Go Down

Topic: Lowest Arduino Power consumption (Read 3 times) previous topic - next topic

simplex

Current drawn by an Atmega328p with external 16 MHz Crystal = 13 mA

I did a test. I run the code from here:
http://arduino.cc/forum/index.php/topic,125248.msg962251.html#msg962251
on a breadboard having, on it, just an Atmega328p connected with a 16 MHz Crystal and two 22 pF capacitors.
The circuit draws 13 mA from the 5V power source.


tim7


Current drawn by an Atmega328p with external 16 MHz Crystal = 13 mA


That sounds reasonable if you are not using any power-saving techniques.  Using code similar to Nick's demo linked above, I could get a 16MHz 5V Arduino down to approx 1uA.  My multimeter is not good enough to read these very low currents with any accuracy, so I cannot say if the real current was less than that.  The datasheet claims 0.1uA at 3V, and I've no reason to doubt that.

MarkT

Once you get to a few uA your battery's internal self-discharge will be the dominant factor (and the duty cycle at which you pull higher currents).  1uA ~= 9mAh/year
[ I won't respond to messages, use the forum please ]

Nick Gammon

#13
Oct 21, 2012, 02:36 am Last Edit: Oct 21, 2012, 02:38 am by Nick Gammon Reason: 1
Exactly. I have a table on the page I linked above. Here it is:

Code: [Select]

Type        Capacity mAH  Discharge %/month   Self discharge (uA)

CR1212            18              1                  0.250
CR1620            68              1                  0.950
CR2032           210              1                  3
NiCD AAA         350             20                 98
NiMH AAA         900             30                375
NiCd AA         1000             20                270
Alkaline AAA    1250              2                 35
NiMH AA         2400             30               1000
Alkaline AA     2890              2                 80
Li-Ion          4400             10                600


These are approximations but the general idea is that you don't need to get excited about using less than 1 uA because the battery is going to self-discharge much faster than that, particularly NiMH batteries.

To confirm MarkT's figure, if you use 1 uA then over a year that would be:

Code: [Select]

0.000001 * 24 * 365 = 0.00876 = 8.76 mAh

spcomputing

I got 8mA with Nick's power sketch J with the same setup sans coin cell (broke, new holder next week).  I think that that the Xbee 3v3 regulator is costing an order of magnitude.  There are two leds, but I am sure they only cost 10-15mA.  I will investigate if they can be disabled other than scrapping.  Considering the LiPo and solar option, I am not sure what we are discussing unless the unit is north/south of 80 degrees.

With an internal clock and no regulator/LEDs, I replicated Nick's sleep tutorial +5% of 0.35uA with a breadboard setup.  I have not tried just the watchdog, which this SeeedStudio Stalker is capable of (Interrupt traces cut to enable).  I am not sure why the Narcoleptic library does not shut the ADC down.

Properly optimized, the coin cell will die before the LiPo gives out.

Go Up