This sections covers a wide range of example low power projects which can be useful references for your designs. Many of these are open source and have information on all of their components and clever system design and firmware used to reduce power consumption.

SOL: Long-term solar intensity sensing

This project is a solar powered pyranometer with an ESP32 providing Wi-Fi connectivity. Early versions used the ESP32 as the only microcontroller onboard, while newer designs have an STM32L4 for sensing and an ESP32 actin only as the Wi-Fi modem.

Indefinite operation from 0.5W Seeed Studio solar panel
Rechargeable 14500 lithium-ion cell
~6.2uA average in deep sleep mode

Ultra Low Power Feather Development Board

This project was built as a challenge to see if I could build a Feather-sized development board which can operate indoors in active mode (i.e. without sleep modes), do some useful sensing, and be powered solely from onboard solar panels. It partially worked, but requires fairly bright lights. Of course, when sleep modes are used the power is vastly lower.

285uA in active mode, much slower in sleep
SAML21 used as microcontroller, with accelerometer, barometer, and ambient light sensors
SMD solar cells mounted on board
Optional supercapacitor and Li-Po battery energy buffers

Thermoelectric Power Harvesting Demo

This was a project I built to test energy harvesting using common, low cost Peltier modules. I was able to run the ultra-low power feather development board from a 40F temperature differential.

MetaShunt

This is a tool I developed for power profiling ultra-low power systems.

LP Mini - Low Power Dev Board

[Max.K] developed a low power Arduino compatible development board based on the standard Atmega328p microcontroller. By removing the typical power LED and using a more efficient regulator, the sleep current was reduced to 2.8uA.

Ultra Low Power thermometer

[Miroslav Hancar] built this thermometer with an always-on screen, powered by a CR2032 coin cell battery or a very clever "solar 2032", which requires ~3uA in operation.

Low Power ESP32 Handheld

[Max.K] built this low power device with a 2.7" always on Sharp memory display that uses an ESP32 and achieves current consumption of ~56uA.

Ultra-Low Power LiPo Charger via Energy Harvesting

[Kris Winer] built this breakout board for the TI BQ25504 Li-Po battery charger. It is now available for purchase on Tindie.

STM32L4 Sensor Tile

[Kris Winer] developed this low power sensor platform around the STM32L4 microcontroller which acheives average current of ~100uA while "smelling and hearing."

Ultra Low Power RF Node

[Charles] developed this "universal" Arduino sensor node which can interface with a wide variety of sensors, has wireless capability, and can run from a few different battery types.

Examples