Maker Jake Wachlin has put collectively a improvement board constructed to ship on a single purpose: drawing beneath 100nA in energy whereas in its deepest sleep mode, but nonetheless permitting for wake-up from an onboard real-time clock (RTC): the Nanosleeper.
“Nanosleeper [is] a ‘Feather-ish’ improvement board reaching <100nA deep sleep present with real-time clock wake-up,” Wachlin writes of his creation. “Leveraging the [STMicro] STM32L412 (able to 18nA in Shutdown mode with pin wakeup), the [Micro Crystal] RV-3028-C7 RTC (able to 1ppm timekeeping at 45nA with interrupt output), and the [Texas Instruments] TPS7A02 voltage regulator (25nA quiescent present), the Nanosleeper is a 1.8V Feather-sized (however not absolutely pin or voltage appropriate) improvement board for ultra-low energy purposes.”
The Nanosleeper aimed to ship a sub-100nA sleep present draw on a 1.8V improvement board, for the longest of battery lives. (📷: Jake Wachlin)
The board was designed, Wachlin explains, to ship a solution to at least one easy query: is it doable to construct a practical improvement board that may sleep whereas drawing beneath <100nA at 1.8V but wake on demand? “Extremely-low energy methods can generally obtain <10uA in deep sleep,” he says. “Getting this right down to <1uA is feasible, however tough (even good, trendy ultra-low energy microcontrollers, RTCs, and voltage regulators can require about 1uA to function). Nanosleeper takes issues one other order of magnitude, right down to <100nA at 1.8V. At <100nA, Nanosleeper would take >256 years to empty a CR2032 coin cell battery.”
The guts of the board is STMicro’s STM32L412 microcontroller, which runs at 1.8V — ensuing within the lack of USB connectivity, Wachlin explains, with the board’s USB Sort-C connector used for energy solely. The board will also be pushed from a battery linked to the TI TPS7A02 voltage regulator, as much as a 6V enter voltage. As a closing power-saving function, the design additionally incorporates a TI TPS22917DBV switched energy output — that means exterior {hardware} working from the Nanosleeper could be powered down utterly whereas the microcontroller sleeps.
Actual-world testing confirmed a sustained sub-95nA energy draw whereas the board was in its deepest sleep mode, with RTC wake-up. (📷: Jake Wachlin)
Examined in {hardware}, the Nanosleeper delivers a solution: whereas working a pair of LEDs the gadget attracts 800µA as measured from a 3.3V battery linked to the regulator, dropping to 600µA when the LEDs are off however the microcontroller is in a busy-wait loop at 4MHz; when the gadget enters deep-sleep, although, the facility draw measured at beneath 95nA. “In abstract,” Wachlin writes, “IT WORKS! Nanosleeper achieves a deep sleep with timed wake-up at as much as 4,095 minute intervals whereas consuming <95nA!”
The complete mission write-up is out there on Wachlin’s Hackaday.io web page, with schematic; the supply code for a pattern firmware has been printed to GitHub beneath the permissive MIT license.
