Weather station system based on nRF24L01, DHT22, ATtiny84, ESP8266, Nokia 5110 LCDs, and a Raspberry Pi

Introduction

This is a complete system for collecting, storing, and displaying environmental sensor data. The system consists of a number of embedded sensor nodes that communicate wirelessly with a base station using the very popular nRF24L01 radio modules.

All sensor data is stored in a InfluxDB time-series database. The plan is to make a couple of display units based on the ESP8266 wifi chip and some Nokia 5110 LCDs. For more thorough analysis a webpage will be implemented too.

In its current form, the project is work-in-progress. Status on the different parts as of 2016-05-20:

• Node firmware: 100%
• Node hardware: 100%
• Database and backend: 100%
• Display firmware: 10% (LCD library nearly complete)
• Display hardware: 5% (incomplete breadboard prototype)
• Web frontend: 10% (currently a single text page with the latest values)

I have successfully tested concurrent operation of 10 sensor nodes with a DHT22 sensor each. I have prepared a couple more for collecting wind and rain data as well.

Sensor node features

• Firmware optimized for ATtiny84 @ 1 MHz (8MHz crystal with the CKDV8 fuse set)
• Temperature and humidity measurement using a DHT22 sensor
• Temperature and humidity measurement using a HTU21D sensor
• Wind speed and wind direction measurement using a La Crosse TX23 anemometer
• Rainfall measurement using a WS-2300-16 rain gauge
• Wireless operation using the very popular nRF24L01+ 2.4 GHz radio chip
• Very compact CRC32 implementation
• Battery powered operation using a very efficient 3.3v DC/DC converter
• Power management by sleeping the CPU and turning off unneeded hardware
• Battery voltage measurement included in data packet
• Typical battery draw while sleeping has been measured to around 17uA
• Total firmware size from 3.0 kiB to 3.5 kiB (depending on sensor type)

Eventually I'll get around to writing a bit about this on my blog at: http://www.atbrask.dk/

/atbrask