[DonpK]

Thanks, I found the section you were talking about. As author of the Low Power Library, I think you are perhaps the best person to answer your own question.

The low power consumption rates I am getting seem reasonable. I’m sure you’ve seen the other articles on the internet using your library. My results seem in line with them.

[DonpK]

Thanks for your answer. “section 23.9.5 of the datasheet (register DIDR0”. What datasheet are you referring to? Do you have a link or more details?

[DonpK]

I installed Low Power Library Ver. 1.60 and…success!

Using the “LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);” statement, the current in the SLEEP mode is 6 uA which is exactly what you found with the WDT on.When my sketch comes out of the sleep mode and turns the on-board LED on, the current jumps up to 27 mA which is around what one would expect.

I tried the “LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);” statement: 27mA with the LED on and “0”uA in the SLEEP_FOREVER mode. Remember, however, that my multimeter only reads down to 1uA, so the small currents you were reading with the voltage regulator removed probably wouldn’t register on my meter.

Since I only want to wake up my Pro Mini every hour or so, and I don’t want to get into external interrupts, the SLEEP_8s mode with some counter code to extend the sleep time is the way I’ll go.

Thank you very much for your patience and help in working this out and, of course, thanks for your LowPower.h library.

[DonpK]

Can you give me a link to Ver.1.50 or above?

[DonpK]

The voltage regulator and power LED have been removed from the board. I also added the following code:

    for(byte pin = 0; pin<22; pin++)
        {
            pinMode(pin,OUTPUT);
            digitalWrite(pin,LOW);
        }

I am using Arduino IDE 1.6.9 (the latest) and the Low Power readme file says: “Low-Power Lightweight low power library for Arduino.Version:1.40 Date: 15-01-2016” I assume this is the latest version of the library? I’ve also tried several different Pro Mini boards with the identical 28uA current draw on each.

Any other ideas?

[DonpK]

I am using LowPower library Ver. 1.40. My multimeter resolves to .001 mA.

In another article using the LowPower with the Pro Mini, the author has almost the same results as I do, 27.4 µA. I’m using a Sparkfun Pro Mini and not a clone, but I wouldn’t think that would make the difference.

In your chart, you list four different current levels for the powerDown mode, but you do not show a current level with the WDT ON, ADC OFF and BOD OFF. I thought this was the default mode for LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF).

[DonpK]

Thanks for your answer.

Yes, I agree, the current spikes I’m seeing are probably due to the WDTimer function which runs every 8 seconds. When I see spikes, they occur at 8 seconds intervals, actually more like 9 seconds, since the watchdog timers are not particularly accurate (see graph on middle of this page).

As you suggested, I changed the for statement to for (i = wdtCounter; i > 0; i--). Interestingly, this reduces the size of the spikes when I do see them on my multimeter. I’m surprised I see anything on my meter since the burst of code is so short.

The current draw is still around 0.028mA. I’ve been working with this article which uses your low power library. In his results chart, I’m using the configuration “No Power LED, no Regulator, 5 volts at the VCC Pin, and PDS, (Power-Down Sleep with Watchdog Timer enabled)”. The author is getting 0.0058 mA, or about a fifth of the 0.028mA I’m getting.

I have no wires connected to the Pro Mini board, just the 5 volt power supply to Vcc. Do you have any suggestions?
Don

[Author]

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