket and connector.

I'm not entirely sure where the problem lies at the moment and thought wiring the 168 direct to a 5V Regulated supply would either eliminate the problem or help me track it down.

Almost certainly your problem is lack of decoupling:- http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

Almost certainly your problem is lack of decoupling:-
De-coupling

Very informative! :smiley:

Thanks for the link. Need to be in the right frame of mind to go through it properly.

The wiring had become such a mess that I decided to strip out all the wiring except for that for the supply for the ATMega and start again. I made sure this time that the 7805 in the box with the ATMega was given plenty of space and that the box could be opened and put back together without worrying about pulling wires etc.

Because the 7805 was no longer shrouded in wires I opted back to using it rather than the one in the adjacent box and things are running fine again.

Guess i'll have to read that link in detail to get to the bottom of it but I'm guessing it had something to do with the gauge of the cable I was using to connect the two boxes together, ie 8" of cable taken from a regular DC PSU adaptor.