emonTH -Temperature & Humidity Node
The emonTH V2 is an open-source, wireless, battery powered temperature and humidity monitoring node.
It is an easy to deploy tool for monitoring building / room temperature and humidity. Data from the emonTH is transmitted via UHF radio (433MHz) to an emonPi / emonBase web-connected base-station for logging to Emoncms for data logging, processing and graphing. Room temperature and humidity data can be used to inform a heating control system, feed into a building performance model or simply for general interest.
Temperature and humidity sensing - using the onboard Si7021 temperature and humidity sensor and (optionally) an external DS18B20 temperature sensor.
- Easy to set-up - the unit comes pre-assembled and pre-loaded with Arduino compatible firmware. If desired the code can easily be modified using Arduino IDE or PlatformIO and uploaded using an USB to UART cable to the on-board ATmega328 microprocessor.
- Long Battery Life - The emonTH is powered by two AA batteries which will last over 4 years. Use alkaline batteries for longest battery life or rechargable eneloops for best environmental benefit.
- Expansion Options - An optical pulse sensor can be attached to the screw terminal connector for interfacing with a pulse-output utility meter. See hardware wiki for optical pulse sensor connection info.
- RF node ID DIP switch Selection - Up to four RF node IDs (23,24,25 & 26) can be set via physical onboard DIP switches. See hardware wiki.
- Microcontroller: Arduino compatible ATmega328p
- Internal Sensor: Si7021 (internal temperature & Humidity)
- External Sensor (OPTIONAL): DS18B20 external temperature sensor. See hardware wiki for connections
- Power: 2 x AA from on-board holder, LTC3525 3.3V DC-DC boost converter to extend battery life
- RF Radio: RFM69CW 433Mhz
- Acrylic enclosure
- 4 year+ battery life
- External dimensions: 71 x 71 x 27 mm
Si7021 Temperature & Humidity Sensor
- Silicon Labs SI7021-A20-GM1R
- Power supply 1.9V - 3.6V
- Operating range humidity 0-80%RH; temperature -40~125 deg C
- Accuracy humidity +-3%RH
- Accuracy Temperature: +-0.4 degC
- Active current: 150uA
- Sleep current 0.06uA
- Measurement time: 2.6ms = 10ms
- emonTH V2 Setup Guide
- emonTH V2 GitHub (firmware & hardware CAD design)
- Technical hardware Wiki Documentation (emonTH V1.5)