Arduino current

How much current does the arduino uno need? Keep in mind that none of the voltage pins will be used ( 5V nor 3.3V ), except for 3 pins for data. All other electronics will have their own power supply.

Y2K986:
How much current does the arduino uno need?
Keep in mind that none of the voltage pins will be used ( 5V nor 3.3V ), except for 3 pins for data. All other electronics will have their own power supply.

Assuming no current is being drawn from digital output pins the board’s current draw from it’s Vcc bus is somewhere in the 50-80ma range.

Lefty

20ma is a good estimate, probably towards the upper end. 5ma is about right.

If you consume materially more than that, there likely is something wrong.

Thank you for your response. So, is it more to around 20mA, or 50-80mA? Again, I'll be using just 3 pins for Clock, Latch and Data, for 75hc595. All other electronics will have it's own power supply. So, should I limit the current on 50mA and sleep tight? :)

If you have a RTC you may be able to configure one of its pins for a 1Hz o/p. This can be attached to an interrupt pin. You can then incorporate a sleep mode, saving power. This is of course if your application doesn't need constant processing.

http://playground.arduino.cc/Learning/arduinoSleepCode

Y2K986: How much current does the arduino uno need? Keep in mind that none of the voltage pins will be used ( 5V nor 3.3V ), except for 3 pins for data. All other electronics will have their own power supply.

According to the datasheet the ATmega328P needs about 10mA, there's also a Mega168 on there so that's another 10mA ... plus some other bits and pieces. I'd guess under 30mA total, but the only way to be sure is to measure it.

nb. The output pins can add up to 40mA each when they're outputting a HIGH so add in whatever you have connected to them.

The Arduino Uno R3 quiescent current is more like the 60 to 80 mA total power LED draws Lefty mentioned. About 10 - 20 mA each for the processors (328 and 16U) about 10 mA of various bias currents and 5 to 10 mA for the regulator does add up to more than 5 to 20 mA total.

Bob

Docedison:
The Arduino Uno R3 quiescent current is more like the 60 to 80 mA total power LED draws Lefty mentioned.
About 10 - 20 mA each for the processors (328 and 16U) about 10 mA of various bias currents and 5 to 10 mA for the regulator does add up to more than 5 to 20 mA total.

Bob

Thanks, and I was going mostly on memory of past posting of other peoples actual measurement of board current consumption, which in the end is the final answer for the OP’s question. measure twice, cut once.

Lefty

@ dhenry The nice thing about an "Opinion"... is that it doesn't need facts...

20ma is a good estimate, probably towards the upper end. 5ma is about right.

If you consume materially more than that, there likely is something wrong.

Bob

Docedison:
About 10 - 20 mA each for the processors (328 and 16U)

Datasheet says otherwise. 16MHz, 5V gives just under 10mA. (this ignores any load on the I/O pins…)

But as I said before, the only way to be 100% sure of the consumption is to measure it.

If power is a problem then use a board which dumps the second AVR chip and voltage regulator.

Not to "HighJack" the thread but Nick Gammon has a very informative page n that subject.. The 328P will work to some astonishingly low currents.

Bob

It will depend somewhat on the input voltage as some power will be wasted as heat in the linear voltage regulator.

From measurements just taken

Totally standard UNO R3 SMD, feeding into the DC power jack

54.7mA @ 9v 48.2mA @ 7.5v

@ fungus.. I was trying to remember what I'd read in Nick's tutorial and thought it better to err 'slightly' (10 - 20 mA..) on the high side as it is a slightly less severe sin than underestimating it. Much better finally, less than more. There are also the 'vampire currents' like the 1.6? mA Iq of the LM 358 and the various voltage dividers and the 3 mA for the power led as well as the (guess) Iq of the regulator that I'd place at 4 to 6 min. My 'assumption' is based on prior experience with other PNP type pass regulators, I have no direct experience of the '1117 family but most of that type just add the control current as the load current increases.

Bob

Great measurements and good to know, I'd guess at about 45 - 46 mA from the usb port which was what I was addressing.instead of implying that the regulator is a part of the 'normal' load current. My comments about the regulator should have been prefaced with 'if used, the regulator will add 4 to 6 mA' and possibly confusing.

Bob

dhenry: 20ma is a good estimate, probably towards the upper end. 5ma is about right.

If you consume materially more than that, there likely is something wrong.

@dhenry, you sound knowledgeable about electronics. Do you own a multimeter? Can you measure current?

In my page:

http://gammon.com.au/power

I actually measured (rather than guessed) the power consumption of a Uno (which this thread is about, not the raw chip). It was from 45 to 55 mA depending on the power source (9V battery or direct 5V input).

Saying 5 mA is about right is just guesswork on your part. Please don't advise people of this nonsense unless you are prepared to back it up with actual measurements, and if you do that, specify exactly what you are measuring.