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I am building a temporary Arduino project, and I need to order an adapter online. I am concerned that, if my adapter has lots of noise, it will affect the Arduino. Since this is temporary, I am going to buy a dirt cheap adapter to save money, but will it be "smooth"? I don't care if it breaks; two of them are much cheaper than the cheapest one that I can find on Sparkfun or a similar website.

If I hook up a fairly 'dirty' adapter, through the VIN pin or the power jack, will it filter out the noise? Will it still filter this noise out if I have a 'dirty' 5V adapter connected through the 5V pin?

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  • \$\begingroup\$ Can you specify exactly which board you were talking about? I can see that you already accepted an answer, but it's really important for future visitors to understand that they need to answer this question for the exact version or variant of the "arduino compatible" board they have. Not all "arduinos" are from Arduino, so without knowing which board you have, it's impossible to give a specifically correct answer. General answers to this question can actually be counter productive to the goal of sharing correct information. Please consider updating your question with your board's info, thanks! \$\endgroup\$
    – Steve Cooley
    Apr 12, 2013 at 19:10

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As far as I can recall, the Arduino doesn't clean up noise in the power supply. Some boards have smoothing capacitors, and other boards have nothing. This means that you'll have to put a smoothing capacitor in between your adapter and your Arduino to avoid accidentally resetting it.

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  • \$\begingroup\$ How big of one do you thing I need? I believe they have capacitor for the regulator, so it might help. Do I just do this on my breadboard (I assume)? \$\endgroup\$
    – Anonymous Penguin
    Apr 9, 2013 at 23:37
  • \$\begingroup\$ @AnnonomusPerson Smoothing capacitors typically aren't very large, as they only hold the charge temporarily to smooth out the noise. You would just put your smoothing capacitor between the output of the adaptor and the VCC of the Arduino. Also, I don't believe that there's a capacitor for the regulator, although I may be wrong - still, it would be best practice to add your own. \$\endgroup\$
    – Polar
    Apr 9, 2013 at 23:41
  • \$\begingroup\$ Check the schematic, there are capacitors for the in and out of the regulator. \$\endgroup\$
    – moenad
    Apr 9, 2013 at 23:56
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    \$\begingroup\$ @AnindoGhosh Some custom boards running Arduino don't necessarily have a voltage regulator. AFAIK, the standard boards do. \$\endgroup\$
    – Polar
    Apr 10, 2013 at 12:42
  • \$\begingroup\$ @Polar So "Some boards have 5V regulators, and other boards have nothing" might be overstating it, when it comes to Arduino boards? \$\endgroup\$
    – Anindo Ghosh
    Apr 10, 2013 at 13:57
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The 5V node is pretty raw with only a small amount of decoupling.

The Vin and Barrel jack are connected to a regulator with significant decoupling capacitors. The regulator will filter out relatively slow changes to the input voltage while the decoupling capacitors will clean up higher frequency content.

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