Using multiple Temperature Sensors with 433 MHz

soesas · October 2, 2018, 12:30pm

Hi,
I want to use multiple NodeMCUs as Nodes.
So NodeMCU equipped with a Temperature Sensor (DHT22,DS18B20 ,BME280)
As of now I am sending temperatures using wifi and mqtt but in order to save power I would prefer sending Temp/Hum and Voltage via RF433.
How do I do that? With Wifi I can just send a Text String or publish in different Topics, which is not possible with RF.
So how do I comply and decode the Readout from the sensor into something that the NodeMCU can send via RF and then later can be decoded in openhab. (Something like "Node ID; Temperature; Humidity; Voltage)

I found this sketch:

github.com

1technophile/low_power_sensor/blob/master/low_power_sensor_inside.ino

/*
  Low power node  - ATMega328p program to send humidity, temperature and battery voltage
 
  This program enables to send sensor data with low power:
 - send sensor data to a 433Mhz gateway
 - with 3 AA batteries measured at 5V the current consumption in sleep mode is around 5uA
  Contributors:
  - 1technophile
  Based on the libraries:
  - RCSwitch
  - LowPower
  Based on the work of:
  Nick Gammon : http://www.gammon.com.au/power
  Rocketscream: https://github.com/rocketscream/Low-Power
  Tinkerit: https://code.google.com/archive/p/tinkerit/wikis/SecretVoltmeter.wiki
  Documentation:
  Project home: https://github.com/1technophile/low_power_sensor
  Blog: http://1technophile.blogspot.com/2016/12/low-cost-low-power-room-sensor.html
Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
and associated documentation files (the "Software"), to deal in the Software without restriction,

This file has been truncated. show original

But it raises more questions then it answers.
Maybe someone can help. I will of course post my working solution here to help others.
Thank you guys so much!!!

1technophile · October 2, 2018, 8:00pm

Hello,

If you want multiple temperature sensors i will advise the use of ble with mi flora or mi jia off the shelves sensors. Nevertheless if you want a more diy solution you can indeed go with an arduino + 433mhz.
In my setup I m managing the value coming from the atmega328p with a simple mapping file.

Example :
The atmega read 22°
It add an offset of 55000
The atmega send 55022 with rcswitch library
OMG receive 55022
OMG transfer it to mqtt
Openhab with the help of mosquitto receive 55022
Openhab search on the mapping file the corresponding value
55022=22
Openhab set 22°

Here is the main principles.