I'm building a custom Arduino compatible with an ATMEGA328P.

Would it be better to get a 5V power supply that plugs into the wall to power the project and gives me a barrel jack, then connect that directly to the uC, or should I instead use something like a 9V power supply, then use a 7805 to regulate down to 5V?

  • \$\begingroup\$ Quick thing - If it's truly going to be compatible with Arduino, ie. use similar shields etc., then you're going to need a 3V3 supply as well. \$\endgroup\$ – NickHalden Jun 8 '13 at 17:45
  • \$\begingroup\$ It's not so much as an Arduino compatible as it is a board that uses the same uC and code. I'm not using anything other than 5V in the project, so I'm going to leave it out. \$\endgroup\$ – tehsusenoh Jun 8 '13 at 17:51
  • \$\begingroup\$ "Would it be better" makes this question different to answer. What do you consider better? What tradeoffs do you want to avoid taking? That's going to determine what is "better". More information on the intended application of the board, the types of loads it will provide power to, and the types of supplies you expect to connect are a BARE MINIMUM to answer which method is "better". \$\endgroup\$ – baldengineer Jun 9 '13 at 1:09

You should go with the 5-V external supply and put a capacitor between 5 V and GND near the ATmega to reduce noise in the power. With the 9-V supply, you still need to have a wall wart but you also have an extra component on the board.

Also, don't use a linear regulator if you do decide to use 9 V. Since you're going from 9 V to 5 V, you're dissipating (9-5)/9 = 44% of the input power as heat.

  • \$\begingroup\$ Okay, thanks. I already had the capacitor in the mix, so that's good. \$\endgroup\$ – tehsusenoh Jun 8 '13 at 17:51

I'd prefer the external 5 volt supply - then I don't have to place a regulator on my board.


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