How to use external power supply for Arduino Uno?

Question

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.

• clabacchio: 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...
• user10874: Aside from cost, why not hook up several 9V in parallel to power the board?
• NickHalden: 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.
• Olin Lathrop: Surely this is spelled out in the documentation of the arduino!?
• aaa: AC power adapter that can be connected through USB port I would not recommend putting a 12V adaptor 'on' your USB port.

Answer 1

An Arduino Uno can be powered by

• 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.

ref: http://arduino.cc/en/Main/ArduinoBoardUno

• Pete Houston: do you have some images as example? I'm pretty much newbie at this stuff.
• razzak: 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?
• Wouter van Ooijen: 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.

Answer 2

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

• mikeY: Yep. I use a 5v regulated myself.

Answer 3

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

• Pete Houston: Why Wouter van Ooijen doesn't recommend 9V battery and you do?
• Wouter van Ooijen: 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.
• user23736: This is what I use broken cell phone chargers for. BTW it's that hello near ths? Or hell on earth is?

Answer 4

Can i use 12V-1500MA adapter?

Since no-one mentioned this: I believe the arduino uses a linear regulator. This converts the input voltage down to 5V by burning the excess power as heat.

For example, if you supply it with 12V and the arduino draws 100mA on the 5V supply, then the regulator will have 12-5=7V dropout, and it will dissipate 7V*0.1A = 0.7W.

Since it is usually a small SMD device, not fitted with a heat sink, it can't dissipate a lot of power. It will overheat very easily if you draw high current.

Thus if you feed it with 12V the limit will not be the supply current (unless your supply is really wimpy) but the onboard regulator dissipation.

This does not apply if you use a 5V supply, like a 2A cellphone charger, although some components on the board, like the ferrite beads on the +5V line, may object to such high currents.

Anyway, if you want to do high current stuff like servos, motors, long LED strips and the like, power them separately from the supply, and definitely not from the arduino itself. The arduino should control your stuff, light a few LEDs for indication, total maybe 100mA, but it is not designed for power.