Low power consumption on Raspberry Pi Pico / Badger / Picowbell

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I’ve just come across GitHub - bablokb/pico-sleepcurrent: Test programs to measure current consumption during sleep for the Pico by @bablokb.

How can I get the lowest possible deep sleep current in a data logging scenario? (Pico wakes every 15 mins, takes readings for a few sec, goes back to deep sleep. Target battery life several months.)

The enviro indoor already does that, but it doesn’t have an sd card. Also, it comes with a set of certain set of sensors, and the rtc doesn’t have external battery backup. (This post is a follow-up to:
Raspberry Pi Pico - why does free space show as 848 kB? (and advice on how to add an SD card to an enviro indoor) - #10 by bablokb which is about adding an sd card.)

I’ve measured the deep sleep current on a badger, and it’s very low: 30 uA (if that can be true?).

I haven’t measured the current on the enviro indoor, but will test that tomorrow.

I suppose I would like to ‘roll my own’ low-power data logger, using Raspberry Pi Pico (or likely a Pico Lipo) and (ideally) a PiCowbell (RTC and SD Card). Any ideas, sample code, etc would be appreciated.

Many thanks!

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One option is the enable-timer Adafruit TPL5111 Low Power Timer Breakout. This will wake up your Pico in fixed intervals, otherwise, it won’t consume any (or almost none) power. This does not need a rtc. The wake up interval is up to two hours. Of course for data-logging, a rtc with correct time would be useful.

As an alternative, you could have a look at: GitHub - bablokb/pcb-pico-en-control: Suport PCB to control the enable pin of a Raspberry Pi Pico This circuit does about the same thing as the power-circuit in the badger does. It has a rtc, does not need a battery backup because the rtc is hooked to the battery. You can start the system using the button or by setting a timer or an alarm.

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I really like the Adafruit TPL5111x, but as you say, an RTC is useful. Depending on power consumption of the measurement cycle, we may also want to schedule measurement a little, i.e., measure more during daytime on weekdays (when classrooms are occupied), and measure less (or not at all) during nighttime and weekends.

This GitHub - bablokb/pcb-pico-en-control: Suport PCB to control the enable pin of a Raspberry Pi Pico is precisely what I had been looking for - absolutely amazing. I see that it’s a fairly recent decision (some months ago): Do you mind sharing the back story? I’m curious :)

I should also give our backstory: https://opendeved.net/programmes/ilce-in-tanzania/. We’re looking to measure temperature / light / sound (and other environmental factors) in schools in Tanzania. Excessive heat is linked to poor learning outcomes. We want to first accurately measure, and then undertake ‘retrofit’ interventions to reduce heat, as well as improve light/sound conditions.

Coming back to the board: Suppose we want to have some of these made - do we just send off the production files to a manufacturer? Do you have an idea of cost?

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Just to add: I’ve now measured the power consumption of the pico indoor as well. During measurement, just below 40 mA. Measurement takes about 5s. During deep sleep, just below 30 uA. (I haven’t measured power consumption during WiFi interaction.) For us, that’s a fantastically low power consumption.

If the environ indoors had enough capacity to store the data (cf. Raspberry Pi Pico - why does free space show as 848 kB? (and advice on how to add an SD card to an enviro indoor) - #10 by bablokb), this would be perfect. Ideally, separate power to the RTC as well, so that they can be configured separately.