We can save energy by deep-sleeping the ESP32. During this time, the chips do not consume a lot of energy but also are not responsive. This is why Espressif included a mysterious Ultra Low Power core (ULP) which is active when the main processor sleeps. People say it has to be programmed in Assembler, and nearly nobody was able to program it in the Arduino environment. Until now. Links: Arduino IDE ULP repository: https://github.com/duff2013/ulptool Sketch: https://github.com/SensorsIot/ESP32-ULP-Arduino-IDE ESP32 module: http://s.click.aliexpress.com/e/bQwDCLQs ESP32 Board: http://s.click.aliexpress.com/e/XAhzEgY ULP commands: https://docs.espressif.com/projects/esp-idf/en/latest/api-guides/ulp_instruction_set.html Technical Reference: https://www.espressif.com/sites/default/files/documentation/esp32_technical_reference_manual_en.pdf Otii power Supply: https://www.qoitech.com/ Supporting Material and Blog Page: http://www.sensorsiot.org/ Github: https://www.github.com/sensorsiot My Patreon Page: https://www.patreon.com/AndreasSpiess Alternative: https://flattr.com/@andreasspiess My Bitcoin address: 19FSmqbBzb5zsYB1d8Bq4KbxVmezToDNTV If you want to support the channel, please use the links below to start your shopping. No additional charges for you, but I get a commission (of your purchases the next 24 hours) to buy new stuff for the channel For Banggood https://bit.ly/2jAQEf4 For AliExpress: http://bit.ly/2B0yTLL For ebay.com: http://ebay.to/2DuYXBp https://www.facebook.com/profile.php?id=100013947273409 https://twitter.com/spiessa https://www.instructables.com/member/Andreas%20Spiess/ Please do not try to Email me or invite me on LinkedIn. These communication channels are reserved for my primary job