Tero Koskinen recently did interesting experiments exploring how low power he can go with Arduino. http://arduino.ada-language.com/saving-power-with-avr-ada.html
He made setup with 5 boards to test:
- original Arduino Duemilanove
- original Arduino UNO
- Olimexino-328 clone
- Arduino DIY PTH kit from Sparkfun
- Diavolino from Evil Mad Scientist
He correctly shut down all not used peripherials, Brown-Out-Detection, slowed down the CPU speed and used Power Saving modes.
the results were:
|Sparkfun PTH Kit||7.60mA|
Diavolino have nothing but the AVR so obviously is winner with this setup with only 0.5mA consumption.
Wait if there is no power regulator where these 0.5mA go when AVR is put in low power mode?
Looking at the schematic you can see R1 RESET pullup 10K resistor which is connected to 5V -> 5V/10K = 0.5mA the whole consumption is taken by R1!!!
Then let’s see OLIMEXINO-328 the second place with 4mA (outch!) this board is promoted by OLIMEX as SUPER DUPER LOW POWER BOARD then why these bad results? Where these 4mA go?
The answer is obvious: Tero is powering OLIMEXINO-328 by the POWER JACK.
In our design we assume if the power come from the power jack it’s unlimited and we can waste it as much as we need – charging Lipo (if attached) etc.
So these 4mA are taken from the DCDC in the input.
If Tero wanted to see how OLIMEXINO-328 shines in low power he should have powered the board by the battery connector. When the power is applied to battery OLIMEXINO-328 is very humble and will need less 20 micro ampers 0.02 mA to operate!
How this is done? If we look at the schematic we will see that there is no RESET pull-up, but the RESET is done by tricky circuit with R12/R13/SD5/C7/C8 this schematic have zero consumption but still perform RESET functionality.
Also unltra-low-power LDO which needs just 3 micro amps to operate MCP1700T-3302E/MB is used for power regulator.
This makes possible complete Arduino to may keep working while consuming less 20 micro amps.
What 20 micro amps consumption means? If you use our standard LiPo 1400 mAh battery your board can work 70 000 hours or 3 years!
The other boards: Sparkfun kit 7.6 mA, Duemilanove 7.5mA and UNO 18.1 mA just use cheap voltage regulators which take this current, but it’s OK they have not been designed to be low power.
What is the conclusion: with right setup (powering from battery) OLIMEXINO-328 is the lowest power Arduino solution on the market! When we add to the low power the industrial temperature operation range -25+85C and the possibility to work with any input voltages from 9 to 30VDC, OLIMEXINO-328 is the most sophisticated board with many features while keeping the price reasonable.