From e80fd401949e5f25691381955a07f4a6286bea0c Mon Sep 17 00:00:00 2001 From: Jannik Beyerstedt Date: Wed, 25 Mar 2020 12:49:32 +0000 Subject: [PATCH] Update 'README.md' --- README.md | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/README.md b/README.md index 6dc2d52..8f65124 100644 --- a/README.md +++ b/README.md @@ -1,7 +1,16 @@ -# Readme +# ESP32-based Environmental Sensor Author: Jannik Beyerstedt **license:** GNU GPL v3 +A simple temperature and humidity sensor node using an ESP32 and a Si7021 sensor element running of a 18650 LiIon battery cell. +The sensor outputs the data to an influxDB instance, which must be reachable via HTTP. + +To save energy, we use a lower CPU frequency. +But this requires compiling the core framework again with the changed settings (see below). + +This repository contains the code running on the ESP32, as well as the PCB and case design. + + ## Dependencies Prepare toolchain (macOS): @@ -43,7 +52,8 @@ git clone --recursive https://github.com/espressif/esp-idf.git ``` -## Checkout this project and configure arduino-es32 with esp-idf: + +## Checkout this project and configure arduino-esp32 with esp-idf: ``` TODO!! @@ -71,3 +81,17 @@ make all make flash ``` You would probably have to adapt the `UPLOAD_PORT` in the `Makefile` or set it via an environment variable. + + + +## Battery Life +The hardware was designed with two options to drop the battery voltage to a level, which can be fed to the ESP32: A voltage regulator or a simple diode. + +A test with increased data rate (for a shorter test duration) showed, that the voltage regulator leads to a slight battery life benefit. +Using a measurement interval of 30 seconds and a WiFi connection interval of 3 minutes, the 2500mAh LiIon (3.7V) battery lasted 30 days with the diode and 36 days using the voltage regulator. + +The selected voltage regulator has a quite low drop-out voltage and more importantly a low leaking current during the deep-sleep phases, which have a very low current needed by the ESP32. +In comparison a diode has no leaking current at all, but a more or less fixed voltage drop. + +The benefit of the voltage regulator is, that the battery voltage range can be exploited further than what can be done with the diode. +The lowest operational battery level was 3.2 V using the diode and 2.8 V using the voltage regulator.