As the title says there are many different wall chargers to choose from.

12v, 9v, 5v, with different mA amounts...

The starter kit on Adafruit's website mentions to get the 9V 1000mA switching power adapter, so I'm curious if that's what we should get?

here is the link to all of them.

There are regular wall adapters, and these big power supplies...


I'm just looking to run some LED Strip lights from the arduino and power some joystick buttons, some rotary encoder/knobs, and a keypad to work the LED lights




This website looks like a pretty official answer for you. http://playground.arduino.cc/Learning/WhatAdapter

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.


The Arduino's on-board regulator can actually handle up to 20V or more, so you can actually use an adapter that puts out 20V DC. The reasons you don't want to do that are twofold: you'll lose most of that voltage in heat, which is terribly inefficient. Secondly, the nice 9V pin on the Arduino board will actually be putting out 20V or so, which could lead to potential disaster when you connect something expensive to what you thought was the 9V pin. Our advice is to stick with the 9V or 12V DC adapter.

  • Thank you very much :). I guess I also could just plug it directly into this computer via USB? I was thinkign that my new build would be done afterwards, but forgot about this comptuer :P Thanks! – XaolingBao Dec 1 '15 at 4:51

Your Arduino Uno will use 35 to 50 mA at 5V. The “joystick buttons, some rotary encoder/knobs, and a keypad” will draw a small amount of current, probably between 1 and 10 mA. Thus, power for the Uno and your controls will be well under 100 mA and can be supplied via USB without any problem. (Also see: How to get more than 100mA from a USB port.)

If your Uno enumerates and negotiates to get 500 mA via USB, you might have 450 mA available out of the +5V pin. However, in some cases if you need more than a few dozen mA to power other devices, it will make sense to get a separate 5V supply for them. (Eg, if the devices drag down the +5V and cause the Uno to reset, or if the devices are electrically noisy, like motors, RC servos, relays, solenoids.) Also, note that thread #70450 at forum.arduino.cc says you can draw 650 mA (or 3.25 W of power) when the Uno is powered via its DC power jack.

If your LED string has up to 6 or 7 WS2812B equivalents, you can power it from the Uno's 5V. Here is the all-lights-on, full-brightness calculation for six of them: 6 WS2812Bs x 3 LEDs per WS8211 x 21 mA per LED = 378 mA. For seven: 7 x 3 x 21 mA = 441 mA, which is out there on the edge.

For longer LED strings, figure on a little over 3 W of power for every 10 WS2812B equivalents. (Calculation: 5 volts x 10 WS2812Bs x 3 LEDs per WS2812B x 21 max mA per LED = 3150 mW = 3.15 W.) For example, get a 10 W (2 A x 5 V) or greater 5V power supply for a meter of 30- WS2812B-per-meter LED strip, etc. This power supply will connect directly to the LED strip's power connectors. The ground from the LED strip will connect to the Uno's ground, to establish a signal reference point.

Note, the absolute max voltage rating for a WS2812B, according to its datasheet, is 5.3 V, so use a supply whose voltage does not exceed 5.3 V. The absolute min voltage rating is 3.5 V; they will work ok on 3.7 V LIPO batteries, but 3V3 power is out of spec for a WS2812B.

As mentioned in a previous question, if your LED strip is being installed inside a desktop PC, the PC's power supply will have lots of 5 V power available, and you can hook on to one of the red +5V wires and black Gnd wires from its supply to power the LEDs, either while powering the Uno itself from USB power or while using the same +5V to power the Uno as the LEDs.

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