bme280 temperature, humidity and pressure sensor

Enfield Cat's Blog: Arduino and other projects.

Introduction

This device measures temperature, humidity, dewpoint and pressure.

Configuration

The minimum configuration is to simply added the sensor and restart the esp32. The configuration of the I2C bus is discussed elsewhere on this page. Each bme280 should have unique address on the bus on which it is located. The bme280 devices are numbered 0 to 3, starting with units on bus 0 then bus one. On each bus the number allocation is in device address sequence.

Configuration commands are:

altitude [<altitude> [m|ft]]
    Set altitude of unit for pressure compensation

critical|extreme|warning <devicetype> <0-3> [temp|humi|pres] disable
critical|extreme|warning bme280 <0-3> [temp|humi|pres] <rpn-expression>
    enable or disable alerting thresholds on sensors

devicename bme280 <0-3> <device-name>
    Name a sensor device

dewpoint bme280 <0-3> <dewpointname|"none">
    Name a dew point for a temperature sensor, or use none to disable

[enable|disable] [showlogic]
    Enable or disable display of rpn logic for alerts

i2c [<0-1> <sda> <scl> [speed]]
    Set i2c pins, eg: 21 and 22 for bus-0, and 5 and 4 for bus-1

interval bme280 <1-300>
    Set the interval between measurements taken by the sensor.

qnh <normalised-pressure-in-hpa>
    set altitude based on normalised pressure (QNH)

rpn variables:
    bme280.dev  - count of bme280 sensors (DEVice count)
    bme280.temp - average temperature for last 5 minute period in Celsius
    bme280.last - last read temperature in Celsius
    bme280.humi - average humidity for last 5 minute period
    bme280.lash - last read humidity
    bme280.dewp - average dewpoint for last 5 minute period in Celsius
    bme280.lasd - last read dewpoint in Celsius
    bme280.pres - 5 minute average of pressure in hpa.
    bme280.lasp - last uncompensated pressure reading
    bme280.unco - 5 minute average of uncompensated presure
    bme280.sos  - 5 minute average speed of sound calculation in meters per second
    bme280.lass - Last speed of sound calculation in meters per second
    bme280.alti - Altitude in meters
    bme280.tsta - OK, warn, critical or extreme status for temperature
    bme280.hsta - OK, warn, critical or extreme status for humidity
    bme280.psta - OK, warn, critical or extreme status for pressure

Other Notes

To enable the display of conditions causing warnings, run "enable showlogic" from the HydraFerret console
Temperatures are reported in both Celsius and Fahrenheit, and pressure in hPa and inch of Hg. The graph value though will only display one or the other value depending on the graph configuration.
To include dewpoint reporting, the dewpoint must be configured with a unique name. One suggestion is to either prefix or suffix the sensor name with "dp". An exmple from the trends display is shown below.
Note any gaps in monitoring due to power outages or network faults will show as gaps in the xymon graphs.

results collected from a bme280 over a 12 day period

Thank you for visiting camelthorn.cloud

Home