# Can't find the current?... :/

Discussion in 'General Electronics Chat' started by Captain E, Jun 19, 2015.

1. ### Captain E Thread Starter Member

Jun 16, 2015
81
6
Hi!

I'm using the Arduino UNO with 5V as the Voltage source, so I know the TOTAL voltage.
I need the TOTAL current to move on and as I dont have any resistors attached yet, so I can't calculate the TOTAL current of my circuit.

Very new I am indeed, and in my "math practice" in electronics I always got the resistance(*) in the entire circuit in the exercise instructions. Now I dont.
So how can I find the total current for the Arduino UNO?

Maybe the way I'm doing this is bad? Please tell me, if so

Thanks! Stay awesome.

*EDITED from Voltage to resistance. remembered incorrectly x)

Jan 29, 2010
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3. ### Captain E Thread Starter Member

Jun 16, 2015
81
6

It says 46.5 mAmps using a USB cable from the first search result from you, so is this value the same for every UNO when using 5V from a USB cable?
Can it change, when always using the same Voltage, 5V?

4. ### DickCappels Moderator

Aug 21, 2008
3,830
1,042
Not necessarily. For example, if you change the clock prescaler you will cause a significant change in current.

By the way, I think there is a good chance that each of us sees different search results from Google based on our search histories.

5. ### Captain E Thread Starter Member

Jun 16, 2015
81
6
Thanks for the reply, but I dont have any access for that right now :/ (we're moving and everything organized in boxes, so no touchy)

(Moderator note: I hope you don't mind that I cleaned things up.)

Last edited by a moderator: Jun 19, 2015
6. ### DickCappels Moderator

Aug 21, 2008
3,830
1,042
Which search result did you take you to your answer (what is the URL)?

7. ### Captain E Thread Starter Member

Jun 16, 2015
81
6
Haha oh ^^
Here I got the 46.5 result: http://gadgetmakersblog.com/arduino-power-consumption/

8. ### DickCappels Moderator

Aug 21, 2008
3,830
1,042
Note that 46.5 ma was when running at 16 MHz.

9. ### Captain E Thread Starter Member

Jun 16, 2015
81
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Yes, I got that Thanks again )

10. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,070
Captain,

Your question is like asking "I have a 12V car, how much current (how big a battery) do I need to power it?"

Let's see. If it is parked, with the key off, a tiny bit...
If the radio is on, but still parked, a bit more...
If the headlights and radio is on, but still parked, quite a lot...
While cranking the starter, a huge amount (100s of Amps)
If driving, almost nothing, because the alternator picks up the load...

Similar with the Arduino. The question should be " what is the worst case power draw if the Arduino is doing something useful, and it is not plugged into the USB (like the car's alternator)"?

11. ### wmodavis Well-Known Member

Oct 23, 2010
739
150
Try measuring it with an ammeter. Every experimenter/learner or what ever you call yourself needs one.

12. ### Captain E Thread Starter Member

Jun 16, 2015
81
6
Ooh I see Thanks a lot, Mike

13. ### Captain E Thread Starter Member

Jun 16, 2015
81
6
Yea I now get that I really need that.. OF TO THE STORE I GO. (tomorrow, I'm lazy..) xD

Thanks!

14. ### #12 Expert

Nov 30, 2010
17,840
9,178
Just a tip...a cheap meter will do for beginners. You can often find one in the range of \$10 or less if you know where to look. (Does Harbor Freight exist in Sweden?)

15. ### Captain E Thread Starter Member

Jun 16, 2015
81
6
Nope, but I know a few nearby places with the things I need, so it's just a matter of time :3