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I'm trying to design an ultra low power audio recorder, in order to monitor ground noise in rural areas. The circuit I'm working on is based on a microcontroller (STM32L100RC) and an audio codec (VS1053) plus a bunch of additional components.

At this point, my circuit estimated current draw is around 300 mA (average, without considering burst due to audio processing and memory card writing).

As I would like to run my setup for about 2 months (around 60 days) to make relevant measurements, at this rate I would need an "immense" battery pack.

I would like to ask if there is something that enables recording 2/4 channels to an SD card in a more energy friendly package (maybe 1/10 of actual 300 mA), where an 80Ah LiPo battery pack would be able running easily for the time span, and enough spare capacity for eventual other sensor samplings.

Thanks in advance.

Edit

Thanks for all your comments. I decided to edit the question to add more details, instead of answering singularly. The actual circuit voltage is 5V, audio cannot be processed onboard and I need only a large audio file (or a lot of smaller ones) for the entire sampling period.

VS1053 audio encoder supports OGG encoding and, considering microphone bandwidth (around 10kHz), I would like to record at 44.1kHz Mono.

My problem is mainly due to expected very high MCU + ENCODER current draw. I can consider a good result something around 4 mA during recording but now I'm out by around two orders of magnitude.

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  • \$\begingroup\$ Are you measuring continuously or sampling every few minutes? \$\endgroup\$ – Trevor_G Oct 18 '17 at 16:50
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    \$\begingroup\$ First you need to define the sampling rate etc. How much data are you expecting total. 300mA sounds more than I would expect - you could record stereo audio for a lot less than that. What voltage are you referring to? Is that 300mA at 3.3v? ie ~1W? \$\endgroup\$ – Kevin White Oct 18 '17 at 16:57
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    \$\begingroup\$ Perhaps too broad a question to answer, but you need to idle the cpu core on the STM32 when your not using it. You should have no trouble getting to 10's of mA if not single mA \$\endgroup\$ – sstobbe Oct 18 '17 at 17:21
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    \$\begingroup\$ Failing all else... consider adding a solar panel. \$\endgroup\$ – Trevor_G Oct 18 '17 at 17:55
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    \$\begingroup\$ You need to start by figuring out what sort of noise you expect, and then figure out how you can efficiently capture that. You probably don't want an SD card, but rather an SPI flash, and you probably don't want to record linear audio continuously. Of course, event-driven recording may yield different battery life in different areas. \$\endgroup\$ – Chris Stratton Oct 18 '17 at 18:25
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You should consider ultra low power MCUs and audio codecs. 300mA is definitely way too much at 5V. Also if you can, and most of the MCUs and codecs can these days, reduce the system power supply voltage to 3.3V or less, say 2.7V or even 1.8V, unless you have a reason not to. Why 5V ? Generally lower power MCUs are considered to be the MSP430s from Ti, and the AIC3204, again from Ti. You should be able to reduce from 300mA to less than 100mA if not more. Good luck.

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