IMP and April on a PP3 Battery

I just got my first IMP and April and want to know if I can power it from a PP3.

If so, any idea how long it would run for?

I will just be using this IMP as remote switch so the battery won’t be powering any other electronics.



PP3’s have fairly low capacity; the switching power supply on april will make the most of it, but there’s not a lot of power there; it’s about 500mAh @ an average voltage of maybe 7v over the usable discharge cycle.

That’s ~3500mWh, which at 90% efficiency turns out to be ~950mAh at 3.3v.

The imp when awake, with imp.setpowersave(true) set, takes maybe 7mAh right now, so that’s about 135 hours of life.

If your switch gives a rising edge on pin1, you can sleep all the time and wake only when the switch triggers, which will give you years of standby - power only being taken when the imp has to wake up and send something.

So… ideally use imp.sleepfor and wake up on pin1, but if not you’ll find that you’ll get under a week of usage even with power save enabled. We’re working on software improvements to this power mode that should get down to nearer 2mA (~3 weeks of life).

Thanks Hugo, that sounds like just the ticket.

If I do the method you suggest, will I have to wait for the IMP to boot up before it sends the command?



Yes, you need to wait for it to boot. You have more control over this in the next release, where you can sleep, wake on the switch transition, then bring wifi up to send the data (skipping the checking the firmware revision).