powering arduino uno

Projects General Guidance
1

Hi there,

This is a novice question but one I assume people will be able to help me with!! I want to use a ac-dc adapter to power my arduino uno when not connected to a computer. I will use a 0-12v variable voltage supply but how many Ma's do I need? amps how many amps?

Thanks

2

Depends on how much current the hardware attached to the Arduino needs.

The Arduino itself is only 30-50mA.

3

I am hooking it up to 4 ultra sonic sensors running at 25ma each - do I just add up the ampage? is that how it works? Sorry total novice here!

So 150 ma or so. I think 200ma is a standard for variable voltage would this be alright?

4

Yes, 200mA is probably okay. I might recommend 500mA to match what your USB port provides.

5

OP, I think you would do better with a fixed voltage wallwart, in the range 6V - 9V.
Also, note that the tiny surface-mount voltage regulator on the UNO board will overheat
if Vin is too high and you draw more than a couple 100 mA load.

6

Thanks very much for your help, much appreciated.

Aphra