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The Cave Pearl Mission, an effort to map and perceive the circulation of water by means of cave methods, has unveiled a brand new variant of its information logging probe — and claims it will probably run for round two years on a single coin-cell battery.
“We’ve continued growth of a ‘lite’ model of our [environmental data] logger with the bottom potential prep,” venture co-founder Edward Mallon writes. “That new child is now prepared for launch with information obtain & management managed by means of the [Arduino] IDE’s serial monitor window.”
A brand new two-part information logger runs for greater than a yr on a single coin cell, with a bit of {hardware} hackery. (📷: Cave Pearl Mission)
The brand new “lite” information logger relies round an Arduino Professional Mini board, related to a real-time clock module. In an effort to scale back meeting time, decrease price, and restrict energy utilization the unique logger’s SD Card slot is eliminated in favor of logging to EEPROM — including complexity to the code, Mallon admits, however for a good trade-off.
Dropping the facility draw, although, required some modification. The actual-time clock module has a number of parts minimize or desoldered to decrease its energy necessities — a hack which, Mallon admits, causes reverse present circulation that the battery producer warns may trigger overheating and potential explosion. “Those I’ve used to date survive the abuse with out situation,” he notes.
The Arduino Professional Mini, working at 8MHz, goes beneath the knife too: The reset swap is eliminated to stop it being pressed when the meeting is put collectively in heat-shrink for stability, a regulator is clipped, together with the resistor related to the facility LED.
Elements on each the RTC module and the Arduino dev board are clipped or eliminated totally to save lots of energy. (📷: Cave Pearl Mission)
“This two module mixture often sleeps round 1µA and most of that’s the RTC’s (IBATT) timekeeping present,” Mallon explains, “because the [ATmega]328P ought to solely draw ~150nA in powerdown mode. A […] practical estimate would begin with the belief that the batteries solely ship about 110mAh with our logger consuming no matter we measured + 3µA (RTC precise) + 0.3µA (self-discharge).
“To be extraordinarily conservative we will spherical that as much as 5µA steady, with 4 5mA*10millisecond sensor readings per hour, and we nonetheless get an estimated lifespan of about two years.”
Extra particulars on the trouble to scale back energy draw and {hardware} complexity can be found on the Cave Pearl weblog, whereas the supply code has been printed to GitHub.
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