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Topic: Nano 33 IoT Vin Voltage range (Read 5559 times) previous topic - next topic

sainohio

I have a nano 33 IoT that uses DHT22 and BMP280. It receives and sends UDP over WiFi. It runs like a clock on any voltage down to and including 4.5 volts. At 4.5 volts the 33 uses about 40 ma base and in the mid 50s ma upon transmit.

At 3.0 volts, the nano 33 power light doesn't come on. The min voltage for the 33 is somewhere between 3.3 and 4.5 volts. I would like to try a 3.7 volt (lithium) battery next. Why anyone wants to use 10-15-20 volts for this seems strange.


pert

As already mentioned above, 4.5 V is the minimum input voltage, as specified in the MPM3610 datasheet. Maybe you can get it to work with less, but you have no guarantee of reliability at lower voltages.

Why anyone wants to use 10-15-20 volts for this seems strange.
If that's the voltage you have available, then you're going to want to use it.

sainohio

Well, just as an anecdotal note, I am currently running the 33, WiFi and all, on a 3.7 lithium battery (fully charged showing 3.96 volts), and it has run perfectly so far, through varied environmental conditions, and distance testing.

As far as the supply voltage goes... 
This is suppose to be a low power device. Are you saying that it will draw no more current at 20 volts than it will at 5 volts?

pert

#18
Feb 18, 2020, 01:31 am Last Edit: Feb 18, 2020, 01:32 am by pert Reason: Embed image
This is suppose to be a low power device.
It's capable of low power operation, but that isn't necessarily going to be the primary consideration in all use cases.

Are you saying that it will draw no more current at 20 volts than it will at 5 volts?
There's a cool chart on the first page of the MPM3610 datasheet:



So you can see the answer is "it depends". There is a range of conditions where it will actually be more efficient with a 19 V supply (<80 mA load current) or a 12 V supply (<65 mA) than a 5 V supply. A low power device will likely be in that load current range almost all the time. You may be used to a different situation with the traditional Arduino boards that use a linear voltage regulator.


sainohio

Sorry, I assumed lower voltage would mean lower current draw. Actually the opposite it true.

At 4.5 volts (battery) the baseline current draw is 42 mA
At 9.0 volts (battery) the baseline current draw is 30 mA
At 12 volts (wallwart, true voltage 13.7 volts) it is 18 mA

So it appears that what I need is a high capacity 20 volt battery about the size of the nano. :-)

The 3 X AAA or 3.7 li-ion idea just won't work unless I can make big magic on the power saving stuff.

sainohio

I ran a test starting at 10 PM. 4.5 volt battery, 42 mA draw. When I got up the next morning the green power light was flashing, it had apparently hit the brownout limit. According to the log, it stopped transmitting about 6 AM. That is 8 hours. The battery pack was down to 3.5 volts. It seems the nano 33 will not run below 3.6 volts.

Unfortunately, the only extensive article I can find about power consumption and power saving was written by Nick Gammon in 2012 and was written about and for the Atmega328P.

Is there currently any similar info available for the new architecture?

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