Arduino: What Adapter?

by djmatic

Ever since the dawn of Arduino, one question has been asked over and over again: "what kind of DC adapter can I use to power my Arduino?"

The short answer is: 9 to 12V DC, 250mA or more, 2.1mm plug, centre pin positive.

The long answer is that an off-the shelf Arduino adapter:

• must be a DC adapter (i.e. it has to put out DC, not AC);
• should be between 9V and 12V DC (see note below);
• must be rated for a minimum of 250mA current output, although you will likely want something more like 500mA or 1A output, as it gives you the current necessary to power a servo or twenty LEDs if you want to.
• must have a 2.1mm power plug on the Arduino end, and
• the plug must be "centre positive", that is, the middle pin of the plug has to be the + connection.

These important details are often contained right on the adapter. Here's a picture of an adapter ideally suited to powering the Arduino. The important info is underlined in red here:

As you can see, it has all the right stuff: 12V, DC, and a little picture that shows you that the middle pin is positive.

Current rating: Since you'll probably be connecting other things to the Arduino (LEDs, LCDs, servos) you should get an adapter that can supply at least 500mA, or even 1000 mA (1 ampère). That way you can be sure you have enough juice to make each component of the circuit function reliably.

One final note. If you check the "Tech Specs" tab on the product page for your Arduino board you may find the input voltage limit listed at as much as 20V (specs vary depending on which board you have). This is an absolute limit. Powering your board at either end of that range is NOT recommended. The reason you don't want to power your board at a voltage near the upper limit is because most of that voltage will be converted to heat. Our advice is to stick with a 9V or 12V DC adapter.