# How to use external power supply for Arduino Uno?

Can I use an AC power adapter that can be connected through USB port? My board is Arduino Uno and usually connect to my computer through the USB cable.

AC power adapter <-> USB port <-(USB cable)-> Arduino USB port

What kinds of components can be used as external power supply for Arduino board? It's really nice if you have some images or names about them.

• Why shouldn't it be good? As long as the voltage and current is the same, there's no difference if it's generated by a PC or a converter... – clabacchio Jan 24 '12 at 10:39
• Aside from cost, why not hook up several 9V in parallel to power the board? – user10874 Jul 15 '12 at 19:08
• electronics.stackexchange.com/questions/17987/… You can also use the Vin pin if you do not want to use a power jack... for example a battery with a clip would work. – NickHalden Jun 3 '13 at 20:33
• Surely this is spelled out in the documentation of the arduino!? – Olin Lathrop Jun 3 '13 at 21:10
• AC power adapter that can be connected through USB port I would not recommend putting a 12V adaptor 'on' your USB port. – Paul Apr 2 '15 at 12:02

• a stable (regulated) 5V DC, which you can either supply via the USB power lines, or via the shield connectors, or
• an unregulated 6-20 V DC (7-12V recommended), which you can supply via the 2.1 mm centre-positive barrel plug connector.

I would not recommend using a 9V battery, because its voltage will drop quickly, but in a pinch this can be used.

• do you have some images as example? I'm pretty much newbie at this stuff. – Pete Houston Jan 25 '12 at 5:39
• What about the maximum allowed current? can i use 12V-1500MA adapter? and also would it be ok if i connect the USB cable while the adapter is plugged in? – razzak May 13 '15 at 18:55
• 12V/1.5A should be OK, but the things you connect to the arduino should not draw too much current. A couple of LEDs will be totally OK. Plugging both USB and external power is not a good idea, the USB could be back-powered. – Wouter van Ooijen May 13 '15 at 19:19

The answer is 6-20V (7-16V recommended). http://arduino.cc/en/Main/arduinoBoardUno

• Yep. I use a 5v regulated myself. – mikeY Jun 3 '13 at 22:39

Yes, you could use a USB battery device or USB charger or a 9V battery clip with a 2.1mm DC power plug.

• Why Wouter van Ooijen doesn't recommend 9V battery and you do? – Pete Houston Jan 25 '12 at 5:40
• I included why I don't recommend a 9V battery. Hence you can infer that Hellonearthis gives less weigth to that argument. Conclude for yourself whether it is relevant in your case. – Wouter van Ooijen Jan 25 '12 at 8:16
• This is what I use broken cell phone chargers for. BTW it's that hello near ths? Or hell on earth is? – user23736 May 9 '13 at 22:25